Characterization of Volatile Substances in Pu-erh Tea (Raw Tea) at Different Storage Times

There is a lack of theoretical evidence regarding the transformation of the aroma of Pu-erh tea (raw tea) during long-term storage. In this study, we comprehensively investigate the aroma characteristics of Pu-erh tea (raw tea) from the same manufacturer, stored for different storage times (7–21 years). Sensory evaluation and qualitative and quantitative analysis of volatile substances were performed on the experimental samples. The results showed that the aroma of Pu-erh tea (raw tea) changed from fruity/floral to smoky and fragrance during the storage process. A total of 290 volatiles were identified by HS-SPME/GC×GC-Q-TOF-MS. The key substances for the fruity/floral aroma are fenchene, (E)-1,2,3-trimethyl-4-propenyl-Naphthalene, (+/−-theaspirane, and decanal, and the key substances for the smoky aroma were 2-ethyl-Furan, camphene, 1-methyl-4-(1-methylethenyl)-Benzene, and cis-β-Ocimene. The key aroma substances for the fragrance aroma are 1-methyl-4-(1-methylethylidene)-Cyclohexene, α-Terpinene, trans-β-Ocimene, (E,E)-2,4-Heptadienal, octanal, 2,5-Dimethoxyethylbenzene, 2,4-Dimethylanisole, 1,2,3-Trimethoxybenzene, and 3,4-Dimethoxytoluene. This study helps us to understand further the aroma changes of Pu-erh tea (raw tea) during long-term storage.