Molecular Insights into Kombucha Tea: A Functional Food Perspective

Kombucha, a fermented tea beverage produced using a symbiotic culture of bacteria and yeast (SCOBY), has gained popularity for its potential health benefits, including antioxidant and detoxifying properties. Fermentation significantly affects kombucha’s safety and functional properties by influencing its pH, acetic acid, and alcohol content. However, the comprehensive scientific evidence from human studies remains limited. This systematic review analyzed 26 studies published between 2020 and 2024 to investigate the relationship between fermentation conditions (pH, acetic acid, and alcohol content) and the health-related compounds in kombucha. Articles were sourced from Scopus, PubMed, and Web of Science. Findings showed significant variation in pH, acetic acid, and alcohol levels depending on raw materials and fermentation duration, with longer fermentations (>14 days) generally resulting in higher acidity. Only three studies fully complied with regulatory standards for pH, acidity, and alcohol content. Six animal model studies identified bioactive compounds, including flavonoids, polyphenols, glucuronic acid, and short-chain fatty acids, associated with antioxidant activity, improved liver function, and support for gut health. While these findings highlight kombucha’s potential as a functional beverage, inconsistent methodologies and a lack of clinical trials limit the current evidence base. Future research should prioritize standardized production methods and investigate health effects in human populations. Regulatory harmonization is also needed to ensure product safety, quality, and consumer trust. The risk of bias in quasi-experimental studies was assessed using the Joanna Briggs Institute’s tool; several studies showed moderate to high risk due to the absence of comparison groups and limited longitudinal outcome measurement.