Nutritive value of protein in soybean residue fermented with Rhizopus oligosporus and Bacillus subtilis

Abstract

The nutritional value of soybean residue from soymilk processing was found to decrease. This experiment fermented the soybean residues and soybeans with Rhizopus oligosporus TISTR 3001 and Bacillus subtilis TISTR 1 to produce tempeh and tooa-nao, respectively. Then the nutritive value of protein in the raw and fermented products were analysed. It was found that the crude protein contents in soybean residue tempeh, soybean residue tooa-nao, soybean tempeh, and soybean tooa-nao were increase 2.40%, 1.65%, 2.55%, and 1.85%, respectively, Valine, tyrosine, and phenylalanine contents were found to increase 9% to 16% after soybean residue tempeh fermentation. The contents of alanine and phenylalanine in soybean tempeh increased 31% and 15%, respectively. In soybean residue tooa-nao, cystine content increased 11.2% but valine content decreased 13%. In soybean tooa-nao, the contents of valine and lysine increased 26% and 11%, respectively but arginine content decreased 15%. Amino acid scores of some essential amino acids in fermented products were increase. The protein digestibility of soybean residue tempeh was increase from 67.68% to 74.95% whereas that of soybean residue tooa-nao remained constant. We also found that protein digestibility of soybean tempeh and soybean tooa-nao increased from 59.65% to 68.18% and 66.92%, respectively. In addition, vitamins contents were also affected by the fermentation process. These results suggest that the nutritive value of protein in soybean residue was improved by the fermentation process.