History and Evolution

**Chapter 2**

## History, Evolution and Future of Starch Industry in Nigeria

*Obi Peter Adigwe, Judith Eloyi John and Martins Ochubiojo Emeje*

#### **Abstract**

Starch industry has progressed into a business that is worth billions of dollars globally, as they have been found useful in the food, textile, biofuel, plastic and the pharmaceutical industries. Nigeria can be the largest producer of starch in the world. Her major sources are roots and tubers (cassava, yam, cocoyam and potato), cereals (maize, sorghum, millet and rice) and fruits (banana, plantain and breadfruit). Although, all the starch crops are abundantly produced in Nigeria, only less than 1% is processed into high quality starch for industrial processes. This chapter therefore examines the past, the progression and the current state of the starch industry in Nigeria and the roles the government and relevant stakeholders must play in order to revolutionize the industry in Nigeria.

**Keywords:** starch, cassava starch, rice starch, potato starch, maize starch, industrial uses, history, evolution, Nigeria

#### **1. Introduction**

Starch is the most abundant edible polysaccharide derived from plants [1]. They are composed of repeating units of amylose and amylopectin that are susceptible to modification by physical, chemical, enzymatic and other means [2]. Starch in its native form is a multipurpose polymer, and an important raw material that finds useful applications in both food and non-food processes [1, 3]. Native starch is susceptible to retrogradation, syneresis, inconsistent viscosity and unordered gelation, hence, cannot withstand the typical industrial processes such as high temperatures, pH, high shear rate, and freeze thaw variations usually encountered during its use in food and other processes. Thus modification transforms native starch into gels or viscous mass in water at room temperature [2]. Furthermore, their properties are improved to yield starches with enhanced pasting properties, decreased retrogradation, reduced tendency to gel, enhanced freeze-thaw stability, improved paste clarity, and texture, and improved film formation and adhesion. These superior properties are what finds application in the food, textile, cosmetics, agro and pharmaceutical industries. The major sources of starch are roots and tubers (cassava, yam, cocoyam and potato), cereals (maize, sorghum, millet and rice) and fruits (banana, plantain and breadfruit) [4, 5]. However, commercially available starches are cassava, maize, potato, and rice starch and they are gluten-free which can

be tolerated by individuals who react to gluten [6]. Even though all the starch crops are abundantly produced in Nigeria, only less than 1% is processed into high quality starch for industrial processes, while about 10% is used as feedstock, 5% is processed into syrup concentrates for the soft drink industry and the rest (84%) is consumed as food [2].

#### **1.1 Cassava starch**

Cassava (*Manihot esculenta*), is extensively cultivated as an annual crop in tropical and subtropical regions, around the South-East, South-South and South-West regions (**Figure 1**), and it serves as an important food crop and a major source of carbohydrate for more than 70% of the Nigerian population, and provide income to over 30 million farmers, industries and traders [7, 8]. Nigeria is the largest producer of cassava in the world, producing over 37 million metric tons with an average yield of 12 metric tons/hectare [9]. Over 90% of these are consumed locally, and used as animal feeds, industrial purposes in pharmaceutical and food industry and only 10% are processed for export [3, 9]. Cassava root contains about 1% protein and 30–35% starch on a dry weight basis, hence, regarded as a starchy food [10]. It is a perishable commodity once harvested with a shelf life of less than 3 days [7]. The greatest potential of cassava as an agricultural crop lies in the production of starch. Two types of starch (sweet and sour) are produced from both varieties of cassava tubers (bitter or sweet). Both forms of starch differ in characteristics and end use. Sweet starch is obtained after an extraction process that separates the starch from other constituents, whereas sour starch is obtained by fermentation following extraction. Sweet starch is used as an adhesive in the textile, paper, and battery industries, while the sour starch is used solely in the food industry [3]. Although cassava starch serves as a cost effective raw material for many industrial processes [1], studies show that 52% of cassava produced is wasted as a result of inadequate production and processing, 43% is consumed as food and 5% is utilized as feedstock [3]. The suitability of cassava starch as a raw material in the food industry is due to its inherent properties such as low gelatinization temperature (71°C), its slow propensity to retrograde, does not have leftover proteinous materials or soil residues, non-cereal flavor, high viscosity, high water binding capacity, bland taste, translucent paste, good stability and reasonably good adhesive strength. It has a rather low lipid profile of less than 0.01%, protein content of 0.15–0.30%, ash value of 0.08–0.15% and phosphorous content of 2.04–2.45 mg/kg. In addition, it is easy to extract, settles rapidly and has a carbohydrate content of 73.7–84.9% [11]. In the paper industry, cassava starch is used as an adhesive; in the cosmetic industry, it serves as a significant raw material in the production of powders, it enhances the recovery and stability of detergents in the soap industry, while it produces a better foaming ability in the rubber and foam industries. In addition, cassava starch can be converted into maltotriose, maltose, and glucose, can be used to make fructose syrups and in the production of gelatin capsules [1]. Although, cassava starch has great potentials, only about 2% of food industries in Nigeria utilize cassava starch and its derivatives [3].

#### **1.2 Potato starch**

Potato (*Solanum tuberosum L*.) belongs to the tuber crops. There are two major types: the Irish potato which are grown through tubers, and the sweet potato (*Ipoema batata*), raised through vines, along the North-Western part of Nigeria (**Figure 1**). The Irish potato was introduced first in Nigeria in the late 19th Century, through missionary activities. Encouraged by the British government during the Second

**Figure 1.** *Map showing regions of some starch-based crops in Nigeria.*

World War in order to feed their troops in West Africa, Irish potato was cultivated extensively and it became an important commodity for both local and international trade [12]. Nigeria is known to be the fourth country in West Africa in terms of potato production; on the African continent, it ranks the seventh. However, little effort is made in its promotion for industrial use, as over 80% are consumed as food [13]. Starch obtained from Potato has been demonstrated as a potential raw material in the pharmaceutical, textile, wood and paper industries as an adhesive, binder, texture agent and filler, and by oil drilling firms to wash boreholes [12]. Sweet potato starch can be utilized in the production of starch syrups, glucose and isomerized glucose syrups, lactic acid beverages, bread and other confectionaries [5, 14]. It can also be used to produce distilled spirits, noodles and isomerized saccharides as sweetener for soft drinks [15]. In addition, they can be utilized in the production of citric acid, ethanol and also used in the paper and textile industries [16]; as stabilizer in the production of yogurt [17]; and as pharmaceutical excipients when modified [18–20]. Potato starch is 100% biodegradable and is utilized as a substitute for polystyrene and other plastics. Hence, can be used in the production of disposable plates, dishes and knives [12].

#### **1.3 Maize starch**

Maize grains (*Zea mays*) are widely distributed worldwide, and grown in abundance in the North-Western and Southern-Western parts of Nigeria (**Figure 1**) during rainy seasons, however, they are subject to post-harvest wastes due to inadequate storage and processing. More maize is produced annually than any other grain. About fifty (50) species exist and consist of different colors, textures and grain shapes and sizes. White, yellow and red are the most predominant types. Maize starch or corn starch is the starch derived from the corn (maize) grain. The starch is obtained from the endosperm of the corn kernel and is a popular food ingredient used in the food, textile, pharmaceutical and paper industries. In the food industry, is used as a thickening agent for sauces, gravies,

glazes, soups, casseroles, pies, and other desserts [21]. In Nigeria and other African countries, corn starch is used in making corn syrup and other sugars like high-fructose corn syrups, obtained from the breakdown of corn starch, utilized in the soft drink and candy industries. And also in the production of bioplastics. It is equally the preferred antistick polymer used in the manufacture of medical products obtained from natural latex, including condoms and medical gloves. In the food industry, corn starch is used to reduce the cost of production by adding varying amounts of corn starch to foods like cheese and yogurt. In the production of ethanol, corn has the least expensive total cost. Here, the yellow specie of corn is used as it contains about 62% of starch [22]. In the industrial production of glucose, corn starch undergoes hydrolysis by a degradation process using amylolytic enzymes found in abundance in nature. The use of enzymes in this process produces a higher yield of pure glucose, that are more stable and environmentally friendly [23]. In 2004 more than 50% of starch was converted to High Fructose Syrups (HFS).

#### **1.4 Rice starch**

There are two main species of rice that are cultivated in Nigeria, the African specie, *Oryza glaberrima* L. and the Asian specie, *Oryza sativa* L., of which 120,000 varieties are known [24]. Rice is the world's second most important cereal crop after maize, based on the volume of production and cultivated mainly along the North-West and South-West regions of Nigeria. Nigeria currently consumes about 7.9 million metric tons of rice annually while production is presently at 5.8 million metric tons. The FAO's report show that rice generates more income for Nigerian farmers than any other cash crop in the country, with small scale farmers accounting for the largest volume in sales of 80% while the remaining 20% is consumed. An average of 7–8 tons of rice can be obtained per hectare. But up to 12 tons per hectare can be obtained depending on the variety of seeds planted. Although rice has been the topic for discussions, it has not benefited from the kind of value-added research required for economic competitiveness on an international scale, in terms of production. Hence, rice producers in the country are peasant farmers who are left to keep the sub-sector afloat against all odds. Industrialists can be encouraged to engage in large-scale production of rice as functional ingredients can be developed from Nigeria local rice cultivars and that these ingredients would stand the world market competitiveness. Of these, rice is starch is the major component of rice constituting about 90% of its dry matter [25]. Another major product obtained from rice starch is liquor, usually called Rice Wine, and it can be made at home or in a processing facility from the fermentation of rice starch that has been converted to sugar. It is widely consumed in Asia, and has an average alcohol content of 18–25%. At the present, this area of investment is yet to be explored in Nigeria [26]. Traditionally, there have been basic attributes associated with rice starch that makes it stand out above other cereal and non-cereal starches. These properties include hypoallergenicity, digestibility, bland flavor, small granule (3–10 μm), white color, greater acid resistance, greater freeze–thaw stability of pastes and a wide range of amylose/amylopectin ratios. These exceptional features are manifested in the different applications of rice starches.

#### **2. History of starch industry in Nigeria**

In Nigeria, in 1940, starch began gaining popularity when cassava starch was produced in response to the demand by the British government during an outbreak of war. In May 1940, starch samples from cassava roots were sent to the Ministry of Food and to Starch Products Limited in London for further experiments [27], and 300 tons of starch was purchased. Following the successful sale of starch and its increased demand by the British government, 10,000 tons of starch was further exported in July, August, and September 1940. However, in October, 1940, there was a drawback in the export of starch due to lack of quality, as a result of delay in processing cassava roots, inadequate washing of the starch after settling, the use of dirty water or dirty utensils, the use of exposed peeled roots to the atmosphere for undue time before grating, storage of starch with high moisture content [27].

By June, 1941, the Ministry of food in London purchased starch "irrespective of quality"; and by September the UK was buying the entire production obtainable [28]. Trade continued in 1942, with the demand of monthly supply set at 300 tons by the Ministry of Food, this continued into 1943, and from January to April, starch was produced in large quantities and became a priceless commodity [27]. In April, 1943, exportation of starch from Nigeria was abolished as a result of a new demand for palm products by the UK. Therefore, in 1943, Nigeria was required to ensure the maximum production of palm products, and to achieve this sole objective, a strategy was implemented to stop the production of starch [29]. Likewise, the oil and kernel producing areas in Nigeria were barred from producing starch, instead, they were encouraged to cultivate cassava enough for local consumption [27, 30]. In May, 1943, the purchase of starch for export ceased and the notice on prohibition was repeated in 1944 and 1945 [27, 31]. Since then, low quality starch was refined and sold locally to be consumed as food or adulterated with cassava flour or garri and sold in the markets [32].

#### **3. Evolution of starch industry in Nigeria**

Starch industrial application has evolved into a multibillion dollar business worldwide and as such, many more industries, mostly within Africa, have now developed multipurpose applications for starch especially cassava starch. The demand for starch in Nigeria alone has recently been estimated to be around 67,100 tons per year and the amount of fresh cassava roots needed to produce that amount of starch is 350,000 tones [1]. The production of cassava has been stagnant since independence to the mid-1980s. however, an increase in production was observed from the mid-1980s to early 1990s where it remained constant again until 1999, at the beginning of the civilian era, where an increase was observed. Although, the Nigerian cassava market is centered on consumption patterns, an industrial market is now evolving (where cassava starch is used in the food, pharmaceutical and other industries) that needs to be explored and utilized. Starch derived from cassava for industrial purposes reveals a great potential for increased earnings for cassava farmers. Howbeit, in order to achieve global competitiveness on the production of cassava, the Obasanjo administration in 2002 established an ordinance on cassava production that led to a 73% growth, an excess in cassava production, which eventually led to wastage and massive financial loss due to poor storage, inadequate distribution and underdeveloped downstream sector [33, 34]. This led to investments in new factories (MATNA foods in Ondo state, built in 2005, Dutch Agricultural Development Company Nigeria Limited, Benue State, built in 2006, and Ekha Agro Farms, Ogun State, a glucose syrup factory built in 2007). These companies used improved production and processing machineries to enhance cassava starch production and also in the production of glucose, sweeteners and ethanol that could meet international standards [33]. Likewise, the annual

production of rice in Nigeria increased from 2.8 million in 2010 to 4.9 million metric tons in 2019, while rice importation decreased by about 60% within the time frame, indicating Nigeria's readiness to achieve self-sufficiency. The improved development warranted product diversification of rice to other value-added products like ethanol, glucose syrup, and starch by making use of the underutilized native rice varieties that had undesirable physical features (short grain length, poor color, etc.), poor cooking quality (soft and sticky grain), and poor consumer acceptability [35].

#### **4. Prospects of starch industry in Nigeria**

Native starch is undesirable for many industrial applications, irrespective of the source. They are susceptible to retrogradation, syneresis, undesirable viscosity and gelation as a result of their inability to withstand high temperatures, pH, high shear rates, and freeze thaw variations when used for food and other applications. Hence, the need for modification by physical, chemical or biological means to yield starch with improved pasting properties, decreased retrogradation, decreased tendency to gel, increased paste freeze-thaw stability, improved paste clarity, film formation, adhesion and gel texture [36].

#### **4.1 The food industry**

The food industry is one major industry that utilize starch and starch-based products. Modified starches have been used as sweeteners, and to improve the texture of gums and pastes, and also to obtain products that thicken in cold water without the addition of heat [2]. They are also used as binders to solidify the mass of food to prevent it from drying out during cooking especially in sausages and processed meats; and as a stabilizer in creams, due to its high water-holding capacity [37, 38]. As thickeners, they are used in soups, baby foods, sauces and gravies. In addition, glucose produced from starch are also used in the production of caramel that are extensively utilized as coloring agents in foods, confectionaries and liquor [39]. Glucose syrup is a solution of glucose, maltose and other nutritive saccharides obtained from edible starch. Although, glucose syrup is not adequately produced in Nigeria as 800 million naira was used to import glucose in 2003 [4]. However, a surge in private sector investments in the large-scale production of starch as reported by the Federal Ministry of Agriculture, Nigeria was observed and companies like the Nigeria starch mills, and the glucose factory in Ogun State began to invest in large-scale production of cassava and processing of its by-products by utilizing improved techniques in the machineries used to peel, grate, dry, fry and mill the raw materials [40].

#### **4.2 The pharmaceutical industry**

In the pharmaceutical industry, starches are one of the most important excipients that have been widely used in the formulation of tablets. They are inert, inexpensive and have been utilized as fillers, binders, disintegrants and glidants. The use of modified starch improves the physicochemical properties of the tablets and other pharmaceutical formulations [36, 41]. Over 1500 tons of starch hydrolysates are used in the pharmaceutical industry annually and about 80% of starch are imported [8]. In addition, crystalline and liquid glucose are imported for the production of cough

syrups, yet, this high demand for starch-based products can be met from the inexpensive and high quality starch found in cassava that is richly available in Nigeria [1].

#### **4.3 The textile industry**

In the textile industry, modified starch (oxidized starch) is employed in the sizing and dyeing of fabrics to improve the weight, clarity and hardness of the fabric [1, 36]. Cassava starch is the most preferred for this application as it gives a better finishing compared to other starches. In addition, modern laundries use soluble starch, incorporated into a suitable propellant sprays for application during steam ironing. In the early 1990s only about 700 tons of cassava starch was produced per annum because the starch was considered to be of low quality. However, maize starch was imported for use in the textile industry which was later replaced with over 67,000 tons of cassava starch [8]. Again, the downturn of the economy during the military era led to the near collapse of the textile industry which further decreased the market prospect for cassava starch. Nevertheless, this industry can be restored if successive leadership can establish and promote the starch industry [42].

#### **4.4 The plastic industry**

Starch has been used in the production of plastics since 1970s based on their biodegradability, renewable nature and freely abundant. Starch is easily dispersed in cold water, however, it thickens when heated to its near boiling point to form a colloidal suspension that gels when cooled. Polymer blends in the presence of plasticizers like water and glycerol, can be distributed or transported to normal plastic converters, which can process the blends to products using normal injection or blow molds [43]. Such biopolymers (consisting of 40% starch and 60% low-density polyethylene) using cassava starch has been produced and commercialized [1]. There are roughly 30 plastic companies in Nigeria, among which are: The Black Horse Plastic Industry Limited, OK Plast Limited, Abbey-Fem Plastics, Celplas Industries Nigeria Limited, among others. Since Nigeria is the largest producer of cassava, the utilization of cassava starch by these companies to produce biodegradable biopolymers is achievable. This will not only protect the environment from the harmful effects of petroleum derived plastics, but will also generate an economic alternative for cassava agriculture [44, 45].

#### **4.5 The biofuel/chemical industry**

In the production of alcohol, starch is hydrolyzed by a two-step process to glucose and then is further diluted and converted to ethanol by the action of yeast [3]. Bioethanol is a form of soi-disant-renewable energy that can be manufactured from agricultural crops like corn, potatoes, cassava, rice and sugar cane [46, 47]. Cassava starch has a much higher yield (150 L/ton of fresh roots) than sugar cane (48 L/ton), a source that was previously used in the production of ethanol without much success in Nigeria. However, difficulty in the local production of cassava in 2001 halted the production of ethanol and since then, all the ethanol used in Nigeria was imported. Although current interests in investment in the Nigerian ethanol industry is increasing, encouraging small industrial production using cassava will lead to the economic growth of the industry [8]. Other starch-derived products such as D-glucose and maltose, butanol, acetone, glycerol acetic, citric, itaconic, gluconic and lactic acids

can also be produced from these starch-based crops by the process of fermentation when the starch is modified [2]. According to **Amenaghawon et al.** [48], the projected yearly production of citric acid is about 1.4–1.5 million tons and this is expected to increase to about 3.5–4.0% yearly. Of this amount, roughly 70% is used by the food industry for its pleasant acid taste, high solubility in water, its chelating, antioxidant and buffering actions. Approximately 12% is used by pharmaceutical industries as liquid elixirs, flavoring agents, anti-coagulant and as preservatives while 18% is used by other industries (cosmetics, toiletry, detergent, textile, oil recovery, paper).

#### **4.6 Other starch-based products**

Other uses of starch are in the production of adhesives; starch (converted to dextrin) is the major raw material in the manufacture of glues and adhesives [1, 42]. In the 1990s, 58,000 tons of adhesives were used in the wood, cable, paper and printing, packaging and footwear industries in Nigeria. Regrettably, they were imported either as adhesives or as dextrin. Adekunle et al. [49–52] demonstrated the potentials of using cassava starch as a raw material in the large-scale manufacture of adhesives in Nigeria. Hence, expanding the starch industry for use in the manufacture of adhesives for these industries would put over 60,000 tons of cassava into use for this industry alone in Nigeria [8]. In the soap and detergent industries, starch is used as a filler to obtain a better yield and enhance the shelf-life of the products; in the production of sugar syrups, starch is subjected to enzyme hydrolysis using α-amylase. Cassava, corn and rice starch have been used in the production of fructose and glucose syrups, and in the manufacture of gelatin capsules [42, 53]. The food and beverage industries in Nigeria depend heavily on glucose syrups and crystalline sugars, and cassava starch are used in the production of candies, in the soft drink industries and in traditional medicines. However, the syrup concentrates are currently imported as cassava starch derivatives (hydrolysates e.g. glucose, sucrose, fructose, maltose, and syrup) are not presently developed in Nigeria [1, 8]. In the production of yeast, starch is enzymatically hydrolyzed to glucose and this leads to the production of certain yeasts that utilize this glucose to produce microbial cellular substances. According to Taiwo et al. [3], this aspect of producing yeast from simple sugars is yet to be exploited in Nigeria, as majority of the yeast used in the food and beverage industries are imported.

#### **5. The future of starch industry in Nigeria**

To achieve sustainable progress in the starch industry in Nigeria, the government, private sectors and key stakeholders must of necessity put all hands on deck to ensure the improvement of the agricultural sector in Nigeria [54]. This can be achieved by implementing programs and policies that will foster the production of starch producing crops, conversion of unused lands into cultivation of starch-based crops, establishment of industries for local production of starch, and improvement in the processing and storage of starch-based crops [1]. Thus, the local industrial products will not only meet local demands but also have the potential of becoming a source of income generation. This demand will aid in the improvement of industry, national and international standards, quality and global supplies leading to a gradual approach to export-oriented production. In addition, private investors may be encouraged to participate in improving the production and conversion of these crops to high quality starch and derivatives, by supporting

*History, Evolution and Future of Starch Industry in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.102712*

market linkages, organizing trainings for farmers, support and development of processor groups, build capacity in quality and standards in product development and intellectual property rights [55]. Government on the other hand can strengthen the policy on the development of starch and starch-based products from the available sources that can be effectively used in the food, feed, textile and pharmaceutical industries [56]. Infrastructure especially electricity supply, railway transport, and water supply can also be improved to achieve success [57].

#### **6. Conclusion**

Nigeria is endowed with starch crops, and ranks third after wood and vegetable oil. it is highly beneficial and an invaluable commodity to the pharmaceutical, textile, food, paper, adhesive, drinks, beverages and the confectionery industries. It can compete favorably on international scale, however, starch in Nigeria is underutilized. The cassava starch is preferred over the corn starch in Nigeria as it is the driving force for the conservation of foreign exchange and to reduce import dependency. The opportunities in the starch industry is incredible and the demand for starch is on the rise, this can create income-generating opportunities for youths and small-scale farmers in the country. Hence, efforts should be made by the government and relevant stakeholders to convert starch-based crops from low-yielding famine crops to high-yielding cash crops in order to foster the economic development of the country.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Author details**

Obi Peter Adigwe, Judith Eloyi John\* and Martins Ochubiojo Emeje National Institute for Pharmaceutical Research and Development (NIPRD), Abuja, Nigeria

\*Address all correspondence to: juditheloyi@gmail.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Tonukari NJ. Cassava and the future of starch. Electronic Journal of Biotechnology. 2004;**7**(1):1982-1985

[2] Daramola B, Falade KO. Enhancement of agronomical values: Upstream and downstream opportunities for starch and starch adjuncts. African Journal of Biotechnology. 2006;**5**(25):2488-2494

[3] Taiwo KA. Utilization potentials of cassava in Nigeria: The domestic and industrial products utilization potentials of cassava in Nigeria. Food Review International. 2006;**22**:29-42

[4] Elizabeth Ojewumi M, Adewale Adeeyo O, Mary Akingbade O, Elizabeth Babatunde D, Ayodele Ayoola A, Olufemi Awolu O, et al. Evaluation of glucose syrup produced from cassava hydrolyzed with malted grains (rice, sorghum & maize). International Journal of Pharmaceutical Sciences and Research. 2018;**9**(8):1000. DOI: 10.13040/ IJPSR.0975-8232.9

[5] Tunde AA. Production of glucose from hydrolysis of potato starch. World Scientific News. 2020;**145**(April): 128-143

[6] Mohamad Yazid NS, Abdullah N, Muhammad N, Matias-Peralta HM. Application of starch and starch-based products in food industry. Journal of Science and Technology. 2018;**10**(2): 144-174

[7] Dada AD. Taking local industry to global market: The case for Nigerian cassava processing companies. Journal of Economics and Sustainable Development. 2016;**7**(19):59-70

[8] Ezedinma CI, Kormawa PM, Manyong VM, Dixon AGO. Challenges, opportunities, and strategy for cassava sub sector development in Nigeria. In: Proceedings of the 13th ISTRC Symposium. Arusha, Tanzania: International Society for Tropical Root Crops; 2007. pp. 627-640

[9] Awerije BO. Technical, cost and allocative efficiency of processing cassava into gari in Delta State, Nigeria. 2016. pp. 1-24

[10] Ogunmuyiwa OH, Adebowale AA, Sobukola OP, Onabanjo OO, Obadina AO, Adegunwa MO, et al. Production and quality evaluation of extruded snack from blends of bambara groundnut flour, cassava starch, and corn bran flour. Journal of Food Processing and Preservation. 2017;41(5):1-11

[11] Falade KO, Akingbala JO. Utilization of cassava for food. Food Review International. 2011;**27**(1):51-83

[12] Ugonna C, Jolaoso MO, Onwualu AP. A technical appraisal of potato value chain in Nigeria. International Research Journal of Agricultural Science and Soil Science. 2015;**3**(8):291-301

[13] Tewe OO, Ojeniy FE, Abu OA. Sweet Potato Production, Utilization, and Marketing in Nigeria. Lima, Peru: Social Sciences Department, International Potato Center (CIF); 2003. pp. 1-52

[14] Etudaiye HA, Oti E, Aniedu C. Utilization of sweet potato starches and flours as composites with wheat flours in the preparation of confectioneries. African Journal of Biotechnology. 2015;**14**(1):17-22

[15] Odebode SO, Egeonu N, Akaroda MO. Promotion of sweet potato for food industry in Nigeria. Bulgarian

*History, Evolution and Future of Starch Industry in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.102712*

Journal of Agricultural Science. 2008; **14**(3):300-308

[16] Betiku E, Adesina OA. Optimization of sweet potato starch hydrolyzate production and its potential utilization as substrate for citric acid production. British Biotechnology Journal. 2013; **3**(2):169-182

[17] Altemimi AB. Extraction and optimization of potato starch and its application as a stabilizer in yogurt manufacturing. Foods. 2018;7(14):1-11

[18] Mohammed KG. Modified starch and its potentials as excipient in pharmaceutical formulations-mini review related papers modified starch and its potentials as excipient in pharmaceutical formulations. Novel Approaches in Drug Designing & Development. 2017;**1**(1):1-5

[19] Jubril I, Muazu J, Mohammed GT. Effects of phosphate modified and pregelatinized sweet potato starches on disintegrant property of paracetamol tablet formulations. Journal of Applied Pharmaceutical Science. 2012;**2**(2):32-36

[20] Odeku OA. Potentials of tropical starches as pharmaceutical excipients: A review. Starch/Staerke. 2013;**65**(1-2): 89-106

[21] Fora/Cornstarch/FMR/165390. Corn (Maize) Starch in Nigeria. The Feasibility Report. 2016

[22] Clifford CB. Alternative Fuels from Biomass Sources. 2017.

