**2.7 Forms of starch**

### *2.7.1 Native starch*

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

glidant properties [81].

**2.6 Food starch properties**

vary from 70 to 92°C [84].

are required in textile industries [87].

crude protein that is high in leucine (19.8%), methionie and cystine (7%) and valine (5.8%) [78]. Fonio grains are mostly consumed wholly, they are also milled into flour and constitute a versatile raw material for preparation varieties of food such as gruels, porridges, couscous, bread, beer, and beverages [79]. Starch extracted from fonio possesses good disintegrant and binding properties [80] and it also has good

The starch granules sizes obtained from different crops vary in properties, because of their sources, extraction methods and cultivars [82]. The purity as well as the granules size can be determined using scanning electron microscopy [83]. The amylose content of starch is one of the most important factors influencing the cooking and textural qualities of whole storage root, and quality of starch-based foods [84]. *Dioscorea* starch granules possess varying shapes, which are spherical, oval and polygonal, depending on the species with granule size varying from 2 to 50 mm [85]. Also the X-ray diffraction pattern of the *Dioscorea* starch granules range from the B to C-type, depending on the *Dioscorea* specie [18]. *Dioscorea* starches contain18 to 30% amylose contents and their gelatinization temperature

Starch particle sizes obtained from white and yellow yam varieties showed similar patterns with a single symmetrical distribution centered at approximately 32 and 35 mm respectively. Sources, varietal differences and growing conditions significantly influence size and shape of starch granules. However, due to better mouth feel, small sized starch granules has been suggested as possible lipid substitute in food systems [86]. They are also used as laundry-stiffening agents because they possess good fabric penetration ability, better glossiness and stiffness, which

Sweet potato starch granules possess spherical, oval, and polygonal shapes, and they are about 2–46 mm in size. The X-ray diffraction patterns of the sweet potato starch granules are of type A and they also exhibit 38% crystallinity [88]. The starch in sweet potato is made of 16.1–24.4% amylose, having a swelling power of 80% at 90°C and gelatinization temperature of 64.6–84.6°C [84]. Cassava starch possesses small spherical granules, having an average granule size of 14.7 mm. Its amylose content ranges from 13.6 to 23.8% [84, 89] and its crystallinity has been reported to be 38% [84], while the gelatinization temperature varies from 59.6 to 87.2°C [84, 89]. The X-ray diffraction patterns of the cassava starch granules depict type A [90]. The cocoyam granules (Taro) are small rounded and ellipsoidaltruncated, with their sizes varying from 0.5 to 5 mm in diameter, making them to be more easily digestible [84]. Taro starch has been used in the preparation of some baby foods and diets of people who are allergic to cereals [91]. The X-ray diffraction patterns of the taro starch granules exhibit the typical A-type pattern, while the starch contains 14.0–19% amylose with the pasting temperatures varying from 81 to 85°C [92]. Interestingly, starch from Tannia (*Xanthosoma sagittifolium*) comprises of small rounded and large truncated ellipsoidal-shaped granules, which possesses granular diameters which range from 2 to 50 mm [91]. The amylose contents of different cultivars range from 21.3 to 25.4% [93]. Tannia starch possesses a type A X-ray diffraction pattern, higher pasting temperatures and lower paste viscosity than those of other starches, such as potato starch [89]. Also, it has higher swelling power and solubility at relatively high temperatures than sweet potato starch granule [84]. The maize starch granules exhibit polyhedral granule shapes and differences in their mean granule size range from 2.3 to 19.5 μm. The starch samples show A-type diffraction pattern with strong reflection at 15.25, 18.11,

**204**

Native starches are crude starches that are extracted directly from their sources and they are mainly used as food, but irrespective of their sources they are undesirable for many applications because of their inability to withstand processing conditions. Each starch has unique functional properties, and much of the starch used industrially is modified before use, giving a wider range of useful products [99]. Starch can be readily converted chemically and biologically into many useful and diverse products such as paper, textiles, adhesives, beverages, confectionery, pharmaceuticals, and plastics, so as to improve desirable functional properties in order to meet the requirements of specific industrial processes [13].

