ABSTRACT
Objective: To reveal the dynamic changing regularity of microflora in the fermentation process of Sojae Semen Praeparatum (SSP) and lay the foundation for revealing the mechanism of SSP processing by denaturing gradient gel electrophoresis (DGGE). Methods: The dynamic changes of microflora, both bacteria and fungi in fermentation process were monitored by PCR-denaturing gradient gel electrophoresis. According to the unweighted pair group method using arithmetic average clustering, the samples of SSP in various stages were analyzed. Results: Bacterial flora had diversity, and Aspergillus was the major fungus in the first stage called "yellow cladding". The major bacteria was Lactobacillus, while the major fungus was Cryptococcus at the "secondary fermentation" stage. The major microorganism was Bacillus subtillis and Pseudomonas putida on day 1, and Stenotrophomonas maltophilia, Sphingobacterium sp, and A. oryzae on day 3. Then on day 6, B. amyloliquefaciens, Aspergillus, and Trichosporon ovoides became the primary microorganisms. B. subtillis, T. ovoides, and A. niger were the major microorganism on day 3 of "secondary fermentation". On day 9 of this stage, the major strains were B. subtilis, L. concavus, L. nasuensis, and Cryptococcus randhawi. On day 15 of "secondary fermentation", they were B. subtilis, L. concavus, C. randhawi, Trichosporon, and two fungi cannot be cultured. Klebsiella oxytoca, B. subtilis, and L. concavus were dominant strains in the whole fermentation process. The composition of microflora in "yellow cladding" stage was different to that of the "secondary fermentation". The microbial community on day 3 and 6 was similar to 76.4%. While the lowest similarity between the samples on day 3 and 9, it was similar to 24.5% during samples on day 6 and 9 in "secondary fermentation" stage. The highest similarity of fungal composition was between day 3 and 6 samples, and the lowest one was between day 3 and 15 of "secondary fermentation", which was similar to 11.2% only. Conclusion: The results show that the unique flavor and function of SSP may be determined by the dynamic microbial communities and microbial flora in the fermentation process, and the secondary fermentation is proved to be irreplaceable from the microbiological point of view.
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.