[23] Ubalua AO. The use of corn starch for growth and production of α-amylase from *Bacillus subtilis*. Journal of Microbiology Research. 2016;**4**(4):153-160

[24] Ombretta M, Valeria S, Dayana C, Giuseppe P. The use of rice in brewing. In: Advances in International Rice Research. UK: Intech Open; 2017. pp. 49-66. DOI: 10.5772/66450. Chapter 4 Abstract

[25] Akintayo E, Ashogbon A. Morphological, functional and pasting properties of starches separated from rice cultivars grown in Nigeria. International Food Research Journal. 2012;**19**(2): 665-671

[26] Nextzon. Rice Production in Nigeria. 2017. pp. 1-12

[27] Falola T. Cassava starch for export in Nigeria during the second World War. African Economic History. 1989;**18**(18): 73-98

[28] David K, Richard R. Africa and the Second World War. London: Palgrave Macmillan; 1986. p. 1-294.

[29] Falcon WP, Jones WO, Pearson SR, Dixon JA, Nelson GC, Roche FC, et al. The Cassava Economy of Java. Stanford: Stanford University Press; 1984. pp. 1-225

[30] Kilby P. The Nigerian Palm Oil Industry. 1967

[31] Byfield JA. Feeding the troops: Abelokuta (Nigeria) and World War II. African Economic History. 2007;**35**(35): 77-87

[32] Falola T. "Salt is Gold": The management of salt scarcity in Nigeria during World War II. Canadian Journal of African Studies. 1992;**26**(3):412-436

[33] Saweda L, Liverpool O. Enhancing the Competitiveness of Agricultural Commodity Chains in Nigeria: Identifying Opportunities with Cassava, Rice, and Maize using a Policy Analysis Matrix (PAM) Framework. 2009. pp. 1-54

[34] Mohammed AI. The dependency syndrome and Obasanjo's national cassava policy in Nigeria. International Journal of Advanced Academic Research. 2018;**4**(11):1-16

[35] Ofoedu CE, Osuji CM, Omeire GC, Ojukwu M, Okpala COR, Korzeniowska M. Functional properties of syrup from malted and unmalted rice of different varieties: A comparative study. Journal of Food Science. 2020; **85**(10):3081-3093

[36] Olu-owolabi BI, Afolabi TA, Adebowale KO. Effect of heat moisture treatment on the functional and tabletting properties of corn starch. African Journal of Pharmacy and Pharmacology. 2010;**4**(7):498-510

[37] Okechukwu PE. Influence of granule size on viscosity of cornstarch suspension. Journal of Texture Studies. 1995;**26**:501-516

[38] Omoregie EH. Chemical properties of starch and its application in the food industry. In: Chemical Properties of Starch. UK: Intech Open; 2020. pp. 1-26

[39] Akusu OM, Emelike NJT. Fermentation of corn starch powder for the production of "Ogi". Journal of Food Research. 2018;**7**(5):49-56

[40] Sanni LO. Recent Developments in Cassava Processing, Utilization and Marketing in Nigeria and Lessons Learned. 2008. pp. 1-11

[41] Adetunji OA, Odeniyi MA, Itiola OA. Compression, mechanical and release properties of chloroquine phosphate tablets containing corn and trifoliate yam starches as binders. Tropical Journal of Pharmaceutical Research. 2006;**5**(2): 589-596

[42] Tonukari NJ, Tonukari NJ, Ezedom T, Enuma CC, Sakpa SO, Avwioroko OJ, et al. White gold: Cassava as an industrial base. American Journal of Plant Sciences. 2015;**06**(07):972-979

[43] Duduyemi O, Mojibayo I, Shonaike G, Olodu OE, Babatunde BH, Adaran AS, et al. Effects of copolymer blends in the production and characterisation of biodegradable polymer from agricultural product-using cassava starch (Manihort Species) as case studies. Greener Journal of Agricultural Sciences. 2020;**10**(1):51-56

[44] Abioye OP, Abioye AA, Afolalu SA, Ongbali SO. A review of biodegradable plastics in Nigeria. International Journal of mechanical Engineering and Technology. 2018;**9**(10):1172-1185

[45] Eterigho EJ. Production and characterization of biodegradable plastic from Nigeria cassava starch. In: Proceedings of the International Conference on Engineering, Science, and Applications. Tokyo, Japan: Global Academic-Industrial Cooperation Society (GAICS); 2018. pp. 78-85

[46] Mbonu OF, Udeozor PA, Umoru GU, Uti DE. Production of Bio-fuel from sweet corn (food to fuel). Journal of Pharmacognosy and Phytochemistry. 2016;**5**(6):43-47

[47] Nwaokocha CN, Giwa SO, Layeni AT, Kuye SI, Oyedepo SO, Lawal NS, et al. Energy generation from corn starch effluent using microbial fuel cell using lead electrodes. Advances in Electrical and Electronic Engineering. 2021;**1**:1-11

[48] Amenaghawon NA, Aisien FA. Modelling and simulation of citric acid production from corn starch modelling and simulation of citric acid production from corn starch hydrolysate using

*History, Evolution and Future of Starch Industry in Nigeria DOI: http://dx.doi.org/10.5772/intechopen.102712*

*Aspergillus niger*. Environment and Natural Resources Research. 2012; **2**(1):1-14

[49] Adekunle OD, Kayode OM, Awoyale OK, Dawodu M. Extraction, characterization and dextrinization of starch from six (6) varieties of tubers from Iwo Osun State Nigeria for application in the production of adhesives. American Journal of Chemical and Biochemical Engineering. 2019;**3**(2):7-11

[50] Akpa J. Production of starch-based adhesives. Research Journal in Engineering and Applied Sciences. 2012;**1**(4):219-214

[51] Chukwuemeka IS, Ugochukwu IW. Production of adhesive from cassava starch in Owerri, Imo State, Nigeria. World News of Natural Sciences. 2017;**11**:5-10

[52] Onyenwoke CA, Simonyan KJ. Cassava post-harvest processing and storage in Nigeria: A review. African Journal of Agricultural Research. 2014;**9**(53):3853-3863

[53] Zainab A, Modu S, Falmata AS. Laboratory scale production of glucose syrup by the enzymatic hydrolysis of starch made from maize, millet and sorghum. Biokemistri. 2011;**23**(1):1-8

[54] Daneji MI. Agricultural development intervention programmes in Nigeria (1960 to date): A review. Savannah Journal of Agriculture. 2011;**6**(1):101-107

[55] Olaoye OA. Potentials of the agro industry towards achieving food security in Nigeria and other Sub-Saharan African countries. Journal of Food Security. 2014;**2**(1):33-41

[56] Nchuchuwe FF, Adejuwon KD. The challenges of agriculture and rural

development in Africa: The case of Nigeria. nternational Journal of Academic Research in Progressive Education and Development . 2012; **1**(3):45-61

[57] Adenle AA, Manning L, Azadi H. Agribusiness innovation: A pathway to sustainable economic growth in Africa. Trends in Food Science and Technology. 2017;**59**:88-104

## Starch: A Veritable Natural Polymer for Economic Revolution

*Obi Peter Adigwe, Henry O. Egharevba and Martins Ochubiojo Emeje*

#### **Abstract**

Amidst growing concerns for environmental degradation by anthropologic activities and use of non-biodegradable materials for industrial and household purposes, a focus on natural polymeric materials offers the veritable prospects for future survival. Although some synthetic polymers are biodegradable, the process of production that is usually non-green adds to environmental pollution. Natural polymers are naturally occurring organic molecules such as cellulose, starch, glycoproteins and proteins. They are mostly obtained from plant sources, but are also produced in animal and microorganisms. One of the most abundant natural polymers of multidimensional and multifaceted application is starch. Starch is used across wide-range applications spanning engineering, food and beverages, textile, chemical, pharmaceuticals and health, etc. This is because it can readily be modified into products of desired physicochemical characteristics, thus making starch a potential tool for industrial and economic revolution. The global trade balance for starch and derived products is about \$1.12 trillion, presenting a huge opportunity for more investment in starch production. Africa's negative starch trade balance of about \$1.27 trillion makes it a potential investment destination for starch production. This chapter discusses the use of starch in various industrial sectors, its potentials for sustainable economic development and as a veritable natural polymer for economic revolution.

**Keywords:** starch, natural polymers, environmental protection, green economy, industrial uses, sustainable development, economic revolution

#### **1. Introduction**

The major form of stored energy as carbohydrate in plants is Starch. It is a naturally occurring biopolymer consisting of a mixture of highly branched amylopectin and linear amylose residues. The two alpha-glucan residues make up 98–99% of the total net weight of starch [1]. Amylopectin residue is made up of linear D-glucopyranose chains linked by O-α-(1 → 4) glycosidic bonds and branching occurring as O-α-(1 → 6) glycosidic bonds. Amylopectin biopolymers are brittle. On the other hand, amylose residue has O-(1 → 4)-α-Dglucan linkages and is film-forming [2].

Naturally occurring starch has limited industrial applications its poor functionality such as poor water solubility at room temperature, retrogradation of its paste or

gel, texture and taste. The functionality of starch can be modified through physical, chemical and/or genetic processes [3]. Due to the reactive nature of its monomers which is mainly as a result of their free hydroxyl (–OH), starch is easily modified to attain required functionalities for industrial purposes. For instance, if heated to high temperatures and in the presence of a plasticizer like glycerol, it exhibits comparable melt and flow characteristics as regular synthetic thermoplastic [4]. Undesirable characteristics such as hydrophilicity and low tensile strength are mitigated by introduction of hydrophobic fillers and materials that could enhance tensile strength. Likewise, different materials are used to improve thermal stability, plasticity and mechanical strength required in packing/packaging materials Advancement in material science which created thermoplastic starch has made starch a veritable resource with tensile applications in packaging and mechanical parts [5].

The ability to modify starch into biomaterials of different functionality has made it one of the most versatile and renewable natural polymer in existence. As a major type of food, it could be modified to enhance flavor, texture, thickness, taste, stability and/or shelf-life. Thus, it has found industrial application in food and beverage industry as food products or additives for enhancing the texture, stability, shelf-life and quality of products. It malleability with new technologies such as nanotechnology has expanded its scope of application in health and pharmaceutical and cosmetics. Starch could be used as both excipients and drug delivery vehicle [6].

The starch industry is at the very heart of food production: supplying hundreds of ingredients for use in thousands of food products and animal feed. At the same time, starches play a vital role in a wide variety of products beyond food. Natural and modified food starches can be found in products and processes in the consumer products, pharmaceutical, energy, industrial and chemical sectors. With the world beginning a gradual shift away from fossil fuels as the primary engine of economic prosperity, there will be a larger opportunity for starch producers to contribute renewable, sustainable materials through the bioeconomy [7]. This chapter discusses the various industrial application of starch which if exploited economically could provide strong foundation for economic revolution.

#### **1.1 Starch sources**

Starch is the second most abundant renewable bioenergy resources after cellulose, with an estimated global production of over 56 million tons per annum since 2006 [8, 9]. A variety of plant serves as the sources of starch consumed by humans. Starch storage in these plants occurs in grains or root tubers. Although the list of these plants which are either cultivated or found in the wild are endless, the major sources of food starch include corn, cassava, sweet potato, wheat, and potato. Sorghum, barley, rice, millet, yam etc. serve as minor sources in different parts of the world [10, 11]. A huge number of unexploited sources exist and majority is in the wild. **Table 1** shows the starch contents of some of these sources.

#### **1.2 Contemporary application of starch and its derived products**

By 2050, the population of the world is projected to exceed 9 billion and the demand for food is expected to rise by 70%. With growing environmental concerns and concept of green economy, reliance on fossil resources for energy and raw materials for industrial use etc. has attracted critical evaluation, and the prospect of a new trajectory for bio-based raw materials has become more imminent. Starch which


#### **Table 1.**

*Starch sources.*

is one of the most abundant and affordable natural polymer poses a more reliable and sustainable substitute to the non-renewable, non-green, and exhaustible fossil sources. This opens prime opportunities for starch-based bio-economic revolution especially for countries with the right cultivation and production technologies for starch sources and starch-based products, respectively [7].

Starch can be used as biopolymers in many ways including as a raw material for human foods and animal feeds/feedstock, as bioethanol for food and fuel, as particulate filler and adhesive in paper and textile sizing, as well as bioplastics in packaging materials (**Figures 1** and **2**) [8, 9, 15]. It is also deployed in a wide array of other consumer goods in health and pharmaceuticals, and chemical sector. Corn starch product is used in 3-D printing inks, and emerging reports indicates its potential for nanomedicine technology as a tool for delivering treatments to specific sites. Some other categories of products include starch-based detergent products, starch-based binders, starch in biodegradable polymers, starch-based products for pharmaceuticals and cosmetics, and starch hydrolysates for fermentation [15].

#### **1.3 Foods**

The food industry is very large and diverse, and includes the raw unprocessed food and the processed and modified ones. Central to world food production and sustainability is the starch industry. Native starch is eaten in unprocessed raw or cooked form as grain or cereal meals, and flour dough or mashes with soups and other forms of condiments, in many developing countries. In West Africa, cooked

**Figure 1.**

*Fermented and refined products from starch. (source: [15]).*

#### **Figure 2.**

*Industrial application of starch. (source: [15]).*

and mashed cassava (*fufu*) or fried cassave (*garri*) meals, corn grains and other starches from millet etc. are the bases for food security.

The food industry is very mindful of safety of chemical residues hence not all types of native or modified starches are used in the foods. Some modified starches are used as binder in assaulted foods, ready-made meat and snack seasonings. Others are used as anti-sticking agents and dustings for chewing gum and bakery products,

crisping coating for fried snacks, fillers to replace fats and in sauces or creams to enhance lusciousness in ice cream and salad dressings. Modified starches are also used as flavor encapsulating agents and emulsion stabilizers in beverages. They are used as creamers, in canned foods, foam stabilizer in marshmallows, gelling agents in gum drops and jelly gum, and as expanders in baked snacks and cereal meals [2]. Starch derived products are used for the production of animal feeds [15]. About 10–15% of corn produced in the US is processed annually for starch derived products by corn refiners. These starch derived products are used in across the food, beverage, healthcare, pharmaceutical and other sectors. This has a dominant multiplier effect on the United States economy [7].

#### **2. Sweeteners (syrups and sugars)**

The CRA 2019 report put US production volume of sweeteners from corn starch refining for 2018 at 14.45 mMt d.w. These include glucose syrups, high fructose corn syrups maltodextrins, dextrose, corn syrup solids etc. [16]. The many other forms of starch are now been adopted as substitute raw material for corn. These products find applications in foods, beverages and pharmaceuticals for taste, flavor, color and texture enhancements.

#### **2.1 Bioethanol**

Ethanol is one of the most important organic solvent in the chemical industry. It is also the basic raw material for the wine, brewery and beverage industries. Due to energy fuel sustainability concern, the world is focusing on renewable energy include energy for renewable biological materials like starch. According to the World Integrated Trade Solution (WITS) data of the World Bank, the global volume of ethanol export in 2020 was over 14.2 billion liters, with a net weight of over 13.3 billion kg, valued at over \$10.2 billion USD. While the volume of imports was 9.3 billion liters of 9.2 billion net weight and valued at \$10 billion USD, with the top 10 importers as Netherlands, European Union, Germany, USA, Canada, Japan, Brazil UK, France and Korea Republic [17].

The production of ethanol from biological materials such as starch has gained interest in recent years because of the low-cost raw materials, starch, and the uncomplicated process involved. These processes, either chemically or biotechnologically based, are environmentally friendly. Bioethanol is already being used in many countries as octane enhancer for gasoline to produce gasohol. Starch from corn and cassava can be used for ethanol production. Due to concerns on quality, corn starch maintains a premium as the primary source of food and pharmaceutical grade starch and may not be very feasible for use as biofuel based on demand. However, sources like cassava may offer a ready source. Nigeria is currently the world's biggest producer of cassava starch although almost 100% of it is consumed locally as food. The rising demand for biofuel offers countries like Nigeria opportunity for economic revolution in the production of biofuel from cassava. Adeleye et al. [18] has report an ethanol yield of 1.5 L of 78% (v/v) from 2.5 kg wet weight of cassava. Countries like South Africa and China are already at advance stages of developing cassava plantations for production of starch for industrial uses [19, 20]. According to the 2019 Corn Refiners Association (CRA) report, the US produced about 6.06 billion liters of Ethanol, and about 3.37 mMt of Starch in 2018 [21].

#### **2.2 Adhesives**

Adhesives are mostly used in wood panels production, leather works and paper and packaging. The global volume of adhesive consumed annually is over 3 billion kilograms, mostly from petroleum derived feedstock and other synthetic materials. Due to environmental and safety concerns, a lot of studies have been ongoing to develop bio-material based hot melt adhesives (HMAs) from starch and its modification derivatives, (poly)lactic acid, soy protein, lignin and tannin [22].

Wood panels are composite products made by bonding wood particles or fibers with adhesive binders to form a board, which may be medium density fiberboard (MDF) or high density fiberboard (HDF). These panels find applications in home, office and industrial building construction. Wood panel makers currently almost depend exclusively on formaldehyde and amino-based adhesives with high formaldehyde emission, and polymeric 4,4-diphenylmethane diisocyanate, which are synthetic products. Concerns for indoor emission of formaldehyde, a known human carcinogen, led to the development of low-emission melamine-fortified urea-formaldehyde adhesives and other adhesive that exclude formaldehyde. Urea has been the primary formaldehyde scavenger for wood-based panels. Environmental consideration has raised interests for more green adhesives from biodegradable polymers like starch, lignin, tannin and protein. Organic scavengers like tannin powder, charcoal and wheat flour have shown promising potentials in reducing formaldehyde emission. Bio-based adhesive for industrial use are few and expensive. Tannin and starch adhesive, soy protein based adhesive and lignin-based adhesive are available for limited application in panel production [23].

Adhesives from native starch rely on hydrogen bonds which is weaker than chemical bonds. Due to their hydrogen bonding, they easily bond with water molecules and are therefore readily soluble and not-water resistant. Crosslinking starch produced with synthetic reagents such as epoxy chloropropane, sodium borate, hexamethoxymethylmelamine, formaldehyde, and isocyanates, tends to give better bonding force and water resist [23, 24]. Although no economically viable bio-based crosslinker reagents for starch are available, research on hot melt adhesives prepared by crosslinking modified propionyl starch with glycerol and polyvinyl alcohol (PVOH) has shown improved tensile strength of up to 2.0 MPa. Hence starch still offers a viable potential for future researches in 100% bio-based adhesive for wood-based panels industry [22].

The global volume of production and consumption of hot melt adhesive is on the increase and is about 15–21%, with an annual consumption growth rate which is 1.5–2 times higher than other adhesives [22]. This presents a huge market potential for starch-based HMAs.

#### **2.3 Pharmaceuticals and cosmetics**

They separate corn kernels into their component parts to make hundreds of products that touch consumer lives in countless ways every day. For years, those ingredients have been used to make food taste better, cosmetics last longer, pharmaceuticals easier to swallow and plastics environmentally-friendly [7].

The fundamental physiochemical and functional properties of natural starches for instance their good biodegradability and safety, make them suitable for a wide array of health and pharmaceutical applications. Several types of modified starch polymers and their application in bone tissue technology as bone tissue engineering

#### *Starch: A Veritable Natural Polymer for Economic Revolution DOI: http://dx.doi.org/10.5772/intechopen.102941*

scaffolding [25, 26], drug delivery system as biodegradable nanomedicine-carrier based delivery system and implants [27, 28], and hydrogels have been studied by different scientists over the past few years [6]. Starch has also been demonstrated as a viable material for capping of nanoparticles from different metals like Au, Ag and Pt, because of their bio-tolerance and cost effectiveness [29]. It has also been demonstrated to have potentials for use as nanoparticles to stabilize emulsions, Pickering emulsions, which are useful in cosmetics, pharmaceuticals and foods [30]. Also, pharmaceutical grade starch from corn is use as coating and filler excipients in tablets and caplets as well as syrups in many pharmaceutical products. It is also applicable as disintegrating agents, carriers, lubricants, matrices for controlled release [15]. For its good qualities of being odorless, decolourisable, environmentally biodegradable and skin friendly, it is used in cosmetics and beauty products as emollients, humectants, thickeners, film forming agents and emulsifiers [15]. Many sources of natural starch have been study and found to be effective for the production of pharmaceutical grade starch.

Starch and its modified derivatives have been used in medicine as biodegradable films, inexpensive cure for athlete's foot, anti-sticking agents, relief rashes caused by prickling heat, relief skin itches caused by shingles, relieves rash caused by baby diapers, wound dressing and bandages and used to treat gastric dumping syndromes in children. It is considered a safe alternative to cancer causing talcum baby powder, and used to remove excess oil from scalps and relieves itching in children [31].

#### **3. Thermoplastics and bioplastics**

Plastic pollution and the global push for a more sustainable environment towards eliminating the use of non-biodegradable materials and reduction of hazardous emission form toxic materials has refocused the worlds efforts towards the use of biodegradable plastics based on natural polymers such as starch, cellulose, lignin and chitosan [32]. The current global annual production of plastics is estimated at about 368 million tonnes, out of which about 1% is bioplastics. It is estimated that bioplastic production capacity will increase from 2.11 million tonnes in 2020 to about 2.87 million tonnes in 2025 [33].

The starch-based bioplastics thermoplastic starch (TPS or TS) is produced obtained from gelatinize starch and plasticizers which is subsequently tuned pellets by extrusion is useless as a material. It can also be produced from polymerization of polylactic acid obtained from starch-derived sugars fermentation. Bioplastics from starch can be used for producing compost bags and disposable plastic household wares [32]. The desire for more ecofriendly plastics gives a huge economic prospect to the growth of biodegradable natural polymer-based bioplastics market [33].

