Nutritional and microbiological attributes of soybean(Glycine max) during fermentation with Rhizopus oligosporus

Abstract

Soybeans (Glycine max) which belong to the family leguminosae constitute one of the oldest cultivated crops of the tropics and sub-tropical regions, and one of the world’s most important sources of protein and oil.  It is being used because of its good quality and functionality of its proteins, surplus availability and low cost. In this study, a mold Rhizopus oligosporus was used to ferment soybean, and the time course (12 h for 3 days) of changes in its characteristic was observed in order to investigate the period of maximum changes, and the consequent effect on nutritional benefits. Proximate composition, vitamins, mineral contents and microbiological characteristics were determined using standard procedures. Results obtained revealed that fermentation for 36 h produced optimal changes (p < 0.05) in terms of the contents of protein, ash, fibre, fat, moisture and carbohydrate.  Low levels of moisture and carbohydrate contents of fermented soybean flour with increase in fermentation period were obtained while vitamins A, B₂ and niacin increased significantly (p < 0.05). Significant increases were also observed with respect to values of the mineral elements. Microbiological analyses indicated that no faecal coliforms were detected, although the populations of other groups of microorganisms increased significantly within the period of fermentation. Therefore, the study has demonstrated a desirable use of Rhizopus oligosporus in order to obtain fermented product of soybean which could be used to fortify starchy foods.

Keywords: Fermentation, soybean, Rhizopus, nutritional and microbiological attributes