Stimulatory effects of tea supplements on the propagation of Lactobacillus casei in milk

The influence of several Chinese teas on the ability of Lactobacillus casei to ferment milk was assessed. The three kinds of tea significantly stimulated the growth and acidification of L. casei. The viable cell counts in tea-supplemented fermented milk were higher than those of the control and were maintained during cold storage. Flavour component content increased significantly, and an additional eight components were detected in fermented milk supplemented with 5% green tea infusion (GTI5%) compared with control fermented milk. Moreover, the increase in total free amino acids after fermentation in GTI5% was 2.5-fold higher than in the control, suggesting that tea stimulated the growth and metabolism of L. casei during milk fermentation. Higher cell numbers, reduced fermentation time, abundant flavour components and free amino acids were achieved during the tea-supplemented fermentation of L. casei. Green tea effectively enhances the growth of L. casei, therefore could be considered for industrial purposes.