**4. Postharvest technologies for enhanced shelf stability and nutrient retention**

To manage postharvest losses, processing is very essential to preserve the crops as well as add value to the crops for food product diversity and improved commercial competitiveness.

#### **4.1 Postharvest utilization and processing of OFSP**

#### *4.1.1 Utilization*

The high content of provitamin A, which is important to health in OFSP has enhanced its utilization in processed forms like diced, mashed, or pureed OFSP. In school feeding program, OFSP in puree or other forms has been added to school menu in some countries like US, Nigeria, Ghana, etc. to boost the nutritional quality of those meals. CIP research has shown the importance of OFSP puree in bakery as it has been able to develop an acceptable OFSP puree-wheat flour composite bread in which 45–50% is OFSP puree. The bread is not just rich in pro-vitamin A but also cut down on quantity of sugar and oil in the formula while reducing use and dependence on wheat flour, which is often imported in some Africa countries, thus cutting down production cost significantly. The OFSP puree-based products are healthier as they retain more nutrients especially pro-vitamin A. Sweet potato purees and powders can also be used as thickening and gelling agents to impart desired textural properties, and at the same time enhance the nutritional values, antioxidant activity as well as natural color (e.g., orange and purple) of many food products. With increased urbanization, there is growing demand for convenient and healthy foods, which sweet potato purees can easily fit in as functional ingredients in processed foods. More so, the novel advancement of processing OFSP puree aseptically with continuous flow microwave heating, is an opportunity for industries to produce nutrient-rich and shelf-stable puree for institutional use in social protection programs.

Sweet potato is a major root crop utilized widely for diverse food products as well as feed and industrial products. As food, sweet potato roots (both orange and white fleshed) are mainly consumed domestically as boiled or fried. In Kenya, 90% of the sweet potato produced is used domestically as food. Use of vines as fodder and leaves as a vegetable is common in some parts of Western Kenya [58].

#### *4.1.2 Processing of OFSP and products*

Despite the importance and knowledge of the nutritional benefits of OFSP, it remains generally underutilized, possibly because the roots are perishable, which reduces their market value. Fresh sweet potato is eaten boiled, steamed, roasted, or fried in most African communities [59], so processing OFSP roots into products create more options for consumption, improve availability, and reduce losses. The fresh roots of sweet potato contain high moisture content (50–70%) and thus relatively low

mechanical strength. They also have a very high respiratory rate, which generates heat that aids softening of the roots, and eventually leads to damage. The shelf-life of sweet potato roots varies from few days to months depending on the cultivar and storage conditions [60]. SP storage roots are subject to several forms of postharvest losses right from harvesting, transportation from farmers' field to market and storage. These are due to mechanical injuries, weight loss, sprouting, diseases, and pests [61]. Since sweet potato does not stay for long after harvest, there is a need for processing and value addition. Also, for diversity in use/consumption and commercialization, sweet potato is processed in various ways, using various techniques, which include cooking, fermentation, and drying. Cooking could be boiling or frying, roasting/baking of the roots while other techniques, either single or multiple, result in the development of other value-added food products for household consumption and/or income generation [35].

Processing or value addition, as a way of diversifying utilization of SP is greatly dependent on the roots' cultivars. SP cultivars' screening, targeting diverse end uses is an important activity in processing and value addition because not all SP root varieties are suitable for all end products. CIP and other related research institutions nationally and internationally test SP cultivars' suitability for diverse end uses. They develop the best food products from different cultivars of SP, promote and transfer the technologies to local farmers and processors. In some cases, they scale up the technology transfer by partnering with selected private companies (medium-large scale).

Postharvest processing of sweet potato involves primarily grading, sorting, peeling, cleaning, etc., and secondarily product making. Sweet potato processing technologies into puree and other forms are available in various parts of the world so that they can be used as functional food ingredients in many food products. The processing operations involved in these technologies and their effect on quality, storability, nutritional values and rheological properties of SP purees and powders/flours have been reviewed by Truong and Avula [62].

