Abstract: The aroma quality of tea is closely related to the harvesting seasons. It is important to identify the difference in volatile compounds of green teas from different harvesting seasons. In our present study, headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to qualitatively and quantitatively analyze the volatiles compounds of green tea samples harvested in spring, summer and autumn. Subsequently, discriminant and cluster analyses of the volatile compounds in these green teas were carried out by using multivariate statistical analysis. The results showed that a total of 32 volatile components were identified, including alcohols, aldehydes, ketones, esters, alkanes, heterocyclic compounds and other substances. A model of partial least squares-discriminate analysis (PLS-DA) based on the relative contents of the identified compounds could effectively differentiate among the green tea samples from spring, summer and autumn seasons (fitting parameters R2Y = 0.903, Q2 = 0.570). A total of 12 key components, including cis-jasmone, benzyl alcohol, (E)-2-octenal, β-cyclocitral, 1-hexanol, 5,6-epoxy-β-ionone, (E,E)-2,4-heptadienal, nonanal, hotrienol, 2,2,6-trimethyl-cyclohexanone, 3-methyl-furan and 1-heptanol were identified. Furthermore, the results of cluster analysis based on the contents of the key components showed that cis-jasmone, aliphatic alcohol and benzyl alcohol in spring green tea, which generally have the characteristic aroma of grass as well as fruits and flowers, were remarkably higher than those in summer and autumn teas. The contents of aldehydes and ketones with sweet and fatty aromas were higher in green tea harvested in summer than those harvested in spring and autumn, among which (E,E)-2,4-heptadienal was the most abundant. Autumn tea contained the fewest number of key volatiles, and only hotrienol with grass, floral and woody scents was higher in most autumn green tea samples than in spring and summer green teas.

Key words: green tea, harvesting seasons, aroma compounds, headspace-solid phase microextraction (HS-SPME), multivariate statistical analysis