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Kishu-Narezushi is a spontaneously fermented food comprising fish, rice, and salt. During spontaneous fermentation, the microbiome may differ among batches, even when manufactured in the same way. In addition, analyses of changes in the chemical composition of the product are important for clarifying flavor characteristics. We collected basic information on the microbiome and chemical composition of Kishu-Narezushi using multiple batches of fermentation and evaluated whether the microbiome was homogeneous. The fungal microbiome of Kishu-Narezushi was dominated by Saccharomycetales and Trichosporonales. The bacterial microbiome was diverse, although seven specific genera of lactic acid bacteria were identified. Glutamic acid, histidine, and serine levels decreased after ∼10 days of fermentation. Succinic acid, characteristic of Kishu-Narezushi, accumulated upon the consumption of glutamic acid. Though the microbiome was diverse, the chemical composition was similar among the batches. [ABSTRACT FROM AUTHOR]

Ishizuchi-kurocha is a popular postfermented tea in Japan. It is performed by domestic and natural fermentation relied on microorganisms derived from tea leaves or the environment of the manufacturing. Ishizuchi-kurocha undergoes aerobic fermentation of fungi first, then second fermented by anaerobic fermentation of lactic acid bacteria during natural fermentation processing. Aspergillus niger that produces mycotoxin is included in natural fermentation. This research aimed to build a novel fermentation method of Ishizuchi-kurocha by adding industrial koji fungi products and laboratory-cultivated Lactobacillus plantarum (Lactiplantibacillus plantarum) artificially. Thus, safety and quality of tea products could be controlled simply. We found artificial fermentation of Ishizuchi-kurocha could get high lactic acid production within 8 days. Final products only consisted of genus Aspergillus and genus Lactobacillus, while harmful Aspergillus niger was not found. However, artificial fermentation methods also decreased the content of polyphenols when compared with commercial tea. [ABSTRACT FROM AUTHOR]