Sucrose-Free Kombuchas Flavored with Fruit Residues: Fermentation Dynamics, Sensory Profiles, Ethanol Stability, and Commercial Benchmarking

This study evaluated the influence of sucrose addition on kombucha fermentation and the use of agro-industrial fruit residues (cashew apple bagasse, mango peels, and grape pomace) as natural flavoring agents. Processing parameters, including pH, total soluble solids (TSS), total titratable acidity (TTA), sugar consumption, and the evolution of organic acids, ethanol, and Total Phenolic Compounds (TPC), were monitored during a 9-day fermentation period and subsequent 30-day refrigerated storage period. Fermentation without added sucrose caused a significant reduction in TPC (p < 0.05), suggesting microbial biotransformation and enzymatic cleavage of bonded polyphenols into smaller, more reactive phenolic monomers. During refrigerated storage, the chemical profiles of the developed beverages remained relatively stable, and ethanol concentrations remained below the regulatory limit for non-alcoholic beverages (0.5% v/v or 4.0 g/L). In addition, four commercial kombucha samples were evaluated over the same storage period to compare ethanol stability and regulatory compliance. Sensory analysis showed that visual appearance and complex flavor profiles were mainly driven by fruit matrices, confirming their effectiveness as natural functional and flavoring agents. These findings demonstrate that initial sucrose can be excluded from kombucha brewing, as fruit residues supported late fermentation dynamics without inducing non-compliant ethanol accumulation.