**1. Introduction**

### **1.1 Prevalence of malnutrition**

**175** The challenge of malnutrition and undernutrition is long-standing globally, with slow progress in interventions despite trends of development; 1.2 billion people lack

key micronutrients, 151 million children are stunted, 50.5 million children are wasted, while an estimated 2 billion and 38.3 million adults and children, respectively, are overweight or obese [1].

Similar trend with worse statistics has been reported in Sub-Saharan Africa (SSA) as stunted children under 5 years of age increased by just 23% in 24 years (1990–2014) [2]. Millions of people in SSA especially women of child-bearing age and children under 5 years from poor households are deficient in key micronutrients [3, 4]. An estimated 24% of all child deaths are due to vitamin A deficiency, out of which 48% are preschool-age children [5].

The consequences of vitamin A deficiency include a high risk of diseases such as diarrhea and measles, growth retardation, and premature death for children under 5 years of age, weakened immune system, visual impairment, and blindness [6].

#### **1.2 Interventions on micronutrient malnutrition**

Efforts to address micronutrient malnutrition using both nutrition-specific and sensitive interventions have been reported especially in SSA. On nutrition-specific interventions, there has been significant support for exclusive breastfeeding (EBF), improved Infant and Young Child feeding (IYCF) practices, micronutrient supplementation, treatment of severe malnutrition with Ready-to-Use Therapeutic Foods (RUTF), mandatory large-scale fortification of selected foods (salt, sugar, oil, and flours), and Home-Grown School Feeding in some developing countries [7]. Nutrition-sensitive agriculture, mainly biofortification, and water, sanitation, and hygiene (WASH) programs have been appreciably promoted under nutrition-sensitive interventions.

However, each of these intervention programs has its limitations, which inhibit impact at scale and sustainability. For instance, women have so many reasons for not practicing exclusive breastfeeding. Micronutrient supplementation programs are mainly funded by external donors with unguaranteed sustainability, and so unable to meet the set goals of the international health organizations. Other limitations include poor access of the poor people to markets, health-care centers, and other places where the supplements are available, as well as lack of public enlightenment on the health benefits of these nutrient supplements [8, 9]. For large-scale food fortification, being a food-based industrial approach for addressing micronutrient malnutrition, and expected to cover a wide population, has so far been largely limited in reaching most rural dwellers. The coverage of fortified foods is dependent on how developed the market infrastructure is, and most rural poor have poor access to market where the fortified foods are [7]. In Nigeria, locally processed and unfortified foods are often more readily available and affordable to the poor rural dwellers who need fortified foods more because of their poor diets. Worst still, some of the industrially produced food vehicles that are expected to be adequately fortified are often times either not fortified at all or not adequately fortified [10].

Poor knowledge of nutrient contents of many indigenous foods hinders promotion and practice of dietary diversification and nutrition-sensitive food production system. Nutrition education as a strategy is yet to reach an impactful scale on behavioral change [7].

Biofortification, therefore, came up as a sustainable agricultural-base complementary approach to address micronutrient malnutrition in developing countries, targeting the vulnerable populations.

*Appropriate Post-Harvest Technologies for Biofortified Crops Pro Enhanced Utilization, Value… DOI: http://dx.doi.org/10.5772/intechopen.110473*

### **2. Biofortification**

Biofortification is the process of breeding staple crops to have higher contents of essential nutrients either through selective breeding or genetic engineering [11]. It is a cost-effective, and sustainable technique of delivering essential micronutrients to populations whose major food crops are deficient in them, and that have limited access to diverse diets and other micronutrient interventions. Biofortification is a globally recognized agricultural-based approach to addressing hidden hunger and food insecurity, especially in the SSA. Biofortification of staple crops, being within the agricultural sector, presents exceptional investment opportunities for addressing this national priority through production, processing, and marketing of diverse and more nutritious crops that can sustainably improve the nutrition status of vulnerable populations. It is cost-effective because the only major cost required is that of initial breeding and introduction; once biofortified crops are in the farmer food system, they can reach remote, rural populations that are difficult and expensive to reach with regular supplementation promotions [12–18]. According to Garg et al. [19], biofortification delivers food crops with improved key micronutrients—iron, zinc, and provitamin A that are usually lacking in the diets of the developing world. International initiatives, such as the HarvestPlus and national programs, are available to achieve these targets and so far, they have delivered crops with the potential to increase the quantity and quality of essential micronutrients in human diets, especially in staples like wheat, maize, cassava, beans, sweet potatoes, and millets [19].

