Impact of processing techniques on chemical compositions and sensory attributes across five types of Yunnan...

Distinct processing techniques form five types of Yunnan large-leaf teas. Besides sensory evaluation, HPLC, UHPLC-QTrap-MS/MS and HS-SPME-GC-MS were performed to explore the overall impact of processing techniques through comparisons among these five types of teas. Principal component analysis basically divided these teas into three groups, confirming that pile-fermentation and anaerobic fermentation have more profound impacts on organic acids, flavonoids and non-volatile metabolites than other typical processes. Different from phenolics oxidative polymerization in enzymatic oxidation and pile-fermentation to formulate thearubigins and theabrownins, anaerobic fermentation of pickled tea (PT) transformed ester catechins and rutin into four non-ester catechins and three simple flavonols (i.e. quercetin, kaempferol and myricetin), respectively. Despite similar volatile profile to raw Pu-erh tea, characteristic organic acids such as succinic acid, lactic acid and 3-phenyllactic acid were formed in anaerobic fermentation, and contributed to sour flavor of PT. This study would promote standardization and optimization for Yunnan tea production.