Effect of Steam Treatment on the Flavor Quality of Yixian Dark Tea

Abstract

To investigate the aging effect of steaming to Yixian dark tea, the flavor quality and metabolite profiles of Yixian dark tea after steaming treatments were analyzed by sensory evaluation, headspace solid-phase microextraction-gas chromatography-mass spectrometry (HP-SPME-GCMS), amino acid analyzer and high-performance liquid chromatography (HPLC). The results showed that the steam treatment could accelerate the aging of black tea, promote the generation of aged aroma and rich flavor. Sensory evaluation showed that, the third steaming obtained the pleasant flavor compared to other dark tea samples. The total volatiles concentration decreased first and then increased after steam treatment, and the total aroma content increased in the third (9113.62 μg/kg) and forth (10222.82 μg/kg) times of steaming. The nonanal, trans-2-octenal and dihydrolinalool with a flowery and sweet odor showed an increasing tendency during steaming, whereas linalool, geraniol and dimethylsulfide showed a decrease in concentrations (P<0.05). The total catechins concentration and concentrations of episturcture catechins such as epigallocatechin and epigallocatechin gallate decreased with steaming (P<0.05). In contrast, concentrations of gallic acid and nonepistructure catechin and gallocatechin gallate increased after steaming, especially theanine (P<0.05), of which content increased by 13.1%. Nonanal, decanal, dimethyl sulfide, 1-octen-3-one, trans-2-octenal, hexanal, epigal-locatechin, epigallocatechin gallate, epigallocatechin, and theanine were the key differential metabolites between dark tea samples according to orthogonal partial least squares-discriminant analysis, variable important for the projection, odor active value, and dose-over-threshold factors. This study would give a insight into improving the rapid aging of Yixian dark tea.

Keywords

• yixian dark tea
• steam action
• flavor quality
• orthogonal partial least squares discriminant analysis