Abstract: According to the current national standards, Tieguanyin Oolong teas would be classified into three flavor types, Fresh-scent, Strong-scent and Stale-scent. In this experiment, Tieguanyin collected from their original regions (Anxi County) were categorized into several groups by preliminary sensory evaluation. Thereafter, aroma components in these tea samples were determined using headspace solid-phase micro-extraction and gas chromatography-mass spectrometry (HS-SPME/GC-MS), and their differences between new Tieguanyin (less than one year storage) with different flavor characteristics and old Tieguanyin (more than one year storage) with different storage time and quality ranks were compared through visual pattern recognition based on principal component analysis (PCA), and orthogonal partial least squares discriminant analysis (OPLS-DA) combined with other statistical methods. The results showed that aroma patterns of all tea samples could be obviously divided into two groups according to storage time. The total amount of aroma compounds was more abundant in new Tieguanyin than that of old Tieguanyin. Alcohols, esters and alkenes were the main compounds which contributed to the new fresh-scent flavor of new Tieguanyin, and aldehydes and ketones were the characteristic compounds of stale-scent flavor in old Tieguanyin. Nerolidol, indole, α-farnesene, 2-phenylethyl 2-methylbutanoate, cis-3-hexenyl hexanoate, formic acid, (2-methylphenyl) methyl ester, phenylethyl butyrate, phenylethyl isobutyrate, 2-tolylisocyanide, isopentyl hexanoate and geranyl acetone could be considered as the key markers to discriminate the two types of Tieguanyin. Moreover, new Tieguanyin could be also classified as Group 1 (Long-time withering), Group 2 (Medium-time withering and Short-time withering), and Group 3 (Strong-scent) based on their aroma constitutes. Aroma components were richer in tea samples from both Group 1 and Group 3 than those from Group 2. The acidic flavor of tea samples from Long-time withering was closely associated with ester compounds, while aroma components of tea samples from Strong-scent were mostly condensed compounds with long carbon chains. No obvious differences could be detected in old Tieguanyin, which had different storage time, but there were some potential differences among tea samples with high quality ranks. Tieguanyin of excellent sensory quality were relatively abundant in ester compounds, and low in contents of aldehydes and ketones. These results could provide references for classification, identification and quality evaluation of Tieguanyin products.

Key words: Tieguanyin, Oolong tea, aroma component, pattern recognition