Analysis of Quality Changes and Plant Cell Wall Degrading Enzymes Producing Microorganism in Sichuan Pickle under Different Air Exposure Conditions

In this study, the Sichuan pickle was selected as the research object. Exposure, intermittent-exposure and closing of the container were used to stimulate different air exposure conditions. The quality changes of the Sichuan pickle fermentation process and the main microbial species of producing the plant cell wall degradation enzymes were explored under those different air conditions. The results showed that all Sichuan pickle had the best texture after 8 days of fermentation. After 16 days of fermentation, the pH of Sichuan pickle dropped rapidly to 3.0 under all three conditions, and the total bacteria and lactic acid bacteria increased first and then decreased. But, with the increase of fermentation time, the quality of Sichuan pickle was changed. For the exposure-fermented Sichuan pickle, the pH increased to 6.5 and the quantity of fungi increased to 7.6 lg CFU/mL after 64 days of fermentation. Compared with the 8 days of fermentation, the hardness and fragility of pickles decreased by 93.2% and 100%, respectively. The pickle was obvious soft rot, and 19 strains (12 of which were isolated after 48 days of fermentation) producing PCWDEs were mostly aerobic microorganisms. For the intermittent-exposured fermented Sichuan pickle, the pH increased to 3.5 after 64 days of fermentation, and compared with the 8 days of fermentation, the hardness and fragility of pickles decreased by 39.1% and 35.6%, respectively. The pickle was slightly spoiled, and most of the 6 strains producing PCWDEs were aerobic microorganisms. In closed fermentation, the pH remained at 3.0 after 64 days of fermentation, and the number of lactic acid bacteria decreased to 5.34 lg CFU/mL, but it was the dominant microorganism in Sichuan pickle still. Compared with 8 days of fermentation, the hardness and fragility of pickle decreased by 52.5% and 24.4% respectively. Under this condition, most of the 5 strains producing PCWDEs were facultative anaerobic microorganisms.