Red Yeast Rice-Driven Kombucha Fermentation: A Novel Strategy for Developing Functional Beverages with Enhanced Hypoglycemic and Hypolipidemic Properties

To address the limited functional diversity of traditional kombucha, this study utilized red yeast rice (RYR) as an alternative substrate and prepared three samples: black tea kombucha (KBT), black tea-red yeast rice mixed kombucha (KBL, at a 1:1 ratio), and red yeast rice kombucha (KRY). After 9 days of fermentation, KRY exhibited the lowest pH, the highest total acidity, and notable sugar metabolic activity. It exhibited in vitro inhibition rates of 82.8%, 78.2%, 70.3%, and 76.9% against cholesterol esterase, pancreatic lipase, α-glucosidase, and α-amylase, respectively, indicating potential hypoglycemic and hypolipidemic activities. In contrast, KBT maintained the strongest antioxidant capacity, with scavenging rates exceeding 90% against both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS). A total of 72 volatile flavor compounds (VFCs) were identified, with 7 key compounds enriched in KRY, which enhanced its sensory acceptance and received the highest scores in color, clarity, and aroma. Microbial community analysis revealed the post-fermentation dominance of <i>Komagataeibacter</i>, Acetobacter, and Saccharomyces, which correlated positively with key VFCs. These findings indicate that RYR as a substrate enhances functional microbial growth, sugar metabolism, organic acid production, flavor enrichment, and in vitro inhibitory activity of enzymes associated with hypoglycemic and hypolipidemic effects.