Characterization of yogurt prepared with kombucha starter culture as inoculum

In recent years, there is a growing demand for healthy and safe food. In this regard, kombucha products have promising future due to their contents of bioactive compounds that exhibit health-promoting properties. Kombucha yogurt is a novel product with unique quality characteristics. So, in this study, the kombucha extract (KE), 5, 10, and 15% (v/v), was applied as a non-conventional starter for yogurt production, and the effect of kombucha on pH and titratable acidity of yogurt during incubation was investigated. Also, some physicochemical properties and overall acceptability of yogurt samples were determined during 21 days of storage at 8ºC. For producing yogurt samples, the amounts of 5, 10, and 15 % (V/V) of concentrate of kombucha layer grown up on black tea, without yogurt starter bacteria, were inoculated to the milk containing 2.2% fat. Meanwhile, the yogurt starter was applied for producing the control sample. The results showed that by increasing the concentration of KE, a slight increase in pH (4-10%) and a decrease (12-35%) in acidity was observed compared to the control sample (p<0.05); syneresis increased and viscosity decreased (p<0.05); the vitamin C (92-200%) and ethanol (0-44%) levels increased (p<0.05) and the overall acceptability decreased (p<0.05) during 21 days of cold storage. The increase of the kombucha concentration in all samples elongated the fermentation period (p<0.05). The best physicochemical and sensory properties were observed in the sample containing 5% KE.