Dynamic changes in physicochemical, bacterial, and volatile profiles during kombucha fermentation of mulberry fruits and leaves.

This study examined the dynamic changes in physicochemical properties, bacterial communities, volatile compounds, and electronic sensory profiles of kombucha produced from mulberry fruits (MFK) and mulberry leaves (MLK), compared to black tea (BTK) and green tea (GTK) over 12 days. Total flavonoid and polyphenol concentrations, along with antioxidant activity, increased during fermentation, peaked around day 6, and then declined. 16S rRNA sequencing identified Komagataeibacter rhaeticus and Komagataeibacter saccharivorans as the dominant bacterial species. Komagataeibacter saccharivorans increased from day 0 to day 6, stabilizing by day 12 in both MFK and GTK. Its abundance increased from day 0 to day 6 before declining by day 12 in BTK, whereas in MLK, it continuously increased throughout fermentation. Komagataeibacter rhaeticus decreased from day 0 to day 6 and then stabilized in GTK. Acetic acid, ethanol, and ethyl acetate were identified as the primary volatile compounds through gas chromatography-mass spectrometry. The ethanol concentration was significantly lower in MLK compared to the other substrates, while acetic acid and ethyl acetate concentrations were higher in MFK and BTK than in MLK and GTK. Correlation analysis indicated a negative association between ethanol and Comamonas in MLK, while ethyl acetate exhibited a positive correlation with Komagataeibacter saccharivorans in both MFK and BTK. E-nose and e-tongue assessments highlighted sourness as the dominant sensory profile. This study characterized the dynamic changes in bioactive compounds, volatile compounds, bacterial communities, and electronic sensory profiles during kombucha fermentation, inferring potential interactions. The findings provide valuable insights and data for optimizing kombucha production.