Available processing technologies at all levels are the key drivers of promoting SP production and consumption. All parts of SP are useful in product making; the roots can be processed into chips, crisps, flakes, flour, granules, starch, and alcoholic beverages [63]. Also, the leaves, into powders and used as functional ingredients in food products like ice cream, juices, tea drinks, and bread due to their high phenolic content and antioxidant activity [64]. In many of the SSA countries, SP has been processed into intermediate and/or finished product [63] to make both traditional and novel OFSP-based products. Some traditional foods have even been enriched with OFSP, because of its high beta-carotene content. In Uganda, an array of novel and traditional food products has been made from OFSP, namely composite flours, chapatti, mandazi, juice, bread, doughnuts, and other confectionary products. Traditional ones, which are produced by the local farmers are pit stored tubers, *Amukeke* (dry white slices), *Inginyo* (dry chips, chunks), *Amukeke* flour and *Inginyo* flour [65]. Also in Kenya, sweet potato processing is reportedly processed into different traditional products like *mandazi bhajia*, among others [58]. In Nigeria, Phorbee et al., [35] produced a recipe book on OFSP and VAC as household guide for processing the two biofortified crops into various nutritious foods. OFSP has also been used to improve carotenoid contents of some Nigerian indigenous foods. One such is the use of OFSP as a functional ingredient in making a local beverage called *Kunu* (a popular local cereal-based beverage) where it serves as both sweetener and nutrient enhancer*.* Others are like OFSP-enriched *Amala, fufu*, semolina, pap, etc. Although mainly at household level and micro/small to medium processing scale, OFSP has also been

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

processed into intermediate products like chips, flour, and puree to make finished OFSP-based pastries (chin-chin, puff-puff, doughnuts, buns, etc.) and confectionaries to increase market options for sweet potato products.

The processing technologies are usually developed by the national and international institutions, and then transferred for adoption, to local NGOs, community health workers, women, and youth groups directly or through training of Trainers.

#### **4.2 Puree overview**

Purée is a cooked food, usually from vegetables, fruits, or legumes, that is ground, pressed, blended, or sieved to a creamy consistency [66]. It is usually a very smooth lump-free food made from a specific food, which the puree is named by, for example, applesauce, mashed potatoes, or tomato purée. Pureed foods are easier to digest as pureeing is like chewing, with the food partially broken down and easier for the system to absorb. Pureeing can be done manually or mechanically. Manual pureeing, depending on the food, can be achieved by simmering, boiling, until it is very soft and then, mashed with a fork or ladle, for example, potato. It can also be done by pushing the food through a strainer, or crushing it in a container until smooth and even in consistency, for example, banana. Pureeing can equally be done using a blender, food processor, or food mill, for example, tomato. However, purées generally should be cooked, either before or after grinding, to remove contaminants, reduce moisture, improve flavor and texture.

#### **4.3 OFSP puree**

Value addition through processing of agricultural products such as OFSP roots to puree is key to ensuring a stable supply of highly nutritious products to consumers. OFSP puree is an ingredient in many foods, including baby foods, casseroles, puddings, soups, pies, cakes, ice creams, breads, and other products [36, 67–69]. Sweet potato purees are also used in fruit/vegetable-based beverages and restructured products as well as commercial ones like jam, ketchup, flakes, and powders while various fermented food products have also been explored [36, 70–74].

OFSP is naturally sweet and when used in baked goods and confectionaries, there is a reduction in the sugar, fats, and oil used thus more nutritious and healthy foods for less cost. With the efforts of CIP in many developing countries, adoption of OFSP puree has empowered women and youths in developing new OFSP-based food products and created opportunities for income generation along the value chain. Farmers are becoming more confident to grow OFSP because there is market for it while puree processors are encouraged to process because there is demand for it. For instance, in Kenya alone, demand for OFSP puree is valued at more than USD 5 million annually. Creating demand for OFSP has increased the crop's market value, encouraging more farming households to grow and consume it, while making pro-vitamin A products available to consumers [75]. Similar trends are found in other African countries like Ghana, Tanzania, Rwanda, Nigeria, and Uganda although no available data on the market value.

#### *4.3.1 Puree technology for OFSP processing*

Use of puree is growing in bakeries, eateries, and restaurants globally [76] and its technology from sweet potato has been developed in industrialized countries like USA since the 1960s [77, 78] as well as in developing countries, especially Africa since the 1990s. OFSP puree processing technologies have advanced over the decades from traditional methods of manual mashing of cooked roots to highly sophisticated and automated systems.

