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

Physical losses could partially explain modest carotenoid retention in dried food products from biofortified cassava

Gari, a fermented and dried semolina made from cassava, is one of the most common foods in West Africa. Recently introduced biofortified yellow cassava containing provitamin A carotenoids could help tackle vitamin A deficiency prevalent in those areas. However there are concerns because of the low retention of carotenoids during gari processing compared to other processes (e.g. boiling). The aim of the study was to assess the levels of true retention in trans–β-carotene during gari processing and investigate the causes of low retention. Influence of processing step, processor (3 commercial processors) and variety (TMS 01/ 1371; 01/1368 and 01/1412) were assessed. It was shown that low true retention (46% on average) during gari processing may be explained by not only chemical losses (i.e. due to roasting temperature) but also by physical losses (i.e. due to leaching of carotenoids in discarded liquids): true retention in the liquid lost from grating negatively correlated with true retention retained in the mash (R = -0.914). Moreover, true retention followed the same pattern as lost water at the different processing steps (i.e. for the commercial processors). Variety had a significant influence on true retention, carotenoid content, and trans-cis isomerisation but the processor type had little effect. It is the first time that the importance of physical carotenoid losses was demonstrated during processing of biofortified crops

Carotenoid stability during storage of yellow gari made from biofortified cassava or with palm oil

The carotenoid composition of gari made from biofortified cassava (BG) was compared to that of existing gari of similar appearance but made from white cassava with added red palm oil (RPG). Storage of both yellow gari products was modelled at ambient temperatures typical of tropical areas (19-40 °C) over a 3 month-period at constant relative humidity. Carotenoid content and hence vitamin A activity of the gari products decreased markedly with time and temperature. Trans-β-carotene degradation fitted well the kinetics predicted by the Arrhenius model, in particular for BG. Activation energies for trans-β-carotene were 60.4 and 81.0 kJ.mol−1 for BG and RPG respectively (R2 = 0.998 and 0.997 respectively): hence the minimum energy to cause degradation of trans-β-carotene in gari was lower with BG. Rates of degradation of 9-cis β-carotene in gari were of the same order as with trans-β-carotene. Although the initial content of trans-β-carotene was twice as high in the BG compared to RPG, trans-β-carotene in BG degraded much faster. Results showed that the average shelf life at ambient temperature for BG was significantly shorter than for RPG and therefore carotenoids in BG were less stable than in RPG

Factors influencing micronutrient bioavailability in biofortified crops

Dietary and human factors have been found to be the major factors influencing the bioavailability of micronutrients, such as provitamin A carotenoid (pVAC), iron, and zinc, in biofortified crops. Dietary factors are related to food matrix structure and composition. Processing can improve pVAC bioavailability by disrupting the food matrix but can also result in carotenoid losses. By degrading antinutrients, such as phytate, processing can also enhance mineral bioavailability. In in vivo interventions, biofortified crops have been shown to be overall efficacious in reducing micronutrient deficiency, with bioconversion factors varying between 2.3:1 and 10.4:1 for trans-β-carotene and amounts of iron and zinc absorbed varying between 0.7 and 1.1 mg/day and 1.1 and 2.1 mg/day, respectively. Micronutrient bioavailability was dependent on the crop type and the presence of fat for pVACs and on antinutrients for minerals. In addition to dietary factors, human factors, such as inflammation and disease, can affect micronutrient status. Understanding the interactions between micronutrients is also essential, for example, the synergic effect of iron and pVACs or the competitive effect of iron and zinc. Future efficacy trials should consider human status and genetic polymorphisms linked to interindividual variations

‘Yellow is good for you’: Consumer perception and acceptability of fortified and biofortified cassava products

Vitamin A, an essential micronutrient for health, can be obtained from various food sources including cassava products made from either traditional white cassava varieties fortified with red palm oil containing provitamin A, or new high provitamin A biofortified yellow cassava varieties. Both products have a similar yellow appearance due to the coloured pigmentation of provitamin A. Using a range of methods to provide a comprehensive understanding of sensory acceptability (blind triangle test, sensory profiling, hedonic preference that included Check-all-that-applies and Just-about-right tests), we tested the acceptability and nutritional perception of traditional West-African food dough-like products (eba and fufu) made from biofortified, fortified, or control products made with non-fortified white cassava (n = 7) at three suburban locations near Ibadan, Nigeria on a total of 122 consumers. Biofortified, fortified, and control products could be differentiated blindly confirming that products clearly differed with respect to other sensory characteristics than appearance. Overall biofortified products were better accepted than control and fortified ones. Three classes of consumer preference were identified based on the dislike for control and fortified products, which indicated that acceptance of biofortified products was not a hindrance. On the contrary the traditional fortified product had poorer acceptance and this was due to its less desirable sensory characteristics as demonstrated by Just-about-right Penalty analysis. A majority of consumers (85%) had previous knowledge of biofortified cassava. Consumers associated ‘yellow colour’ with ‘good for eyesight’, ‘good for children’s health’ and ‘new’. More nutritional benefits were attributed to biofortified than fortified products although they had similar provitamin A contents and this demonstrates a bias. We suggest that nutrition promotion campaigns to improve the vitamin A status should also encompass all natural sources of provitamin A, including biofortified and traditional fortified products