Fermentation of Green Tea Extract by Streptococcus thermophilus FUA329 and Evaluation of Storage Characteristics

In order to evaluate the effect of Streptococcus thermophilus fermentation on green tea extract and its storage characteristics, this study used Streptococcus thermophilus FUA329 and S. thermophilus ST1.8748 (control group) to conduct experiments on green tea extracts. After fermentation and storage at 4 ℃ for 0, 30, 60, 120 and 180 d, pH, viable bacterial count, tea polyphenol content, ellagic acid content, and urolithin A content were used as the main evaluation indicators, combined with anti-oxidation activity to evaluate the storage quality of fermented green tea extract. The results showed that compared with the S. thermophilus ST1.8748 control group, the pH of S. thermophilus FUA329 fermented green tea extract during the storage period was between 5.39 and 5.71. The highest number of viable bacteria at 48 h was 9.97×10⁸ CFU/mL. The content of tea polyphenols gradually decreased and the ellagic acid content tended to be stable. Urolithin A was produced at 48 h, and its concentration was 0.664 μmol/L. The antioxidant activity was always maintained at a high level. In summary, S. thermophilus FUA329 fermented green tea extract can significantly delay the quality decline and nutrient loss of green tea extract during storage.