Several techniques have been developed for puree processing in order to produce purees with consistent quality, despite variations in carbohydrate content and starch degrading enzyme activities due to cultivar differences, and postharvest handling practices [67, 79]. Process operations for pureeing of sweet potato include washing, peeling, hand-trimming, cutting, grinding, pre-cooking/finish-cooking. The cooking temperature-time must be programmed to suit the enzymatic starch conversion in order to produce puree with desired maltose levels and viscosities. For SP puree that are thermally processed, the starch is gelatinized and produces thick slurry puree with cooked feel that may not be acceptable in juicy products. This is a limitation to the heat treatment technology of SP puree but fortunately overcome with an alternative approach of grinding the raw sweet potato and treating with acid to inactivate oxidizing enzymes during juice extraction. At the same time, the ungelatinized starch and flour with high dietary fiber can be recovered as other by-products from this alternative process [80]. **Figure 1** shows the schematic representation of SP puree processing with all the unit operations highlighted for puree preserved by both freezing and use of preservative. Raw sweet potato roots are peeled either by abrasive rollers or steam flashing, followed by thorough washing, trimming, and cutting into slices, strips, chunks, or dices. The cut roots are steam cooked and then passed through a pulp finisher to make the purees. The peeled sweet potato roots are cut into desired shapes with specific sizes recommended by Walter and Schwartz [81]; For cubes, it is 2 cm; strips, 2 × 2 × 6 cm; and slices, 0.5–0.95 cm thickness or mashed using a hammer mill with rotating blades to chop and push the materials through a 1.5–2.3 mm mesh screen [81]. The cut or mashed roots are then steamed blanched at 65–75°C to activate the amylases and gelatinize the starch for hydrolysis. For the sliced, striped, and cubed roots, hammer mill is used to pulverize the blanched materials into puree. For puree that targets high maltose content, the blanched puree is pushed into a surge tank and hold at 65–75°C for more starch hydrolysis [68].

#### **Figure 1.** *Flow chart of OFSP Puree processing. Adapted from Owade et al. [95].*

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

Hoover and Harmon developed another technique called "enzyme activation technique" for processing sweet potato puree [82, 83]. The technique, which is now commonly used in food industry uses endogenous amylolytic enzymes to hydrolyze starch in sweet potato to process the puree.

SP puree can be further processed and used in other forms for various purposes in food industry. SP flour from puree can be made by drying while extrusion technology and chemical treatment are explored for specific use of the flour. Drying of SP puree can be through high-tech drum or spray drying but in many African countries, solar and mechanical drying in cabinets is common in producing sweet potato dried chips which are then milled into flours [84, 85]. For OFSP flour from puree, choice of drying technology is important, technologies that retain the provitamin A should be the priority so as not to defeat the purpose of its biofortification. Change of flour color from orange to white after drying is an indication of carotenoid loss to drying, which should be avoided as much as possible by choosing technologies that prevent prolonged exposure to heat and sunlight. With high level of carbohydrate, B-carotene (orange-fleshed varieties), and anthocyanin (purple-fleshed varieties), SP purees and dehydrated forms can be used as functional ingredients to impart desired textural properties and phytonutrient content in processed food products [62].

Fermentation (bio-processing) of OFSP is another processing technology that can produce functional foods and beverages such as sour starch, lacto-pickle, soy-sauce, acidophilus milk, etc. through either solid-state or submerged fermentation [86]. These foods are opportunities to diversify OFSP utilization options, increase use and consumption as well as commercialization for improved health and wealth.

#### *4.3.2 Puree technology for OFSP preservation and packaging*

Purees processing technologies go hand in hand with preservation and packaging, which are achieved by various methods namely; low temperature storage (refrigeration and freezing), canning, aseptic packaging and chemical treatment of puree for prolonged shelf-life over its supply chain.

The finish-cooked puree can be packaged in can to produce a shelf-stable product or in plastic containers for a low-temperature storage (refrigeration or freezing) [79, 86, 87]. However, each of the two preservation approaches has its constraints in puree processing. For canning, in as much as it does not require special storage facilities and conditions, the finished product is prone to some sensory (flavor, texture & color) and nutrient degradation. This is because the canned SP (a low-acid food, pH 5.8–6.3) puree is subjected to high conductive heat treatment for a long time (e.g., 165 minutes at 121°C for an institutional #10 can size). On the other hand, if the sterilization is done through slow rate of heat transfer from the wall to the center of the can, there is a limit to the can size and number that can be produced, which again restricts production capacity of the industry and availability of SP puree for use as a food ingredient.