#### **3.1 Carbon/carbonaceous foams**

Carbonaceous foams (CFs) are used all over the world and find application in military, industrial and domestic use, such as heat exchanger, electrode materials, catalyst carrier, adsorption, vibration damping and impact or sound absorption, electromagnetic shielding, radar absorption, filtration, and aerospace material, etc. Carbon/carbonaceous materials are generally made from non-renewable raw materials like coal tar pitch, mesophase pitch and synthetic materials, at high temperature (above 1000°C) and high pressure (in MPa). Although other materials such as sucrose and tannin have been used, more cost effective biomaterials have been successfully investigated. A more energy efficient process of producing CFs with excellent compressibility and mechanical strength has been demonstrated by using starch as raw material. The production requires much lower temperature (<500°C) and lower pressure (about 190 Pa) than conventional approaches [34]. The world annual production of polysaccharides is in excess of 150,000 million tonnes. But the production of CFs from polysaccharides such as starch is still very much at low level. This gives good opportunity for economic exploitation.

#### **3.2 Other industrial uses**

In the industry, starch powder is used in textiles, paper, inks and paints. They serve as fast absorbent polymer in water treatment, as cleaning agent in detergents, as desiccants to prevent mildew from ruining paper documents in storage, as fabric stiffener and yarn sizing, remove wax from wooden furniture, and as organic pesticide [6, 15]. Starch based alkylpolyglucosides (APG) are used in detergents with superior skin compatibility.

#### **3.3 Economy of starch**

The economy of the starch industry largely depends on the availability of sufficient volumes of raw materials and the value of the so-called co-products. During corn starch processing, for example, all components of the maize grain are valorized: after steeping and coarse crushing the germ is separated and yields the valuable maize germ oil while the steeping water is concentrated and sold as nutrient for fermentations. The oil press cake together with the corn gluten (protein) and the hulls (fiber), which are separated after fine grinding in additional refining steps from the pure starch granules, are utilized as components in animal feed. The starch as the main product is either dried and sold as native starch, or chemically modified to make it more suitable for more demanding end uses, or hydrolyzed to yield refinery products such as hydrolyzates (dextrin), glucose syrups, and high fructose syrups [31].

In wheat starch processing, the value of the vital gluten is an essential source of income and could be regarded as the head product. In contrast to cereal and pulse starch production, the extraction of root and tuber starches does not deliver coproducts of comparable value. As the processes for the extraction are different for the mentioned crops the starch industry cannot easily switch from one source to the other in order to adapt to fluctuating market conditions both on the raw material and on the end products.

Statistics on starch production and export are only available for the US, UK, the European Union and a few other countries. According to a 2014 report, Africa consumes the least starch per capita, and accounts for just about 2% of the global consumption market of starch and its derivatives. The two leading raw materials, cassava and maize are mainly consumed as food. Production of derived products is concentrated in few countries, Nigeria, Egypt and South Africa, with South Africa in the lead. While maize is the general source of starch for food in Egypt and South Africa, cassava starch plays an equally significant role as food in Nigeria and the West African region [19, 35, 36].

Importation and cultivation of *Manihot esculenta* for Cassava starch in commercial quantities for production of derived products for industrial use is now a major trade in

#### *Starch: A Veritable Natural Polymer for Economic Revolution DOI: http://dx.doi.org/10.5772/intechopen.102941*

Asia countries of Thailand and China. A 2018 FAO report put the global production of cassava at 277 million tonnes (fresh root equivalent) and was project to rise by 0.5% annually. The 85.7 million tonnes production from Africa represents about 31%. Only 27.7 million tonnes were traded in same year. Wheat production and trade was 727.9 million tonnes and 173.2 million tonnes respectively. No country in Africa is among the top 10 importers and exporters of starch products [37].

The starch consumption per capita for 2012 was in the order of Africa < South America < Asia < Europe < North America. Country-wise is Nigeria < Egypt < Mexico < Turkey < Russia < UK < South Africa < China < US. Africa also consumes the least sweetener per capita. This is followed by Asia, South America, Europe and North America. Africa consumed less than 1 kg per person while North America consumed over 40 kg per person in 2012 [36]. This scenario has not changed significantly. South Africa produces over 280,800 tons of corn starch annually and is experimenting on local cultivation of *M. esculenta* for local production of cassava starch [19]. It is estimated that about 72% of Africa's population have yet to participate in the formal starch and syrup market. Apart from few cassava production plants, ethanol plants are springing up in Nigeria that targets cassava starch as raw material for production of ethanol for industrial use and biofuel.

According to the International Federation of Starch Association (IFSA), starch and its derived products accounts for an annual revenue of \$47.50 billion in the United States in 2020, and supported about 167,786 jobs to the tune of about \$10.01 billion wages. It accounted for about \$1.91 billion worth of US export with the value of starch only products amounting to about \$339.62 million [7]. The overall industry impact on US economic output (direct and indirect impact) was estimated by the Corn Refiners Association (CRA) to be about \$7.16 trillion annually with an average growth rate of about 6% between 2017 and 2019 (**Figure 3**), while the value of impact on export was about \$149.19 billion annually with an average growth rate of about 0.77% (**Figure 4**). However, the industry impact of export actually grew at 4.5% between 2017 and 2018. The impact on jobs (**Figure 5**) and wages (**Figure 6**) was actually higher in terms of growth. Capital investments in starch manufacturing were about \$20.62 billion and \$20.28 billion annually in 2018 and 2019, respectively [16, 21]. The US data presents a good indication of the potential of starch-economy as an economic revolutionary tool

**Figure 4.** *Starch and derivative export value of the US, 2017–2019.*

**Figure 5.** *Impact of starch industry on jobs in US, 2017–2019.*

**Figure 6.** *Impact of starch industry on wages in the US, 2017–2019.*

for job creation and export revenue. This potential is estimated to be higher for developing economies with higher opportunities for more investment in both upstream and downstream starch products value chain.

#### *Starch: A Veritable Natural Polymer for Economic Revolution DOI: http://dx.doi.org/10.5772/intechopen.102941*

In 20 of the 28 EU member states, the European starch industry's 28 member companies process 24 million tons of EU agricultural raw materials into 11 million tons of starch-based ingredients and five million tons of proteins and fibers. Of starchbased ingredients, approximately 60% go to the food and beverage industry, and 40% to industrial applications (mainly to the paper, cardboard, pharmaceutical, and chemical industries as a renewable alternative to fossil fuel ingredients). Of the proteins and fibers, approximately 90% go to the animal feed industry and 10% to the food industry. The EU has 75 producers or plants and rely on Maize, wheat and starch potatoes, barley, rice, peas as feed stock to produce Native maize, wheat and potato starches, modified starches, maltodextrins, glucose syrups, dextrose, glucose fructose syrups, polyols, wheat gluten, other proteins. The industry supports 15,000 direct jobs, supports 100,000 indirect jobs, exports 1.6 billion Euros, and the annual industry turnover is 7.4 billion Euros [7]. The EU uses starch and starch products for confectionery, drinks, processed food, animal feeds, corrugating and paper making, pharmaceuticals and chemicals, as well as other non-food applications (**Figure 7**).

The Turkish starch industry contributes to local farming by processing 25% of locally grown maize from thousands of local farmers each year. The industry separates its starch from corn, drying it to native and modified starches or breaking it down to its sugars and other value-added products. Almost 100% of corn kernels are converted to economically valuable products. The industry supplies edible oils, fish, calf, lamb and poultry meat, paper, textiles and more to local and international food and beverage industries. With its wide-ranging portfolio, from basic to high-end products, the Turkish starch industry is competitive and has the capacity to grow. There are 9 producers which use maize as feed stock and produces Glucose and fructose syrups, native corn starch, modified corn starches, crystalline fructose, polyols, maltodextrins, corn gluten and feed, and ethanol. The industry supports 1,900 direct jobs and export over 400,000 tons annually.

Mexico has an evolving industry with annual output of between \$300 million and \$500 million USD. The industry supports 2,500 direct jobs and 7,500 indirect jobs. The brewing and paper markets depend largely on corn-based starch. The industry is growing due to investments in brewing capacity [7].

**Figure 7.** *Uses of starch in the European Union (source: [15]).*

Founded in 1984, the China starch industry association has 280 members. Revolution in starch development has rebound in progressive development in the food, medicine, biology and chemical industries. It has also significantly contributed to growth of the national economy especially in agriculture where it has helped to sustain livelihood of local farmers through agro-economy. The annual industry output for starch and starch-based deep-processing products is estimated at 30.1 million tons and 16.3 million tons, respectively, from 170 producers. Major products include native starch, pregelatinized starch, chemically modified starch, starch sugar, polyols and ethanol, from feed stocks of corn, potato, cassava, sweet potato and wheat [7].

Starch development in Russia has put the country in an upward trajectory for economic revolution. For instance, the industry has 30 starch enterprises and 23 production plants. Ten of the Russia's 23 plants are responsible for 90% of all starch products from Russia. Annual production of starch and derivatives rose from less than 180,000 tons in 2013 to over 1.3 million tons in 2020. 70% of this production figures were sweeteners (**Figure 8**). The industry has a cumulative average growth rate (CAGR) of 8.65, 8.69 and 8.65 for starch, sugary products and total starch-based products, respectively. Corn accounts for about 800 thousand tons, wheat about 500 thousand tons, and potatoes about 30 thousand tons. The industry has invested about \$358.4 million between 2013 and 2020 (**Figure 9**). **Table 2** provides Russian industry statistics on starch production and derived sugary products as obtained from Russian Federation Starch Union (RFSU) for 2013–2016 [39]. The 2015 import and export data is as provided in **Table 3**. The industry supports 4,000 jobs, has an annual output of \$600 million and exports worth \$28.5 million. The major products include native corn, wheat and potato starches, modified starches, glucose syrups, HFS, dextrins, maltodextrins, wheat and corn gluten, from the feed stock of corn, wheat, potatoes [7].

#### **Figure 8.**

*Russian industry development indicators in the period 2013–2020 (according to the strategy for the development of the food and processing industry of the Russian Federation for the period up to 2020) [39].*

#### **Figure 9.**

*The volume of investments in the development of the Russian industry for the period 2013–2020.*


#### **Table 2.**

*Production in 2013–2016.*

#### **3.4 Global starch trade and opportunities**

The value of starch and starch derived products imported and exported globally in year 2020 was \$20,367,050,000 and \$19,251,015,000, respectively according to figures from Trade Map [35]. African import and export were \$1,921,266,000 and \$652,628,000 (**Figure 10**), respectively, representing about 9.4% and 3.3%, of global figures respectively. This deficit represents a huge investment opportunity in starch production for the entire world. **Table 4** provides details of the starch products considered.

The high four years AGR of 10 for the global trade in flour (1105) and 7 for both cereal flour (1102) and inulin (1108) is a pointed to rising demands for these products. The imbalance in trade in wheat (1101) and malt (1107) for Africa expose the gap in export and import to Africa (**Table 4**). These rising demands and trade deficits could be bridged through more investments in starch production.


#### **Table 3.**

*Starch products export and import in 2015 in Russia federation.*

#### **Figure 10.**

*Comparison of value of imported and exported in year 2020.*


*Starch: A Veritable Natural Polymer for Economic Revolution DOI: http://dx.doi.org/10.5772/intechopen.102941*


*Products code: 1101 (Wheat or meslin flour); 1102 (Cereal flours excluding wheat or meslin); 1103 (Cereal groats, meal and pellets); 1104 (Cereal grains otherwise worked, e.g. hulled, rolled, flaked, pearled, sliced or kibbled; germ); 1105 (Flour, meal, powder, flakes, granules and pellets of potatoes); 1106 (Flour, meal and powder of peas, beans, lentils and other dried leguminous vegetables of heading); 1107 (Malt, whether or not roasted); 1108 (starches; inulin); 1109 (Wheat gluten, whether or not dried).\* AGR means global annual growth rate for the products' trade between 2016 and 2020 (% p.a).*

#### **Table 4.**

*Table of Africa and global starch trade in year 2020 in thousand US \$ [35].*

#### **4. Conclusion**

Starch is an abundant natural polymer with great industrial versatility. Various sources including maize, wheat, cassava, potato, rice and millet, abound in different countries of the world. Many countries especially those in Africa have not fully realized their starch production capacity and export potentials for international trade. The negative world trade balance of about \$1.12 trillion for starch means opportunity for more investment in starch production. Starch and inulin with the highest world trade imbalance, and Malt, cereal and wheat gluten with relatively high world trade imbalance, could benefit more in future investment prospect (**Table 4**). A closer analysis shows that Africa has a higher negative trade balance of about \$1.27 trillion than the world. As bad as this may look for Africa, it presents a huge opportunity for investments in global starch production. But Africa will have to do more to reduce the widening trade imbalance in starch products, especially in wheat and malt.

#### **Conflict of interest**

The authors declare no conflict of interest.

### **Author details**

Obi Peter Adigwe, Henry O. Egharevba\* and Martins Ochubiojo Emeje National Institute for Pharmaceutical Research and Development (NIPRD), Abuja, Nigeria

\*Address all correspondence to: omoregieegharevba@yahoo.com

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Haroon M, Wang L, Yu H, Abbasi NM, Abdin ZU, Saleem M, et al. Chemical modification of starch and its application as an adsorbent material. RSC Advances. 2016;**6**:78264-78285. DOI: 10.1039/ c6ra16795k

[2] Egharevba HO. Chemical properties of starch and its application in the food industry. In: Emeje M, editor. Chemical Properties of Starch. London, UK: IntechOpen; 2019. DOI: 10.5772/ intechopen.87777

[3] Ashogbon AO, Akintayo ET. Recent trend in the physical and chemical modification of starch from different botanical sources: A review. Starch/ Staerke. 2014;**66**:41-57

[4] Quirino RL, Garrison TF, Kessler MR. Matrices from vegetable oils, cashew nut shell liquid, and other relevant systems for biocomposite applications. Green Chemistry. 2014;**16**:1700-1715. DOI: 10.1039/c3gc41811a

[5] Bodirlau R, Teaca CA, Spiridon I. Influence of natural fillers on the properties of starch-based biocomposite films. Composites Part B Engineering. 2013;**44**(1):575-583

[6] Palanisamy CP, Cui B, Zhang H, Jayaraman S, Kodiveri MG. A comprehensive review on corn starchbased nanomaterials: Properties, simulations, and applications. Polymers (Basel). Sep 22, 2020;**12**(9):2161

[7] International Federation of Starch Associations (IFSA). Washington, DC, USA: Corn Refiners Association. Available at: https://internationalstarch. org/#about [Accessed: 26 July 2021]

[8] Glittenberg D. Polymers for a sustainable environment and green energy. In: Matyjaszewski K, Möller M, editors. Polymer Science: A Comprehensive Reference. Vol. 10. Amsterdam, Oxford, Waltham: Elsevier; 2012. pp. 165-193

[9] Endres HJ, Siebert-Raths A. Polymers for a sustainable environment and green energy. In: Matyjaszewski K, Möller M, editors. Polymer Science: A Comprehensive Reference. Vol. 10. Amsterdam, Oxford, Waltham: Elsevier; 2012. pp. 317-353

[10] Raji AO. Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects. London: IntechOpen; 2020. p. 24. DOI: 10.5772/ intechopen.95020

[11] Horstmann SW, Lynch KM, Arendt EK. Starch characteristics linked to gluten-free products. Food. 2017;**6**(4):29. DOI: https://doi. org/10.3390/foods6040029

[12] Punia S, Kumar M, Siroha AK, Kennedy JF, Dhull SB, Whiteside WS. Pearl millet grain as an emerging source of starch: A review on its structure, physicochemical properties, functionalization, and industrial applications. Carbohydrate Polymers. 2021;**260**:117776. DOI: https://doi. org/10.1016/j.carbpol.2021.117776

[13] Mahajan P, Bera MB, Panesar PS, Chauhan A. Millet starch: A review. International Journal of Biological Macromolecules. 2021;**180**:61-79

[14] Coronell-Tovar DC,

Chávez-Jáuregui RN, Bosques-Vega A, López-Moreno ML. Characterization of cocoyam (Xanthosoma spp.) corm flour from the Nazareno cultivar. Food Science Technology. 2019;**39**(2):349-357

[15] Röper HH. Industrial products from starch. In: Presentation at the 56th Starch Convention, Detmold, April 20-22, 2005. Cargill TDC Food, Cerestar R&D Centre, Vilvoorde, Belgium

[16] Corn Refiners Association (CRA). CRA Industry Overview 2019. Available from: https://corn.org/wp-content/ uploads/2020/02/CRA-Industry-Overview-2019-Final.pdf [Accessed: July 29, 2021]

[17] World Bank (WB). World Integrated Trade Solution (WITS) Data. Available from: http://wits.worldbank.org/WITS/ WITS/Results/Queryview/QueryView. aspx?Page=DownloadandViewResults HYPERLINK "http://wits.worldbank.org/ WITS/WITS/Results/Queryview/ QueryView.aspx?Page=DownloadandVie wResults&Download=true"& HYPERLINK "http://wits.worldbank.org/ WITS/WITS/Results/Queryview/ QueryView.aspx?Page=DownloadandVie wResults&Download=true"Download=t rue [Accessed: July 30, 2021]

[18] Adeleye TM, Kareem SO, Bankole MO, Atanda O, Adeogun AI. Ethanol production from cassava starch by protoplast fusants of Wickerhamomyces anomalus and Galactomyces candidum. Egyptian Journal of Basic and Applied Sciences. 2020;**7**(1):67-81. DOI: https://doi.org/ 10.1080/2314808X.2020.1746884

[19] Phaleng L. Trade analysis of the starch industry in South Africa (HS 1108). Trade Probe. 2017;(68):3-5

[20] Industrial Development Corporation (IDC). A study on the market potential for increased industrial starch production in South Africa. Urban-Econ Development Economists. Lake View Office Park Area 7, 137 Muckleneuk Street, Brooklyn; 2017 Available from:

https://www.idc.co.za/wp-content/ uploads/2018/11/APCF-Research-Grant\_ Starch\_Final-Report-2017-October-2017. pdf [Accessed: July 28, 2021]

[21] Corn Refiners Association (CRA). CRA industry overview 2020. Available from: https://corn.org/wp-content/ uploads/2021/02/CRA-Industry-Overview-2020.pdf [Accessed: July 29, 2021]

[22] Zhang Z, Macquarrie DJ, Clark JH, Matharu AS. Chemical modification of starch and the application of expanded starch and its esters in hot melt adhesive. RSC Advances. 2014;**4**:41947-41955

[23] Hemmila V, Adamopoulos S, Karlsson O, Kumar A. Development of sustainable bio-adhesives for engineered wood panels—A review. RSC Advances. 2017;**7**:38604-38630

[24] Qiao Z, Gu J, Lv S, Cao J, Tan H, Zhang Y. Preparation and properties of isocyanate prepolymer/corn starch adhesive. Journal of Adhesion Science and Technology. 2015;**29**:1368-1381

[25] Salgado AJ, Figueiredo JE, Coutinho OP, Reis RL. Biological response to pre-mineralized starch based scaffolds for bone tissue engineering. Journal of Materials Science: Materials in Medicine. 2005;**16**:267-275

[26] Gomes ME, Godinho JS, Tchalamov D, Cunha AM, Reis RL. Alternative tissue engineering scaffolds based on starch: Processing methodologies, morphology, degradation and mechanical properties. Materials Science and Engineering: C. 2002;**20**:19-26

[27] Liu C, Ge S, Yang J, Xu Y, Zhao M, Xiong L, et al. Adsorption mechanism of polyphenols onto starch nanoparticles and enhanced antioxidant activity under *Starch: A Veritable Natural Polymer for Economic Revolution DOI: http://dx.doi.org/10.5772/intechopen.102941*

adverse conditions. Journal of Functional Foods. 2016;**26**:632-644

[28] Xiao SY, Liu XM, Tong CY, Zhao LC, Liu XJ, Zhou AM, et al. Dialdehyde starch nanoparticles as antitumor drug delivery system: An in vitro, in vivo, and immunohistological evaluation. Chinese Science Bulletin. 2012;**57**:3226-3232

[29] Ban DK, Pratihar SK, Paul S. Controlled modification of starch in the synthesis of gold nanoparticles with tunable optical properties and their application in heavy metal sensing. RSC Advances. 2015;**5**:81554-81564

[30] Cazotti JC, Smeltzer SE, Smeets NMB, Dubé MA, Cunningham MF. Starch nanoparticles modified with styrene oxide and their use as Pickering stabilizers. Polymer Chemistry. 2020;**11**:2653-2665

[31] Ulery BD, Nair LS, Laurencin CT. Biomedical applications of biodegradable polymers. Journal of Polymer Science Part B: Polymer Physics. 2011;**49**:832-864

[32] Di Bartolo A, Infurna G, Dintcheva NT. A review of bioplastics and their adoption in the circular economy. Polymers. 2021;**13**:1229. DOI: https://doi.org/10.3390/polym13081229

[33] European Bioplastics. Bioplastics Market. Available from: https://www. european-bioplastics.org/market/ [Accessed: July 30, 2021]

[34] Lei H, Wu Y, Yang S, Fu C, Huo J. A simple strategy for converting starch to novel compressible carbonaceous foam: Mechanism, enlightenment and potential application. RSC Advances. 2018;**8**: 32522-32532

[35] International Trade Centre (ITC). Available from: https://www.trademap. org/Index.aspx [Accessed: July 30, 2021] [36] Giraldello S, Ribeiiro M, Elrington J, Todd M, Bentley S. Starch and Fermentation Analysis. Oxford, UK: LMC International Limited; 2014. http:// projects.nri.org/cassava-ipci/images/ documents/LMC-SFA-2014-Mar.pdf [Accessed: July 28, 2021]

[37] FAO. Food Outlook - Biannual Report on Global Food Markets— November 2018. Rome; 2018. p. 104

[38] Corn Refiners Association (CRA). CRA Industry Overview. 2018. Available from: https://corn.org/wp-content/ uploads/2019/02/CRA-Industry-Overview-2018-Final.pdf [Accessed: July 29, 2021]

[39] Russian Federation Starch Union. Industry overview. Moscow, Masha Poryvaeva: Domnikov Business Center; Available from: https://starchunion.com/ obzor-otrasli/ [Accessed: July 27, 2021]

## **Chapter 4** Health Benefits of Starch

*Teodoro Suarez-Diéguez and Juan Antonio Nieto*

#### **Abstract**

In recent years, scientific research has focused on evaluating the relationship between consumption and the effect of food components on the body, with the aim of improving the health condition of the population. In particular, starch is the main component in grains and provides most of the energy in the diet. It is classified according to its nutritional characteristics as rapidly digestible starch (RDS), slowly digestible starch (SDS), and non-digestible starch (RS). Several studies have reported that different starch fractions show a correlation between digestibility and assimilation with physiological effect and metabolic impact. Each type of starch fraction consumed shows a different postprandial response, such that SDS and RS generate a slower absorption rate and lower serum glucose concentration, leading to a gradual uptake of glucose into the tissue, as well as a probiotic effect. Current reports suggest that consumption of SDS- and RS-rich products can generate a postprandial response of prolonged glucose uptake without hyperglycemic peaks, and improve the efficiency of modulation of carbohydrate metabolism. In this regard, there is a growing interest in carbohydrates with functional effects generating an emerging area of study. The aim of this chapter is to describe the potential functional effect and metabolic impact of consumption of the SDS and SR fractions of starch.

**Keywords:** starch, digestion, gradual energy, functional properties, health benefits

#### **1. Introduction**

Several research has been focused on investigating the relation between the intake of the different compounds existing in food and their health benefits [1]. A special emphasis has been paid to study their potential benefit effects on chronic and metabolic diseases, such as diabetes or obesity, in order to improve the life quality of the individuals with these pathologies [2, 3]. In this context, carbohydrates (CH) are the main macronutrient in food and contribute 45–55% of the required energy [4]. Specifically, starch is the main CH of the diet, and therefore, it provides the majority of the required energy. Starch is content on cereals, legumes, roots, nuts, and their derived products. During gastrointestinal digestion, starch is first hydrolyzed in the mouth by the activity of the salivary α amylase, able to hydrolyze the glucose-glucose bonds with direction α(1-4), releasing diverse dextrins and maltose [5]. The starch digestion is completed in the intestine by the digestive action of the intestinal enzymes α amylase, isomaltase, and glucoamylase, that provoke the starch debranching on the α(1-6) bonds and the hydrolysis of the α(1-4) bonds, releasing high amounts of glucose [6, 7]. These glucose are absorbed in the intestine by the

Sodium-Dependent Glucose Transporter 1 (SGLUT-1), causing a glycaemia increase that provokes the release of insulin [8, 9]. However, the various botanical and industrial starches show different behaviors during the gastrointestinal digestion process, as a consequence of their different structural characteristics and physicochemical properties [7]. Therefore, regarding their digestion behavior, the diverse starch fractions can be classified as rapidly digestible starch (RDS), slowly digestible starch (SDS) [7, 10] and a crystallized starch fraction non-digestible denominated resistant starch (RS) [11–13]. The botanical origin shows a great influence in starch digestibility since it set up their structural characteristics and physicochemical properties, and therefore, the amount of each starch fraction [5, 7, 10].