Biofortification has enabled a shift in agricultural system from "increasing crop yield and productivity," which has resulted in a high rise of micronutrient-deficient food crops to "producing nutrient-rich crops in sufficient quantities," which will help address micronutrient malnutrition, especially in the developing countries [20].

#### **2.1 Biofortification techniques**

Biofortification techniques can be transgenic, conventional, and agronomic approaches, using biotechnology, crop breeding, and fertilization strategies, respectively. The three approaches have been targeted for cereals, some legumes, and vegetables (rice, wheat, maize, sorghum, common bean, potato, sweet potato, and tomato) while some crops could only be achieved by one or two of the techniques. However, more crops have been targeted by transgenic approach, but in practice, conventional breeding technique has been the highest [19].

To date, more than 400 biofortified varieties of 12 crops have been released in over 40 countries, facilitated by HarvestPlus and CIP that is exclusively on biofortified sweet potato varieties [19]. **Table 1** shows biofortified crop varieties of sweet potato available in some countries [21].

#### **2.2 Biofortified crops**

Some common staples in Africa have been successfully biofortified with provitamin A (cassava, maize, and sweet potato), beans with iron as well as sorghum and millet with iron and zinc. Biofortified cassava and sweet potato are gradually growing in awareness and adoption in Nigeria and other parts of SSA where they are staples, to address vitamin A deficiency. Biofortified crops with increased contents of essential micronutrients are delivered to consumers through the same familiar traditional practices by the key actors of the value chain, thus reaching the target populations


#### **Table 1.**

*Orange flesh sweet potato available/released in some African countries and USA.*

of undernourished and low-income groups that have limited access to diverse diets, supplements, and fortified foods [7].

#### *2.2.1 Biofortified versus non-biofortified crop varieties*

The principle of biofortification is to nutritionally improve the existing regular staple crops without altering the traditionally known identity of the crops. No significant differences are expected, rather improvement in all the attributes of biofortified cassava, sweet potato, and white maize compared to those of their non-biofortified varieties except for orange (sweet potato) or yellow (cassava) color, which is indicative of the beta-carotene present. For biofortified millet and sorghum, which are biofortified with iron and zinc, there is no difference in the physical traits between the two breeds except that their micronutrient contents, precisely iron, and zinc are higher in the biofortified ones. However, biofortified cassava, maize, and sweet potato have been reported to have less dry matter (more moisture content) and so softer in texture than the non-biofortified varieties. Breeders are working on these so that they can match up with the regular non-biofortified varieties, to boost farmers' adoption and consumers' acceptance. Improvement on biofortified varieties of the crops is being geared towards increased dry matter and recently released varieties like "solo gold" variety of OFSP in Nigeria has higher dry matter content. Every new variety released is an advancement on the former one, based on micronutrient concentration as well as farmer and consumer-preferred quality traits especially yield, drought tolerance, and resistance to pest.

