The present study develop various microorganisms for starter culture purpose from fermented sweet potato and used the developed starters in the fermentation of sweet potato and products for consistent quality product with improved hygiene. Sweet potato was purchased from different markets and microorganisms were isolated and developed as starters. Comparative studies on different starters for the fermentation of sweet potato for 48 h were investigated. The microbial count of the starter cultures increased as fermentation period increased from 6.06 to 9.14 cfu/ml, the pH reduced from 5.49 to 3.28 while the total titrable acid increased from 0.001 to 0.04. Amongst the various starters used, the use of the mixed cultures (combination of lactic acid bacteria L201 and yeast 601A) as starter cultures in the fermentation of sweet potato for 48 h had the best attributes in terms of texture, flavour, rate of fermentation and consistency when prepared as meal (bolus). The mineral analysis showed that most of the mineral content in the sample increased after fermentation for calcium (Ca) 2043.9 to 2177.5 ppm and Mn 6.29 to 26.32 ppm. The functional properties of the fermented sweet potato flour produced showed moisture content of 10.42%, water absorption capacity of 1.77 g/g and swelling capacity of 86.67%.

Objective: To determine the best starchy food substrate for the fermentative production of lactic acid. Methodology and Results: Five starchy-based food substrates (maize ogi, sorghum ogi, millet ogi, mashed cassava for gari production and steeped cassava for fufu production) were prepared fresh and allowed to ferment spontaneously for a period of 7days during which samples of the substrates were subjected to microbiological and chemical analysis. Four growth media were used for the isolation of the different common group of organisms implicated. Yeasts and Molds were identified as Saccharomyces cerevisiae, Candida sp., Aspergillus niger, Aspergillus flavus and Penicillium sp. The bacteria were Lactobacillus plantarum, Lactobacillus casie, Lactobacillus fermentum, Lactobacillus lactis, Klebisella pnemoniae, Escherichia coli, Flavobacterium sp., Proteus vulgaris. The pH decreased with increase in fermentation time, and it ranged from 3-6 while the total titratable acidity increased within the first 2-3days in cereal-based foods and within the first 4-5days in cassava based food substrates, followed by a gradual decrease. Though the lactic acid content fluctuates during the fermentation period, statistical analysis shows that fermentation time has significant effect (p<0.05) on the quantity of lactic acid produced. The two methods (total titratable acidity and spectrophotometric) used to measure the lactic acid content gave similar result of increase within the first 2-3days with an intermittent decrease and increase at subsequent days. Statistical analysis revealed that both the method and substrate used has significant effect (p<0.05) on the quantity of lactic acid content produced. Conclusion and application of study: from this study, the steeped cassava produced the maximum lactic acid on the 4 th day of fermentation by the two methods used. The results of this study revealed that lactic acid could be produced naturally from steeped cassava. Therefore, the best processing conditions and other optimization parameters should be investigated. Application of results: The study shows the possibility of Lactic acid biosynthesis using cassava, a low-cost and readily available substrate as source for laboratory/ small scale and eventually large-scale production.

Starch is the major component of cereal grains and starchy foods, and changes in its biophysical and biochemical properties (such as, amylose, amylopectin, pasting, gelatinization, viscosity) will have a direct effect on its end use properties (such as, bread, malt, polymers). Lactobacillus brevis and Debaromyces polymorphous earlier obtained from fermented sweet poatao broth were used to ferment sweet potato and these starter cultures broke down the carbohydrate (starch) to produce alcohol, organic acid and carbon dioixde (CO 2). The study identified that starter cultures L. brevis and D. polymorphous fermented the sweet potato thereby breaking down the carbohydrate (starch) to produce alcohol, organic acid and CO 2 hence lactic acid fermentation occurred. Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography Mass Specrometry (GCMS) were used to identify the chemical properties of starter culture fermented sweet potato flour. The FTIR spectra showed peaks at 3322.15, 3298.87, 3292.59, 3279.59 and 3274.59 cm-1 for the raw sweet potato, starter culture fermented sweet potato flour at various periods (24, 48 and 72 h) and spontaneous fermented sweet potato (control) respectively. The peaks at 2930, 2928.10, 2930.33, 2929.48, 2929.31 and 2927.29 cm-1 are attributed to C-H bond stretching. Functional groups such as hydroxyl, aldehydes, alcohol and carboxyl were detected in the fermented samples. The GCMS analysis detected the presence of alcohol such as ethanol, butanol etc., and carboxylic acid such as hexadecanoic acid, octadecadienoic acid etc. They were produced in situ from the fermentation process and this can serve as antioxidants, help inhibit spoilage organisms and serve as preservatives, thereby increasing shelf life of the product.