Also freezing, which is a long-known preservation technique with relatively less sensory and nutrient degradation is capital intensive in term of energy, storage space, distribution logistics. It has restricted product package sizes and above it, the puree has to be defrosted before use, which is not user-friendly. With these limitations, few food companies are into commercial production of canned and frozen puree even in developed countries and almost none in the SSA countries [84].

However, to address the limitations of canning and freezing in producing high quality shelf-stable purees, aseptic packaging and continuous flow microwave system for rapid sterilization are being used [62].

Aseptic processing uses the principle of high temperatures (≥125°C) short time (HTST) to produce a higher quality puree with comparable level of microbiological safety as that of a conventional canning system [88]. Coronel et al. developed a process for rapid sterilization and aseptic packaging of OFSP purees using a continuous flow microwave system operated at 915 MHz [88]. In this process, the SP puree is loaded into a hopper, and pumped through the system. Microwaves from a generator are delivered to sterilize the puree at 130–135°C, retain in the holding tube for 30 seconds, rapidly cool in a tubular heat exchanger, and then aseptically package in aluminum polyethylene laminated bags [89]. The process is short and produces at least 1 year shelf-stable product, packed in flexible polythene bags, with relatively less sensory and nutrient degradation. The process is protective of micronutrients so there is the possibility of retaining at least 85% of carotene and anthocyanins in the finished puree. **Figure 2** shows an overview of typical puree machine with aseptically packaged OFSP puree. CIP has also developed a shelf-stable, vacuum-packed OFSP puree that is increasing the supply of OFSP puree and making it available at all seasons.

This process is reportedly suitable for OFSP as well as purple-fleshed sweet potato puree processing [90] especially in the developing African countries. It has opened

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

up new market opportunity for the SP industry generally and can also be applied to purees from other fruits and vegetables [91].

With the recent commercial development of the microwave-assisted processing and aseptic packaging of sweet potato purees, it is expected that more processed food products from the puree will be developed. African countries, precisely Kenya, Rwanda, Malawi, and Uganda among others, have been growing gradually in the commercialization of OFSP puree and the subsequent wheat flour substitution in bakery products. Private companies in Malawi and Kenya are now manufacturing OFSP puree and selling it to bakeries that substitute OFSP puree for up to 40% of the white wheat flour in bread and other baked goods. Recently, orange-fleshed sweet potato puree has replaced 20–50% of wheat flour in cookies, donuts, and breads by some commercial bakeries in Ghana, Kenya, Malawi, Rwanda, and Uganda [92]. Some processing companies in some African countries have been committed to OFSP processing and product development using OFSP puree-Tehila Bakery and Value Addition Center in Malawi; Organi Limited and Euro Ingredients Limited in Kenya; Sinagerard in Rwanda; Sanavita, SUGECO and Better Markets for Crop Products Limited (BMC) in Tanzania; Farmorganics Nigerian Limited in Nigeria. These have resulted in positive impacts on income generation for small-scale farmers and businesses, employment opportunities for women and youths, and improved nutritional status of target communities are some of the targeted outcomes. With these innovative processing technologies and successful piloting of the product, OFSP puree has been described as "breakthrough product" for Africa that offers the much-needed nutritious products, with consumer accepted organoleptic properties [93]. However, further work needs to be done in scaling up through more public awareness and education on its multiple health benefits for all, for consumption and commercialization.

