The impact of tea supplementation on microflora, pH and antioxidant capacity of yoghurt

Yoghurts prepared from cows’ milk with 5, 10 or 15% (v/v) addition of green or Pu-erh tea infusions were subjected to analyses of the antioxidant capacity by the ‘diphenyl picrylhydrazyl’ (DPPH) and ‘ferric reducing antioxidant power’ (FRAP) methods, pH and the count of yoghurt bacteria at the 1st, 7th, 14th, 21st and 28th day of cold storage. The average DPPH radical scavenging activity of yoghurts with 15% of green tea and Pu-erh tea was respectively 31 and 15-fold higher in relation to the yoghurt without tea, the respective FRAP values were 12 and 5-fold higher. Moreover, tea supplementation positively influenced the initial acidity of yoghurts and the count of Lactobacillus delbrueckii ssp. bulgaricus compared with the plain yoghurt, with no significant differences between the types and levels of tea used. That effect was also found for the Streptococcus thermophilus number in yoghurts with 10 and 15% of tea infusions.