Dynamic changes of volatiles and key odorants underlying the tender chestnut aroma of Shangnan Xianming green tea during manufacturing

Shangnan Xianming (SNXM) is a typical high-quality green tea characterized by a pleasant 'tender chestnut-like' aroma. However, the dynamic changes of volatile compounds during its manufacturing process and the key odorants responsible for this specific aroma profile remain poorly understood. Here, gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) combined with chemometric analysis were employed to track the changes in volatile components during processing. In total, 59 and 86 volatile compounds were identified via GC-IMS and GC-MS, respectively. The total content of volatile compounds exhibited a variation trend of initial increase, subsequent decrease, and final rebound during processing, with alcohols, aldehydes, and esters serving as the dominant volatile components. Partial least squares discriminant analysis (PLS-DA) demonstrated that spreading, fixation, and drying were the three pivotal stages regulating the transformation of aroma components. Gas chromatography-olfactometry (GC-O) analysis identified 19 aroma-active compounds in the finished tea, with aroma intensity values ranging from 1.17 to 3.67. Furthermore, combined absolute quantification and odor activity value (OAV) analysis confirmed ten key odorants with OAV values greater than 1, including linalool, (E)-β-ionone, nonanal, hexanal, 1-octen-3-ol, geraniol, heptanal, phenylethyl alcohol, indole, and (E)-2-nonenal, among which linalool and (E)-β-ionone exhibited the highest OAVs at 518.25 and 215.40, respectively. These findings reveal the critical processing stages and key odorants responsible for SNXM aroma formation and provide a theoretical basis for quality evaluation and targeted processing of tender chestnut-like green teas.