#### *4.3.3 OFSP puree in bread bakery*

Bread has been an important, common exotic cereal product consumed by most individuals in Africa. Incorporating OFSP puree into bread would significantly increase the number of OFSP consumers and reduce VAD [94, 95]. According to Wanjuu et al., "OFSP puree can replace up to 50% of the wheat flour in bread, while reducing sugar (90%), fat (50%) and eliminating artificial colorings (egg yellow). The baked bread retains over 50% of the β-carotene, and the OFSP puree improves the texture of wheat products, making them easy to chew and digest" [96]. The composite bread has a better sensory quality (flavor, color, and soft texture), which contribute to its acceptability. Other benefits include low production costs and improved vitamin A content [97]. The OFSP puree-based bread is commercially available across sub-Saharan Africa (SSA) and is being promoted for its added nutritional benefits, which is increased β-carotene. This serves as a good medium for intake of β-carotene and to alleviate vitamin A deficiency (VAD) especially among the vulnerable populations in SSA. OFSP puree can replace some of the white, wheat flour in baked and fried products especially in the SSA where some of the countries import wheat flour at very huge costs. According to Moyo et al., African millers spend millions importing wheat, with East African countries being among the top importers. Kenya's wheat import bills are estimated at \$250 million, Tanzania's at \$150 million, Uganda's at \$53 million, and Rwanda's at \$35 million per year [93]. Substitution of wheat flour with OFSP puree up to 50% can significantly reduce dependency on imported wheat flour, enhance utilization and consumption of locally produced OFSP, create jobs for smallholder farmers, women and youths, and ultimately contribute to national economy.

OFSP puree in bread and other baked products makes puree a sustainable solution to the perishability and all-year unavailability of the crop [96]. It also encourages expanded production, utilization and consumption of OFSP-based baked products as well as meeting consumers' daily requirement of vitamin A either fully or partially. According to Wanjuu et al., (2018), bread made with OFSP puree had a longer shelf-life than the conventional white bread from 100% wheat flour, probably because of the significantly higher water activity in white bread than in the OFSP bread [96]. Using OFSP, either as flour or puree in bread making has implications on its sensory characteristics, and quality control of wheat flour-based bread [98]. OFSP pureed bread has been described by Olatunde et al. as having deeper brown colored crust, softer crumb, more uniform crumb cell, higher loaf volume (872–885 cm3 ), specific volume (4.59– 4.76 g/cm3 ), oven spring (0.50–1.00 cm), softness (18.35–20.20 mm), crust moisture (18.05–18.17%) and consumer acceptability (7.14–7.50). In terms of consumer acceptability, bread from OFSP puree was more acceptable than that of OFSP flour [98].

## **4.4 VAC processing and products**

Like the white varieties of cassava, yellow cassava also starts to spoil within 2 days after harvest, hence the need to process the roots into various intermediate and finished products through different processing techniques.

Yellow cassava roots can be dried in peeled, cut into chunks/sizes, or grated form for different value-added products. As much as possible, drying conditions for yellow cassava should be protective of the provitamin A (carotenoid) in it.

Similar to the white varieties, yellow cassava can be processed into traditional foods such as *gari, fufu, akpu, tapioca*, and starch; the only difference is the color of the food products, which in this case is the yellow color and it is an indication that provitamin A is present in the food. It is an added advantage over the white varieties. **Figure 3** shows various traditional products from cassava processing-*Pupuru, Garri,* 

#### **Figure 3.**

*Traditional VAC products. Source: Phorbee et al. [35].*

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

*Fufu/Akpu*, *Abacha*, and Tapioca, which are processed through various unit operations like grating, pressing (dewatering), soaking, fermentation, roasting, etc.

Novel food products like pastries and some confectionaries have also been made with yellow cassava through high-quality cassava flour or grated and dewatered fresh roots, for both household dietary diversity and income generation/livelihood. Some Nigerian recipes have been developed for novel VAC-based foods, which use high-quality cassava flour for household consumption of carotenoid-rich foods as well as income generation at micro scale [35]. These include VAC pastries and snacks, puree, etc.

#### **4.5 Drying technologies of cassava and VAC**

Drying is a unit operation aimed at removing nearly all the free water present in a food stuff [99]. The commonly used methods of drying cassava in SSA include open sun drying on bare ground, raised platforms, road sides, roof tops, and tarpaulins as well as use of solar dryers. The selection of an appropriate drying method is necessary to ensure good quality products and prolonged shelf life.

