Insights into key aroma of vine tea (Ampelopsis grossedentata) for grade evaluation integrating relative odor activity value, gas chromatography-olfactometry and chemometrics approaches

It is an urgent requirement to explore the key aroma of vine tea to provide the guidance for tea quality evaluation. In this study, three levels of vine tea of bud tip, tender leaf, and aged leaf were characterized by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS). The relative odor activity value (rOAV) calculation coupled with gas chromatography-olfactometry (GC-O) technology were implemented to seek the aroma-active compounds. Afterwards, the chemometrics methods were employed to explore the critical volatile compounds on the basis of S-line, variable importance for projection (VIP), jack-knifing confidence interval, p values (<0.05), and fold change (FC). As a result, five aroma compounds of ethyl acetate, (E,E)-2,4-heptadienal, geraniol, hexanal, and geranyl acetone were considered as key markers by taking an overall consideration of rOAV, GC-O and chemometrics methods. Finally, the mathematical equation of the vine tea grade with respect to the key aroma was established. The ethyl acetate and geraniol were positively related with the vine tea level evaluation, whereas the hexanal, geranyl acetone, and (E,E)-2,4-heptadienal were negatively correlated with the tea grade, among which the hexanal played a significant role on tea level assessment. This study provides compelling evidence for the vine tea quality evaluation in the perspective of key aroma compounds.