#### *2.7.2 Extraction techniques*

Starch granules' settling is often prevented by presence of various components like mucilage and latex, which may lead not only to loss of starch, but also reducing the quality of extracted starch. However, microbial growth can also be promoted if the extraction residence time is prolonged than necessary, which may also result into breakdown of starch and resultant loss of starch quality. It also affects the color of the starch limiting its utilization in food and industrial applications. Therefore, optimum recovery of starch having physicochemical and functional qualities coupled with economical extraction of starches from cereals and tubers is important. Extraction of starch with water is the most common form of starch extraction, but this has been improved upon over time. The Central Tuber Crops Research Institute, Trivandrum, India research on various chemicals that could improve the yield of starch from various tubers [100, 101]. It was discovered that ammoniacal solutions gave the best results. However, when aqueous ammonia (0.03 M) was used for starch extraction, the yield, paste viscosity and swelling capacity of the extracted starch improved. Ammonia formed a complex with the mucilagenous material in the slurry, thereby releasing the starch granules and promoting faster settling of starch in less viscous slurry, which prevents microbiological damage of the starch due to short residence time. Moorthy [101] observed that lactic and citric acids improved the yield and color of starch from sweet potato tubers. Interestingly, an enzymatic method for enhancing the recovery (26% increase) of starch from cassava tubers using pectinase and cellulase enzymes [101]. The aforementioned enzymes work by altering the integrity of the pectin-cellulosic matrix of cell membranes and thereby promoting the release of the starch granules. The same technique was used to promote starch recovery from sweet potatoes by 20% without affecting starch properties [101].

#### *2.7.3 Modified starch*

Modified starches are native starches whose physical and chemical characteristics have been altered in order to improve their functional characteristics [102]. However, modification of starch is done to tailor starch to a specific food application, to stabilize starch granules during processing and make it suitable for many foods and industrial applications. During modification, starch properties are altered, including solution viscosity, gelatinization properties, pasting properties, retrogradation behavior, association behavior, and shelf-life stability in final products [102, 103]. Modification can be achieved through etherification, esterification, cross-linking/grafting of starch, decomposition (acid or enzymatic hydrolysis and oxidization of starch) and physical treatment of starch using heat or moisture [104].

Modified starches produced from different methods and sources are usually used as thickening agents to provide desired structures in food products [105]. Acid-thinned starch is starch that has been treated in acid slurry [1]. This starch possesses faster gelatilization, low viscosity, and could produce a weak gel (Abbas *et al*., 2010). Oxidized starch is a starch which has undergone oxidation and it has a low hot paste viscosity. Both of acid-thinned and oxidized starches are suitable for confections because they allow rapid and efficient cooking of starch solution in the presence of concentrated sugar syrups [106]. Stabilized starch is a type of modified starch that possesses a resistant property against acid degradation under dry acidic storage. Stabilized starch can be produced by adding buffer (pH 6–9) to starch slurry and drying the starch-buffer slurry in a conventional oven [107]. Stabilized starch has a reduced starch gelatinization temperature; it's easier to cook and allows for the formation of stronger gel with increased clarity and longer self-life. Converted starch, such as dextrin, which possesses a good film forming capacity, can be used with high-sugar solutions to produce stable and flexible coatings [108]. Thin boiling starch is a modified starch that can be produced by treatint the starch with amylase enzyme to hydrolize the α-1, 4 glycosidic bonds. This starch possesses gelling properties and low hot paste viscosity, which make it suitable for gum drops since this type of starch allows better evaporation and pouring [104].

Octenyl succinic anhydride (OSA) starch is a recent type of chemically modified starch, possessing surface active properties [109]. Octenyl succinic anhydride (OSA) starch is produced by esterification of different sources of starch with anhydrous octenyl succinic acid under alkaline conditions [110]. The adsorption of the OSA starch molecules at the oil/water (O/W) interface might be as a result of hydrophobic short octenyl succinate side chains in octenyl succinic anhydride (OSA) starch molecules and the long amylopectin backbone which protect the droplets against flocculation by the mechanism of steric stabilization [111]. OSA behaves like a typical surfactant and forms a strong film at the O/W interface which provides a good resistance against re-agglomeration [111]. The increase in the viscosity of the continuous phase in conjunction with its ability of adsorption at interfaces enables OSA starch to behave as a stabilizer and also as an emulsifier in O/W emulsion systems. OSA starch type of modified starch has been approved as a food additive by the Food and Drug Administration (FDA) and European Union [112].

#### **2.8 Utilization of starch in food industries**

Starch plays a crucial role in food systems by stabilizing and creating the food structure. Starch also co-exists with other components to deliver or maintain nutrient and flavor [113]. However, starch importance in some food applications are elaborated below.

