Influence of green, white and black tea addition on the antioxidant activity of probiotic yogurt during refrigerated storage

The present study investigated the effect of green, white or black tea (Camellia sinensis) on the fermentation of milk and antioxidant potential of yogurt during 21 days of storage at 4 degrees C. All yogurts were analyzed for total phenolic content (TPC), identification of phenolic compounds and antioxidant potential using diphenyl picrylhydrazyl radical scavenging (DPPH), ferric reducing antioxidant power (FRAP) and ferrous ion chelating (FIC) assays. Green tea yogurt showed the highest phenolic content (p < 0.05) followed by white tea yogurt and black tea yogurt. LCMS/MS analysis revealed the absence of several phenolic compounds in tea yogurts, despite their presence in tea water extracts, as well as the presence of new phenolic compounds. All tea yogurts showed higher (p < 0.05) FRAP and FIC values than respective control during 21 days of storage. However, BTY showed the lowest values of DPPH scavenging activity and FRAP during storage period. In addition, the antioxidant activity for all tea yogurts remained almost constant over storage period. In conclusion, green, white and black tea can be successfully employed to improve the antioxidant properties of yogurt and provide sustained antioxidants during storage. (C) 2016 Elsevier Ltd. All rights reserved.