#### *4.5.1 Sun-drying of pressed cassava mash*

Sun drying is an ancient drying technology of cassava when processing into chips, flour, or starch. Fresh cassava roots are highly perishable as they contain 65–70% moisture, and take time to sun dry. Prolonged sun drying has implications on the product quality as it is prone to spoilage and/or contamination from rain, wind, dust, insect infestation, animal attack, and microbes. Reduction of moisture is a key step in processing cassava roots into flour and must be done quickly to avoid lowering product quality. It is therefore better to remove as much water as possible by grating and pressing the cassava mash in a jack press for about 2 hours (dewatering) before drying. Sun drying is done by spreading the wet product on a clean concrete drying floor or a black plastic sheet laid on top of a concrete drying floor. The wet product needs sunlight, dry air (low humidity), and good airflow over it to dry effectively. Sun drying, therefore, depends on availability of sunlight and so it is challenging during raining season, which limits availability of cassava flour or starch all year round. Also, it is best suited for small-scale rural operations where product volumes are low (50–100 kg of dry product per day) [100]. Furthermore, sun drying exposes cassava to sunlight and so not suitable for biofortified cassava varieties.

Just like white cassava varieties, yellow cassava varieties have been reported to be relatively high in moisture content and so prone to deteriorations after harvest [101], thus necessitate post-harvest processing. However, yellow cassava being biofortified with carotenoid (pro-vitamin A), is thermal and photo sensitive so exposure to sunlight during drying can lead to significant loss of the carotenoid and therefore defeat the purpose of its biofortification.

To preserve the carotenoid content and also process yellow cassava roots into chip or flour all year round, alternative drying technologies that are protective of the biofortified vitamins in the cassava roots have been exploited over time. These include cabinet/tray dryer, drum dryer, solar dryer, and flash dryer.

#### *4.5.2 Flash drying technology*

The flash drying technology is a high-precision indoor novel drying technology that involves instant drying of a wet material by passing hot air through it, to quickly evaporate free moisture in the material, using rapid heat transfer. Flash drying is an efficient and effective drying technology as the process facilitates fast evaporation through speedy heat transfer. The technology can be applied to food, feed, and some other industrial materials. The drying process, being rapid makes it a suitable technology for nutrient-dense foods as the short exposure to heat favors retention of nutrients especially the thermally sensitive micronutrients.

### *4.5.2.1 Principle of flash drying*

The principle of flash drying is instant evaporation of free surface moisture from a wet material mixed with hot air. Wet particle material is passed through hot air or steam where the particles are dried almost immediately and the gas or steam temperature decreases due to heat transfer [102]. The wet material, either in paste or cake is pulverized into fines and increase the surface area, to hasten the drying process. The dried material (usually in powder form) remains suspended in air and conveyed while drying [103]. Being a short-time dryer, it is very suitable for biofortified provitamin A cassava as it protects the beta carotene in the cassava unlike sun drying with a prolonged exposure to sunlight. According to Kuye et al., the output of flash drying technology is significantly improved compared to those of general drum or cabinet drying. Through it, users can achieve higher economic benefits in the short term.

#### *4.5.3 Flash drying technology for VAC*

For cassava, flash drying technology came at an opportune time, using flash dryer, which was fabricated and introduced in Nigeria by CAVA-Cassava: Adding Value in Africa project in 2016 [28]. Flash drying is achieved with flash dryer, a high-tech equipment, designed to dry pressed (dewatered) cassava mash into High Quality Cassava Flour (HQCF) within seconds, and can process 3–7 tons of HQCF per day. Flash dryers have been reported suitable for drying mash and solids of moisture content between 30 and 40% and applicable not just in food industry but also other industries like feed, chemical, and pharmaceutical [28]. A flash dryer is generally constructed with devices, which can simultaneously dry, pulverize and classify materials by particle sizes. It is a continuous drying device specially designed for drying cake, paste and muddy materials. A flash dryer must be able to resist the intense heat and rapid movement required in the drying process, so it must typically be fabricated with strong, detailed construction materials and accurate temperature control device. While other features of the dryer are specific to intended use, it is usually customized for purpose. Flash dryers, although expensive in fabrication, is low in energy consumption, high in thermal efficiency, occupies small area thus saving factory space and efficient in continuous mass production.

