Search

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]

In order to screen out the appropriate sterilization method for sun-dried green tea, six sterilization methods including irradiation sterilization, ultraviolet sterilization, microwave sterilization, high-pressure steam sterilization, pasteurization and ozone sterilization were used to treat sun-dried green tea, then total viable counts, biochemical composition and sensory evaluation of sun-dried green tea after sterilization were determined. The results showed that microorganisms in tea leaves were sterilized fully by methods of high-pressure steam sterilization and irradiation sterilization, 7.5 kGy irradiation sterilization had the least effect on the biochemical compositions of tea, only the contents of soluble sugar, catechin, flagellin, rutin and luteolin changing significantly (P<0.05). Meanwhile, sensory evaluation also confirmed that 7.5 kGy irradiation sterilization had the least effect on sensory quality of sun-dried green tea. In conclusion, the best sterilization method of sun-dried green tea was 7.5 kGy irradiation sterilization. [ABSTRACT FROM AUTHOR]