The consumption of food rich in SDS is associated with a progressive release of glucose, maintaining a sustained energy source along the time compared with products with low SDS amounts and higher RDS contents [6, 10, 12, 13]. As consequence, the metabolic response generated by foods with higher SDS content shows a clear association with better postprandial metabolic parameters in healthy people but also in diabetic and obese individuals [13–16]. Thus, it is necessary to study and identify the mechanisms that relate the differences between the total glucose intake under starch form and the total absorber glucose after starch intake in order to understand the glycaemia response and metabolic profile of the different starches [14, 15]. The kinetic of the intestinal absorption of the released glucose can be used as valuable information to predict the postprandial changes in the blood glucose concentration and plasmatic insulin circulation [17, 18]. In this context, the diverse postprandial glycemic responses have been associated with the different starch fractions, where SDS and RS fractions show a slower glucose absorption rate, and therefore, attenuated glycemic response as well as less intense insulinemic responses [15, 19, 20]. Since high glycemic and insulinemic responses are associated with chronic diseases, mainly with the development of type 2 diabetes, a growing interest in the study of the CH and their metabolic responses exists, principally focused on the CH associated with a lower and maintained glucose absorption and therefore a mitigated glycemic response, characterized by the lack of hyperglycemic peaks and a maintained provided energy [19, 20].

#### **2. Digestibility**

Starch is largely digested among the gastrointestinal tract, being hydrolyses and absorbed at least 75% of the intake molecules [7, 21]. However, starch digestibility is conditioned by diverse factors, such as the acidity of the medium (a factor that reduces the activity of the amylase) or the cooking process, which gelatinize and solubilize the starch, increasing the accessibility of the digestive enzymes [4, 7, 9]. The starch digestion in the gastrointestinal tract occurs in diverse steps with the contribution of different digestive enzymes [8, 9, 16].

The first digestion step occurs in mouth digestion. Together with the reduction of the particle size of the intake of food by the chewing process, the release of salivary α amylase rules the digestion in the mouth. This enzyme shows a specific endo-hydrolytic activity on glucose-glucose α-(1,4) bonds but without activity on α-(1,6) bonds [10, 16, 22]. The endo-hydrolytic activity allows to hydrolyze the α-(1,4) bonds within the polymeric molecule, releasing lower glucose chains with direction α-(1,4), such as oligomers, maltotriose, or maltose [9, 18]. The mouth phase of the starch digestion is a short event because of the few time that takes the chewing and swallowing process,

#### *Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

even though the first digestion products appears at 10–20 s after ingestion, increasing the digestion products as the mouth digestion progress. It is important to point that in contrast to other substrates, the starch size is higher than the digestive enzymes α-amylases, allowing many possible points within the molecule for the enzyme union, thus facilitating the enzyme activity [4, 9, 22].

The stomach digestion does not release specific enzymes with digestive action for the starch molecule. However, the swallowed saliva together with the alimentary bolus may exert a residual activity until reaching an acid pH able to inactivate the salivary α amylases. Consequently, the digestion of the complex CH can undergo total hydrolysis of 10–40% before reaching the small intestine [4, 22, 23]. During the intestinal digestion, starch is hydrolyzed by the activity of the intestinal α amylase, other endo-hydrolytic enzymes with activity on the glucose-glucose α-(1,4) bonds. However, this enzyme is not able to hydrolyze the α-(1,6) bonds existing in the branching amylopectin [10, 16, 18, 23]. Because of that, the activity of this enzyme is complemented with the activity of the isomaltase (able to hydrolyze the α-(1,6) bounds) and the glucoamylases, that hydrolyze α-(1,4) bounds mainly of glucose oligomers, such as dextrins. The combined action of these three enzymes becomes the successive digestion products, such as dextrins, oligosaccharides, and maltotriose, into maltose and glucose molecules. Besides, the action of the maltase enzyme of the intestine brush border becomes maltose into two glucose molecules [9, 16, 22]. The result of the complete digestion process of the ingested starch is a high amount of released glucose, being transported into the enterocytes by the transporter SGLUT-1 and excreted to the portal vein by the intestinal Glucose Transporter 2 (GLUT-2), provoking an increase of the glycaemia and an insulinemic response [14, 22, 23].

Starch digestibility is a factor of the food quality. The effect of the different starch fractions on the postprandial metabolism depends on the velocity and degree of the starch digestibility. SDS and SDS are categorized as glycemic starches and constitute the digestible starch fraction (DS). This DS fraction is hydrolyzed along the gastrointestinal tract whereas a fraction of the starch remains non-digestible, corresponding to the RS [4, 6–8]. The DS fraction is completely assimilated in the small intestine, responsible for the increase of the postprandial glycaemia [13, 14, 16, 24]. RS is characterized by a crystalline structure that avoids the digestibility of the molecule by the human digestive enzymes. As consequence, this fraction reaches the colonic tract, being fermented by the bacteria of the colonic microbiota, releasing short chain fatty acids (SCFA), such as butyric acid [11, 12, 25, 26]. The different digestibility found in the NS of the diverse botanical species has been explained as the interaction of various factors, such as the botanical source that condition the amount of each starch fraction, the starch granule size, the presence or absence of superficial pores on the starch granules, the relation amylose/amylopectin, the crystallinity degree on the molecule (correlated with the X-ray diffraction pattern) [24, 27], the association degree between diverse starch chains, the distribution and length of the branched chains of the amylopectin or the existence of interior channels and fractures on the starch molecule [24, 27, 28]. In addition, the industrial processing and cooking of starchy food can alter the starch properties, influencing the digestibility properties and also, the amount of each starch fraction [6, 7, 22, 29].

The rate and degree of starch amylolysis is determining factor in establishing the magnitude and duration of the postprandial glycaemic response. Currently, different in vitro tests have been considered to evaluate the rate and degree of starch hydrolysis as predictors of the physiological effect of food consumption [8, 17, 18, 23]. However, establishing the comparison of digestibility values found in the literature is a

complicated task due to the variability in the methodology [8, 23, 27, 28, 30], as well as the variability of the type of enzyme used for the starch hydrolysis [16, 17, 28, 30]. In this context, the susceptibility level of the hydrolysis of retrograde samples depends on the type of α-amylase used (bacterial, fungal, pancreatic), enzyme concentration, hydrolysis time, and purity of the enzyme [17, 18, 28, 30, 31].

Among the aspects to consider studying and interpreting the in vitro digestibility of starch, and thus being able to establish postprandial physiological predictions, the understanding of the mechanics of action of digestive enzymes on starch hydrolysis should be studied. Currently, a kinetic model has been established that follows a pseudo-first order reaction for the analysis of starch hydrolysis, using as a tool the graph from the "logarithm-of-slope" (LOS) plot [17, 18]. This model allows conducting an analysis to be performed to classify the RDS, SDS, and RS fractions based on kinetic behavior in terms of a rate constant and the degree of hydrolysis. The in vitro hydrolysis level of starch is a frequently used indicator to determine the degree of total digestibility in starch samples. This parameter is represented by the equilibrium concentration (C∞) at the end time of the kinetics of amylolysis, represented by the digestograms [16–18, 23]. Digestion rates are measured by the kinetic rate constant (k) (pseudo-1st order rate constants for starch amylolysis).

The kinetic constants of amylolysis in native starches (NS) and gelatinized, as in the case of cereals such as corn and legumes such as beans and broad beans, present a similar degree of level of enzymatic activity and affinity of the enzyme for the substrate [32]. In general, the gelatinized NS LOS plots of corn, beans, and broad beans show similar kinetic behavior. This implies that in the fastest phase the easily accessible starch is hydrolyzed, presenting a relative duration of 30 min, and later it simultaneously passes to a slower phase, which shows that the behavior of the graphics tends to be of a single phase. This implies that the easily accessible fraction is more available to the action of α-amylase, resulting in an increase in the degree of digestibility expressed as C∞. The LOS graphs show a single linear phase hydrolysis process, considering a constant k with a similar behavior between the different varieties obtained by this method. Hydrolysis of gelatinized starches generally occurs in a single phase as gelatinization makes the starch fully accessible to the enzyme [33].

In the case of RS obtained by debranching and subsequent retrogradation of corn, beans, and broad beans, the LOS graphs show the behavior of an initial fast phase that inevitably has a prolongation. This implies that the reaction is characterized by a slower phase, and represents the fraction of starchless available, which is reflected in the values of k and C∞ [32]. Thus, the slopes of the LOS graphs of the RS are notably lower than the NS, consequently, lower values of k are obtained in the RS samples compared to the NS samples that reflect a slow phase of hydrolysis, showing a lower affinity of the enzyme for the substrate.

Studies in NS of these varieties have shown that hydrolysis is faster in the first phase because the enzyme more easily accesses the starch fractions of the amorphous regions [16, 18, 34]. Type A starch, which is characteristic of cereal starches, shows a high proportion of short chains in the cluster, due to a large number of branches, which are more widely dispersed within the cluster, increasing the number of access points for amylase and substrate [24, 35, 36]. In addition, it has been considered that the crystallinity pattern of starches conditions their digestibility. NS with type A crystallinity patterns have pores and channels, whereby the enzyme penetrates into them and the hydrolysis reaction starts from the hilum region towards the outside of the granules, thus favoring the degree and speed of starch hydrolysis [35, 36]. On the other hand, NS with a type B crystallinity pattern does not present pores, showing a

#### *Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

non-porous surface, thus giving a different hydrolysis pattern than type A, because the enzymatic digestion starts from the starch surface. This promotes the degree and rate of hydrolysis to be lower [24, 33, 37]. Likewise, it has been observed that legume NS with a crystallinity pattern of type C (A + B) shows a lower degree of hydrolysis. It has been reported that the difference in the degree of amylolysis in starches with type C patterns, is influenced by the presence of fissures or cracks on the surface of the granule that some varieties of legumes present. These cracks would allow the enzymes to have a higher diffusivity and to penetrate more quickly into the granule, hydrolyzing more easily the starch chains close to the granule surface [34, 36, 37].

This phenomenon would explain the difference in RDS levels between the different legume varieties. Likewise, the levels of SDS and RS depend on the degree of structural organization of the double helices within the crystalline lamellae and the distribution of these lamellae in the granule [38, 39]. A starch with higher SDS and RS content is characterized by a decreased level of susceptibility to hydrolytic enzymes and consequently lower digestibility, generating a moderate postprandial response without hyperglycemic peaks [13, 19, 20, 40]. This type of starch is the most suitable for consumption in the diet, especially in diabetic situations [13, 14, 19, 20]. In the case of RS, they have a lower k constant compared to the digestion kinetics of NS and represent a decrease in the catalytic efficiency of α-amylase due to the high degree of crystallinity of RS [11, 12, 25]. A low value of k is estimated to reflect a lower diffusion and a slower phase in the hydrolysis process by α-amylase, due to the degree of crystallinity of the different fractions of RS which inhibits the action of α-amylase [16–18, 28].

#### **3. Nutritional characteristics of the starch**

Starch is constituted by two different CH polymers, amylose, and amylopectin. Amylose consists of linear chains of glucose molecules linked by α(1-4) bounds, whereas amylopectin is constituted by linear chains of glucose molecules linked by α(1-4) bounds, with branching points linked by α(1-4) bounds every 15–30 glucose molecules [24, 35, 36]. Regardless of the botanical origin of starch, it is always composed of these two polymers, changing their amylose/amylopectin ratio in relation to their botanical origin [24, 35, 36]. Therefore, the differences in the nutritional characteristics of the diverse starches are a consequence of their bioaccessibility and bioavailability that depends on their composition on RDS, SDS, and RS.

#### **3.1 Factors that influence bioavailability**

The starch digestibility is a consequence of intrinsic factors, such as the starch morphology and physicochemical properties, and of extrinsic factors, determined by the physiological conditions of the individuals [6, 7, 9, 28], with a variability regarding genetic factors [41].

The intrinsic factors are referred to the structural and physicochemical characteristics. These properties are related to the granule and highly influenced by the botanical origin [6, 7, 9], or are the result of applied processes during the industrial processing or cooking processes. These factors condition the ability and accessibility of the digestive enzymes to starch molecule, influencing the hydrolysis degree [41, 42], and therefore, the intrinsic properties condition the bioaccessibility and bioavailability degree of the molecule [40–42]. Since these factors directly modulate the digestibility, condition also postprandial response [39–41]. Diverse processes modify starch assimilation. The grinding of the grain provokes ruptures of the starch molecule, enhancing the efficiency of the gelatinization and allowing a greater interaction of the digestive enzymes, increasing the starch bioavailability. The food products elaborated with grinding grains are characterized by faster starch hydrolysis and an immediately postprandial response [6, 7, 9, 34, 40].

The extrinsic factors are referred to the physiological conditions of the individuals that determined the bioaccessibility and bioavailability of the starch. These factors include age, gender, metabolic conditions, pathological alterations of the digestive tract, the efficiency of the digestive process, gastrointestinal transit time, and genetic variations, among others [9, 22, 42]. Due to the genetic variation in the expression of the digestive enzymes [22, 41, 42] or because of specific physiological conditions, some individuals do not completely absorb the glucose release from the starch hydrolysis [6, 41, 42]. The food emptying from the stomach is a consequence of the gastric emptying, regulated by diverse factors such as the amount and volume of the ingested food, the type of macronutrient, the energy density of the intake, the particle size of the food matrix, the viscosity, the osmolality and the pH [7, 9]. Once the gastric content is released to the intestine, factors such as the viscosity influence the accessibility of the digestive enzymes to the chime and the nutrient releasing [9, 22]. In this context, the gastrointestinal transit time of the starch is inversely correlated with the amount of ingested starch and the contact time of the enzymes with the substrate [41, 42].

#### **3.2 Classification of the diverse starch fractions**

The digestibility and bioavailability of the starch vary depending on the intrinsic and extrinsic factors, closely related to the starch type and the botanical origin [6, 7, 9]. As consequence, starch can be classified according to their digestibility degree and releasing velocity of their constituent CH [6, 8, 10, 19, 21, 22, 43]. In this context, the diverse starch fractions can be classified according to these two parameters, the digestibility and assimilation degree, in three different fractions: rapid digestible starch (RDS), the slow digestive starch (SDS), and the resistant starch (RS) [6, 21, 28, 43]. All the starches are naturally constituted by an RSD and an SDS fraction, and a minor fraction of RS. The whole digestibility of the starch is a consequence of these three fractions and can be determined in vitro by measuring the glucose release of each fraction, as a predictor of their potential postprandial response [39, 40, 43].

The RDS is characterized to be the first completely digested fraction, showing a characteristic high velocity of glucose release, occurring the whole hydrolysis of this fraction within the first 20–30 min [6, 27, 28, 30]. The digestion of this fraction release oligosaccharide that are quickly hydrolyzed to glucose molecules [44]. This fraction is completely assimilated, being digested, and absorbed in the proximal duodenum [7, 24, 27, 28]. The behavior of this starch fraction during gastrointestinal digestion is a consequence of the amorphous structure of this starch fraction and the high gelatinization degree, being easily hydrolyzed by the digestive enzymes [6, 27, 28]. The RDS generate a fast increase of the glucose concentration in the blood after the starch intake and frequently provoke a hyperglycemic response. These highly fluctuant glucose levels generate increased stress on the regulatory systems of the glucose homeostasis with possible alterations or damages in cells, tissues, and organs [44]. Food with this characteristic (rich or enriched in RDS fraction) are the products

#### *Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

with a high refinery degree, such as cereals flours used for bakery, pastries, biscuits, breath or fried foods, among others [24, 27, 29, 39].

Conversely, the SDS fraction is characterized by slow and progressive digestion, showing an intestinal absorption of the almost entire starch fraction. This starch fraction is composed of an amorphous but rigid structure, generating a more inaccessible structure that hinders the enzyme accessibility and an imperfect crystalline structure that limits the action of the digestive enzymes. As a consequence of this more complex accessibility for the digestive enzymes, the hydrolysis velocity is dramatically reduced, showing a slower digestion velocity [16, 39, 45]. The progressive release of glucose molecules resulting from its hydrolysis, allowing a progressive intestinal absorption of the glucose products, avoids high glycemic peaks, showing a lower but maintained postprandial response. This glycemic response is beneficial for healthy people but especially for diabetics [13, 14, 19, 30, 44]. The slow digestion and assimilation are related to several intrinsic factors of the starch molecule, as well as to structural changes that occurred during industrial processing or cooking [4, 6, 19, 27, 29, 44].

The structural properties of the food matrix may play an important role during starch digestion. When starch is contained internally in the food matrix, it plays an important role in reducing the velocity of the starch digestion because it get caught on the food matrix or by a barrier action of the rigid cell walls. This events are commons in legumes [7, 10, 27, 29, 45]. This coughed starch fraction is especially interesting for people with metabolic or chronic diseases, particularly type 2 diabetic or hyperlipidaemic ones [45].

RS is the starch fraction characterized by not be hydrolyzed by the digestible enzymes, reaching entirely the colonic tract [6, 11, 12, 21, 24, 25]. The European Research Project on Resistant Starch (EURESTA) defines RS as "the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals" [11, 12]. When RS reaches the colonic tract, it is fermented into diverse SCFA, especially propionic and butyric acids, or conversely, it is eliminated through the fecal material [11–13, 25, 26]. Regarding their chemical nature, RS can be classified into diverse categories. **Table 1** summarizes the diverse types of RS currently identified and their main characteristics. Some RS occurs naturally in food, existing in the starch


#### **Table 1.**

*Classification of the diverse types of RS.*

granule, whereas others RS are the result of a structural reorganization on the molecule or the molecule interaction with other compounds, as a consequence of industrial processing, cooking, or intentioned chemical modifications [11, 12, 24, 25]. In any case, the RS formation is due to a structural reorganization of the amylose linear chains and their association with the amylopectin [25, 46, 47]. Accordingly, RS frequently occurs in starch molecules with a higher amylose/amylopectin ratio, increasing the available lineal chains of α-glucans to form crystalline and organized structures [24, 25, 46–48]. The molecular weight of these RS crystalline structures is close to 100 kDa.

#### **4. Functional properties of the starch fraction**

#### **4.1 Functional properties of the SDS and RS**

The functional properties of a compound are defined by the way to modify the metabolic patterns, generating a beneficial property. Diverse compounds present in plants show functional properties [2, 49]. In this context, the possible functional properties of SDS and RS have been specially studied in the last years because of their capacity to provide a maintained source of energy avoiding hyperglycemic responses, especially beneficial for diabetic patients. It is important to note that the attenuated glycemic response during starch consumption is dependent on the digestibility behavior that depends on the starch composition and physicochemical properties [50]. The influence on the variability in the glycemic response is considered as an important factor to control the glycemic response in diabetic and obese patients, frequently measured as the concentration of glycated hemoglobin (HbA1c) [51, 52].

Diverse investigations support the evidence of this beneficial effect of the SDS or RS fractions. Hasek et al. [53] studied the effect of the consumption of SDS using obese rats how experimental animal models fed with high fat diet (HFD). A group supplemented with SDS was compared with a group with RDS supplementation. The experimental group fed with SDS reduced the total daily intake of food compared with the RSD group. In addition, when evaluating the expression levels of (mRNA) of hypothalamic orexigenic neuropeptide Y (NPY) and Agouti-related peptide (AgRP), they observed that their expression was significantly reduced in the group fed SDS, as well as an increase in the hormone that produces anorexigenic corticotropin-releasing hormone (CRH). These researchers suggest that SDS can contribute to modulating the frequency of food consumption by activating the gut-brain axis, in addition to generating a reduction in the expression of genes of appetite-stimulating orexigenic neuropeptides and an increase in hypothalamic appetite-suppressing neuropeptide. Therefore, SDS may exert beneficial functional properties.

Breyton et al. [50] compared the effect of the consumption of a diet high or low in SDS in a group of diabetic patients. They observed a reduction in the variability of the glycaemia as well as the lower postprandial area under the curve (AUC) of the glycaemia when the high SDS consumption was considered. These authors consider that the modulation of the starch digestibility may be used as a useful tool for controlling the postprandial glycemic response in diabetic patients. Similar results were reported by Lambert-Porcheron et al. [54], that evaluated the postprandial response and digestibility of a product based on cereals with high or low SDS content in patients with overweight o metabolic risk. They observed a 2 h postprandial glycemic and insulinémica response lower in the group of patients that consumed the product with high SDS compared to the other group.

#### *Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

Considering the effect of RS consumption, diverse studies have reported beneficial effects on human health [11–13, 26, 50] (**Table 2**). In this context, the physiological effect of the RS consumption shows a great dependence on the biological origin, the total amount intake and the type of RS consumed [11, 12, 24–26]. In general, it can be considered that the RS consumption reduces the postprandial glycemic response and improve the glucose metabolism and homeostasis [11, 12, 14, 26] as a consequence of not being digested in the upper human tract [12, 45, 47, 50] and by contributing to a lower but maintained postprandial glucose in the diet [11–13]. These properties are especially beneficial for type II diabetic patients allowing better control of the glycaemia [11–13, 26], as well as for healthy individuals [12, 13, 26]. In addition, RS can exert a modulation effect on the satiety by modifying the secretion of adipokines and peptides responsible for this physiological process [12, 13, 26], such as an increase of the release of ghrelin, leptin, adiponectin, glucagon-like peptide 1 (GLP-1), peptide tyrosine (PYY) and gastric inhibitor peptide (GIP). The satiety promotion reduces the total food and calories intake preventing the excess of calories and the accumulation of fatty acids in the adipose tissue [12, 47, 50, 53]. Therefore, RS can be used as a useful tool to prevent and manage obesity [12, 13, 21, 26].

Other beneficial effect attributed to RS is its capacity to act as a prebiotic compound. Since RS is low or not digested in the upper gastrointestinal tract, it reaches the colon as part of the dietetic fiber [24, 25, 28, 46]. RS is fermented by the colonic microbiota bacteria releasing SCFA, especially butyric acid, an essential compound to maintain the intestinal epithelium permeability and associated with colon cancer


### **Table 2.**

prevention. In addition, the SCFA can modulate satiety and lipid metabolism and are also substrates of the intestine gluconeogenesis. This process is associated with a reduction of hepatic gluconeogenesis and therefore a direct impact on the postprandial glycemic response [12, 13, 21, 25, 26, 50].

The prebiotic effect of the RS is associated with the RS fermentation by Bifidobacterias and Lactobacillus species allowing to promote the growth of this beneficial bacteria in terms of total amount and diversity [12, 25, 26]. Dysbiosis, defined as a negative alteration of the microbiota population, is generally associated with a reduction of the microbiota diversity and especially with the alteration of the Bacteroidetes and Firmicutes phyla, characterized in general by the increase of the Firmicutes/Bacteroidetes ratio and the reduction of the Bifidobacterias group. These microbiota alterations are associated with intestinal complications and the increase of the incidence of chronic diseases such as obesity, type 2 diabetes, cardiovascular diseases, and also with cancer [55–57]. The prebiotic effect of RS promotes the growth of Bifidobacterias and Lactobacillus species, contributing to maintaining a healthy microbiota, a continuous production of SCFA, maintaining the integrity of the intestinal epithelium, and as consequence, reducing the intestinal absorption of bacterial lipopolysaccharide (LPS) and therefore, reducing and preventing the endotoxemia, metabolic stress and chronic systemic inflammation, responsible or contributors of many chronic metabolic diseases [56, 57].

This prebiotic action of RS may exert an effect on glucose metabolism through different mechanisms, such as decreasing the gastric emptying, decreasing the glucose absorption in the intestine, favoring or promoting the production of GLP 1, as well as decreasing the expression in the transcriptional factors that intervene in the oxidation of fatty acids and lipogenesis, generating a decrease in the free fatty acids levels in the blood [56, 57].

#### **4.2 Modulation of the glycaemia homeostasis by SDS and RS**

As was exposed before, the nutritional characteristics of starch depend on its structural and physicochemical properties, responsible for the different digestibility, bioavailability, and postprandial glycemic and insulinemic response [4, 14, 15, 19]. Starches with higher SDS and RS fractions show a slower digestibility, progressive assimilation, and therefore a lower glycemic response. Conversely, high RDS contents are characterized by rapid digestion, assimilation and an elevated glycaemic response [19, 44, 50, 53, 54]. Therefore, the starch characterized by high SDS or RS contents can be used to avoid hyperglycemia [19, 26, 44, 45] and get a higher control of the postprandial glycemic response and glucose homeostasis in metabolic syndrome diseases, especially for diabetic patients [13, 54, 56]. The replacement of natural starchy foods by starches with higher SDS and RS content together with the commonly prescribed drug is an adequate strategy to get an integral control of the glycaemia response [4, 13, 15, 19, 26, 44, 47, 50, 54, 56].

