Non-Volatile Metabolite Changes in Green Tea Following Helium-Flushed Enclosed-Chamber Pretreatment of Fresh Leaves Across Five Tea Cultivars

Postharvest atmospheric pretreatment can alter tea-leaf metabolism, yet its influence on the non-volatile composition retained after green tea processing is not well understood. Fresh leaves from five tea cultivars were subjected to helium-flushed enclosed-chamber pretreatment or conventional spreading and were then processed into green tea under the same manufacturing procedure. HPLC and untargeted LC–MS metabolomics were used to examine treatment-associated differences in non-volatile composition. HPLC revealed significant differences in catechins, gallic acid, and caffeine, although the response patterns varied among the five cultivar comparisons. Of 2304 MS/MS-annotated metabolic features detected by LC–MS, 2291 with pooled QC relative standard deviations (RSDs) ≤ 30% were retained for further analysis. Among these, 232, 169, 10, and 30 met the predefined differential screening criteria in Huangshan Quntizhong, Longjing 43, Zhongbai 1, and Zhonghuang 1, respectively, whereas none met all criteria in Jiukengzao. The differential features were mainly annotated as amino acid-related, lipid-related, and shikimate- and phenylpropanoid-related compounds. KEGG mapping associated these features with pathways involving amino acid, lipid, carbohydrate, and secondary metabolism. Overall, helium-flushed enclosed-chamber pretreatment was associated with changes in the non-volatile composition retained in processed green tea, with the magnitude of the detected differences varying among cultivars.