Microbiological and physicochemical properties of fermented and unfermented sweet potato flour

Abstract

The need for suitable wheat flour substitute from indigenous crop flours based on their physiochemical and microbiological properties is the focus of this research. Raw yellow sweet potato tubers were purchased from local Nigerian market and processed into fermented and unfermented sweet potato flours. Analysis for their physiochemical properties (proximate and functional properties) and microbiological properties were executed using customary analytical routines. Findings revealed that fermenting sweet potato flour decreased the pH from 8.8 at 0 hr to 5.0 at 72 hrs, improved protein and moisture proximate components and enhanced some functional attributes like water adsorption and oil adsorption capacities over their unfermented counterpart. The total viable bacteria count for the fermenting bacteria ranged from 7.5 – 10.6 Log10 cfu/g, while fungi count ranged from 0 – 3.9 Log10 cfu/g. Six (6) genera of bacteria, Bacillus, Klebsiella, Micrococcus, Staphylococcus, Lactococcus and Enterobacter were isolated with Bacillus spp being the most dominant genera (33.3%), while five (5) Fungi genera; Aspergillus, Penicillium, Mucor, Candida and Saccharomyces were also isolated at the end of the 72 hrs fermentation with Aspergillus spp., the most dominant genera (44.44%). Microbes isolated from this study are generally associated with plant, environment and fermentation processes. This study shows that fermentation helps to improve nutritive composition of yellow fleshed sweet potato which when directly consumed or processed into flours would improve the health status of consumers.