G. Yadang, I. L. Mbome, R. Ndjouenkeu
In order to improve the sensorial qualities of sweet potato for use in infant food formulation, tuber slices were wet-fermented for 5 days and aliquots were collected and treated for various analyses. Acidification during fermentation resulted in pH drop in slices from 6.3 to 3.9 during the process. Amylase activity of sample extracts fell from about 2400 units per 100g fresh weight of slices to about 280 units. Hot-paste viscosity of flour from unfermented slices displayed a typical profile of amylase-rich flours, with values staying at 0.3 Pa.s up to 20% flour concentration in hot water and then climbing gradually to 4.3 Pa.s at 33% flour concentration. Upon fermentation, and for 10% flour concentration, the hot-paste viscosity increased from about 0.3 Pa.s on day 0 to 24 Pa. s on day 5 of fermentation, in line with the loss of amylase activity. Total 80% alcohol-soluble sugars, mostly made of sucrose (90%), fell abruptly and significantly from 12.66 g/100 g dry basis at the start of fermentation to 2.10 g/100 g on day 5, reflecting their use by fermentation microorganisms as substrates for their multiplication and growth. There was a consequential increase in starch levels from 76.56 g/100 g to 91.25 g/100g during the same period. Maltodextrins remained stable, while crude fibre decreased slightly. Fermented flours were void of amylase activity and the sweetness of sweet potato. They were of finer texture than the unfermented flour and produced smooth hot-water gruels with attractive cream colour. Their use for making low viscosity semi-solid gruels for young infants could be achieved by mixing them with the amylase-rich unfermented flour, or any other amylase-rich source, before or during cooking. They could be quite appealing for preparing some African dishes like fufu, by virtue of their sweetless taste.
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