Abstract: In order to demonstrate the interaction effect of different tea aqueous extracts and intestinal microorganisms, anaerobic fermentation in vitro by the intestinal bacteria from healthy college students’ feces were conducted in this study. Traditional culture techniques and gas chromatography technology were employed to study the changes of pH, short-chain fatty acids and intestinal microbes in different tea aqueous extracts (green, black and Fu brick tea) during 24 h of in vitro fermentation, and calculate the prebiotic index PI and B/E values (Bifidobacterium/Enterobacterium). The results show that the tea aqueous extracts significantly decreased the pH value compared with the blank control group, and the biggest drop was identified in the Fu brick tea group. Besides, the tea aqueous extracts significantly increased the production of short-chain fatty acids. Green tea had the largest increase in acetic acid, propionic acid, isobutyric acid, iso-pentanoic acid, pentanoic acid and total short-chain fatty acids, while Fu brick tea had the largest increase in butyric acid. All three kinds of tea aqueous extracts could affect the composition of intestinal microorganisms, promoted the growth of Bifidobacterium and inhibited the growth of Bacteroides, Enterobacterium and clostridium. Fu brick tea group had the largest promoting effect on Bifidobacterium, had the most obvious inhibiting effect on Enterobacterium and clostridium, and green tea group had the largest inhibiting effect on Bacteroides. However, both green and black tea groups could promote the growth of Lactobacillus, while Fu brick tea group showed inhibition of Lactobacillus growth. In addition, by analyzing PI value and B/E value, It was found that green, black and Fu brick teas had the function as probiotics. The largest PI value at the 4 h stage appeared in fu brick tea, while the largest PI value at the 8 h, 12 h and 24 h stages appeared in green tea. the largest B/E value throughout the fermentation process appeared in Fu brick tea group. This study provided basic data and scientific basis for the further expansion and promotion of different teas in the youth consumption market.

Key words: green tea, black tea, Fu brick tea, in vitro fermentation, short-chain fatty acid, intestinal microbiota