#### *2.2.2 Cassava—overview*

Cassava is a major vegetable root staple in several countries of Sub-Saharan Africa, Latin America, and Asia. Of all root crops, it is the most important crop in Africa [22]. The world production of cassava is estimated at 242 million tons, out of which 54% (130 million tons) is produced in Africa, and 52% (68 million tons) of it from west Africa alone [23]. Nigeria is the number one producer of cassava in the world with an annual production of 59 million tons in 2019, followed by the Democratic Republic of Congo, 40 million tons. Ghana is the third African producer with an annual production of approximately 22.4 million tons [24, 25]. In terms of calorie contribution, cassava is the number three source of calories in the tropics [26], with about 500 million people relying on it for at least 10% of their daily caloric intake. In West Africa, cassava is a major source of carbohydrates in human diet, a well-placed, relatively cheap staple crop in developing countries as tpulp is an important source of energy with a calorific value of 250 kcal ha−1 day−1 [26]. However, cassava, which is mainly grown for its starchy tuberous roots and is a valuable source of cheap calories for low-income earners has now gained a strategic position in world trade. Besides its direct use as food, cassava is also used as a livestock feed and a raw material in the production of starch, tapioca, and snack foods [27]. As food, it can be boiled or roasted for consumption or can be milled into flour and used in making common dishes such as *Ugali* in East Africa as well as *garri* and *fufu* in West Africa. Dried cassava chips have varied applications by end users like breweries, confectionaries, starch, and flour for food. The crop is now produced for food and income, traded in different forms targeting diverse end uses; cassava flour, dried cassava chips, and raw cassava. In Uganda, 200,000 MT of cassava flour is consumed per annum, with most of it being traded in traditional informal markets [28].

#### *2.2.3 Biofortified cassava (yellow cassava or vitamin A cassava)*

Cassava is one of the staples targeted for biofortification as it is consumed daily by populations in some SSA countries like Nigeria, Ghana, Cameroon, Sierra Leone, Uganda, and DR Congo. Biofortified (vitamin A cassava) or yellow cassava is a relatively new breed of cassava that is rich in beta-carotene for improved nutrition of the consumers. In the African continent, it is being used as a vehicle to alleviate vitamin A deficiency through its biofortification with provitamin A (beta-carotene) by HarvestPlus in collaboration with International Institute of Tropical Agriculture (IITA) [19]. Under these collaborations, six biofortified provitamin A cassava varieties have been released in Nigeria namely; TMS 01/1368—UMUCASS 36, TMS 01/1412—UMUCASS 37 and 2014; TMS 01/1371—UMUCASS 38 and NR 07/0220— UMUCASS 44, TMS 07/0593—UMUCASS 45, and TMS 07/539—UMUCASS 46) and one in the Democratic Republic of Congo (Kindisa [TMS 2001/1661]) [19, 29, 30]. The yellow cassava varieties are similar to those of white in all attributes except for the color, which is an indication of its biofortification with beta-carotene. They are also high-yielding and resistant to many pests and diseases.

#### *2.2.4 Sweet potato—overview*

Sweet potato is an important root crop globally, with an annual production of 112.8 million tons in 115 countries in 2017, and China is the leading producer, followed by Nigeria with 3.9 million metric tons per year [31], Tanzania, Indonesia, and Uganda [32]. In recent times, although SP production and consumption have significantly increased in Africa, Asia, South American continents, and Caribbean islands, it is more profusely grown in Africa. International Potato Center (CIP) [33] reported that sweet potato is the third important food crop in seven central and eastern African countries, fourth priority crop in six South African nations, and eighth in four West African countries. SP, which is known as a food security crop due to its low agriculture input requirements [34], is recently changing to a significant cash crop. Sweet potato is a versatile crop that serves the roles of food and nutrition security as well as cash crop in both raw and processed forms. SP is an important root crop that can thrive in marginal soil with wide agro-ecological adaptability. In Nigeria, it can grow in all 36 states of the country plus the federal capital territory. It has a short maturity period of 3–4 months while its roots and vines are used for both human and animal consumption [35]. Sweet potato roots contain various kinds of physiologically functional components such as polyphenolics, anthocyanins, fibers, and carotenoids.

Value addition of sweet potato roots with these functions has resulted in their commercial utilization as an ingredient in confectioneries, noodles, alcoholic drinks, and beverages [36]. All varieties of SP are good sources of vitamins C, E, and K, several B vitamins, and the key minerals of magnesium and potassium. The leaves have appreciable levels of protein, and are widely used in the dairy industry in East Africa. It is a source of livestock feed with great potential as an industrial raw material.

