Characterization analysis of flavor compounds in green teas at different drying temperature

Drying is an important factor in the formation of green tea flavor. In this study, metabolomic analysis were used to detect characteristic components of four green teas with clean aroma (CA), chestnut-like aroma (CLA), bean-like aroma (BLA) and high-fired aroma (HFA) produced by adjusting drying temperature. The sensory evaluation results showed that the tea dried at 90°C, 110°C, 140°C and 160°C had a clean aroma, chestnut-like aroma, bean-like aroma and high-fired aroma respectively. A total of 95 volatile compounds were identified. Linalool, naphthalene, 2-methyl-naphthalene, 1-octen-3-ol contributed most to the clean aroma. 1,2-dihydro-1,1,6-trimethyl-naphthalene was the key component of the chestnut-like aroma. 2,3-diethyl-5-methyl-pyrazine, 2-methyl-butanal, 3-ethyl-2,5-dimethyl-pyrazine had the biggest contribution to the bean-like aroma. 2,3-diethyl-5-methyl-pyrazine, 3-ethyl-2,5-dimethyl-pyrazine and 2-ethyl-5-methyl-pyrazine contributed most to the high-fired aroma. A total of 838 non-volatile compounds were detected and amino acids, saccharides decreased while catechins, flavonols increased during the increasing of drying temperature. It's found that they were related to the taste of umami, astringency and bitterness. This result provides a guidance and theoretical basis for the processing of green tea with different aroma types.