Effect of secondary fermentation on processing technology for fermented soybeans / 中草药

ABSTRACT

Objective: To optimize the fermentation processing technology for fermented soybeans, and to identify that the secondary fermentation process is an important link in fermentation processing of fermented soybeans. Methods: According to Chinese Pharmacopoeia 2010, combined with the ancient way to produce fermented soybeans, the contents of total isoflavones, daidzein, and genistein were as chemical indexes, the finished product properties (color, smell, degree of shrinkage, cross section, and hardness) were as organoleptic quality indexes, and the processing parameters before and within the secondary fermentation process, including cooking time, fermentation temperature, fermentation time, secondary fermentation temperature and time were optimized. Results: The optimal processing technology was as follows soybeans were boiled for 1.5 h after absorbing drug juice, and then fermented for 6-8 d at (30 ± 2)°C until yellow cladding. After washing off yellow cladding, soybeans were placed in the container, sealed using water, and put into secondary fermentation process. The container was in secondary fermentation for 12-15 d at (30 ± 2)°C. During the period of secondary fermentation, the soybeans were poured out every 3 d with stiring and slightly drying for four to five times, and at last was slightly steamed and dryed. The quality of fermented soybeans after secondary fermentation had more obvious advantage than that without secondary fermentation. The finished product had aromatic odor with light color and grain soft. The cross section color was brownish black and hand skin shrivel. The contents of total-isoflavones, daidzein, and genistein were at the highest value. Conclusion: The secondary fermentation process is an important link in fermentation processing of fermented soybeans and the key factor to affect the change of main chemical composition content and the finished product properties of fermented soybeans. The fermentation processing technology of fermented soybeans after optimization would lay the foundation of the regulation of production and the research of fermentation processing mechanism.