Investigating carotenoid loss after drying and storage of orange-fleshed sweet potato

Biofortified orange-fleshed sweetpotato (OFSP) is being promoted to tackle vitamin A deficiency, a serious public health problem affecting children and pregnant/lactating women in sub-Saharan Africa. The aim of the study was to quantify and understand the factors influencing carotenoid losses in dried OFSP. Losses were determined in chips after drying and storage. A preliminary study demonstrated that carotenoid levels were not significantly different following either solar or sun drying. Carotenoid loss after drying was generally correlated with high initial moisture content and high carotenoid content in fresh sweetpotato roots. Losses of pro-vitamin A were less than 35% in all cases. Flour made from OFSP could therefore be a significant source of provitamin A. In contrast, storage of chips at room temperature in Uganda and Mozambique for four months resulted in high losses of pro-vitamin A (ca. 70-80% loss from the initial dried product). Low-cost pre-treatments, such as blanching, antioxidants and salting, did not reduce carotenoid losses during storage. Enzymatic catabolism of b-carotene in dried OFSP was considered unlikely because of low peroxidase activities at low water activities and the loss of peroxidase activity during storage. To understand further the factors causing the losses, dried sweet potato chips were stored under controlled conditions of temperature (10; 20; 30; or 40ºC), water activity (0.13; 0.30; 0.51; 0.76) or oxygen (0 [under nitrogen]; 2.5; 10 or 21% [air]). Oxygen was the main cause of degradation followed by temperature. An Arrhenius kinetic model was used to show that carotenoid breakdown followed first order kinetics with an activation energy of 68.3kJ.mol-1 that was in accordance with the literature. Experimental observations fitted well with data predicted by the kinetic model. The formation of the volatile compounds,b-ionone; 5,6-epoxy-b-ionone; dihydroactinidiolide; b-cyclocitral that were clearly related to the degradation of b-carotene, helped further understand breakdown patterns of b-carotene

Use and nutritional value of cassava roots and leaves as a traditional food

Cassava is second after rice in importance as a source of carbohydrates in developing and tropical countries, and the fifth most important staple crop globally (FAOSTAT 2013). In developing countries, over half a billion people consume cassava as food and rely on it as important sources of nutrition and income. Cassava’s main commercial product is the long tuberous starchy root. Size varies widely, but averages about 5 to 7 cm diameter and 20–40 cm long. The root has a mostly dark brown, but sometimes light brown or white, peel, and generally a white or cream interior fl esh. Cassava leaves are alternate palmate and smooth leaves with lobes between 7 cm and 15 cm long that are also edible

On-farm evaluation of the impact of drying and storage on the carotenoid content of orange-fleshed sweet potato (Ipomea batata Lam.)

Drying of orange-fleshed sweet potato was evaluated under African rural conditions. Three locally built dryers (open- air sun, tunnel and shade) were tested using Resisto and MGCL01 varieties in Mozambique. Total carotenoid losses were low in all dryers being 9.2% on average. After drying, sweet potato chips were stored in a traditional way (jute bags inside a mud house). Chip size (thin, thick chip or slice) had a significant effect on drying (P < 0.05) but not on storage and variety had an effect on both. Total carotenoid losses during storage were much higher being 83.7% on average, after 4 months, with main individual carotenoids fitting a first-order kinetics degradation. Globally, carotenoid losses on-farm or on-research station were of similar level

Women eat more rice and banana: the influence of gender and migration on staple food choice in East Africa

An original approach was used to examine how staple food choice differs by gender and migration: this consisted of a quantitative survey (6 locations with urban consumers from various economic classes (n=123)), a qualitative in-depth interview with a subset of those consumers (n=18), and focus group discussions (n=13). Men and women had similar results in terms of their preferred staple food choice attributes; yet women indicated consuming more rice and banana, and men, more maize and cassava (Chi-squared test; p<0.05). Migration status and life stage (formative or adult years) also influenced the type and diversity of staple crops reported

