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Nutritional, sensory and health-promoting properties of provitamin A-biofortified maize stiff porridges and extruded snacks.

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Provitamin A-biofortified maize has been developed to contribute to the alleviation of vitamin A deficiency (VAD), which is prevalent in the sub-Saharan African region where vitamin A- deficient white maize is a leading staple. The biofortified maize is new compared to white maize and as such its grain properties, including milling, nutritional composition (save provitamin A composition) and sensory characteristics, are barely known. There is a challenge in the adoption of the biofortified maize as a food crop due to its low consumer acceptance, which necessitates more consumer studies. Furthermore, there is a need to develop high value commercial food products using provitamin A-biofortified maize to promote its wide spread utilisation and thereby enhance the vitamin A status of the population. The milling and nutritional properties of grains of 34 varieties of provitamin A-biofortified maize were assessed relative to a white variety (control/reference). The milling properties of the biofortified varieties as indicated by the milling index (69.9-112.1) and hectolitre mass (65.8-82.9 kg/hl) were better compared to 93.5 and 78.5 kg/hl of the white variety, respectively. The ash content of one biofortified maize variety PVAH 48 was comparable to that of the white variety (1.02 g/100 g), whilst five biofortified varieties showed significantly high Fe content (25.67-70.33 mg/kg) compared to the white variety (20.67 mg/kg). The protein (9.8-12.8 g/100 g) and lysine (0.16-0.37 g/100 g) content of the biofortified varieties were significantly high compared to 10.5 g/100 g and 0.21 g/100 g of the white variety, respectively. The sensory quality of stiff porridges made with provitamin A maize varieties were evaluated using descriptive analysis and the 5-point facial hedonic test by a trained panel and an untrained consumer panel, respectively. The provitamin A maize porridges were described as having a cooked maize flavour and aroma, sticky, fine with low intensity of residual grain and slight bitter aftertaste. Provitamin A carotenoid retention in the porridges was determined. Provitamin A carotenoid retention in the porridges was considerably high (91-123%). Relative to white maize porridge, the biofortified porridges were fairly acceptable, although their acceptability seemed to be reduced by their stickiness and bitter aftertaste. Leaf powder of Amaranth (Amaranthus cruentus), a vegetable widely consumed by rural communities in Southern Africa and reported to have good nutritional and health-promoting properties, was used to partly replace flours of four biofortified maize varieties at 0%, 1% and 3% (w/w) and extruded into snacks. The effects of Amaranth addition on the quality and health-promoting potential of the snacks was assessed, as well as the physical and sensory quality. The physical and sensory qualities of the extruded snacks, in terms of texture and expansion, tended to decrease with increasing Amaranth concentration. However, as Amaranth concentration was increased, the levels of many nutrients (including provitamin A carotenoids and protein) as well as health-promoting potential as indicated by phenolic content (31.0-98.7 mg of GAE/g dry weight) and antioxidant activity (114.3-186.7 μmol TE/g dry weight) also increased. The less acceptable sensory attributes observed in the biofortified maize should be attenuated through the manipulation of food product formulations. Other plant materials, such as Amaranth, can be used to enhance the nutritional and health-promoting properties of provitamin A-biofortified maize foods. Provitamin A-biofortified maize seems to have a potential for use in the alleviation of VAD and the general enhancement of food and nutrition security, as well as overall wellbeing.


Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.