**207**

*Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects*

Starch is generally used in the production snack foods to achieve desired textural and sensory attributes by improving crispiness, oil binding properties, expansions, and overall eating quality [113]. The properties of the amylopectin and amylose of starch are important for the texture creating of this kind of foods. The highly branched amylopectin might increase dough expansion and viscosity, which could result to production of light, crispy, and expanded products. The amylase on the other part strengthens the dough and improves its forming and cutting properties. Consequentially, a more crunchy final texture could be obtained [114]. Furthermore, a high quality fiberfortified snack could be developed by incorporating modified starch [108].

Starch contribution to baked products quality is through its important properties, such as gelatinization, water absorption, and retrogradation [115]. The gelatinization property of starch is very important in building the structure and texture of baked products. However, starch ability to bind water could reduce the stickiness of dough, improve handling, and increase cake volume. It could also improve the

Starch behaves as a structure builder in coatings and also acts as a medium for molding to support desired shapes in confectionaries. Starch is used in the production of pastes, gums, and molds; it is also in the manufacture of dusting sweets to prevent them from sticking together. Starch is selected because of its ease of cooking in high-sugar environments and also based on its ease of handling during processing [108]. In most cases, starch is modified to possess specific properties that

Starch application in gravies, soup, and sauces depends on the production process, which is usually influenced by pH of products and heat during processing [114]. Compared to neutral products, high acid products (pH < 4.5) require a higher-degree of cross-linking starch. The production of cross-linked starch is achieved by the reaction in which a small number of hydroxyl groups on the glucose units of amylose and amylopectin, mostly in the amorphous are modified without destroying the granular nature of starch [116]. Since sterilization of acidic products require shorter processing time and lower temperature, other factors such as shelflife requirements, fill-viscosity, and heat penetration also influence the suitability of starch used in these types of food products. Hydroxypropylated starch which possesses high freeze thaw stability is suitable for chilled and frozen foods [108]. Hydroxypropylated starch is produced by reaction of starch with propylene oxide. Aside its better freeze thaw stability, modification improves hydroxypropylated starch shelf-life, cold-storage stability, past clarity and texture properties of its paste. Generally, gravies, soups, and sauces require starch with opaque paste [108].

The function of starch in these products is mainly to thicken and stabilize the dispersed phase [108]. Basically, these food products are produced under acidic

moistness and softening the texture of baked products [108].

*DOI: http://dx.doi.org/10.5772/intechopen.95020*

*2.8.1 Snack foods*

*2.8.2 Baked products*

*2.8.3 Confectionery*

suit certain applications.

*2.8.4 Gravies, soups, and sauces*

*2.8.5 Mayonnaise and salad dressing*

*Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects DOI: http://dx.doi.org/10.5772/intechopen.95020*

#### *2.8.1 Snack foods*

*Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

Modified starches are native starches whose physical and chemical characteristics have been altered in order to improve their functional characteristics [102]. However, modification of starch is done to tailor starch to a specific food application, to stabilize starch granules during processing and make it suitable for many foods and industrial applications. During modification, starch properties are altered, including solution viscosity, gelatinization properties, pasting properties, retrogradation behavior, association behavior, and shelf-life stability in final products [102, 103]. Modification can be achieved through etherification, esterification, cross-linking/grafting of starch, decomposition (acid or enzymatic hydrolysis and oxidization of starch) and physical treatment of starch using heat or

Modified starches produced from different methods and sources are usually used as thickening agents to provide desired structures in food products [105]. Acid-thinned starch is starch that has been treated in acid slurry [1]. This starch possesses faster gelatilization, low viscosity, and could produce a weak gel (Abbas *et al*., 2010). Oxidized starch is a starch which has undergone oxidation and it has a low hot paste viscosity. Both of acid-thinned and oxidized starches are suitable for confections because they allow rapid and efficient cooking of starch solution in the presence of concentrated sugar syrups [106]. Stabilized starch is a type of modified starch that possesses a resistant property against acid degradation under dry acidic storage. Stabilized starch can be produced by adding buffer (pH 6–9) to starch slurry and drying the starch-buffer slurry in a conventional oven [107]. Stabilized starch has a reduced starch gelatinization temperature; it's easier to cook and allows for the formation of stronger gel with increased clarity and longer self-life. Converted starch, such as dextrin, which possesses a good film forming capacity, can be used with high-sugar solutions to produce stable and flexible coatings [108]. Thin boiling starch is a modified starch that can be produced by treatint the starch with amylase enzyme to hydrolize the α-1, 4 glycosidic bonds. This starch possesses gelling properties and low hot paste viscosity, which make it suitable for gum drops

since this type of starch allows better evaporation and pouring [104].

the Food and Drug Administration (FDA) and European Union [112].