Micronutrient (provitamin A and iron/zinc) retention in biofortified crops

For biofortification to be successful, biofortified crops must demonstrate sufficient levels of retention of micronutrients after typical processing, storage, and cooking practices. Expected levels of retention at the breeding stage were verified experimentally. It was proven that the variety of biofortified crop, processing method, and micronutrient influence the level of retention. Provitamin A is best retained when the crops are boiled/steamed in water. Processing methods that are harsher on the food matrix (i.e. drying, frying, roasting) result in higher losses of provitamin A carotenoids. Degradation also occurs during the storage of dried products (e.g. from sweet potato, maize, cassava) at ambient temperature, and a short shelf life is a constraint that should be considered when biofortified foods. Iron and zinc retention were high for common beans (Phaseolus vulgaris) and cowpeas (Vigna unguiculata), indicating that iron and zinc were mostly preserved during cooking (with/without soaking in water)

Exploring the complementarity of fortification and dietary diversification to combat micronutrient deficiencies: a scoping review

Achieving a balanced and diverse diet remains a challenge for many people, contributing to an ongoing burden of micronutrient deficiencies, particularly in low-income settings. Fortification or dietary diversification are common food-based approaches. We conducted a scoping review to: 1) find evidence on whether combined food–based strategies are more effective than single strategies, and 2) understand how strategies implemented together could complement each other to achieve optimal nutritional impact on populations. Peer-reviewed articles selected (n = 21) included interventions or observational studies (n = 13) and reviews (n = 8). We found little evidence of an added nutritional impact. On the other hand, it is apparent that fortification and dietary diversification target different types of settings (urban compared with rural) and foods (that is, low priced compared with highly priced). Further research is needed to understand the complementarity of these approaches and establish evidence of the effectiveness of combined strategies to foster policy adoption

Staple food cultures: a case study of cassava ugali preferences in Dar es Salaam, Tanzania

This study examines the relationship between food choice and food culture, in relation to staple foods and cassava in particular, within the context of migration and the urban environment Dar es Salaam, Tanzania. The analysis provides an understanding of the different drivers of food choice, and how they may differ by gender and other factors of social difference such as age, ethnicity and region of origin, in the context of a city with a rapid growth rate, and wealth and ethnic diversity. In-depth interviews suggest that people a structure their food cultures as primarily juxtaposing hard versus soft foods, and traditional versus modern foods. Ugali, particularly cassava ugali, typically falls into the latter categories. The type of ugali that one prefers, which is determined by the type of flour used (cassava, maize, sorghum and/or millet) is profoundly influenced by their region of origin. However, after migration to Dar es Salaam, people typically adopt the food culture of the city over time, which mainly consists of sembe, a processed maize-based ugali that is categorised as a modern food. Availability, quality and storage time of cassava flour for ugali is limited. Cassava ugali also took longer, required more strength and continuous monitoring to prepare, compared to other flours. There were also negative perceptions that cassava was associated with poverty. However, perceptions of cassava’s nutritional value as a ‘traditional’ food were positive. Cassava ugali was also considered to be one of the most strength-inducing types of ugali and therefore important for stamina, and a reason it is often consumed during Ramadan. Social norms also played an important role in influencing people’s shift towards sembe as their staple food. Ugali in Dar es Salaam is commonly viewed as a food consumed by men, because it is needed for strength. Women are perceived to undertake less physically demanding activities after they migrate to the capital, because they may move away from farm work, and are therefore more likely to prefer and consume rice. Rice and more modern foods were also preferred among youth. The different intrahousehold staple food preferences meant that different staples were often prepared by women, reinforcing the importance of ease of preparation for making ugali. Overall, cassava plays less of a role in diets of people who do not traditionally consume cassava and among those who have settled in Dar es Salaam, particularly women and youth born in the city. However, there are also positive perceptions of cassava as promoting dietary diversity and a return to natural foods. Awareness of the availability and quality of cassava flour, particularly HQCF, and increase in the ease of preparation and storage, will require improvement if it is to be a viable alternative to the city’s main staple. As both men and women consume and purchase staples in the household, products need to be geared towards the needs and preferences of men and women

Determinants of postharvest losses along smallholder producers maize and sweetpotato value chains: An ordered probit analysis

