A primary study on texture modification and proteolysis of mao-tofu during fermentation

A strain of Mucor was isolated from mao-tofu, a local fermented soybean product in central China, and used in this study to evaluate its role on texture modification and proteolysis of mao-tofu. Texture and microstructure of mao-tofu was monitored by texture analyzer and scanning electron microscopy (SEM). Proteolysis occurred during fermentation was evaluated by SDS-PAGE and chemical analysis. Results from Texture Profile Analysis showed that adhesiveness of mao-tofu had an increase trend while hardness, cohesiveness and springiness had a decrease trend as fermentation progressed. SEM analysis showed that the microstructure of mao-tofu was modified from a typical network structure to a more homogeneous structure. SDS-PAGE profiles indicated that cleavage of native soybean proteins occurred during fermentation and that molecular weights of most peptides were less than 20 kDa. The contents of water-soluble protein, total free amino groups and water-soluble free amino groups in maotofu fermented for 6 days were increased from 0.33%, 47.3 mmol/100 g and 120.7 mmol/100 g to 5.46%, 158.2 mmol/100 g protein and 338.2 mmol /100 g protein, respectively. All these results indicated that the texture or microstructure of mao-tofu was greatly modified as the results of soybean protein degradation during fermentation.