#### *2.2.5 Biofortified sweet potato (orange-fleshed sweet potato)*

Orange-Fleshed sweet potato is a breed of sweet potato that is additionally rich in beta-carotene, a precursor of vitamin A through biofortification using conventional breeding practices, and drawing on the rich genetic diversity of sweet potato. OFSP is a proven, effective, and sustainable source of vitamin A, significantly contributing to the fight against vitamin A deficiency (VAD) in Africa [37–39]. Just 125 g of boiled OFSP roots can meet the daily recommended intake levels of vitamin A for a child. The orange color of OFSP shows the concentration of beta-carotene present; the deeper the orange color of the root flesh, the more the beta-carotene content present. OFSP as a staple food can serve as a cheap and sustainable source of Vitamin A in developing countries, where malnutrition is a big problem, and are growing 95% of the world's sweet potato crop. OFSP also contains antioxidants that help prevent degeneration of cells, as well as natural sugars, which are slowly released into the bloodstream, thus ensuring a balanced source of energy, without spikes in blood sugar that is associated with fatigue and weight gain. It again has vital, life-promoting phytochemicals that enhance protection from peroxides [40].

HarvestPlus and International Potato Centre (CIP) have developed and released several varieties of orange sweet potato with high vitamin A across sub-Saharan Africa. In Nigeria, three OFSP varieties are available namely; UMUSPO3-Mothers Delight, UMUSPO1-King J, and UMUSPO4-Solo Gold [35]. In Uganda, six varieties have been released, namely; Ejumula, Kakamega, Vita, Kabode, Naspot 12O, and Naspot 13O); and three in Zambia (Twatasha, Kokota, and Chiwoko). Zambia

#### *Appropriate Post-Harvest Technologies for Biofortified Crops Pro Enhanced Utilization, Value… DOI: http://dx.doi.org/10.5772/intechopen.110473*

Agriculture Research Institute has successfully completed the development of 15 new varieties of vitamin A fortified sweet potatoes [41].

OFSP is widely consumed as a vegetable dish (boiled, fried or roasted) as well as in different products through processing and value addition for improved household food intake. These include pastries, beverages as well as enriching existing indigenous foods, which are described in details by Phorbee et al. [35]. OFSP products can also be a source of income as they can be commercialized at all levels for income generation, job and wealth creation for all especially women and youths.

#### *2.2.6 Carotenoids in biofortified sweet potatoes and cassava*

Carotenoids are well known for their health-promoting benefits, which include immune boosting and reduced risk of developing some non-communicable degenerating diseases like cancers, cardiovascular diseases, cataracts, and mascular degeneration [42]. Carotenoids are made up of many other components that result in provitamin A activity. These include alpha-carotene (α-carotene), beta-carotene (β-carotene), beta-cryptoxanthin, Lutein, zeaxanthin, and lycopene. Among the carotenoids, α- and β-carotenes have a high provitamin A activity [42]. Orange fleshed varieties are appreciably rich in proVitamin A [43] with some having as much as 8000 μg β-carotene per 100 g of fresh weight while some Kenyan varieties have reportedly yielded 1240–10,800 μg per 100 g of fresh weight. However, carotenoids are known to be thermal and photo sensitive as they undergo degradation when exposed to heat and light, [44] and also through some processing techniques like cooking [45]. There is, therefore, the need to process OFSP with techniques that minimize carotenoid loss, so as to achieve the purpose of its biofortification.

Yellow cassava varieties are being grown and disseminated in many West African countries especially Nigeria, for their high concentrations of beta-carotene and being used to fight vitamin A deficiency. According to Harvestplus, yellow cassava can provide up to 100% of daily recommended vitamin A intake for women of reproductive age and children when eaten regularly [46]. Since cassava is a major part of many people's diets, introducing cassava bio-fortified with vitamin A is an excellent innovation and a significant contribution towards improving the food system transformation in the SSA.