Postharvest loss reduction throughout commodity value chains is an important pathway to food and nutrition security in sub-Saharan Africa. However, lack of understanding of the location and share of the losses and associated factors along the postharvest value chains remains a major challenge to operationalizing postharvest loss mitigation strategies. This paper assesses the determinants of postharvest losses at each postharvest stage of maize and sweetpotato (white fleshed and orange fleshed) value chains for smallholder farmers using our cross-sectional field survey data from two districts in Uganda. An ordered probit model estimation reveals that self-reported perceptions of the level of quantitative postharvest losses at different stages of commodity value chains are influenced by socio-economic factors as well as existing postharvest handling and storage practices. Increased years of education and training received on postharvest management are related to lower perceived levels of postharvest losses at key stages of value chains. Lower perceived postharvest losses are also associated with: at transport to homestead the use of sacks and bicycles as opposed to the use of baskets or transporting by trucks; at drying the use of tarpaulins as opposed to use of plastic sheets; shelling using bare-hands as opposed to beating cobs in sack with sticks; storage in a brick and mortar store as opposed to storing in living room in the house

Reducing postharvest losses in the OIC member countries

It is universally understood that postharvest losses are high, particularly in less developed economies, and that this is an issue of keen interest to researchers, practitioners and policy makers alike. Postharvest losses are defined by COMCEC as food damage or degradation of food during different stages of the food supply chain that are incurred between the farm-gate and prior to retail and consumption. Highlights of this report. • Clear evidence of substantial postharvest losses across all Members and commodity groups and these are similar to those reported in non-OIC Member Countries. Figures are estimates though. • Pockets of high physical losses identified: e.g., fruit and vegetables, root and tuber crops and meat and meat products • High economic losses for cereals and fish and fish products • Nutrition losses were rarely reported but for cereals in Sub-Saharan Africa losses could be equivalent to the annual caloric requirement of 48 million people • Weak policy support to effecting loss reduction strategies almost universal • Limited on-going measurement of postharvest losses means impact of innovation and policy was hard to measure This analysis of postharvest losses in the OIC Member Countries, conducted by a team from the Natural Resources Institute (NRI), University of Greenwich between January and July 2016, sought to provide ways to contribute to reduced postharvest losses. The analysis sought to identify approach and practices, and policy recommendation for future investments. The methods used were a combination of a brief literature review, an on-line survey of key informants, and a series of commodity specific case studies that included three field visits. The scope of the study included all OIC Member Countries, all three official Regional Groups of OIC Member Countries (African, Asian and Arab), and representation from seven commodity groups (cereals, roots and tubers, oilseeds and pulses, fruit and vegetables, meat and meat products, milk and dairy products and fish and seafood). Field visits were conducted in Indonesia, Bangladesh and Oman. A conceptual framework was developed from knowledge of the literature and the challenges and complexities of measuring postharvest losses. The postharvest physical losses in OIC countries reported by commodity group for the literature review, online survey and case/field studies suggested that they were not that different from the global losses for each commodity that the authors extracted from FAO data. For cereals, root and tuber crops, oilseeds and pulses, fruit and vegetables, meat and meat products, milk and dairy products and fish and fish products, the extrapolated losses from FAO data was 12-15%, 22-34%, 15-38%, 11-12% and 16-25% respectively. Compared to this, the range found from the OIC study was 9-48%, 7-50%, 14%, 3-65%. 6-40%, 2-30% and 3-50% respectively. Although the spread is wider that the estimates from FAO reports, it is considered to be consistent. Thus the postharvest losses in OIC countries are not that different from elsewhere. Some commodities and countries are well covered (e.g. maize in Uganda), but most are poorly analysed in existing research, with some significant knowledge gaps identified (e.g., some countries with little or no literature, other commodities under researched). The postharvest economic losses were less consistently reported and difficult to compare with the global situation due to differences in reporting (monetary amounts or percentages), different sizes of economies and differing product values. For example, postharvest losses were considered large and the order of US$1 to 4 billion and US$4.8 billion per annum for cereals (Egypt and Uganda) and fish (Indonesia) respectively but as low as US$8 to 21 million per annum for tomatoes in Bangladesh. This probably reflects the difficulties in estimating losses as well as valuation. The least known/understood postharvest loss in our analysis was regarding the quality/nutrition losses and was limited to calories in cereals to vitamin A for biofortified cassava. Such information will be critical for countries suffering from nutrition deficiency. Bringing together the estimates for physical, economic and quality/nutrition losses in the OIC Member Countries along with comparisons with the global situation has highlighted a few lessons and