The research was carried out to determine the effect of adding fermentable sugars that could be utilized by the indigenous fermenting microorganisms to the ferment, with the aim of producing a sustained low pH level. Type, concentration and time of adding sugar at the beginning (Day 0) and during (Day 3) fermentation of orange-fleshed sweet potato were evaluated. Addition of fermentable sugars, which are intrinsically present in orange-fleshed sweet potato, such as sucrose, glucose and fructose at Day 0 and Day 3 of the fermentation, resulted in a decrease in pH level that was not sustained in the natural (control) fermentation. More importantly, the experiment identified that 5 or 8% w/v fructose were the optimum concentrations that resulted in pH level falling to 3.5, which was the minimum pH level recorded. It was also discovered that addition of 5 or 8% w/fructose at the beginning of fermentation resulted in a greater fall in pH level than adding the sugar on Day 3 of the fermentation. The findings suggest that in the traditional fermentation the fermentable substrate is a limiting factor and once used up the pH starts to rise.
Key words: Orange-fleshed sweet potato traditional, fermentation, sucrose, glucose, fructose, pH, Nigeria
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