Changes in the metabolite composition and enzyme activity of fermented tea during processing

As the dominant microbial strain in Fuzhuan brick tea, Eurotium cristatum (E. cristatum) can biotransform the fermentation substrate during growth and reproduction, and in so doing enhance the tea’s health benefits. Green tea contains a large number of bioactive compounds with antihypertensive potential. However, as a nonfermented tea, inactivation of various enzymes (such as polyphenol oxidase) during processing results in a single secondary metabolite with limited health effects. The novel fermented tea we studied was processed by solid-state fermentation (SSF) with E. cristatum, and the substrate was a mixture of green tea and Radix Puerariae (RP). This study was aimed at evaluating the multiple effects by E. cristatum during fermentation. Compared to the unfermented control groups, the sample groups secreted enzymes (such as polyphenol oxidase and α-amylase), and the bioactive compounds content of sample groups changed, as well as significantly higher inhibition of Angiotensin-converting enzyme (ACE) in vitro (which also implies greater antihypertensive potential). These results will help further investigations of the antihypertensive bioactive compounds of green tea and the fermentation potential of E. cristatum.