Starch plays a crucial role in food systems by stabilizing and creating the food structure. Starch also co-exists with other components to deliver or maintain nutrient and flavor [113]. However, starch importance in some food applications are

**2.8 Utilization of starch in food industries**

Octenyl succinic anhydride (OSA) starch is a recent type of chemically modified starch, possessing surface active properties [109]. Octenyl succinic anhydride (OSA) starch is produced by esterification of different sources of starch with anhydrous octenyl succinic acid under alkaline conditions [110]. The adsorption of the OSA starch molecules at the oil/water (O/W) interface might be as a result of hydrophobic short octenyl succinate side chains in octenyl succinic anhydride (OSA) starch molecules and the long amylopectin backbone which protect the droplets against flocculation by the mechanism of steric stabilization [111]. OSA behaves like a typical surfactant and forms a strong film at the O/W interface which provides a good resistance against re-agglomeration [111]. The increase in the viscosity of the continuous phase in conjunction with its ability of adsorption at interfaces enables OSA starch to behave as a stabilizer and also as an emulsifier in O/W emulsion systems. OSA starch type of modified starch has been approved as a food additive by

*2.7.3 Modified starch*

moisture [104].

**206**

elaborated below.

Starch is generally used in the production snack foods to achieve desired textural and sensory attributes by improving crispiness, oil binding properties, expansions, and overall eating quality [113]. The properties of the amylopectin and amylose of starch are important for the texture creating of this kind of foods. The highly branched amylopectin might increase dough expansion and viscosity, which could result to production of light, crispy, and expanded products. The amylase on the other part strengthens the dough and improves its forming and cutting properties. Consequentially, a more crunchy final texture could be obtained [114]. Furthermore, a high quality fiberfortified snack could be developed by incorporating modified starch [108].

#### *2.8.2 Baked products*

Starch contribution to baked products quality is through its important properties, such as gelatinization, water absorption, and retrogradation [115]. The gelatinization property of starch is very important in building the structure and texture of baked products. However, starch ability to bind water could reduce the stickiness of dough, improve handling, and increase cake volume. It could also improve the moistness and softening the texture of baked products [108].

#### *2.8.3 Confectionery*

Starch behaves as a structure builder in coatings and also acts as a medium for molding to support desired shapes in confectionaries. Starch is used in the production of pastes, gums, and molds; it is also in the manufacture of dusting sweets to prevent them from sticking together. Starch is selected because of its ease of cooking in high-sugar environments and also based on its ease of handling during processing [108]. In most cases, starch is modified to possess specific properties that suit certain applications.

#### *2.8.4 Gravies, soups, and sauces*

Starch application in gravies, soup, and sauces depends on the production process, which is usually influenced by pH of products and heat during processing [114]. Compared to neutral products, high acid products (pH < 4.5) require a higher-degree of cross-linking starch. The production of cross-linked starch is achieved by the reaction in which a small number of hydroxyl groups on the glucose units of amylose and amylopectin, mostly in the amorphous are modified without destroying the granular nature of starch [116]. Since sterilization of acidic products require shorter processing time and lower temperature, other factors such as shelflife requirements, fill-viscosity, and heat penetration also influence the suitability of starch used in these types of food products. Hydroxypropylated starch which possesses high freeze thaw stability is suitable for chilled and frozen foods [108]. Hydroxypropylated starch is produced by reaction of starch with propylene oxide. Aside its better freeze thaw stability, modification improves hydroxypropylated starch shelf-life, cold-storage stability, past clarity and texture properties of its paste. Generally, gravies, soups, and sauces require starch with opaque paste [108].

#### *2.8.5 Mayonnaise and salad dressing*

The function of starch in these products is mainly to thicken and stabilize the dispersed phase [108]. Basically, these food products are produced under acidic

#### *Innovation in the Food Sector Through the Valorization of Food and Agro-Food By-Products*

condition and the process involves application heat and shear thinning. Therefore, starch which has ability to tolerate acidity, heat, and shear is suitable for these products. Also, lipophilic starch which has potential to stabilize emulsions, other modified starches such as cross-linked starch and stabilized starch are the most commonly used for these products [117]. Lipophilic starch is produced by esterification with n-octenyl succinic anhydrate, which led to a starch structure comprising both hydrophilic and lipophilic properties. This starch can be used for mayonnaise and salad dressing, lipophilic starch might be used to replace animal-derived sodium caseinate and gum Arabic [102].