Diverse in vivo studies show that RS consumption is associated with benefits in glucose homeostasis [13, 54, 56, 58]. Sun et al. [58] evaluated the consumption effect of RS-II in rats with type 2 diabetes, fed with a diet high in lipids and glucose for 4 weeks. The experimental group showed a reduction trend in glycaemia compared to the diabetic control group (without RS-II). Also, higher glycogen levels were determined in the liver and muscle of the experimental group compared to the diabetic control but similar levels that the non-diabetic group fed without RS-II. Similar results were determined by Zhou et al. [59] when RS from high amylose maize were evaluated

#### *Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

during 4 weeks. The experimental group of diabetic rats fed with RS significantly reduced the glucose cholesterol and triglycerides blood levels compared with the control diabetic rats (non-fed with RS) and even HDL levels were determined twice as high in the first group. Zhou et al. [59] and Sun et al. [58] suggest that the biological mechanism responsible for the beneficial RS effects in the glycemic response is mediated by the promotion of the hepatic glycogen and the gluconeogenesis inhibition together with higher efficiency in the glucose intake by the muscular tissue [13, 59]. Gluconeogenesis is the metabolic pathway responsible for the endogenous synthesis of glucose molecules through the use of non-carbohydrates precursor molecules such as pyruvate, alanine, or glycerol. The phosphoenolpyruvate carboxykinase enzyme (PEPCK) converts the oxaloacetate to phosphoenolpyruvate during the gluconeogenesis pathway, whereas during the last step of this pathway the glucose-6-phasphatase (G6Pase) removes the phosphorous group in the 6 positions of the glucose-6-phasphate releasing glucose [13, 60, 61]. Diabetic patients are characterized by continuous activation of the PEPCK and G6Pase enzymes as a response to the low glucose intake by the muscle tissue as a consequence of an inadequate insulinemic response, causing hyperglycemia under fasted state [13, 61, 62]. In this context, diverse in vivo studies have observed a reduced expression of the PEPCK and G6Pase enzymes in diabetic rats treated with RS and therefore, a reduction of the gluconeogenesis activation [58, 59]. The glucose intake by the muscle tissue and the inhibition of gluconeogenesis provokes the activation of the AMP-activated protein kinase (AMPK) restoring the cell energy or ATP. Both mechanisms have been associated with SDS consumption since in vivo studies show the activation of the AMPK with SDS intake [13, 62, 63].

Other authors suggest that the benefits in the glucose homeostasis derived from the RS intake are a consequence of improved lipid homeostasis. The improvement in lipid metabolism is modulated through the promotion of muscular lipid oxidation and cholesterol homeostasis, both related to the improvements in glucose homeostasis. Whereas, other authors suggest that the improvement of the glucose homeostasis is a consequence of the SCFA released, contributing to promote the satiety process and improving the serum lipid profile, both related to an improvement in the prognostic of the insulin resistance [56, 58, 59, 61].

Many researchers suggest that SDS or RS consumption improves the glycaemia in diabetics through the activity reduction of the enzymes of the hepatic gluconeogenesis and the augmentation of the glucose intake by the muscle tissue [58, 59, 61], as well as by the improvement of the lipid homeostasis consequence of the release of SCFA during colonic fermentation of RS [26, 53, 57]. The improvement of glucose homeostasis is an efficient mechanism to reduce the long-term complications consequence of diabetes, mainly related to oxidative stress and cell damage [61–63]. In this context, the glycemic response in healthy individuals and type 2 diabetic patients is correlated with the type and amount of RS ingested [63, 64]. Other biomarkers related to glucose modulation are the C peptide, leptin, PYY, GLP-1, GIP, and some inflammatory cytokines. The RS consumption is associated with the increase of plasmatic levels of GLP-1, GIP, and PYY, responsible for the insulinemic response, glucose regulation, and satiety process. The released SCFA during RS colonic fermentation could be associated with the increase in the expression of PYY and GLP-1 genes, establishing a relation between RS consumption and intestinal hormones production [63, 64]. Maziarz et al. [65] demonstrated that RS consumption reduces leptin production probably a consequence of augmentation on the fatty acids oxidation since serum circulating levels of leptin are associated with the total body fat mass and negatively correlated with fatty acids oxidation.

#### **5. SDS and RS as potential functional ingredients**

As a consequence of the improved awareness of the consumers in the relation of diet and health, the food industry has focused on the production of functional foods based on cereals, legumes, and other products with low glycemic index (GI) [11–13, 25, 29, 32]. Currently, new sources for RS obtention or production have been investigated as alternatives to the conventional sources (maize, wheat, rice, among others) since RS beneficial effects are dependent on the botanical origin, type of RS, and total intake amount [12, 25, 29, 32]. RS is shown as a great potential functional ingredient because of their great techno-functional properties such as small particle size, color, soft flavor, well properties for the extrusion process, high temperatures of gelatinization, and low water retention capacity, together with their low caloric values (1. 6–2.8 kcal/g) [5, 11, 25]. In addition, may improve the lifespan of dry products and avoid the ice crystals during the ice creams production [5, 25, 29, 46]. These properties allow to incorporate RS as an ingredient in many different food matrixes such as dairy products, bakery products, or pastas [5, 11, 25, 46].

RS can be used also to increase the total fiber content of food products or to reduce the low available CH contents in the production of dietetic food products focused on reducing the bodyweight through a lower caloric content [25, 46]. The incorporation of RS to the food formulation does not change the flavor neither produce significant changes in the texture, whereas may improve the product sensorial properties compared with many available fibers such as brans or gums [11, 25, 46], also, the final product texture can be improved by using RS because of their low water retention capacity [29, 46–48]. RS has been also used as a cover ingredient during probiotics microencapsulation to be incorporated into dairy products, allowing increasing the viability of the probiotics. Also, RS has been used to encapsulate fish oils to reduce the odor and lipid oxidation [5, 25, 46, 47]. RS can be used in bakery products and breakfast cereals as a functional ingredient and fiber source but attention to the technological properties of the products should be observed to ensure to reach the desirable properties on the product [5, 11, 25, 29, 46]. The addition of RS-III to sourdough breaths may improve the toasted color and the crunch properties of the product [25, 46, 47]. However, the addition of green banana flour (rich in RS-II) to pasta may provoke a weaker mass as a consequence of the gluten dilution effect but less oil is required to fry these products [5, 25, 46]. The addition of RS-III ha can generate in the flour tortillas lower flexibility, rolling capacity, and cohesion. High concentrations of RS-III reduce structural integrity and therefore product quality [5, 25, 29, 32, 46].

On the other hand, the evaluation of the impact and benefits in the consumption of SDS as a functional ingredient for the elaboration of products that improve the postprandial glycemic response has increased in recent years. Rebello et al. [66] evaluated the effect of the consumption of SDS as a functional ingredient in a Snack, with the purpose of improving the postprandial response, the degree of satisfaction, and appetite in people with overweight and obesity. The consumption of the snack with SDS at breakfast improved the postprandial glycemic and insulinemic response by decreasing the concentrations of glucose and serum insulin in the blood per unit of time (minutes), compared to a control product without SDS. In addition, they estimated that the relative glucose responses in the evaluated products were 40% lower compared to the control product. They attribute this effect to the characteristics and type of CH ingested, and to a lower rate of digestion and absorption of the same. These results are consistent with that reported by Péronnet et al. [67], where they

#### *Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

evaluated the consumption of a cereal product with different SDS contents (high and low) to evaluate the type of glycemic response in relation to the underlying changes in the kinetics of plasma glucose, on the increase in the rate of production (appearance) and consumption (disappearance) of serum glucose in the blood in healthy young women. They observed that the consumption of the product with a high content of SDS generated a significant reduction in the absorption and consumption kinetics of plasma glucose concentrations, compared to the consumption of the control products. This group considers that the consumption of the product with a high content of SDS generates a slow absorption of glucose, reducing its availability, and promotes a continuous gradual effect, attenuating sudden changes in concentration in the kinetics of plasma glucose, improving its homeostasis.

#### **6. Conclusions**

The impact of starch consumption on the human health is dependent on the starch composition and physicochemical properties, highly dependent on the botanical origin of the starch or the processes applied. In this context, the major factor associated with the impact of starch consumption on the human health is the hydrolysis behavior during the gastrointestinal tract, and therefore, with the composition and amount of RDS, SDS, and RS fraction in the starch molecule. Starches with high RDS amounts are characterized by rapid and high glycaemic and insulinemic peaks, being a risk for further diabetes and other chronic diseases. Conversely, SDS and especially RS are associated with low or very low but maintained glycemic and insulinemic responses, and therefore, are associated with benefits for the glucose homeostasis in diabetics but also in healthy people. RS is shown as a promising functional ingredient since this molecule, depending on its morphological structure and physicochemical characteristics, is low or non-digested and shows other potentially beneficial properties. The majority of RS is fermented by the colonic microbiota allowing to growth of the Bifidobacterias and Lactobacillus species, acting as a prebiotic compound. Also, SCFA is released from their colonic fermentation, associated with the increase in the expression of satiety hormones such as GLP-1, GIP, and PYY, contributing to reducing the total calories intake. It has been suggested that RS and SDS consumption is also associated with the glucose homeostasis, contributing to reduce the expression of the gluconeogenic enzymes (PEPCK and G6Pase) and improving the glucose intake by the muscle tissue. In addition, RS and SDS may contribute to lipid homeostasis, increasing HDL release and lipid oxidation. However, more detailed studies are required to clarify the capacity of RS and SDS to modulate glucose and lipid homeostasis. In conclusion, starches with high SDS and especially RS are associated with health benefits such as low insulinemic responses, glucose homeostasis control, prebiotic effects, and satiety, being RS as a promising but low exploited functional ingredient.

#### **Conflict of interest**

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

#### **Author details**

Teodoro Suarez-Diéguez1 \* and Juan Antonio Nieto2,3

1 Academic Area of Nutrition, Institute of Health Sciences, Autonomous University of the State of Hidalgo, Pachuca de Soto, Hidalgo, México

2 AINIA Technological Centre, Paterna, Valencia, Spain

3 International University of Valencia, Valencia, Spain

\*Address all correspondence to: tsuarez@uaeh.edu.mx

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Gul K, Singh AK, Jabeen R. Nutraceuticals and functional foods: The foods for the future world. Critical Reviews in Food Science and Nutrition. 2016;**56**(16):2617-2627. DOI: 10.1080/10408398.2014.903384

[2] Galanakis CM. Introduction. In: Galanakis CM, editor. Nutraceutical and Functional Food Components. Academic Press is an imprint of Elsevier; 2017. pp. 1-14. DOI: 10.1016/B978-0-12- 805257-0.00001-6

[3] Gerschenson LN, Rojas AM, Fissore EN. Carbohydrates. In: Galanakis CM, editor. Nutraceutical and Functional Food Components. Academic Press is an imprint of Elsevier; 2017. pp. 39-101. DOI: 10.1016/B978-0-12- 805257-0.00003-X

[4] Lovegrove A, Edwards CH, De Noni I, Patel H, El SN, Grassby T, et al. Role of polysaccharides in food, digestion, and health. Critical Reviews in Food Science and Nutrition. 2017;**57**(2):237-253. DOI: 10.1080/10408398.2014.939263

[5] Sharma A, Sing-Yadav B, Ritika B. Resistant starch: Physiological roles and food applications. Food Review International. 2008;**24**(2):193-234. DOI: 10.1080/87559120801926237

[6] Englyst KN, Englyst HN. Carbohydrate bioavailability. The British Journal of Nutrition. 2005;**94**(1):1-11. DOI: 10.1079/BJN20051457

[7] Singh J, Dartois A, Kaur L. Starch digestibility in food matrix: A review. Trends in Food Science and Technology. 2010;**21**(4):168-180. DOI: 10.1016/j. tifs.2009.12.001

[8] Butterworth PJ, Warren FJ, Ellis PR. Human α-amylase and starch digestion: An interesting marriage. Starch/Stärke. 2011;**63**(7):395-405. DOI: 10.1002/ star.201000150

[9] Lapis TJ, Penner MH, Balto AS, Lim J. Oral digestion and perception of starch: Effects of cooking, tasting time, and salivary α-amylase activity. Chemical Senses. 2017;**42**(8):635-645. DOI: 10.1093/chemse/bjx042

[10] Hoover R, Zhou Y. In vitro and in vivo hydrolysis of legume starches by α-amylase and resistant starch formation in legumes—a review. Carbohydrate Polymers. 2003;**54**(4):401-417. DOI: 10.1016/S0144-8617(03)00180-2

[11] Fuentes-Zaragoza E, Riquelme-Navarrete MJ, Sánchez-Zapata E, Pérez-Álvarez JA. Resistant starch as functional ingredient: A review. Food Research International. 2010;**43**(4):931-942. DOI: 10.1016/j. foodres.2010.02.004

[12] Lockyer S, Nugent AP. Health effects of resistant starch. Nutrition Bulletin. 2017;**42**(1):10-14. DOI: 10.1111/ nbu.12244

[13] Ting-Wong TH, Yu-Louie JC. The relationship between resistant starch and glycemic control: A review on current evidence and possible mechanisms. Starch/Stärke. 2017;**69**(7-8):1600205. DOI: 10.1002/star.201600205

[14] Nazare JA, de Rougemont A, Normand S, Sauvinet V, Sothier M, Vinoy S, et al. Effect of postprandial modulation of glucose availability: Short- and long-term analysis. The British Journal of Nutrition. 2010;**103**(10):1461- 1470. DOI: 10.1017/S0007114509993357

[15] Vinoy S, Meynier A, Goux A, Jourdan-Salloum N, Normand S,

Rabasa-Lhoret R, et al. The effect of a breakfast rich in slowly digestible starch on glucose metabolism: A statistical meta-analysis of randomized controlled trials. Nutrients. 2017;**9**(4):318. DOI: 10.3390/nu9040318

[16] Dhital S, Warren FJ, Butterworth PJ, Ellis PR, Gidley MJ. Mechanisms of starch digestion by -amylase: Structural basis for kinetic properties. Critical Reviews in Food Science and Nutrition. 2017;**57**:875-892. DOI: 10.1080/ 10408398.2014.922043

[17] Edwards CH, Warren FJ, Milligan PJ, Butterworth PJ, Ellis PR. A novel method for classifying starch digestion by modelling the amylolysis of plant foods using first-order enzyme kinetic principles. Food & Function. 2014;**5**(11):2751-2758. DOI: 10.1039/ C4FO00115J

[18] Butterworth PJ, Warren FJ, Grassby T, Patel H, Ellis PR. Analysis of starch amylolysis using plots for firstorder kinetics. Carbohydrate Polymers. 2012;**87**(3):2189-2197. DOI: 10.1016/j. carbpol.2011.10.048

[19] Gourineni V, Stewart ML, Skorge R, Sekula BC. Slowly digestible carbohydrate for balanced energy: In vitro and in vivo evidence. Nutrients. 2017;**9**(11):1230. DOI: 10.3390/ nu9111230

[20] Marinangeli CP, Harding SV. Health claims using the term 'sustained energy' are trending but glycaemic response data are being used to support: Is this misleading without context? Journal of Human Nutrition and Dietetics. 2016;**29**(4):401-404. DOI: 10.1111/ jhn.12359

[21] Van-Dam RM, Seidell JC. Carbohydrate intake and obesity. European Journal of Clinical Nutrition. 2007;**61**(Suppl. 1):S75-S99. DOI: 10.1038/ sj.ejcn.1602939

[22] Goodman BE. Insights into digestion and absorption of major nutrients in humans. Advances in Physiology Education. 2010;**34**(2):44-53. DOI: 10.1152/advan.00094.2009

[23] Martens BM, Bruininx EM, Gerrits WJ, Schols HA. The importance of amylase action in the porcine stomach to starch digestion kinetics. Animal Feed Science and Technology. 2020;**267**: 114546

[24] Cornejo-Ramírez YI, Martínez-Cruz O, Toro-Sánchez CLD, Wong-Corral FJ, Borboa-Flores J, Cinco-Moroyoqui FJ. The structural characteristics of starches and their functional properties. CyTA—Journal of Food. 2018;**16**(1):1003-1017. DOI: 10.1080/19476337.2018.1518343

[25] Sofi SA, Ayoub A, Jan A. Resistant starch as functional ingredient: A review. International Journal of Food Sciences and Nutrition. 2017;**2**(6):195-199. DOI: 10.1016/j.foodres.2010.02.004

[26] Keenan MJ, Zhou J, Hegsted M, Pelkman C, Durham HA, Coulon DB, et al. Role of resistant starch in improving gut health, adiposity, and insulin resistance. Advances in Nutrition. 2015;**6**(2):198-205. DOI: 10.3945/ an.114.007419

[27] Ma M, Wang Y, Wang M, Jane J-l, Du S-k. Physicochemical properties and in vitro digestibility of legume Starches. Food Hydrocolloids. 2017;**63**:249-255. DOI: 10.1016/j.foodhyd.2016.09.004

[28] Zhang B, Li H, Wang S, Junejo SA, Liu X, Huang Q. In vitro starch digestion: Mechanisms and kinetic models. In: Wang S, editor. Starch Structure, Functionality and Application in Foods.

*Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

Singapore: Springer Nature; 2020. pp. 151-167. DOI: 10.1007/978-981- 15-0622-2\_9

[29] Ren Y, Yuan TZ, Chigwedere CM, Ai Y. A current review of structure, functional properties, and industrial applications of pulse starches for valueadded utilization. Comprehensive Reviews in Food Science and Food Safety. 2021;**20**:3061-3092. DOI: 10.1111/ 1541-4337.12735

[30] Dona AC, Pages G, Gilbert RG, Kuchel PW. Digestion of starch: In vivo and in vitro kinetic models used to characterize oligosaccharide or glucose release. Carbohydrate Polymers. 2010;**80**(3):599-617. DOI: 10.1016/j. carres.2017.05.016

[31] Li Y, Xu J, Zhang L, Ding Z, Gu Z, Shi G. Investigation of debranching pattern of a thermostable isoamylase and its application for the production of resistant starch. Carbohydrate Research. 2017;**446-447**:93-100. DOI: 10.1016/j. carres.2017.05.016

[32] Suárez-Diéguez T, Pérez-Moreno F, Ariza-Ortega JA, López-Rodríguez G, Nieto JA. Obtention and characterization of resistant starch from creole faba bean (*Vicia faba* L. creole) as a promising functional ingredient. LWT. 2021;**145**:111247. DOI: 10.1016/j. lwt.2021.111247

[33] Yu W, Tao K, Gilbert RG. Improved methodology for analyzing relations between starch digestion kinetics and molecular structure. Food Chemistry. 2018;**264**:284-292. DOI: 10.1016/j. foodchem.2018.05.049

[34] Guo L, Xiao Y, Zhu C, Wang S, Du X, Cui B. In vitro enzymatic hydrolysis of amylopectins from rice starches. International Journal of Biological

Macromolecules. 2017;**105**:1001-1009. DOI: 10.1016/j.ijbiomac.2017.07.138

[35] Bertoft E. Understanding starch structure: Recent progress. Agronomy. 2017;**7**(3):56. DOI: 10.3390/ agronomy7030056

[36] Ai Y, Jane J-l. Understanding starch structure and functionality. In: Sjöö M, Nilsson L, editors. Starch in Food. 2nd ed. Ámsterdam: Woodhead Publishing Series in Food Science, Technology and Nutrition; 2018. pp. 151-178. DOI: 10.1016/B978-0-08-100868-3.00003-2

[37] Robyt JF. Enzymes and their action on starch. In: Be Miller J, Whistler R, editors. Starch, Chemistry and Technology Food Science and Technology. 3rd ed. London, United Kingdom: Academic Press; 2009. pp. 237-292. DOI: 10.1016/ B978-0-12-746275-2.00007-0

[38] Ambigaipalan P, Hoover R, Donner E, Liu Q, Jaiswal S, Chibbar R, et al. Structure of faba bean, black bean and pinto bean starches at different levels of granule organization and their physicochemical properties. Food Research International. 2011;**44**(9):2962- 2974. DOI: 10.1016/j.foodres.2011.07.006

[39] Dhital S, Shrestha AK, Gidley MJ. Relationship between granule size and in vitro digestibility of maize and potato starches. Carbohydrate Polymers. 2010;**82**(2):480-488. DOI: 10.1016/j. carbpol.2010.05.018

[40] Villas-Boas F, Facchinatto WM, Colnago LA, Volanti DP, Franco CML. Effect of amylolysis on the formation, the molecular, crystalline and thermal characteristics and the digestibility of retrograded starches. International Journal of Biological Macromolecules. 2020;**163**:1333-1343. DOI: 10.1016/j. ijbiomac.2020.07.181

[41] Walther B, Lett AM, Bordoni A, Tomás-Cobos L, Nieto JA, Dupont D, et al. GutSelf: Interindividual variability in the processing of dietary compounds by the human gastrointestinal tract. Molecular Nutrition & Food Research. 2019;**63**(21):1900677. DOI: 10.1002/ mnfr.201900677

[42] Date K. Regulatory functions of α-amylase in the small intestine other than starch digestion: α-Glucosidase activity, glucose absorption, cell proliferation, and differentiation. In: Takada A, editor. Metabolic Syndrome. London: IntechOpen; 2020. pp. 1-14. DOI: 10.5772/intechopen.92660

[43] Englyst KN, Liu S, Englyst HN. Nutritional characterization and measurement of dietary carbohydrates. European Journal of Clinical Nutrition. 2007;**61**(Suppl. 1):S19-S39. DOI: 10.1038/ sj.ejcn.1602937

[44] Zhang G, Hamaker BR. Slowly digestible starch: Concept, mechanism, and proposed extended glycemic index. Critical Reviews in Food Science and Nutrition. 2009;**49**(10):852-867. DOI: 10.1080/10408390903372466

[45] Toutounji MR, Farahnaky A, Santhakumar AB, Oli P, Butardo VM, Blanchard CL. Intrinsic and extrinsic factors affecting rice starch digestibility. Trends in Food Science and Technology. 2019;**88**:10-22. DOI: 10.1016/j. tifs.2019.02.012

[46] Raigond P, Ezekiel R, Raigond B. Resistant starch in food: A review. Journal of the Science of Food and Agriculture. 2015;**95**(10):968-1978. DOI: 10.1002/ jsfa.6966

[47] Ma Z, Boye JI. Research advances on structural characterization of resistant starch and its structure-physiological function relationship: A review. Critical

Reviews in Food Science and Nutrition. 2018;**58**(7):1059-1083. DOI: 10.1080/10408398.2016.1230537

[48] Ma Z, Hu X, Boye JI. Research advances on the formation mechanism of resistant starch type III: A review. Critical Reviews in Food Science and Nutrition. 2020;**60**(2):276-297. DOI: 10.1080/10408398.2018.1523785

[49] Frank J, Fukagawa NK, Bilia AR, Johnson EJ, Kwon O, Prakash V, et al. Terms and nomenclature used for plant-derived components in nutrition and related research: Efforts toward harmonization. Nutrition Reviews. 2020;**78**(6):451-458. DOI: 10.1093/ nutrit/nuz081

[50] Breyton AE, Goux A, Lambert-Porcheron S, Meynier A, Sothier M, VanDenBerghe L, et al. Starch digestibility modulation significantly improves glycemic variability in type 2 diabetic subjects: A pilot study. Nutrition, Metabolism, and Cardiovascular Diseases. 2021;**31**(1):237- 246. DOI: 10.1016/j.numecd.2020.08.010

[51] Caprnda M, Mesarosova D, Ortega PF, Krahulec B, Egom E, Rodrigo L, et al. Glycemic variability and vascular complications in patients with type 2 diabetes mellitus. Folia Medica (Plovdiv). 2017;**59**(3):270-278. DOI: 10.1515/folmed-2017-0048

[52] Sakamoto M. Type 2 diabetes and glycemic variability: Various parameters in clinical practice. Journal of Clinical Medical Research. 2018;**10**(10):737-742. DOI: 10.14740/jocmr3556w

[53] Hasek LY, Phillips RJ, Zhang G, Kinzig KP, Kim CY, Powley TL, et al. Dietary slowly digestible starch triggers the gut-brain axis in obese rats with accompanied reduced food intake. Molecular Nutrition & Food Research.

