Effects of yellowing and drying treatment temperatures on the taste of autumn green tea

This study aimed to reduce the bitterness and astringency properties of autumn green tea using different yellowing and drying treatments. The results showed that as the yellowing temperature increased, the contents of tea polyphenols, gallated catechins, flavonol glycosides, and bitter amino acids decreased, while the content of soluble sugar and flavonols increased. The tea sample (YEL35 °C) subjected to yellowing treatment at 35 °C exhibited weak bitterness and astringency intensities and a relatively low content of flavonol glycosides. As the drying temperature increased, the content of gallated catechins decreased. In addition, the tea sample (DRY75 °C) subjected to drying treatment at 75 °C exhibited weak bitterness and astringency intensities, the highest contents of umami amino acids and Thea, and a relatively low content of gallated catechins. Multivariate statistical analysis revealed that vitexin-2-O-rhamnoside, pferol-3-O-rutinoside, myricetin-3-O-galactoside, and quercetin-3-O-glucoside played an important role in the astringency property of the tea. In addition, Asn, Thr, Pro, and Met were positively correlated with umami. Hence, the quality of autumn green tea was improved under optimal yellowing and drying temperatures of 35 and 75 °C, respectively.