Development of an owoh-type product from African yam beans (Sphenostylis stenocarpa) (Hoechst (ex. A. Rich.) Harms.) seeds by solid substrate fermentation.

ABSTRACT

African yam beans were fermented to obtain an owoh-type product. Microorganisms associated with the fermentation were Bacillus licheniformis, B. pumilus, B. subtilis and Staphylococcus sp. Total microbial counts increased from 1.53 x 10(5) cfu/g to 1.51 x 10(9) cfu/g under aerobic conditions, and from 8.0 x 10(3) cfu/g to 1.35 x 10(7) cfu/g under conditions of reduced oxygen tension. The pH of the substrate increased throughout the fermentation, from 6.8 to 7.5. A comparison of unfermented seeds with the fermented product showed that there were decreases in the levels of total nitrogen, crude protein, crude fiber and lipids, and that there were increases in the levels of carbohydrate and total organic matter. Enzyme activities during fermentation revealed that amylase production was erratic showing a slight increase during the first 24 h followed by a steep rise in activity in the next 24 h. By contrast, lipase activity increased rapidly throughout the first 72 h while proteinase activity followed a type of sigmoid curve with a steady increase in activity within the first 48 h and a relatively high activity until the 96th h before plunging downwards.