*Health Benefits of Starch DOI: http://dx.doi.org/10.5772/intechopen.101534*

2018;**62**(5):1700117. DOI: 10.1002/ mnfr.201700117

[54] Lambert-Porcheron S, Normand S, Blond E, Sothier M, Roth H, Meynier A, et al. Modulation of starch digestibility in breakfast cereals consumed by subjects with metabolic risk: Impact on markers of oxidative stress and inflammation during fasting and the postprandial period. Molecular Nutrition & Food Research. 2017;**61**(12):1700212. DOI: 10.1002/mnfr.201700212

[55] Khosroshahi HT, Abedi B, Ghojazadeh M, Samadi A, Jouyban A. Effects of fermentable high fiber diet supplementation on gut derived and conventional nitrogenous product in patients on maintenance hemodialysis: A randomized controlled trial. Nutrition & Metabolism (London). 2019;**16**:18. DOI: 10.1186/s12986-019-0343-x

[56] Halajzadeh J, Milajerdi A, Reiner Ž, Amirani E, Kolahdooz F, Barekat M, et al. Effects of resistant starch on glycemic control, serum lipoproteins and systemic inflammation in patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled clinical trials. Critical Reviews in Food Science and Nutrition. 2020;**60**(18):3172-3184. DOI: 10.1080/10408398.2019.1680950

[57] Cani PD, Delzenne NM. The role of the gut microbiota in energy metabolism and metabolic disease. Current Pharmaceutical Design. 2009;**15**(13):1546-1558. DOI: 10.2174/138161209788168164

[58] Sun H, Ma X, Zhang S, Zhao D, Liu X. Resistant starch produces antidiabetic effects by enhancing glucose metabolism and ameliorating pancreatic dysfunction in type 2 diabetic rats. International Journal of Biological

Macromolecules. 2018;**110**:276-284. DOI: 10.1016/j.ijbiomac.2017.11.162

[59] Zhou Z, Wang F, Ren X, Wang Y, Blanchard C. Resistant starch manipulated hyperglycemia/ hyperlipidemia and related genes expression in diabetic rats. International Journal of Biological Macromolecules. 2015;**75**:316-321. DOI: 10.1016/j. ijbiomac.2015.01.052

[60] Oikonomou E, Tsioufis C, Tousoulis D. Diabetes mellitus: A primary metabolic disturbance. Metabolomics underlying vascular responses to stress and ischemia? Clinical Science. 2020;**135**(3):589-591. DOI: 10.1042/CS20201299

[61] Hatting M, Tavares C, Sharabi K, Rines AK, Puigserver P. Insulin regulation of gluconeogenesis. Annals of the New York Academy of Sciences. 2018;**1411**(1):21-35. DOI: 10.1111/ nyas.13435

[62] Dong Y, Gao G, Fan H, Li S, Li X, Liu W. Activation of the liver X receptor by agonist TO901317 improves hepatic insulin resistance via suppressing reactive oxygen species and JNK pathway. PLoS One. 2015;**10**(4): e0124778. DOI: 10.1371/journal. pone.0124778

[63] Nuttall FQ, Ngo A, Gannon MC. Regulation of hepatic glucose production and the role of gluconeogenesis in humans: Is the rate of gluconeogenesis constant? Diabetes/Metabolism Research and Reviews. 2008;**24**(6):438-458. DOI: 10.1080/10408398.2020.1747391

[64] Guo J, Tan L, Kong L. Impact of dietary intake of resistant starch on obesity and associated metabolic profiles in human: A systematic review of the literature. Critical Reviews in Food Science and Nutrition. 2021;**61**(6):

889-905. DOI: 10.1080/10408398. 2020.1747391

[65] Maziarz MP, Preisendanz S, Juma S, Imrhan V, Prasad C, Vijayagopal P. Resistant starch lowers postprandial glucose and leptin in overweight adults consuming a moderate-to-high-fat diet: A randomized-controlled trial. Nutrition Journal. 2017;**16**(1):14. DOI: 10.1186/ s12937-017-0235-8

[66] Rebello CJ, Johnson WD, Pan Y, Larrivee S, Zhang D, Nisbet M, et al. A snack formulated with ingredients to slow carbohydrate digestion and absorption reduces the glycemic response in humans: A randomized controlled trial. Journal of Medicinal Food. 2020;**23**(1):21-28. DOI: 10.1089/ jmf.2019.0097

[67] Péronnet F, Meynier A, Sauvinet V, Normand S, Bourdon E, Mignault D, et al. Plasma glucose kinetics and response of insulin and GIP following a cereal breakfast in female subjects: Effect of starch digestibility. European Journal of Clinical Nutrition. 2015;**69**(6): 740-745. DOI: 10.1038/ejcn.2015.50

#### **Chapter 5**

## Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers

*Saleem Siddiqui, Naseer Ahmed and Neeraj Phogat*

#### **Abstract**

Potato is among the widely grown crop of the world. It is likely that a large portion of the crop is consumed fresh but majority of it is processed into various products, starch being the predominant one. Starch can greatly contribute to the textural properties of many foods and is widely used in food industry as raw material. Since raw potatoes are perishable and accessible only for few months of the year, the food and starch industry has to rely on stored potatoes during off-season. The various varieties of the crop available in the region, storage conditions, pre and post-storage treatments given to the tubers, packaging materials used, etc. are influencing the physical, chemical and functional characteristics of starch extracted from it. The extraction technology from tubers is also having a significant effect on the quality of starch. The knowledge of physical, chemical and functional characteristics of potato starch as affected by varieties, storage treatments and conditions of tubers will help in ensuring uniform and desirable quality of starch for food industry and also provide information for breeding programs and developing the proper postharvest management practices of potatoes.

**Keywords:** curing, extraction methods, functional properties, packaging potato starch, sprout suppressants, storage conditions, varieties

#### **1. Introduction**

Potato (*Solanum tuberosum* L.) is the most important food crop in the world after wheat, rice, and maize. UNESCO (United Nations Educational, Scientific and Cultural Organization) declared potato as the food of the future during the 'International Year of Potato 2008' and stated potato as the third most important world food crop. Potato production increased significantly in India during the last six decades and it became the second-largest producer of potatoes after China [1]. Potatoes contain 70–80% water, 16–24% starch (85–87% dry mass), and trace amounts of proteins and lipids [2].

Potatoes are a perishable crop, and due to insufficient, expensive, and widely dispersed refrigerated storage facilities, there are frequent instances of market oversupply, resulting in significant economic damage to farmers and agricultural wastage. Various storage treatments and technologies have been proposed to extend the shelf life of potato tubers. Because raw potatoes are accessible only for few months of the year, the food and starch industry has to rely on stored potatoes during off-season. A proper storage climate helps keep potatoes in excellent condition by avoiding excessive weight loss, microbial spoilage, sprout development, and quality degradation. Potatoes are often stored in long-term postharvest cold storage (8–12°C, 85–90% RH) to retard physiological processes and extend shelf life. Maintaining low temperatures during the storage time is dependent on the tubers' intended usage

Prolonged storage of potatoes requires sprout inhibition either by use of irradiation or sprout inhibitor chlorpropham (CIPC, isopropyl 3-chlorocarbanilate) treatment [3, 4] or the usage of heat treatment [5]. The CIPC alternatives for sprout inhibition are maleic hydrazide (MH), 1,4-Dimethylnaphthalene, and ethylene [6]. Heat treatment, essential oils of some herbs and spices—also effectively reduce sprouting and can be applied to organically grown potatoes [7, 8]. The sprout inhibiting treatments besides affecting the physiology of tubers also alter the properties of starch [9].

Starch plays a major role in the sensory characteristics of a wide variety of foods and is extensively used in agro-industrial applications as a thickener, colloidal stabilizer, gelling agent, bulking agent, and water retention agent. Because of the higher granule size and purity of potato starch, as well as the amylose and amylopectin chain lengths and the presence of phosphate ester groups on amylopectin, it stands apart from other cereal starches (corn, wheat, rice, etc.). Potato starch is an excellent texture stabiliser and regulator in food production systems.

The adaptability of starch in a wide range of food items makes it a hot topic among researchers studying carbohydrate polymers. As the genetic basis of the starch changes, so do its physicochemical attributes and functional features, as well as how unique they are in different foods and drinks [10]. Even within the same botanical species, cultivars of the same plant grown in different environments and cultural settings have vastly different starch structures and functions. This diversity results in a wide variety of starches with varying cooking, textural, and rheological characteristics that are linked to their physicochemical, morphological, and thermal properties. The following sections of the chapter deal with the starch characteristics as influenced by extraction methods, cultivars, curing, sprout inhibitors and storage conditions of potato tubers.

#### **2. Effect of extraction methods**

Depending on the plant source and intended application for the starch, several techniques can be used to extract it. Different researchers have utilized a variety of extraction methods to separate starch, including steeping periods, extraction temperatures, chemical concentrations and nature, enzymes, and so on. The chemical composition and physical characteristics of starch are both influenced by the extraction processes. To procure a pure product with maximum yield and recovery, lowest cost, and application of a series of interrelated stages allowing the non-starchy fraction to be removed without affecting the granule native structure and minimal incidence on its physico-chemical and mechanical properties, selecting an appropriate starch extraction method is desirable.

The chemical and physical characteristics of starch are altered throughout the extraction process. According to Neeraj *et al*. [11], water temperature affected

#### *Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

potato tuber starch extraction. Extraction temperatures of 30°C and 60°C produced improved starch yields, water absorption capacity (WAC), and whiteness. The use of 0.25% NaOH for chemical extraction increased WAC while decreasing ash content. The combination of sodium dodecyl sulphate (SDS) and mercaptoethanol (ME) to remove lipids increased amylose and starch purity while reducing amylopectin, moisture, and fat. Whiteness values were greater in the extraction employing NaOCl bleaching agent, while starch yields were higher in the enzymatic extraction by cellulose. The combination treatment of NaOH, SDS-ME, Na-hypochlorite and cellulase produced significantly higher starch yield and WAC than the simple cold water extraction method. It also resulted in significantly higher swelling power and solubility, light transmittance and whiteness, as well as trough and final viscosity of the extracted starch.

The different extraction techniques resulted in varying proportions of tiny and big starch granules. The Na-bisulphite treatment had the highest percentage of smallsized particles, whereas the other methods had no noticeable variations in particle size. Intact starch granules with smooth surfaces were found in the water-treated starch, but granules of starch treated with Na-bisulphite or propanol-water had somewhat rough and pitted surfaces, as well as fractures inside the granules (**Figure 1**) [11]. Lin *et al*. [12] reported that alcohol treatment caused not only the disappearance of 'Maltese cross' pattern in the center of granule but also the occurrence of cracks inside the granule. Betancur *et al.* [13] observed that Na-bisulphite treatment resulted in acid hydrolysis, with the hydroxonium ion attacking the glycosidic oxygen atom and hydrolyzing the glycosidic linkage, altering the physicochemical properties of starch and causing the formation of some cracks on the starch surface.

Phosphorus is present as phosphate monoesters and phospholipids in potato starches [14]. Phosphorus alters the functional characteristics of starches, which is significant both technologically and nutritionally. The phosphate monoesters are covalently linked to the starch's amylopectin portion. The majority of the phosphate groups are covalently linked to the amylopectin fraction at the C-6 (70%) and C-3 (30%) locations of the glucose units. It has been demonstrated that the phosphate concentration of starches has an effect on their physicochemical qualities and end applications, including starch pasting capabilities, gel strength and clarity, stickiness and viscosity [15]. Neeraj *et al*. [11] reported that starch extracted by water had higher, while extracted by Na-hypochlorite lower phosphorus content. The decrease in phosphorus content by Na-hypochlorite (NaOCl) was attributed to acid hydrolysis of amylose and amylopectin chains, reducing the ash content of starch and hence its mineral content. NaOCl may have caused oxidative degradation of amylopectin and amylose chain and thereby reducing the phosphorus content [16].

#### **Figure 1.** *Effect of various methods of extraction on potato starch granule (source: [11]).*

The variations in WAC between different starches are attributable to the degree to which water binding sites are available in their granules. The hydroxyl groups and inter-glucose oxygen atoms are thought to be the binding sites. The capacity of these starches to interact with water is determined by their ultrastructural (molecular arrangement, amorphous and crystalline regions) and compositional variations (primarily amylose and amylopectin). The capacity of commercial starches to bind water is critical to the quality and texture of some food items because it protects them from effects such as syneresis, which can occur during retorting or freezing [15]. It has been reported that different extraction techniques significantly affected WAC of potato starch. The alkali treatment with NaOH resulted in a greater WAC, but the NaOCl extraction technique resulted in a lower WAC [11, 17]. The increased WAC in alkali treated starch might be due to ions (Na+ ) diffusing into the amylose-rich amorphous areas of the granules, destroying intermolecular interactions, altering the starch's crystalline structure, and leading the granules to absorb more water [18, 19]. Fat and protein that are located on the surface of starch granules are crucial for maintaining its structural stability [20]. Additionally, their presence has been demonstrated to significantly slow the rate of starch retrogradation [21]. Lipids have also been observed to form complexes with amylopectin's outer branches, therefore inhibiting starch retrogradation. It has been reported by Neeraj *et al* [11] that different extraction techniques have an effect on the protein and fat content of potato starch. The combined treatment of NaOH, SDS-ME, Na-hypochlorite and cellulose resulted in low protein content, but the cold water extracted potato starch had high protein content. The decreased protein content seen in combination treatment may be a result of the alkali, SDS, and protease present. Because NaOH is an excellent solvent and can solubilize the main protein enclosing the starch, alkaline steeping technique softens the protein-starch matrix, resulting in a starch deficient in protein and lipids [22]. SDS treatment was also found to be effective in removing the protein and lipids from the surface of starch granules [20].

Different extraction treatments resulted in significant variations in swelling power and solubility index of the extracted starch. Neeraj *et al*. [11] reported that the swelling power and solubility were maximum for starch extracted by NaOH, while it was minimum in Na-bisulphite. Wang and Wang [23] reported that NaOH treatment caused the removal of protein and lipids from the surface of the starch granules and then allowed the starch granules to swell more and open up the small pores or crevices on the granule surface. Sajeev and Moorthy [24] reported that reduced swelling power of sulphite-treated starches may be owing to the fact that sulphite interacts stoichiometrically with oxygen (2 moles of sulphite to 1 mole of oxygen), forming sulphite free radicals and the superoxide ion (˙O2 -).

The freeze-thaw stability (syneresis) of starch is a helpful indication of its retrograde tendency. Syneresis is a critical characteristic that is used to determine a starch's capacity to survive unfavourable physical changes that occur during freezing and thawing. Extraction procedures also have a major influence on syneresis. Neeraj *et al* [17] reported that the maximum synerisis was observed in potato starch extracted by Na-bisulphite and minimum in starch extracted by combined treatment of NaOH, SDS-ME, Na-hypochlorite and cellulose. The enhanced syneresis induced by starch following Na-bisulphite treatment may be attributed to the acid-thinning process increasing the fraction of linear chain starch in the sample, which enhanced the inclination to retrograde.

Granule swelling, granule remnants, leached amylose and amylopectin, as well as the molecular weights and chain lengths of amylose and amylopectin, have all been

*Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

reported to vary with granule size, resulting in the development of turbidity and reduced light transmittance in refrigerated starch pastes [25]. It has been reported by Neeraj *et al.* [11] that the potato starch extracted by Na-hypochlorite treatment showed higher transmittance than native starch because the oxidized starch had a lower tendency for molecular re-association. The presence of hydrophilic functional groups in oxidised starches, particularly carboxyl groups, may account for the increased transmittance. It can also be ascribed to the chemical replacement of carbonyl and carboxyl functional groups for the hydroxyl groups in starch molecules, leading to repulsion between neighbouring starch molecules and decreased inter-chain interaction, allowing for increased transmittance [26].

#### **3. Effect of potato varieties on starch**

Tuber starches from different potato breeds vary in terms of crystallinity, granule shape, and other physical and chemical characteristics. The reactivity of the starches in various potato genotypes varied significantly [27]. The accumulation of starch in potatoes is genotype- and environment-dependent, as well as genotype-environment interaction dependent [28]. Due to the variations in tuber development rates amongst cultivars, the harvest dates and hence the dry mater accumulation varied for different potato cultivars. Early maturing cultivars showed lower dry matter content and a lower starch content than late maturing types. Kufri Chipsona-4 produced the most, followed by Kufri Badshah, Kufri Sindhuri, and Kufri Bahar; and Kufri Pushkar produced the least amount of starch. Since Kufri Chipsona-4 is a medium to late maturing variety, it produced more starch than other cultivars [11].

Kaur *et al.* [29] screened 21 different potato varieties and reported lowest amylose content of 15.0% for Kufri Ashoka (Patna) and the highest of 23.1% for Kufri Badshah (Jalandhar) starch. Singh *et al.* [30] compared the starch amylose content among the potato varieties and reported that Kufri Jyoti starch had the highest amylose content, whereas Kufri Sindhuri starch had the lowest. The variations in amylose concentration across types of starch granules have been attributed to the activity of enzymes involved in the production of linear and branching components inside the starch granules during plant development [11].

Singh and Singh [31] reported that Kufri Badshah (KB) and Kufri Jyoti (KJ) starch paste showed higher light transmittance and lower turbidity values than Kufri Pukhraj (KP) potato starch pastes. Kaur *et al.* [32] observed that starches separated from varieties KJ and KB had lower transition temperatures (To; Tp and Tc), peak height indices (PHI), higher gelatinization temperature range (R) and enthalpies of gelatinization (∆Hgel) than KP. The swelling power, solubility, amylose content, and transmittance values of KJ and KB potato starches were found to be greater, whereas turbidity values were found to be lower. KP starch showed the highest WAC, while it was lowest for KJ starch, which can be attributed to the variation in granular structure and loose association of amylose and amylopectin molecules. Singh and Kaur [33] reported that large-size fractions from Kufri Sutlej (KS) and Kufri Jyoti (KJ) starch showed the highest retrogradation, while the same fraction from Kufri Chandermukhi (KC) starch showed the lowest retrogradation.

The water absorption capacity (WAC) has been reported to be different for the starches extracted from different varieties. Singh and Kaur [33] reported that Kufri Chandermukhi small granule fraction showed the highest WAC as compared to Kufri Sindhuri and Kufri Jyoti. Kaur *et al.* [29] observed that pasting temperature (PT) of

different potato starches ranged from 64.5 to 69.5°C, the highest for Kufri Sindhuri and the lowest for Kufri Bahar. Neeraj *et al.* [11] maximum WAC in Kufri Chipsona-4 followed by Kufri Sindhuri, while it was minimum in Kufri Badshah. Differences in WAC across cultivars may be related to their starch's amylose and amylopectin levels. Additionally, it can be ascribed to granular structural variation. The presence of a significant number of phosphate groups on the amylopectin molecule may help explain the variations in WAC between starches isolated from various potato types [34].

The phosphorous content of extracted starch was found to be different for different potato varieties. It was minimum in Kufri Pushkar followed by Kufri Sindhuri, while it was maximum in Kufri Chipsona-4 [11, 17]. Pineda-Gomez *et al.* [35] studied the starch of potato cultivars growing in the Andean region in the south of Colombia. It was observed that the apparent amylose and phosphorus concentrations of starches extracted from Mambera, Ratona, and Pastusa cultivars of potato were much greater than those recovered from Unica and Roja-huila. Kaur *et al* [29] reported that the phosphorus content of starch granules is positively linked with the phospholipid concentration. Phospholipids are often abundant in phosphorus-rich starch granules, either adhering to their surface or enclosed within.

There were marked differences in swelling power (SP) of extracted starch from different potato varieties. It was maximum in Kufri Chipsona-4 followed by Kufri Bahar, while it was minimum in Kufri Badshah [11, 17]. Additionally, it was observed that Kufri Chipsona-4 included the least amylose and the most phosphorus, indicating a greater swelling power; however, Kufri Badshah contained the most amylose and the least phosphorus, indicating a lesser swelling power. The difference in SP between starches from various potato cultivars indicates that the affective bonding forces between granules are stronger in certain. The swelling ability of starch is directly proportional to its amylopectin concentration, since amylose functions as a diluent and swelling inhibitor.

Starches' swelling ability and solubility are strongly linked. Neeraj *et al.* [11] reported that maximum solubility was for the starch extracted from Kufri Chipsona-4 followed by Kufri Pushkar, while it was minimum in Kufri Badshah. The variations in swelling power and solubility of the starches among different varieties can be attributed to the differences in granule size, amylose content, molecular structure of amylopectin and the crystallinity as well as the granule organization.

Neeraj *et al.* [11] observed maximum light transmittance in starch extracted from Kufri Chipsona-4 followed by Kufri Bahar, while it was minimum in Kufri Pushkar. Higher transmittance led to greater starch paste clarity. The clarity of the paste varied significantly depending on the starch source, amylose/amylopectin ratio, chemical or enzymatic changes, and solute inclusion. Potato cultivars with a substantial increase in transmittance may be used in the jelly, beverage, and fruit paste sectors to get the appropriate consistency.

Syneresis, or freeze-thaw stability, is a critical characteristic used to assess a starch's capacity to survive the undesired physical changes that occur during freezing and thawing. Syneresis was discovered to be least in starch extracted from Kufri Pushkar, followed by Kufri Bahar, and to be most in Kufri Chipsona-4 [11, 17].

Kaur *et al.* [32] reported that endothermic peaks for several potato cultivars ranged from 59.96 to 68.89°C, the peak temperature was 63.37–64.58°C, and the final temperature was 67.4–68.9°C.

*Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

#### **4. Effect of curing treatment of tubers**

Freshly harvested potatoes have very short shelf life due to thin skin. Curing is accomplished by holding potatoes in dark at ~22°C and RH 90% for 10—15 days. During curing potatoes utilize the reserved food material to provide energy and metabolites to heal bruises and cracks and to develop periderm layer making the peel thick and impermeable to water. The various changes taking place in the characteristics of extracted starch from different varieties of potato due to curing of tubers was studied in detail by Neeraj *et al* [11]. It was reported that curing of tubers resulted in decreased starch yield, amylose content, swelling power, and solubility; but increased phosphorus content, WAC, and light transmittance of the extracted starch. The lower starch content in cured potatoes compared to fresh potatoes may be due to its utilisation in the process of periderm layer formation [36]. Van Der Maarel *et al.* [37] reported a decrease in amylose content in cured potatoes as a result of increased activity of the debranching enzyme glucoamylase, which breaks the -1,6 glycosidic bonds present in amylose to form linear amylose. The amylase, pullulanase, glucoamylase, and isoamylase further breakdown amylose into sugars. The increased phosphorus concentration in cured tubers might be attributed to the poor starch recovery from cured tubers that resulted in a greater phosphorus content per unit of recovered starch. The greater WAC content of cured potato starch can be attributed to its reduced amylose and higher phosphorus content. Liu *et al.* [38] found a negative connection between WAC and amylose and a positive correlation between WAC and phosphorus in starches. Reduced swelling power, solubility, and light transmittance of cured potato starch were attributed to its decreased amylose and high phosphorus concentrations.

Curing did not significantly affect the size of the starch particles and syneresis [39]. The syneresis exhibited a significant positive correlation with amylose content. Though the amylose content was slightly reduced by curing, still the syneresis was not affected [11, 17]. This might be because the amount of the change in amylose concentration was too little to have a meaningful influence on syneresis, or because other variables such as crude fibre, fat, protein, and granular structure also playing a role in syneresis [18].

#### **5. Effect of sprout inhibiting treatments**

The sprout inhibiting treatments besides affecting the physiology of tubers also alter the properties of various biochemical constituents. CIPC, also referred as chlorpropham is the most commonly used sprout suppressant on potatoes when stored at 8–12°C. Potatoes can also be stored for at least 12 weeks at either 8 or 18°C without sprouting, if tubers are dipped in hot water (57.5°C and 20 or 30 min) [5, 40]. It was reported by Hu *et al.* [40] that there were no significant differences in the pasting properties and onset (*T*O), peak (*T*P) and endset (*T*E) temperatures of gelatinisation of sweet potato starch among heat treated (HWT) and non heat-treated samples. Peak viscosity decreased gradually and fluctuated around 310–357 RVU in variety Kanoya control samples, while it increased gradually and fluctuated around 209–308 RVU in Kanoya hot water treated samples, indicating that heat treatment reduced the peak viscosity of potato starch.

