Study on the preparation of non-alcoholic kombucha beverages by re-fermenting kombucha beverages with Acetobacter and Lactobacillus

Kombucha is a traditional fermented beverage derived from sweetened black tea using a symbiotic culture of bacteria and yeast (SCOBY), which faces consumption restrictions due to the small amount of ethanol produced during the fermentation process. This study proposes an innovative method to produce non-alcoholic kombucha beverages (NAKB) by re-fermenting sterilized kombucha with Acetobacter sp. GDMCC 1.152 (AB) and Lactiplantibacillus plantarum GDMCC 1.191 (LP). Results showed that both AB alone and AB+LP combined fermentation could reduce the ethanol content (from 0.66% to 0%), mainly because AB oxidizes ethanol into acetic acid via the tricarboxylic acid (TCA) cycle. Sensory evaluation showed that NAKB produced by AB + LP had the best flavor and overall acceptability. Compared to the acetic acid produced by AB, the lactic acid produced by LP has a milder acidity and a higher taste threshold. Additionally, co-refermentation significantly enhanced bioactive compounds, with total polyphenol content increased from 215.32 mg GAE/L to 336.33 mg GAE/L, and total flavonoid content increased from 163.38 mg CE/L to 196.35 mg CE/L, alongside elevated antioxidant activity. These findings highlight the efficacy of bacterial re-fermentation in producing NAKB with improved sensory and functional properties, offering a viable strategy to meet diverse consumer demands.