The biological activity of fermented dairy products obtained by kombucha and conventional starter cultures during storage

The effects of kombucha inoculum as a new starter culture for milk fermentation were investigated, during 14 days of storage. The antioxidant capacity, angiotensin converting enzyme (ACE) inhibitory activity, degree of proteolysis (DP), content of vitamin C as well as sensory properties of kombucha fermented milk, were analysed and compared with fermented milk products obtained by commercial probiotic (ABT-10) and yoghurt (YF-L812) starter cultures. The kombucha fermented milk product (K) showed similar trend of changes in pH, DP and sensory properties as products obtained by probiotic (P) and yoghurt (Y) starters. Significant ACE inhibitory was determined in all fermented products, which increased during storage. Kombucha product had the highest ACE activity (63.43%) at the end of storage compared with probiotic and yoghurt products. In all products, higher 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) than 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was determined, while both activities slightly decreased during storage. Based on estimated biological activity the kombucha product can be considered as an innovative fermented dairy product suitable for human nutrition.