#### *2.2.7 Biofortified maize*

Maize is a versatile cash crop grown for food, feed, and industrial purposes (an important source of sugar, oil, starch, and ethanol). For example, corn starch is an important raw material in pharmaceutical, food, and textile industries. The diverse end uses of maize globally have informed the basis for breeding higher yielding varieties of maize. Further research on maize has also led to the discovery of varieties that are naturally high in beta carotene contents, which HarvestPlus uses to breed high-yielding varieties of biofortified maize. These varieties have higher contents of provitamin A, which are being used to fight vitamin A deficiency is a major output in biofortification. In Zambia, three PVA maize varieties have been commercially grown namely, GV662A, GV664A, and GV665A. Also in Nigeria, four varieties have been released out of which two are hybrid; Ife maizehyb-3, Ife maizehyb-4, and 2 open pollinated varieties-Sammaz 38 and Sammaz 39 while one OPV CSIR-CRI Honampa has also been grown in Ghana since 2013 [47]. Malawi, Zimbabwe (ZS242) and Tanzania have also released PVA maize recently [48]. In a study conducted among Zambia,

an increased pupillary response was observed among children who consumed PVA maize [48]. Breeders have also assessed antioxidants like tocochromanols, oryzanol, and phenolic compounds in PVA maize, which are health-beneficial [49].

#### *2.2.8 Biofortified sorghum and millet*

The prospects of breeding for micronutrients and beta-carotene rich sorghums have been discussed by Reddy et al. [50]. ICRISAT has successfully bred and released five lines of iron biofortified varieties of sorghum in India and two in Nigeria. Three of the Indian lines are hybrids (ICSA 661 × ICSR 196, ICSA 318 × ICSR 94, ICSA 336 × IS 3760) while two non-hybrid (ICSR 14001, ICSH 14002) and those in Nigeria are 12KNICSV-22 and 12KNICSV-188 whose iron content is three times higher than typically grown sorghum. The iron biofortified varieties of sorghum are bred and targeted at boosting iron intake of the malnourished populations especially northern Nigeria where sorghum is a staple cereal with relatively high production and consumption. These new varieties involved crossing local Nigerian germplasm with improved lines from ICRISAT (Mali).

Pearl millet is reportedly the cheapest source of iron and zinc [51] and large variation has been seen in its germplasm for these micronutrients [52]. In India, ICRISAT has also released iron and zinc biofortified pearl millet variety "Dhanashakti" and a hybrid ICMH 1201 (Shakti-1201). Many other commercial varieties and hybrids containing high content of iron and zinc have also been reported [52, 53].

## **3. Perishability of root and tuber biofortified crops at postharvest**

Postharvest losses of food crops are traced to history especially in the tropics where the temperature is relatively high. This is a big challenge in the agriculture sector as over one-third of produce is lost after harvest [54] before they reach consumers. The losses, both physical and biological are due to poor management of the produce along the value chain, which are poor packaging from field after harvest and use of inappropriate packaging materials, transportation, poor handling in marketing and display of produce for sale, exposure to heat and sunlight, which subject fruits to undue ripening, lack of good storage facilities and conditions prior to sales. Generally, the key actors of agricultural produce (producers, wholesalers, and retailers) in the SSA lack capacities and facilities to maintain highquality and safe perishable plant produce from farm to table [55]. Losses of perishable crops have implications on quality, quantity, market value, and safety of the produce. According to RAS (2015), insufficient and poorly maintained transport and market infrastructure for handling food products in both urban and rural areas have frequently resulted in high level of waste and spoilage [56].

OFSP and VAC crops, like the non-biofortified varieties are perishable after harvest. Fresh sweet potato having relatively high moisture contents are very sensitive to microbial spoilage, even at refrigerated conditions, hence they must be consumed within a few weeks after harvest or be processed into various products. Cassava can barely stay for 48 hours post-harvest before physiological deteriorations start. Also, cassava roots are bulky and therefore transportation from farm to market or other destinations within the value chain can be challenging in term of cost and stability, thus reduced quality, quantity, and market value. More so, most of the farmers are small holders who harvest manually so the roots are at risk of bruises, which stress

*Appropriate Post-Harvest Technologies for Biofortified Crops Pro Enhanced Utilization, Value… DOI: http://dx.doi.org/10.5772/intechopen.110473*

and damage the roots. Also, during packaging and transportation, skin of the roots could remove, causing more bruises to the root and opening them up for rapid spoilage [57]. The packing sacks are also often times over filled with the crops, which can further impair the roots.
