Selected physicochemical properties and overall acceptability of yogurt made from inoculation of yogurt starter bacteria and Kombucha extract

In this research, the effect of kombucha on physicochemical (pH, acidity, syneresis, viscosity, vitamin C and ethanol) and overall acceptability of yogurt samples were measured during 21 days of storage at 8ºC. Thus the amounts of 5, 10 and 15 %(V/V) of concentrate of kombucha layer grown up on black tea, with yoghurt starter, were inoculated to the milk containing 2.2 % fat. Meanwhile, the yogurt starter was applied for producing control sample. Fermentation in all samples was stopped when the pH reached 4.6. The results showed that during the storage, decrease of pH and increase of acidity were minor (p<0.01), and with raising the kombucha concentration, these changes were significantly less than control sample (p<0.01); syneresis in all samples (the same as control) increased while viscosity decreased (p<0.01) and increasing of kombucha concentration was caused increase of syneresis and decrease of viscosity (p<0.01); vitamin C decreased and ethanol increased very little (p<0.01) and as the kombucha concentration increased, the quantities of vitamin C and ethanol increased (p<0.01). Raising the kombucha concentration caused reduction of overall acceptability score in samples (p<0.01); and during storage, this score decreased (p<0.01) a little in comparison with that in control sample. After production and during storage, the best physicochemical and sensory properties was observed in sample containing yogurt starter and 5% kombucha concentrate.