gaps. The bulk of the information obtained from the literature review, online survey and case/desk studies concerned the physical losses. This is probably because physical losses are easier to estimate either by direct measurement or by visual inspection. It should be noted however, that all are estimates and few studies are quantitative. Much less was reported concerning the economic losses and the amounts will differ markedly from one value chain for another, even for the same product and commodity. This, therefore, is an area of research that would require more inputs and due to the high cost of undertaking such work, the target value chains would need to be selected according to economic contribution to the OIC Member Country. In all cases the monetary cost of the losses was significant but it was not always known how the costs were estimated. If the monetary losses could be captured, this will lead to benefits for the consumer and actors in the value chain along with potential benefits to national balance of payments. The least known was regarding the quality/nutrition losses but such information may be critical for countries suffering from nutrition deficiency, particularly calories and vitamins. Key findings concerning specific postharvest research issues was sparse and geographically scattered. Some commodities have a greater coverage than others (e.g. artisanal fisheries and maize are far more researched that cattle or bananas). Some OIC Member Countries and regions have seen much more postharvest loss research and practice than others. For example, the Africa Group and low income countries has seen more support, probably from donors, which has been driving postharvest loss research. Commodity specific findings are reported and these relate to the product characteristics, uses and markets they each fall into. For example for the cereals, the challenges were related mainly to drying and storage, especially related to pests in store, whereas for other root crops peeling, storage and marketing were the highest postharvest loss elements reported. For oilseed and pulses, key issues related to storage largely due to the impact of storage pests. For fruit and vegetables, the issue was the high perishability and ease of damage. Meat and meat products issues related to high transport losses for live animals are often a factor of distance to market or slaughter and the absence of infrastructure including adequate cold chains. For milk and dairy products, key issues were related to the need to upgrade the milk and dairy value chains, particularly setting standards, organising farmers and supporting the emergence of cool-chains. Lastly for fish and fish products, the key issues related to postharvest losses in aquaculture. Investments in cold chains and improved postharvest handling could substantially reduce postharvest losses and food safety concerns. A range of common challenges were identified. These include the underestimation of the impact of rodents on losses, the importance of the impact of actions taken on farm that can affect postharvest losses, the impact of toxins such as aflatoxin, the benefit from development of cold-chain infrastructure and the existence of policies supporting strategic crops has, in some cases, led to a history of under-investment in postharvest management by the private sector. The impact of gender also appears to have under investigated or reported. A range of common solutions were identified on the farm, in the postharvest value chain and ones that were systemic such as rules and standards, capacity and training etc. For example breeding to improve the storability of fruit and vegetables and root and tuber crops would reduce losses, early quality differentiation to improve marketability etc. A number of examples of best practice were given related to ownership, the value of ICT technology, investment for stored fruit and vegetables and sharing information via mobile phones, strategic investment such as cold chain infrastructure, the emergence of new industries from waste, multi-actor collaboration and the importance of national loss-reporting systems (for example APHLIS and Indonesian Fisheries Sector). A number of policy recommendations were suggested to advise OIC Member Countries locate and quantify postharvest losses. These focused on the need for establishing national postharvest loss reduction coordination approaches, establishing consistent methods, sharing best practice and promoting system wide efforts, promoting capacity building and sharing among OIC Member Countries, facilitating local, national and, potentially, regional multi-stakeholder commodity platforms etc. Lastly, to overcome the challenge that postharvest losses is generally more complex than pre-harvest losses due to the greater diversity of products and end uses and markets that the products are directed at a strategy for prioritise which commodity groups and value chains are most important at the national level was suggested

Relationship among the carotenoid content, dry matter content and sensory attributes of sweet potato

The sensory characteristics of biofortified sweet potato in Africa were explored over a wide range of carotenoid (0.4–72.5 μg/g fresh weight) and dry matter contents (26.8–39.4%). The logarithm of the total carotenoid content was correlated with the dry matter content (declining by 1.2% with each doubling of the carotenoid content) and a wide range of sensory characteristics that involve visual, odour, taste and textural characteristics. Multiple linear regression models were developed. The logarithmic relationship of colour to the carotenoid concentration means that those varieties with a relatively low carotenoid content may appear to be of similar intensity to those with a much higher and hence nutritionally beneficial carotenoid content