Analysis of Sensory Quality, Physicochemical Characteristics and Microbial Diversity of Kombucha Beverages

In order to investigate the flavor, fermentation performance and microbial composition of kombucha in China, 12 simples were gathered from different regions to produce kombucha beverages. The physicochemical, sensory properties and microbial diversity of the beverages were evaluated in detail. Results indicated that the sensory properties of the beverages were different from each other. The simple liq2 had moderate sour and sweet taste and fragrant acid flavor, and the tastes of simple liq4 and liq10 were sour and bitter with putrefactive odor by contrast. Although the remaining simples tasted too sweet or too sour, no distinct bad odors were noticed. While the pH values and soluble solids content decreased, the total acidity value increased. Total phenolic content of the beverages fluctuated during fermentation process. The organic acids were mainly composed of gluconic acid, acetic acid and lactic acid, meanwhile the simple liq2 had the most abundant species of organic acids and high content of malic acid. Kombucha beverages fermented for 3 and 7 days exhibited good DPPH free radical scavenging activities with scavenging rates over 75%. The results of microbial diversity analysis showed that the dominant bacterial genus in each sample included Komagataeibacter, Gluconobacter and Acetobacter, while the dominant fungal genus were Dekkera, Starmerella and Zygosaccharomyces. There were also some harmful microorganisms such as Pseudomonas, Acinetobacter and Fusarium existed in some simples. The results indicated that the fermentation performance of the collected kombucha samples were different from each other while all the beverages exhibited good antioxidant activity. The flavour of the beverage was affected by the composition and content of organic acids. Also it should be noticed that there were some safety problems about the microbiological compositions of part of the simples. This study provided the basis for further investigation of the properties of kombucha in China and development of kombucha products with regional characteristics.