Research on the fermentation of Pu-erh tea through inoculation with Aspergillus amstelodami.

Aspergillus amstelodami A1 isolated from Pu-erh tea was inoculated in sterilized or unsterilized sun-dried green tea leaves to develop pure culture fermentation and enhanced fermentation (EF) of Pu-erh tea. The results showed that the content of tea polyphenols and five catechins in tea decreased significantly, and the content of thearubigins and theabrownins increased significantly after pure culture fermentation. Compared with natural fermentation, the levels of soluble sugars and theabrownins in EF were significantly higher, whereas the levels of gallic acid, (+)-catechin, (-)-epicatechin, (-)-epigallocatechin and caffeine were significantly lower; the scores of sensory evaluation including appearance, color of infusion, taste, aroma and infused leaves in EF were significantly higher; while the value of a* and b* of EF's tea infusion were higher and the value of L* was lower. A. amstelodami A1 didn't become the dominant fungi in EF, while the microbial communities in EF were different from those in NF. Therefore, the enhanced fermentation by inoculation of A. amstelodami A1 changed the chemical components of tea leaves through the synergistic effect with other microorganisms, therefore improving the sensory quality of Pu-erh tea. [ABSTRACT FROM AUTHOR]