Specifically for drying cassava and VAC, the flash dryer by feature, typically consists of a blower, air pre-heater, feeding mechanism, (hopper, pulverizer, screw conveyor, and a rotary air lock), dryer, cyclone, and filter as shown in **Figure 4**. Wet-pressed (dewater) cassava to be dried is loaded into the feed mechanism while the air, after passing through an air filter, is heated in a hot air generator (steam can also be used). The wet cassava mash is circulated into the hot-air for thorough mixing. The pulverized cassava mash and the hot air mixture is conveyed through the dryer to the cyclone using pressure from the blower. The cassava mash gets dried through quick moisture loss and the moisture absorbed by the hot air, thus lowering the air temperature (and increasing the humidity). The mixed air and dried cassava flour

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

**Figure 4.** *Schematic diagram of a Flash Dryer: Source: Kuye et al. [103].*

are separated in the cyclone, and the flour is let out from the cyclone through the discharge valves. Fine cassava flour particles that escape from the cyclone are trapped by a bag filter. Kuye et al., gave the specification of all the devices of a typical cassava flash dryer [103].

This flash dryer is not only for making high quality cassava flour, but can also be used to dry cassava starch and *fufu* cake for dried cassava starch and instant *fufu* flour, respectively. VAC can also be used to make *fufu* mash and instant *fufu* flour, which are cooked at home as a meal ("swallow") and consumed with any choice of soup in West Africa. Use of flash dryer is very suitable for VAC as it is a rapid drying process, which favors retention of the pro-vitamin A in the biofortified cassava. With flashdried cassava flour and *fufu* from VAC, consumers' access to vitamin A is guaranteed because of high retention of the vitamin after processing. Consumption of instant *fufu* flour is growing in Nigeria and Ghana due to increased urbanization and reliance on instant convenient foods. This presents a good opportunity for the consumers to be reached with VAC *fufu,* dried with flash dryer that retains the beta carotene in the biofortified cassava and contributes to the fight against vitamin A deficiency in the consuming countries of SSA. However, increased consumers' acceptance and access to these products is still necessary.

## **5. Conclusion**

With the advances made so far, on appropriate post-harvest technologies, processed biofortified crops have potentials to improve food and nutrition security in the sub-Saharan Africa, if fully exploited. Processing the biofortified crops into products improve availability, reduce post-harvest losses significantly, and create more options for consumption and commercialization, as the crops can be processed in various ways, using various techniques of cooking and drying. With these available technologies, the shift from non-biofortified to biofortified food consumption is a significant move towards improved food system transformation. OFSP puree with the SSA-friendly technology of aseptic packaging and continuous flow microwave system of rapid sterilization ensures a stable supply of high-quality shelf-stable nutritious product, with minimal carotenoid degradation to consumers. The technologies are indeed breakthrough within the biofortification sector in the SSA, leveraging on the versatility of the crops especially OFSP, which contains some functional components. OFSP puree is an important intermediate product with existing and potentials for diverse finished products in the food industry especially confectionaries and beverages. Similarly, biofortified cassava processing into flour, starch, and instant *fufu* flour using the flash drying technology of rapid evaporation through heat transfer, produces high-quality products that ensure delivery of pro-vitamin A to consumers. With cassava being a key staple in many SSA countries, consumer shift from white to yellow cassava will be a major revolution in household reach with vitamin A especially the rural consumers who are easily left out of the micronutrient interventions.

The shelf stability of the products from these advanced technologies also favors sustainability of consumers' access to nutritious crops thus realizing the purpose of biofortification, which is to contribute to the fight against vitamin A deficiency. In response to food insecurity and poor livelihood, the available technologies for enhanced biofortified nutritious food product development, present opportunities to significantly contribute to improved food system through enhanced utilization and consumption of locally produced crops, create jobs for smallholder farmers, women and youths, and ultimately contribute to national economy. OFSP puree makes consumer-acceptable bread, which compares very well with 100% wheat flour bread organoleptically, with increased micronutrients and functional components, reduced production cost from reduced use of wheat flour and sugar.

However, there is need for continued research on biofortified crop cultivar screening targeting more diverse end uses, with technology transferred to the end users through private-public engagement. This way, interest of the key actors of the value chain (Breeders, Farmers, Processors, and Marketers) will be stimulated towards biofortified crops. This is an awareness/adoption strategy, which should also be scaled up with favorable polices.

### **Acknowledgements**

The authors wish to acknowledge Oluwole, Funmilola Akanbi and other staff of Food Agriculture Nutrition Network (FANN) for their support in reading through and editing the manuscript severally. Thanks to Blessing and Emmanuel for ensuring adherence to the author's guidelines.