Potatoes treated with CIPC to inhibit sprouting contained greater amounts of total starch as well as resistant starch (RS) than untreated potatoes tubers [41]. Lu *et al.* [4] investigated potato varieties treated with CIPC and stored at 8°C for 5 months and found that the least shifting of gelatinization peaks to lower temperature for CIPC treated samples. Ezekiel and Singh [42] studied starch properties of potato cultivars treated with CIPC. Swelling volume of starch decreased significantly with CIPC in all varieties.

Neeraj [43] studied the effect of various sprout inhibiting treatments viz., hot water dip treatment (HWT, 57.5 ± 0.1°C for 20 min) and single spray of 50% formulation of CIPC treatments on the characteristics of starch extracted from Kufri Chipsona 4 variety of potato stored at low temperature (12 ± 1°C). It was observed that significantly higher starch yield was observed in CIPC treated tubers followed by hot water treatment and untreated. The CIPC treated tubers retained higher starch than other treatments until the end of the storage period, which can be attributed to inhibited sprouting and low respiration rates. Hot water treatment may also have resulted in higher starch yield because of its inhibitory role on sprouting of tubers. Kyriacou *et al.* [44] also observed that CIPC and HWT retained higher starch concentrations during the storage period.

There was no significant effect of HWT on particle size, however, CIPC treatment significantly increased the percentage of small size particles of starch from LT stored tubers [43]. Ezekiel *et al.* [45] reported that CIPC treated potatoes subsequently stored at 12°C for 90 days showed an increase in the proportion of small size granules. The granule diameter ranged from 18 to 25 μm.

The effects of CIPC and HWT were found to be non-significant with respect to untreated tubers for extracted starch's moisture content, protein content, fat content, crude fiber, ash content, purity, WAC and colour whiteness values; while starch yield, amylopectin, phosphorus content, swelling power, solubility, light transmittance and peak viscosity were higher for starch extracted from tubers treated with CIPC than HWT [43]. The nonsignificant effect on purity of starch was attributed to nonsignificant changes in moisture, fat, crude fibre, protein and ash contents of the starch extracted from tubers subjected to various sprout inhibiting treatments.

Hot water dip treated tubers resulted in significantly lower swelling power than untreated tubers at RT storage, however, significantly higher swelling power was observed in CIPC treated tubers stored at LT [43]. Additionally, Lu *et al.* [4] discovered that tubers treated with CIPC exhibited a greater swelling capacity of the extracted starch. The considerably increased phosphorus content of the CIPCtreated tuber starch might account for its relatively strong swelling power. The lack of internal structure produced by negatively charged phosphate ester groups inside starch granules has been attributed to potato starches' greater swelling potential [46]. Eerlingen *et al.* [47] attributed increased swelling power to the amorphous AM being transformed into a helical shape, increased contacts between AM chains, and altered interactions between crystallites and the amorphous matrix. The development of cross links in the amorphous area and consequent rise in crystallinity during HWT might possibly account for the decrease in swelling power and solubility of the extracted starch [48].

Significantly lower syneresis was observed in the starch extracted from CIPC treated tubers followed by HWT tubers and untreated tubers [43]. Singh *et al.* [14] reported that lower amylose content and high percentage of small size granules caused lower syneresis. Thus, lower amylose content and higher percentage of small size granules may be responsible for lower syneresis exhibited by the starch

*Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

extracted form CIPC treated potatoes. Hu *et al.* [49] reported that HWT reduced the setback viscosity value of sweet potato starch during storage that decreased its syneresis.

Verma *et al.* [50] observed that increasing gamma (γ) irradiation dosage resulted in a substantial drop in the apparent amylose content, swelling index, enthalpy of gelatinization, transition temperature, and overall crystallinity of the starches. Similarly, increasing the ionising dosage resulted in a substantial decrease in the pasting characteristics (peak, trough, setback, ultimate viscosity, and pasting temperature) of the extracted starches. On the contrary, the enhanced solubility index of the starch was caused by gamma irradiation. Irradiation treatment increased the total free glucose content of potato and lowered the starch thermal transition and pasting temperatures. Starch crystallinity reduced substantially in irradiation potatoes, which may account for the lower resistant starch concentration.

#### **6. Effect of storage conditions and packaging**

The starch content of potatoes has been reported to decrease during storage due to conversion of starch to sugar and its utilization in respiration [51]. The rate of starch depletion and sugar buildup vary with cultivar and storage temperature, presumably due to variations in enzyme activities [52]. Johnston *et al.* [53] observed an increase in amylose to amylopectin ratio in the starch granules during storage of tubers. Golachowski [54] studied the properties of starch separated from potato tubers stored at 20°C, 8°C, 4°C and 0°C. The study included also potato tubers having been frozen, thawed and refrozen as well as potato tubers before storage. Starch separated from the stored potato tubers showed differences in chemical composition, reducing power, granularity, whiteness and viscosity as well as gelatinization temperatures in comparison with the starch separated from potato tubers before storage. Ridley and Hogan [55] reported a reduction in the viscosity of starch isolated from potatoes that were stored at 1.7 and 7.2°C for three months. Peak viscosity was reduced after 90 days of storage at 8°C but increased at 16°C, with no significant change at 4 or 12°C. Separated starches from potatoes kept at a higher temperature demonstrated increased transition temperatures and decreased pasting temperatures, and vice versa. Separated starch from potatoes kept at 8°C exhibited increased peak, trough, and breakdown viscosity, as well as a reduced setback. After storage at 4, 8, and 20°C, the fraction of large size granules decreased and the proportion of smaller granules increased.

Cottrell *et al.* [56] investigated the physicochemical properties of starch produced from several potato cultivars and kept at temperatures of 4, 8, 10, and 20°C. At harvest, the surface of the starch granules was smooth but during storage the surface of the granules became progressívely more pitted. Potato starches kept at 4°C had reduced To, Tc, and Hgel values, as well as lower transmittance values. The peak viscosity and setback of starches isolated from potatoes stored at a higher temperature (20°C) were the greatest.

Kaur *et al*. [57] reported that the starches extracted from potatoes kept at 4°C had significantly greater proportion of tiny granules, pitted with rougher surfaces lower commencement and conclusion gelatinization temperatures than those held at 8 and 20°C.

Ezekiel *et al.* [52] detected a substantial reduction in the amylose content of starch with increase storage period of tubers. Separated starch from potatoes that had been

kept at a higher temperature demonstrated a lower pasting temperature. Potato starch kept at 8°C had a larger peak, trough, and breakdown viscosity, as well as a lower setback. Peak viscosity rose as storage temperature increased, whereas swelling volume dropped. After 90 days of storage of tubers at 4°C, a substantial decrease in swelling volume but no significant changes in phosphorus content of the extracted starch were observed.

Neeraj [43] reported that as the storage time for tubers increased, the moisture, fat, ash, crude fibre, amylopectin, phosphorus, water absorption capacity, light transmittance, and peak viscosity of the extracted starch increased; while yield, purity, amylose, swelling power, solubility, syneresis, and colour whiteness value decreasedIt has been reported that pastes prepared from potato starches with higher percentages of small granules exhibit lower syneresis. The decrease in syneresis of starch extracted from stored tubers could be due to the decreased amylose, and increased amylopectin, phosphorus and percentage of small size particles [17, 18].

Neeraj [43] reported that the starch extracted from the tubers stored at low temperature (LT) with different packaging viz., nylon mesh bags or MAP or vacuum did not show significant differences in its moisture, fat, protein, ash, crude fiber, purity, amylose, amylopectin, WAC, swelling power and whiteness values; while minimum syneresis and maximum starch yield, phosphorus content, solubility, light transmittance and peak viscosity were observed for starch extracted from tubers packed in net bags followed by vacuum and modified atmosphere packaging. Significantly higher peak viscosity of starch was observed for starch extracted from net bag packed tubers followed by vacuum, while it was minimum in modified atmospheric packaging. The various packaging methods did not significantly affect the starch yield from tubers stored at room temperature, however, for tubers stored at low temperature, maximum starch yield was observed for tubers packed in net bags, while modified and vacuum packed tubers were showing at par but lower starch yields. Similarly, it was reported by Mare and Modi [58] that Taro cormels of Dumbe-dumbe and Pitshi packaged in mesh bags also displayed higher starch content compared with those packaged in polyethylene bags and boxes.

#### **7. Conclusion**

The growing starch markets have led to food industries to a constant demand for starches with specific properties that meet the demands of applicability. The quality of extracted starch form potato tubers, however, are significantly affected by environmental, cultural and storage conditions. The available information of the various physico-chemical and functional characteristics of potato starch as affected by extraction methods, varieties, curing, sprout inhibitors, and storage conditions. Some more information still need to be generated with respect to the effect of preharvest cultural practices, organic raising, extent of sprouting of tubers, application of other sprout suppressants (irradiation, isopropyl phenylcarbamate, ozone, ethylene, MH, carvones, etc) and various storage structures on the quality of extracted potato starch. The information w.r.t. verities may be helpful in identifying phenotyping trait(s) in potato breeding processes to create special potato genotypes for manufacturing of starch with the characteristics specially tuned for certain industrial processing technologies. On the basis of information, the potato starch industry may also select specifically pre- and postharvest treated stored potatoes of a given variety for extracting starches having the desired functional characteristic.

*Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

#### **Acronyms and abbreviations**


### **Author details**

Saleem Siddiqui1 \*, Naseer Ahmed2 and Neeraj Phogat3

1 School of Agricultural Sciences, Sharda University, Greater Noida, Uttar Pradesh, India

2 Department of Food Technology, DKSG Akal College of Agriculture, Eternal University, Baru Sahib, Himachal Pradesh, India

3 Centre of Food Science and Technology, CCS Haryana Agricultural University, Hisar, Haryana, India

\*Address all correspondence to: saleem.siddiqui@sharda.ac.in

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

### **References**

[1] FAO. FAOSTAT Statistical Database. Rome: FAO; 2019

[2] Huang C-C, Lin M-C, Wang C-C. Changes in morphological, thermal and pasting properties of yam (*Dioscorea alata*) starch during growth. Carbohydrate Polymers. 2006;**64**(4): 524-531

[3] Paul V, Ezekiel R, Pandey R. Sprout suppression on potato: Need to look beyond CIPC for more effective and safer alternatives. Journal of Food Science and Technology. 2016;**53**(1):1-18

[4] Lu Z-H, Donner E, Yada RY, Liu Q. Impact of γ-irradiation, CIPC treatment, and storage conditions on physicochemical and nutritional properties of potato starches. Food Chemistry. 2012;**133**(4):1188-1195

[5] Ranganna B, Raghavan G, Kushalappa A. Hot water dipping to enhance storability of potatoes. Postharvest Biology and Technology. 1998;**13**(3):215-223

[6] Boivin M, Bourdeau N, Barnabé S, Desgagné-Penix I. Sprout suppressive molecules effective on potato (*Solanum tuberosum*) tubers during storage: A review. American Journal of Potato Research. 2020;**97**:1-13

[7] Frazier MJ, Olsen N, Kleinkopf G. Organic and Alternative Methods for Potato Sprout Control in Storage. University of Idaho Extension, Idaho Agricultural Experiment Station; 2004

[8] Aina AJ, Falade KO, Akingbala JO, Titus P. Physicochemical properties of Caribbean sweet potato (*Ipomoea batatas* (L) Lam) starches. Food and Bioprocess Technology. 2012;**5**(2):576-583

[9] Ezekiel R, Singh B, Kumar D, Mehta A. Processing quality of potato varieties grown at two locations and stored at 4, 10 and 12°C. Potato Journal. 2007;**34**(3-4):164-173

[10] Villarreal ME, Ribotta PD, Iturriaga LB. Comparing methods for extracting amaranthus starch and the properties of the isolated starches. LWT-Food Science and Technology. 2013;**51**(2):441-447

[11] Neeraj P, Siddiqui S, Dalal N, Srivastva A, Bindu B. Effects of varieties, curing of tubers and extraction methods on functional characteristics of potato starch. Journal of Food Measurement and Characterization. 2021;**14**(6):3434-3444

[12] Lin J-H, C-y L, Chang Y-H. Change of granular and molecular structures of waxy maize and potato starches after treated in alcohols with or without hydrochloric acid. Carbohydrate Polymers. 2005;**59**(4):507-515

[13] Betancur AD, Chel GL, Cañizares HE. Acetylation and characterization of *Canavalia ensiformis* starch. Journal of Agricultural and Food Chemistry. 1997;**45**(2):378-382

[14] Singh J, Singh N. Studies on the morphological and rheological properties of granular cold water soluble corn and potato starches. Food Hydrocolloids. 2003;**17**(1):63-72

[15] Xu X, Huang X-F, Visser RG, Trindade LM. Engineering potato starch with a higher phosphate content. PLoS One. 2017;**12**(1):e0169610

[16] Adebowale KO, Olu-Owolabi BI, Olawumi EK, Lawal OS. Functional properties of native, physically and

*Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

chemically modified breadfruit (*Artocarpus artilis*) starch. Industrial Crops and Products. 2005;**21**(3): 343-351

[17] Neeraj P, Siddiqui S, Dalal N, Srivastva A, Pathera AK. Physicochemical, morphological, functional, and pasting properties of potato starch as a function of extraction methods. Journal of Food Measurement and Characterization. 2021;**15**(3): 2805-2820

[18] Raj N, Dalal N, Bisht V, Dhakar U. Potato starch: Novel ingredient for food industry. International Journal of Current Microbiology and Applied Sciences. 2020;**9**(1):1718-1724

[19] Karim A, Toon L, Lee V, Ong W, Fazilah A, Noda T. Effects of phosphorus contents on the gelatinization and retrogradation of potato starch. Journal of Food Science. 2007;**72**(2):C132-C1C8

[20] Chan H-T, Bhat R, Karim AA. Effects of sodium dodecyl sulphate and sonication treatment on physicochemical properties of starch. Food Chemistry. 2010;**120**(3):703-709

[21] Wang S, Li C, Copeland L, Niu Q, Wang S. Starch retrogradation: A comprehensive review. Comprehensive Reviews in Food Science and Food Safety. 2015;**14**(5):568-585

[22] Palacios-Fonseca A, Castro-Rosas J, Gómez-Aldapa C, Tovar-Benítez T, Millán-Malo B, Del Real A, et al. Effect of the alkaline and acid treatments on the physicochemical properties of corn starch. CyTA-Journal of Food. 2013;**11**(Suppl. 1):67-74

[23] Wang L, Wang Y-J. Rice starch isolation by neutral protease and highintensity ultrasound. Journal of Cereal Science. 2004;**39**(2):291-296

[24] Sajeev M, Moorthy S. Swelling and viscometric characteristics of cassava starch settled in the presence of different chemicals. Trends in Carbohydrate Chemistry. 2000;**7**:117-125

[25] Perera C, Hoover R. Influence of hydroxypropylation on retrogradation properties of native, defatted and heat-moisture treated potato starches. Food Chemistry. 1999;**64**(3):361-375

[26] Lawal OS. Composition, physicochemical properties and retrogradation characteristics of native, oxidised, acetylated and acid-thinned new cocoyam (*Xanthosoma sagittifolium*) starch. Food Chemistry. 2004;**87**(2): 205-218

[27] Khlestkin V, Eltsov I. Different reactivity of raw starch from diverse potato genotypes. Molecules. 2021; **26**(1):226

[28] Mareček J, Frančáková H, Bojňanská T, Fikselová M, Mendelová A, Ivanišová E. Carbohydrates in varieties of stored potatoes and influence of storage on quality of fried products. Journal of Microbiology, Biotechnology and Food Sciences. 2021;**2021**:1744-1753

[29] Kaur A, Singh N, Ezekiel R, Guraya HS. Physicochemical, thermal and pasting properties of starches separated from different potato cultivars grown at different locations. Food Chemistry. 2007;**101**(2):643-651

[30] Singh N, Kaur L, Sandhu KS, Kaur J, Nishinari K. Relationships between physicochemical, morphological, thermal, rheological properties of rice starches. Food Hydrocolloids. 2006; **20**(4):532-542

[31] Singh J, Singh N. Studies on the morphological, thermal and rheological properties of starch separated from some Indian potato cultivars. Food Chemistry. 2001;**75**(1):67-77

[32] Kaur L, Singh N, Sodhi NS. Some properties of potatoes and their starches II. Morphological, thermal and rheological properties of starches. Food Chemistry. 2002;**79**(2):183-192

[33] Singh N, Kaur L. Morphological, thermal, rheological and retrogradation properties of potato starch fractions varying in granule size. Journal of the Science of Food and Agriculture. 2004;**84**(10):1241-1252

[34] Hoover R. Composition, molecular structure, and physicochemical properties of tuber and root starches: A review. Carbohydrate Polymers. 2001;**45**(3):253-267

[35] Pineda-Gomez P, González NM, Contreras-Jimenez B, Rodriguez-Garcia ME. Physicochemical characterisation of starches from six potato cultivars native to the Colombian andean region. Potato Research. 2021;**64**(1):21-39

[36] Smith O. Effect of cultural and environmental conditions on potatoes for processing. In: Talburt WF, Smith O, editors. Technology of Potato Processing. India: Medtech - A Division of Scientific International; 2018. p. 70-109

[37] Van Der Maarel MJ, Van der Veen B, Uitdehaag JC, Leemhuis H, Dijkhuizen L. Properties and applications of starchconverting enzymes of the α-amylase family. Journal of Biotechnology. 2002;**94**(2):137-155

[38] Liu Q, Weber E, Currie V, Yada R. Physicochemical properties of starches during potato growth. Carbohydrate Polymers. 2003;**51**(2):213-221

[39] Phogat N, Siddiqui S, Dalal N, Srivastva A, Bindu B. Effects of varieties, curing of tubers and extraction methods on functional characteristics of potato starch. Journal of Food Measurement and Characterization. 2020;**14**(6):3434-3444

[40] Hu W, Tanaka S-I, Hori Y. Effect of heat treatment on quality of sweet potato in wrapper type cold store during long-term storage. Japan: Journal of the Faculty of Agriculture-Kyushu University. 2004;**49**(1):129-138

[41] Vaughn KC, Lehnen LP. Mitotic disrupter herbicides. Weed Science. 1991;**39**(3):450-457

[42] Ezekiel R, Singh B. Effect of cooking and processing on CIPC residue concentrations in potatoes and processed potato products. Potato Research. 2007;**50**(2):175-184

[43] Neeraj P. Studies on starch isolated from potato subjected to various storage conditions [Ph.D. thesis (Food Science and Technology)], Hisar, Haryana, India: CCS Haryana Agricultural University; 2017

[44] Kyriacou MC, Gerasopoulos D, Siomos AS, Ioannides IM. Impact of hot water treatment on sprouting, membrane permeability, sugar content and chip colour of reconditioned potato tubers following long-term cold storage. Journal of the Science of Food and Agriculture. 2008;**88**(15):2682-2687

[45] Ezekiel R, Singh B. Changes in contents of sugar, free amino acids and phenols in four varieties of potato tubers stored at five temperatures for 180 days. India: Journal of Food Science and Technology-Mysore. 2007;**44**(5):471-477

[46] Kim YS, Wiesenborn DP, Orr PH, Grant LA. Screening potato starch for novel properties using differential scanning calorimetry. Journal of Food Science. 1995;**60**(5):1060-1065

*Potato Starch as Affected by Varieties, Storage Treatments and Conditions of Tubers DOI: http://dx.doi.org/10.5772/intechopen.101831*

[47] Eerlingen RC, Jacobs H, Block K, Delcour JA. Effects of hydrothermal treatments on the rheological properties of potato starch. Carbohydrate Research. 1997;**297**(4):347-356

[48] Sharma M, Yadav DN, Singh AK, Tomar SK. Rheological and functional properties of heat moisture treated pearl millet starch. Journal of Food Science and Technology. 2015;**52**(10):6502-6510

[49] Hu W, Jiang A, Jin L, Liu C, Tian M, Wang Y. Effect of heat treatment on quality, thermal and pasting properties of sweet potato starch during yearlong storage. Journal of the Science of Food and Agriculture. 2011;**91**(8):1499-1504

[50] Verma K, Jan K, Bashir K. γ irradiation of cowpea and potato starch: Effect on physicochemical functional and rheological properties. Journal of Food Processing & Technology. 2019;**10**:810

[51] Smith AM, Zeeman SC, Smith SM. Starch degradation. Annual Review of Plant Biology. 2005;**56**:73-98

[52] Ezekiel R, Rana G, Singh N, Singh S. Physico-chemical and pasting properties of starch from stored potato tubers. Journal of Food Science and Technology. 2010;**47**(2):195-201

[53] Johnston F, Urbas B, Khanzada G. Effect of storage on the size distribution and amylose/amylopectin ratio in potato starch granules. American Potato Journal. 1968;**45**(9):315-321

[54] Golachowski A. Properties of starch obtained from potato tubers influenced by various temperatures. Starch-Stärke. 1985;**37**(8):263-266

[55] Ridley S, Hogan J. Effect of storage temperature on tuber composition, extrusion force, and Brabender viscosity. American Potato Journal. 1976;**53**(10): 343-353

[56] Cottrell J, Duffus C, Mackay G, Allison M. Changes in the surface morphology of starch granules of the cultivated potato, *Solanum tuberosum* L. during storage. Potato Research. 1993;**36**(2):119-125

[57] Kaur A, Singh N, Ezekiel R, Sodhi NS. Properties of starches separated from potatoes stored under different conditions. Food Chemistry. 2009;**114**(4):1396-1404

[58] Mare R, Modi A. Taro corm quality in response to planting date and postharvest storage: I. Starch content and reducing sugars. African Journal of Agricultural Research. 2012;**7**(19): 3014-3021

#### **Chapter 6**

## Comparative Study of the Physiochemical Composition and Techno-Functional Properties of Two Extracted Acorn Starches

*Youkabed Zarroug, Mouna Boulares, Dorra Sfayhi and Bechir Slimi*

#### **Abstract**

Due to the increase of search for new promising ingredients with interesting properties to develop new industrial food products, the valorization of undervalued resources became a challenge. Considering this, various species of genus *Quercus* acorns represent new resources of highly-valued food ingredients such as starch which encourage its extraction and valorization in food industries. In this regard, collected data from the literature provide an evidence review on the physiochemical and techno-functional properties of different acorn starches extracted from Tunisian species, especially; *Quercus ilex* L. and *Quercus suber* L. The reported data on X-ray diffraction analysis are, also, discussed. Data highlighted the possibility of using the extracted *Quercus* starches to develop new functional food products and improve technological properties and shelf life of products solicited by consumers.

**Keywords:** acorn starch, physiochemical composition, techno-functional properties, X-ray diffraction analysis

#### **1. Introduction**

Genus *Quercus* acorns belong to the family *Fagaceae*, which includes several species such as *Quercus robur, Quercus petraea, Quercus suber, Quercus ilex*, and *Quercus pubescens* [1]. These species produce a widely known fruit, named acorns, which are of vital importance for both humans and animals. The acorn fruits composition varies with species and origin. Acorn fruits are good source of carbohydrates (starch), proteins, fats, minerals, essential amino acids, vitamins (mostly A and C), unsaturated fatty acids (oleic acid) and sterols [2]. The nutritional composition of acorn fruit is comparable to many cereal grains. Moreover, acorns are a good source of active compounds, such as phenolic acids, and flavonoids, with an interesting

antioxidant activity [1]. Acorns also contain a high content of tannic acid, a mild toxin giving them a bitter taste that can be removed by many methods such as soaking in water, boiling, or roasting [3]. Traditionally, acorns were used in the human diet, generally as flour for bread production, or as a coffee substitute beverage (after a roasting process) [4]. Recently, acorn fruit flour was included in many other food preparations such as pasta, biscuits, hot beverages, cakes, and cookies [5]. Among all the nutrients present in acorn fruit, starch was the predominant component with content ranging from 31 to 55% [1]. Thus, further interest must be given to acorn starch extraction and valorization. Starch is a biodegradable carbohydrate polymer which has been widely studied due to its availability, price, and extensive industrial use. Recent research has shown that acorn starch can be used as an ingredient for food and nonfood applications [6, 7]. Acorn starch was used in many industrial applications like in the cases of paper, plastics, textile, pharmaceutical, and cosmetic industries [8]. Also, starch is a raw material representing the principal component of many food formulations being responsible for important functional and textural properties and nutritional characteristics of the many food products [9]. Owing to its interesting properties such as high resistance and paste consistency, acorn starch can be used as thickening and stabilizing agents in food formulations [2, 7]. The chemical composition and physicochemical features of starch are mainly characteristic of their biological origin. Starch from all plant sources has many similar properties but they do also differ in many aspects. Variation in structure, crystallinity, chemical composition and functional properties of starch granules are depending on their botanical origin and growth conditions. For the selection of the specific use of acorn starch, it is necessary to understand the physicochemical and functional properties of extracted starches from various acorn species. From all the above, collected data related to the chemical and technological properties of acorn starches extracted from *Q. ilex* L. and *Q. suber* L. species as well as characteristics of other starches obtained from various botanical sources such as corn, potato and cassava are discussed to highlight the importance to valorize acorn starches and their potential applications. Thus, it will be interesting to valorize acorn known as a Tunisian under valuated resource by providing promising new ingredients to formulate new food products.

