Dynamic Change Of Microorganisms During Traditional Fermentation Process Of Broad Bean Paste

Dynamic change of microorganisms during traditional fermentation process of broad bean paste has a great influence on its maturity, flavor and food safety. All paste samples were provided by huyumei fermentation Co., LTD in Anqing city, Anhui province. In order to effectively analyze the dynamic changes of the species and microbial community structure during the process of the traditional fermentation of broad bean paste under sun exposure, paste samples of continuous- and discontinuous-fermentation were detected using PCR fingerprint technology based on cultivation and PCR- DGGE(PCR-denatured gradient gel electrophoresis) technique based on no culturing.Several media were used to compare their separation effect of aerobic bacteria. LB medium and MRS medium were chosen to separate aerobic bacteria and anaerobic bacteria respectively. CHAPMAN medium and YAP medium were chosen to culture staphylococcus and yeasts respectively. Two batches of samples were analyzed. First batch of samples were got at different time during continuous fermentation, while second batch of samplee were got at the same time during discontinuous fermentation. There was no big difference between total numbers and changes of these two batches of samples on microbial colonies using plate culture method. Total number of aerobic bacteria remained at high level, namely(107~108) CFU·g-1, and that of anaerobic bacteria was(103~104) CFU·g-1. Staphylococcus was not detected in either batch of samples under given condition. Total number of yeasts was(102~103) CFU·g-1. Colonies were classified using Rep-PCR fingerprint technique to identify and analyze the composition and proportion of dominant microorganisms. It turned out that aerobic bacteria mainly belonged to bacillus, including Bacillus subtilis, B. amyloliquefaciens, B. amyloliquefaciens and B. methylotrophicus. B. cereus was the dominant anaerobic bacterium. And several lactobacillus were separated in 1 d paste sample, including Weissella paramesenteroides, W. confuse, Streptococcus macedonicus and Pediococcus acidilactici. In all the dominate bacteria, no lactobacillus was detected. Detectable amount of yeasts was low in first batch of paste samples and all yeasts separated were Zygosaccharomyces rouxii. In second batch of paste samples, no yeast was detected.Bacillus subtilis, B. amyloliquefaciens, and Staphylococcus gallinarum were detected by optimized PCR-DGGE analysis as dominant bacteria in all paste samples. Some uncultured bacteria were also detected using this method. Results of both batches of samples were almost the same. So during huyumei broad bean fermentation, aerobic bacillus were detected as dominate microorganisms and there is some changes in their composition diversity. Numbers of lactobacillus and yeasts were low, so their growth may be suppressed. Main anaerobic bacteria were B. cereus and remained at a low level. They may be inhibited by aerobic bacillus. This can ensure food safety of broad bean paste.pH value, salinity, total acid, amino acid nitrogen and free amino acid of both batches of paste samples were measured. p H value ranged from 4.0 to 5.5 and salinity ranged from 12.0% to 15.3%. These two indexes remained steadily during whole fermentation. Content of total acid and amino acid nitrogen were significant different between samples of fermentation prophase and of fermentation anaphase and their ranges were(1.4~2.8) g·100 g-1 and(0.5~0.9) g·100 g-1 respectively. Free amino acid content of batch one samples was lower than that of batch two samples. Each of the free amino acid content of batch one samples remained steadily while that of batch two samples presents the rising trend. Content of Glu was the highest in both batches of samples.