Microorganisms Contributing to the Quality of Awa-Bancha, a Post-Fermented Tea

Awa-bancha is a post-fermented tea traditionally produced in Tokushima Prefecture, Japan. After boiling, the tea leaves and broth are packed into barrels, fermented, and then dried. Anaerobic fermentation is performed using lactic acid bacteria derived from the production environment. This study aimed to clarify the relationship between the quality of Awa-bancha and microorganisms. Thus, we investigated that the bacterial flora of products and fermentation solutions of Awa-bancha from various production years and locals. In addition, we analyzed the polyphenol resistance of the isolated strains from Awa-bancha. Consequently, many saprophytic bacteria were detected in fermentation solutions in which Lactiplantibacillus plantarum group was not present. The isolates of Awa-bancha showed high polyphenol resistance in the order of yeast, lactic acid bacteria, and other bacteria. The polyphenol resistance of many saprophytic bacteria was also the same. Results indicated that maintaining the polyphenol concentration in the fermentation solution at 15-20 mM inhibits the growth of saprophytic bacteria and promotes lactic acid fermentation. The viable counts of all products were below the standard. Staphylococcus spp. were detected in several tea samples. It has become clear that Awa-bancha products made through natural fermentation have consistent quality.