#### **2. Starch extraction methods**

Generally, fresh acorn fruits were manually collected from the North West of Tunisia. *Q. ilex* L. is abundant in Bizerte (north east of Tunisia) region, while, *Q. suber* L. is provided from the mountainous region of Ain Drahem from Jendouba in the north west of Tunisia. Due to their short shelf life, acron fruits are, first, handpeeled, dried in mild conditions and then milled into fine flour.

The extraction technologies of acorn starch consist of dry and wet methods. The use of dry methods is shown unsucceful for the elimination of protein, fat, and tannins from acorn flour, which need to use some other absorbents.

The acorn flour is used for starch extraction using different methods as alkaline washing, hot-water soaking, ultrasonic-assisted ethanol soaking and ultrasonicassisted hot-water soaking [10]. The three later methods lead to starch granules with similar internal structure. However, starch granules isolated using hot-water methods are complete and glossy with a few numbers of pits. It's important to know that the ultrasonic technology became the most effective in food applications compared with conventional technologies.

*Comparative Study of the Physiochemical Composition and Techno-Functional Properties… DOI: http://dx.doi.org/10.5772/intechopen.101562*

#### **3. Starch extraction yield**

Numerous studies have already been conducted on the starch yield of acorn species originating from countries all over the world. It is stated in previous studies that starch is the main component of acorns and usually constitute more than 50% of the kernel [11]. The yield of starch extracted from acorn species cultivated in Tunisia and other countries of the world as reported in different studies is presented in **Table 1**. The starch yield varied from 17.3 to 89.83% in acorn species. The starch content in *Q. ilex* L. and *Q. suber* L*.* were reported to vary from 48.93 to 89.83% [14] and 86.9 to 88.5% [12], respectively. The values indicated that acorn fruits are promising crops as an alternative source of starch. In general, the authors concluded that starch content in *Q. suber*. L is higher than that in *Q. ilex* L. reporting a starch yield of about 34.5% [7]. As it can be also seen from **Table 1** that *Quercus palustris Muenchh* [15] contain the lowest amount of starch (17.3%) as compared to other acorn species. Correia et al. [13] and Masmoudi et al. [17] reported values of 88.5% and 63% of starch content in the Portuguese and Tunisian *Q. suber* L. fruits.

Irinislimane and Belhaneche Ben semr [18] and Correia et al. [12] isolated starch from *Quercus Suber* L. acorns and observed a starch yield accounting 21% and 31.4%, respectively. The starch content in potatoes, tubers and roots are reported to vary from 75 to 80% and 75.4 to 77.4% [5], respectively.

This variability in the starch yield was due to the difference in plant species, cultivation climate, ripening stage, harvesting time of fruits, and extraction method used [7].

The obvious retained conclusion is that the high content of starch makes the *Quercus* species particularly *Q. suber* L. ideal for starch extraction and valorization in many food and nonfood industries applications. Besides, the content of starch in acorn flour gave it good functional characteristics related to starch such as viscosity, swelling, and gelling [17]. In fact, it is suggested that acorn starch might be used as thickening and stabilizing agent, owing to its high paste consistency [2]. Since this polysaccharide is present as resistant starch in a high percentage, it can be very useful as a prebiotic growth promoter, constituting a good alternative to other current prebiotic agents such as fructo-oligosaccharides, inulin, isomalto-oligosaccharides, polydextrose, and lactulose [19].

Several studies have examined the effect of different methods using both physical and chemical methods on acorn starch yield. Differences in starch content are


#### **Table 1.**

*Extraction methods and starch yield of various acorn species.*

observed using alcohols-based extraction, alkaline-based extraction, acetone-based extraction, hot-water soaking, ultrasonic-assisted ethanol soaking and ultrasonicassisted hot-water soaking [10].

#### **4. Physico-chemical composition**

The physico-chemical composition of acorn starch extracted from *Quercus* species is affected by extraction and purification methods and the origin of raw materials [7]. The extracted acorn starch contained water and minor components such as lipids, proteins and ash (**Table 2**). The moisture content of acorn starch species varies from 7.22 to 15.91%. The moisture content of *Q. ilex* L. extracted starch from four different areas in Algeria varied from 2.2% to 15.9% [14]. The moisture content is very important parameters for the determination of the starch quality. A low moisture content of the acorn starch less than 20% is acceptable for commercial starch and a value less than 13% is recommended for safe storage [9]. Such values are close to those reported in cereal (10–12%) and some roots and tubers (14–18%) starches [20].

Several studies show low lipids, proteins, and ash contents in starches extracted from different acorn species.

Lipids have an essential role in the properties of starch, which is associated with the textural properties of various foods. The lipid content in all starches extracted from *Quercus* species is below 1%. Tunisian *Q. ilex* L. starch contains a high amount of lipid content (0.51%) than both potato and wheat starches [21].

The ash content of the extracted starch from *Q. ilex* grown in Tunisia (20.66%) is relatively high. The review of Taib and Bouyazza, [5], reported ash values ranged from 0.01 to 1.41% in different *Quercus* species. The low ash content illustrates the purity of starch after the extraction and isolation processes. The protein contents of starches obtained from different *Quercus* species ranged from 0.25 to 1.05%. These low values show a high extracted starch purity and quality [7]. The pH values in *Q. suber* was about 5.6 units, while it ranged between 4.73 and 6.43 units in *Q. ilex* starches. Such value is lower than that (6.22 units) reported for the potato starch [22]. High pH value could lead to undesirable protein modification as well as molecular


*L\*, a\* and b\* are the color parameters.*

#### **Table 2.**

*Physico-chemical composition of acorn species starches.*

*Comparative Study of the Physiochemical Composition and Techno-Functional Properties… DOI: http://dx.doi.org/10.5772/intechopen.101562*

cross linkage and rearrangements resulting in the formation of toxic compound [23]. A positive correlation was obtained between the pH value, the fat and the protein contents [24]. The variation observed in the chemical composition of starches is assigned to the extraction and purification methods, environmental conditions (climate and soil composition), growth stage of plant and genotype. During different seasons of the year (summer and autumn), protein and fat contents vary in four collected acorn species (*Q. suber*, *Q. ilex*, *Q. faginea* and *Q. pyrenaica*) [25]. From these findings, we conclude that the chemical content of starches is influenced by the botanical source and the extraction methods used.

Concerning the color parameters, the extracted starches from Tunisian *Quercus* species exhibited a slightly yellow-white color. Indeed, extracted *Q. ilex* L. starch showed a high lightness L\* value (85.03) [7] compared to the *Q. suber* L. (61.13). While, the obtained values of a\* (0.52) and b\* (10.2) were lower than those found in *Q. suber*. L (0.84 and 15.07, respectively) [7]. These findings showed that acorn fruit is a good source of starch that can be used in food industry without the necessity of chemical or genetic modifications. This polysaccharide may be industrially applied as emulsifiers, stabilizers, and thickeners in food as well as prebiotic growth promoter [26].

#### **5. Swelling power, solubility and water absorption**

When starch is heated in excessive amount of water, its crystalline structure is disrupted, and water molecules become linked by hydrogen bonding to the exposed hydroxyl groups of amylose and amylopectin [5]. These phenomena results in the swelling, solubility and increasing volume of starch granules. The swelling power, solubility, and water absorption values of extracted acorn starches from *Q. ilex* and *Q. suber* species are presented in **Table 3**. These parameters increased progressively with the increase of temperature from 60 to 90°C. The solubility of the extracted *Q. ilex* starch is higher than that of *Q. suber*, and ranged from 0.2 to 12.95% at 60°C and 4–64.22% at 90°C.

However, the swelling power and the water absorption values are lower in *Q. ilex* starch compared to the *Q. suber* starch. Diversity in swelling, solubility and water absorption of acorn starches has been observed. Boukhelkhal and MoulaiMostefa. [14] reported low solubility and swelling power of four species of acorn starches at temperature of 90°C ranging from 4 to 14% and 11 to 13 g/g, respectively. Values related to the swelling power are low compared to those found by Singh et al. [27] and Elmi Sharlina


#### **Table 3.**

*Swelling power solubility and water absorption of acorn species starches.*

et al. [22] on sweet potato starch (35 to 40 g/g) and chestnut starches (13.6–17.3 g/g), respectively. These low values are attributed to the amylose content of the acorn starch species [28], starch molecule's ability to hold water, hydrogen bonding, and the degree of crystallinity [29]. According to Jiang et al. [30], the solubility values of starches extracted from five different *Dioscorea* L. species, which are *D. opposite Thunb, D. alata Linn, D.nipponica Makino, D. bulbifera Linn* and *D.septemloba Thunb*, varied from 11.14 to 30.04% at the temperature of 95°C. A comparative study showed that swelling power and solubility of acorn starch at 90°C were higher than those of black wheat, buckwheat, coix and naked oat starches and lower than those of corn, jiaoyu, kuzhu, and longya lily starches [31].

The solubility suggests that additional interactions may have occurred between amylose-amylose and amylopectin-amylopectin chains [32]. Concerning, the water absorption capacity of starch, it corresponds to the hydrogen bonding between water molecules and hydroxyl groups in the starch molecules and starch chains as well as diversification of the starch granule structures [33]. In general, the starch extraction methods have important effect on swelling power, water absorption and solubility parameters of starch. Zhang et al., [10] reported a relatively higher value of swelling power (24.99 g/100 g) and solubility (15.22%), at temperature of 90°C, in acorn starch extracted by an ultrasonic-assisted ethanol soaking method. Variation of these parameters in extracted starches is associated to various factors such as: amylose content, granule size, structure of starch granules, viscosity patterns, and presence of non-starch compounds (lipids, ash and proteins) [5].

#### **6. Refrigeration and freezing stability**

In order to evaluate the stability of starch during storage, it was necessary to verify the expulsion of water, expressed by syneresis, contained in gels as a consequence of the reorganization of starch molecules [34]. Collected syneresis values during refrigeration and freezing time are grouped in **Table 4**. Results showed that *Q. suber* starch lost less water than the *Q. ilex* starch under refrigeration (4°C) with the increase of the storage time. However, the latter presents higher syneresis values already from the first freeze time, showing low stability to freezing under the conditions used in the studies and a richness in amylose content [9]. It is known from the literature, that starches with high amylose content such as potato (20.1–31.0%), maize (22.4–32.5%), taro (28.7–29.9%), and cassava (18.6–23.6%) present high syneresis, due to the large amount of water expelled during the retrograding process [25]. It known that during freezing of the starch paste, the cohesive portion of the starch formed a layer and the rest separated into a water layer.


#### **Table 4.**

*Refrigeration and freezing stability of acorn species starches.*

*Comparative Study of the Physiochemical Composition and Techno-Functional Properties… DOI: http://dx.doi.org/10.5772/intechopen.101562*

#### **7. X-ray diffraction analysis**

Starch is a semi-crystalline material affected by amylose content and amylopectin chain length that consists of amorphous and crystalline regions. The amylose content directly affects the crystallinity degree of the starch, such that when there is a lack of amylose content, the crystallinity degree increases, whereas the longer chain amylopectin forms have a more stable crystalline structure [31].

Generally, starch is present in three different crystalline structures which are A-type, B-type, and C-type that depended essentially on the variety of starch source.

The difference between A- and B-types of starch granules is due to the arrangement of double helices. A-type starches form dense packing with four water molecules, whereas B-type starch is more open causing more water molecules (36 water molecules) to be located in the center of a hexagonal packing of helices. For this reason, it is indicated that the A-type is more stable and requires a higher temperature than B-type starch for gelatinization [31].

X-ray diffraction analysis was employed to observe the changes in the degree of crystallinity of starch as a result of gelatinization. **Figure 1** resume the X-ray diffraction patterns observed on acorn starches extracted from *Q. suber* and *Q. ilex*. The X-ray diffraction patterns provide a classification of the two acorn starches under an A-type crystalline structure, which characterized most cereal starches [35] showing two strong reflections at 15.2° and 22.7°. The X-ray diffraction patterns of both acorn starches showed four intense diffraction peaks at 15.2°, 17.2°, 19.52°, and 22.7° of 2ϴ. The strong reflections at 15.2° and 22.7° of 2θ were classified as the A-type crystalline structure, which characterized most cereal starches [35]. The observed peaks at approximately 17.2° and 19.52° of 2θ were characterized as the B-type pattern. However, the C-type crystalline structure consisted of A- and B-type crystallites. Thus, the X-ray diffraction pattern can contain various superpositions of the characteristic diffraction peaks depending on the ratio between the contents of these polymorphs [35]. In general, cereal starches have an A-type pattern, whereas tuber starches display the B-type pattern, and certain roots and legumes starches show a C-type pattern [36]. Such results were close to those found on starch from *Quercus glandulifera* Bl. [37] and *Dioscorea pyrifolia* tubers [2]. Numerous studies have already

been conducted on the X-ray diffraction of starches extracted from acorn species originating from countries all over the world. Deng et al. [26] reported that acorn starch from china was B-type. A-type polymorph was reported for acorn starch [38]. However, Zhang et al. [10] and Molavi et al. [39] noted also a C-type polymorph in acorn starches. The difference in the diffraction pattern of starch granules was mainly influenced by genotypic, agronomic, and growing conditions such as temperature [7]. According to Dereje, [40] the type of crystallinity of the extracted starch was influenced by growth temperature, alcohols, fatty acids, and the chain length of amylopectin.

### **8. Conclusion**

Despite that acorns are underutilized fruits, they represent a good alternative source of starch. The acorn starch yield differs from one specie to another representing about 50%. It can be extracted using various methods. The acorn starch was characterized by a yellow color and good technological properties allowing its use during manufacturing of food products. Thus, acorn starch can represent an interesting functional ingredient capable to improve the properties of the final product.

### **Acknowledgements**

This work was supported by the Ministry of Higher Education and Scientific Research Tunisia and the Ministry of Agriculture, Water Resources and Fisheries, Tunisia.

### **Conflict of interest**

The authors declare no conflict of interest.

*Comparative Study of the Physiochemical Composition and Techno-Functional Properties… DOI: http://dx.doi.org/10.5772/intechopen.101562*

### **Author details**

Youkabed Zarroug1 \*, Mouna Boulares2 , Dorra Sfayhi1 and Bechir Slimi3

1 University of Carthage, Field Crops Laboratory (LR16INRAT02), National Agronomic Research Institute of Tunisia (INRAT), Ariana, Tunisia

2 University of Carthage, Research Unit: Bio-preservation and Valorization of Agricultural Products, Higher Institute of Food Industries (ESIAT), Tunis, Tunisia

3 Laboratoire des Nanomatériaux et Systèmes pour les Energies Renouvelables (LANSER), Centre de Recherches et des Technologies de l'Energie Technopole Borj Cedria, Hammam Lif, Tunisia

\*Address all correspondence to: zarrougyoukabed@yahoo.fr

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Korus J, Witczak M, Ziobro R, Juszczak L. The influence of acorn flour on rheological properties of gluten free dough and physical characteristics of the bread. European Food Research and Technology. 2015;**240**(6):1135-1143

[2] Vinha AF, Barreira JCM, Costa ASG, Oliveira MB, Beatriz PP. A new age for *Quercus* spp. fruits: Review on nutritional and phytochemical composition and related biological activities of acorns. Comprehensive Reviews in Food Science and Food Safety. 2016;**15**(6):947-981

[3] Salkova T, Divisova M, Kadochova S, et al. Acorns as a food resource. An experiment with acorn preparation and taste. Interdisciplinaria Archaeologica Natural Sciences in Archaeology. 2011;**II**(2):133-141

[4] Rakić S, Povrenović D, Tešević V, Simić M, Maletić R. Oak acorn, polyphenols and antioxidant activity in functional food. Journal of Food Engineering. 2006;**74**(3):416-423

[5] Taib M, Bouyazza L. Composition, physicochemical properties, and uses of acorn starch. Journal of Chemistry. 2021;**2021**:9. DOI: 10.1155/2021/9988570

[6] Ozunlu O, Ergezer H, Gokçe R. Improving physico-chemical, antioxidative and sensory quality of raw chicken meat by using acorn extracts. LWT. 2018;**98**:477-484

[7] Zarroug Y, Boulares M, Mejri J, et al. Extraction and characterization of Tunisian *Quercus ilex* starch and its effect on fermented dairy product quality. International Journal of Analytical Chemistry. 2020;**2020**:9. DOI: 10.1155/2020/8868673

[8] Rodrigues A, Emeje M. Recent applications of starch derivates in nanodrug delivery. Carbohydrate Polymers. 2012;**87**:987-994

[9] Pérez-Pachecoa E, Moo-Huchin VM, Estrada-León RJ, Ortiz-Fernández A, MayHernández LH, Ríos-Soberanis CR, et al. Isolation and characterization of starch obtained from *Brosimum alicastrum* Swarts Seeds. Carbohydrate Polymers. 2014;**101**:101920-101927. DOI: 10.1016/j.carbpol.2013.10.012

[10] Zhang Z, Saleh ASM, Wu H, Gou M, Liu Y, Jing L, et al. Effect of starch isolation method on structural and physicochemical properties of acorn kernel starch. Starch–Stärke. 2019; **72**(1-2):1900122

[11] Rababah T, Ereifej K, Al-Mahasneh M, Alhamad M, Alrababah M, Al-u'datt M. The physicochemical composition of acorns for two Mediterranean *Quercus* species. The Journal of Agricultural Science. 2008;**4**:131-137

[12] Correia PR, Nunes MC, Beirãoda-Costa ML. Effect of starch isolation method on physical and functional properties of Portuguese nut starches. II. *Q. rotundifolia* lam. and *Q. suber lam*. acorns starches. Food Hydrocolloids. 2013;**30**(1):448-455

[13] Correia PR, Leitao AE, Beiraoda-Costa ML. Effect of drying temperatures on chemical and morphological properties of acorn flours. International Journal of Food Science & Technology. 2009;**44**:1729-1736

[14] Boukhelkhal M, Moulai-Mostefa N. Physicochemical characterization of starch isolated from soft acorns of holm *Comparative Study of the Physiochemical Composition and Techno-Functional Properties… DOI: http://dx.doi.org/10.5772/intechopen.101562*

oak (*Quercus Ilex Subsp. Ballota* (Desf.) Samp.) grown in Algeria. Journal of Food Measurement and Characterization. 2017;**11**(4):1995-2005

[15] Stevenson G, Jane JL, Inglett GE. Physico-chemical properties of pin oak (*Quercus palustris muenchh*.) acorn starch. Starch-Starke. 2006;**58**(11):553-560

[16] Soni PL, Sharma H, Dun D, Gharia MM. Physicochemical properties of *Quercus leucotrichophora* (Oak) starch. Starch/Stärke. 1993;**45**:127-130

[17] Masmoudi M, Besbes S, Khlifi M, Yahyaoui D, Attia H, Hamadi A. Optimization of acorn (*Quercus suber* L.) muffin formulations: Effect of using hydrocolloids by a mixture design approach. Food Chemistry. 2020;**328**: 127082

[18] Irinislimane H, Belhaneche-Bensemra N. Extraction and characterization of starch from Oak acorn, sorghum, and potato and adsorption application for removal of maxilon red GRL from wastewater. Chemical Engineering Communications. 2017;**204**(8):897-906

[19] Siro I, Kapolna E, Kapolna B, Lugasi A. Functional food. Product development, marketing and consumer acceptance—A review. Appetite. 2008;**51**:456-467

[20] Wani IA, Sogi DS, Hamdani AM, Gani A, Bhat NA, Shah A. Isolation, composition, and physicochemical properties of starch from legumes: A review. Starch-Starke. 2016;**68**(9-10): 834-845

[21] Jiang Q, Liang S, Zeng Y, Lin W, Ding F, Li Z, et al. International Journal of Biological Macromolecules. 2019;**125**:1147

[22] Elmi Sharlina MS, Yaacob A, Lazim A, et al. Physicochemical properties of starch from *Dioscorea pyrifolia* tubers. Food Chemistry. 2017;**220**:225-232

[23] Muhammad U, Tahir I, Raza MS, Muhammad I, Bushra I. Alkaline extraction of starch from broken rice of Pakistan. International Journal of Innovation and Applied Studies. 2014;**7**(1):146-152

[24] Awoyale W, Sanni LO, Shittu TA, Adebowale AA, Adegunwa MO. Development of an optimized cassava starch-based custard powder. Journal of Culinary Science & Technology. 2017:1- 23. DOI: 10.1080/15428052.2017.1404534

[25] Canellas I, Roig S, San MA. In: Robles AB, Ramos ME, Morales MC, Simon E, Gonzalez-Rebollar JL, Boza J, editors. Caracterizacion y evolucion anual del valor bromatologico de las quercıneas mediterraneas. Granada: Pastos, desarollo y conservacion; 2003. pp. 455-462

[26] Deng M, Reddy CK, Xu B. Morphological, physicochemical, and functional properties of underutilized starches in China. International Journal of Biological Macromolecules. 2020; **158**:648-655

[27] Singh V, Ali SZ, Somashekar R, Mukherjee PS. Nature of crystallinity in native and acid modified starches. International Journal of Food Properties. 2006;**9**:845-854

[28] Kaur L, Singh J, Singh N. Effect of cross-linking on some properties of potato (*Solanum tuberosum* L.) starches. Journal of the Science of Food and Agriculture. 2006;**86**(12):1945-1954

[29] Correia PR, Beirão-da-Costa ML. Starch isolation from chestnut and acorn flours through alkaline and enzymatic methods. Food and Bioproducts Processing. 2012;**90**(2):309-316

[30] Jiang Q, Gao W, Li X, et al. Characterizations of starches isolated from five different *Dioscorea* L. species. Food Hydrocolloids. 2012;**29**(1):35-41

[31] Thanyapanich N, Jimtaisong A, Rawdkuen S. Functional properties of banana starch (*Musa* spp.) and its utilization in cosmetics. Molecules. 2021;**26**:3637. DOI: 10.3390/molecules 26123637

[32] Hughes T, Hoover R, Liu Q, Donner E, Chibbar R, Jaiswal S. Composition, morphology, molecular structure, and physicochemical properties of starches from newly released chickpea (*Cicer arietinum* L.) cultivars grown in Canada. Food Research International, Barking. 2009;**42**(5-6):627-635

[33] Dome K, Podgorbunskikh E, Bychkov A, Lomovsky O. Changes in the crystallinity degree of starch having different types of crystal structure after mechanical pretreatment. Polymers. 2020;**12**(3):641. DOI: 10.3390/ polym12030641

[34] Ojogbo E, Ogunsona EO, Mekonnen TH. Chemical and physical modifications of starch for renewable polymeric materials. Materials Today Sustainability. 2020;**7-8**:100028

[35] Ovando-Martınez M, Osorio-Dıaz P, Whitney K, Bello-Perez LA, Simsek S. Effect of the cooking on physicochemical and starch digestibility properties of two varieties of common bean (*Phaseolus vulgaris* L.) grown under different water regimes. Food Chemistry. 2011;**129**(2):358-365

[36] Zhang P, Whistler RL, Be Miller JN, Hamaker BR. Banana starch: Production, physicochemical properties, and digestibility. Carbohydrate Polymers. 2005;**59**:443-458

[37] Singh N, Singh J, Kaur L, Singh Sodhi N, Singh GB. Morphological, thermal and rheological properties of starches from different botanical sources. Food Chemistry. 2003;**81**(2):219-231

[38] Chen LX, Shi X, Li L. Analysis on basic physicochemical properties and antioxidant activities of the starch from acorn. Hans Journal of Food and Nutrition Science. 2019;**8**(3):195-207

[39] Molavi H, Razavi SMA, Farhoosh R. Impact of hydrothermal modifications on the physicochemical, morphology, crystallinity, pasting and thermal properties of acorn starch. Food Chemistry. 2018;**245**:385-393

[40] Dereje B. Composition, morphology and physicochemical properties of starches derived from indigenous Ethiopian tuber crops: A review. International Journal of Biological Macromolecules. 2021;**187**:911-921

Section 3
