Biochemical, textural and microstructural changes in whole-soya bean cotyledon sufu during fermentation

This study aims to investigate the nutritional value of sufu and reduce environmental problems caused by okara, which results from the traditional processing method of sufu. The feasibility of the whole-soya bean cotyledon sufu (WSCS) processing method, which does not produce okara, was investigated. WSCS was prepared by ripening okara-containing tofu through various hydrolytic enzymes secreted by Actinomucor elegans for 70 days. After fermentation, total nitrogen, amino nitrogen and lipid contents were found to be lower in WSCS than in traditional sufu (TS), whereas contents of reducing sugar, dietary fibre, isoflavone aglycone and soya bean polysaccharide were higher in WSCS than in TS. The hardness, springiness and adhesiveness of WSCS were 249.703 +/- 0.500 g, 0.606 +/- 0.008 and 8.393 +/- 0.032 J, respectively. The corresponding values for TS were 264.863 +/- 0.572 g, 0.615 +/- 0.007 and 7.516 +/- 0.031 J, respectively. In addition, microstructural changes in WSCS and TS during fermentation were observed through scanning electron microscopy. The results from this study may provide a basis for industrial production of WSCS.