Analysis of Microbial Changes in Fermented Beverage of Pitaya during Low Temperature Fermentation
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Abstract:
To explore the changes of main microorganisms and understand the effects of inoculated fermentation and natural fermentation on microorganisms in the fermentation process of pitaya beverage, the pH, soluble solids and main microbial species were assayed in the inoculated and natural fermentation processes of Hongxin pitaya beverage at low temperature (18 ℃). The results showed that lactic acid bacteria reached the maximum values of 5.20×108 cfu/mL using inoculated fermentation and 1.14×109 cfu/mL using natural fermentation on the 9th day. The decrease rate of lactic acid bacteria in natural fermentation was higher than that in inoculated fermentation during further fermentation period. Yeast maintained a growth trend during the whole fermentation process, while the number of inoculated yeasts was lower than that of natural fermentation. The number of mold and coliform group grew vigorously in the middle fermentation period, the mold reached the maximum values of 11.60 cfu/mL using inoculated fermentation and 602.00 cfu/mL using natural fermentation on the 13th day of fermentation, and coliform group reached the maximum values of 0.36 MPN/mL and 46 MPN/mL on the 9th day of fermentation. The study revealed that inoculated fermentation had dominant lactic acid bacteria compared with natural fermentation, which inhibited the growth and reproduction of some hybrids, and also effectively reduced the growth and reproduction of mold and coliform bacteria, and was more beneficial to the quality control of fermented pitaya beverage. This study provides a reference for further research on low temperature-fermented pitaya juice.
