Sensomics analysis of the effect of the withering method on the aroma components of Keemun black tea

Withering is a key process that affects the aroma of Keemun black tea (KBT). In this study, the aroma composition of KBT through natural withering, sun withering, and warm-air withering was analysed using gas chromatography-mass spectrometry. The results revealed significant differences in the three samples. Gas chromatography-olfactometry and aroma extract dilution analysis were performed with screening through a relative odour activity value (rOAV) > 1. In total, 11 aroma-active compounds (geraniol, (Z)-4-heptenal, 1-octen-3-ol, (E)-beta-ionone, 3-methylbutanal, linalool, beta-damascenone, (E, E)-2,4-decadienal, methional, (E, E)-2,4-nonadienal, and (E)-2-nonenal) were found to be responsible for the differences in aroma caused by different withering methods. Linalool (rOAV, 161) and geraniol (rOAV, 785) were responsible for the higher flowery and fruity aromas when sun withering was applied, whereas methional (rOAV, 124) contributed to the intense roasty aroma when warm air withering was employed. Moreover, our results were verified by quantitative descriptive analysis and addition experiments.

Automated summary

This study analyzed the aroma composition of Keemun black tea (KBT) under different withering methods, including natural withering, sun withering, and warm-air withering. Significant differences were found among the three samples. Eleven aroma-active compounds were identified as responsible for the differences in aroma caused by different withering methods. Linalool and geraniol were responsible for flowery and fruity aromas when sun withering was applied, while methional contributed to the intense roasty aroma when warm air withering was employed. The results were further validated by quantitative descriptive analysis and addition experiments.