Beyond Tea: Kombucha SCOBY as a Starter Culture Across Food Matrices

The kombucha symbiotic culture of bacteria and yeast (SCOBY) is a multispecies microbial consortium distributed between cell-containing fermentation liquid and a cellulose-rich pellicle. Here, "kombucha SCOBY" denotes the viable consortium delivered through either compartment or both compartments. Dominated by fermentative yeasts and acetic acid bacteria, the consortium produces ethanol and organic acids and biotransforms phenolic compounds, enabling fermentation beyond conventional sweetened teas. This review critically evaluates studies in which viable consortia directly fermented food matrices. In dairy systems, kombucha-derived inocula acidify milk and induce casein gelation, although more slowly than yogurt starters, and kombucha broth has also supported fresh cheese production. In soy-based matrices, fermentation converts isoflavone glucosides to aglycones, and fermented soy whey can coagulate tofu. Applications have also been reported in fruit and vegetable juices, agro-industrial by-products, botanical infusions and breadmaking. However, microbial composition and performance vary with the inoculum source, propagation history, and storage. Strain-defined preserved starters remain unvalidated in non-tea matrices, and potential hazards include mycotoxin formation and post-production ethanol accumulation. Therefore, standardized, comprehensively characterized, and matrix-specific starters are required for safe and reproducible translation across food matrices.