Change in Aroma Components of Raw Pu-erh Tea from Ancient Tea Trees during Storage

The aroma components of 11 raw Pu-erh tea samples of different ages made from ancient tea trees growing in three tea-producing areas in Xishuangbanna prefecture, Yunnan province were analyzed using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), and their sensory characteristics were evaluated by professional tea tasters. Orthogonal partial least squares discriminant analysis (OPLS-DA) with variable importance in the projection (VIP) was used to identify the major differential aroma components. Results showed that fresh raw Pu-erh tea had a clean aroma with methylbenzene, 1-octene-3-ol, D-limonene, cis linalool oxide (furan) and linalool being the major aroma components. After a long period (more than six years) of storage, the aroma turned stale, showing the characteristic flavor of aged Pu-erh tea. The contents of D-limonene, hexaldehyde, and alcohols, such as α-terpineol, 4-terpineol, dehydrolinalool, and nerolidol, methylbenzene, 1-isopropyl-3-methylbenzene and methoxybenzenes increased with prolonged storage time, whereas the contents of 1-octene-3-ol, cis linalool oxide (furan), and linalool decreased. We concluded that sensory properties of raw Pu-erh tea from ancient tea trees could be improved with prolonged storage (more than 6 years), which may be related to the decrease in alcohols with floral and fruity flavor and the increase in methoxybenzenes with stale flavor.