Metabolome analyses of two varieties of Anhua dark tea

We performed volatile and nonvolatile metabolome analysis of Zhuyeqi (Z) and Baihaozao (B) dark teas during three stages of tea processing: (1) after withering and kneading (S), (2) after pile-fermenting (M), and (3) during drying and second kneading (Z). Our results indicate that the Z variety was rich in glycerophospholipids, isoflavonoids, morphinans, organic oxides, organic phosphonic acids, purines, and thiadiazines. A total of 427 metabolites were differentially accumulated between Z and B during three stages of processing (S, M, and Z). These metabolites were significantly enriched in ABC transporters, flavonoid biosynthesis, tyrosine metabolism, glutamic acid, linoleic acid metabolism, etc. Epicatechin, phenylacetic acid, (-)-cis-carveol, and neochlorogenic acid had higher levels in Z. Forty-three volatile compounds were differentially accumulated in BvsZ and their accumulation levels were affected by processing. The variety Z had a higher relative percentage of alcohols, and esters. Forty-six of the 75 substances contributed to the tea aroma. ZT had compounds with higher ROAV values such as furan (caramel-like and sweet fruity), 2-pentyl- (green beans, vegetable), heptanal (citrus, fatty, and rancid), and others. In total, 113 unique flavors were associated with substances that accumulated at higher levels in ZT. Our results suggest that Z offers a better composition and flavor profile than B due to the higher quantities of several health beneficial and taste-related compounds at the same processing stages.