| The paper conducted the study on the extraction method of HS-SPME on the aroma of green tea, then, the suitable extraction method was chosen. The green teas were recognized by discriminant analysis, after the distinguishing components, which could disguished chestnut-like aroma form non-chestnut aroma, were selected from the 102 tea samples by the process of stepdisc, then the recognition effects on tea samples with chestnut-like aroma and those with non-chestnut aroma were inspected. After the diverse aroma components were screened by the application of variance analysis and the discrimination effects were inspected by the principal component analysis, the characteristic aroma components were concluded further, according to the information of threshold value, aroma type, and so forth. The main results were as follows:1. Study on four kinds of HS-SPME extraction methods set up beforehand was carried out, and then the selected extraction method was analyzed on the repetition. The results indicated that CVs of the relative contents of 33 aroma components, accounting for 79.64% of the total essential oils, were all below 15%, the detected amounts were stable. Specific parameters were as follows:10.0g ground tea was put into the conical flask, 500μL ethyl decanoate, acting as internal standard and the concentration was 100mg/L, and 100 ml boiling distilled water were added, then the conical flask was stuffed up by the rubber stopper, which was immersed in acetone for 12 hours for the odor desorption, magnetic stirring speed, 450rpm, the extraction needle (50/30μm PDMS/DVB/CAR) was inserted into the conical flask to adsorp the aroma componets for 60 min over the tea infusion after 5 min balance at 50℃in water bath, then retracted and connected to GC-MS for detection.2. The divisive components, which could disguished teas with chestnut-like aroma form those with non-chestnut aroma, were screened using stepdisc process form the 102 tea samples—butylated hydroxytoluene,α-calacorene, ledol, copaene, tetradecane,4,11-dimethyl-,α-cyclocitral, naphthalene, 1,2,3,4-tetrahydro-1,1,6-trimethyl-, tau.-cadinol, naphthalene, Dodecanol,3,7,11-trimethyl-, geranyl acetone, cadinadiene,β-cadinene, nerol, 2,6-di-tert-butyl-p-benzoquinon and tetradecane, 16 aroma components in total. Then the screened components were taken as variables for the methods of Bayes discrimination and canonical discrimination respectively to recognize the teas with chestnut-like aroma and teas with non-chestnut aroma. The results showed that the correct rate of discrimination on the 102 tea samples was 100.00% using Bayes discrimination method, and that of cross-validation was also 100.00%, the effects were significant. Then, the tea samples were identified by the discrimination equation established by the extracted canonical variables based on the screened variables. 2 tea samples of 102 ones were misjudged, the correct rate of discrimination on the total tea samples was 98.04%, the correct rate on the 15 tea samples with chestnut-like aroma was 86.67%, and the correct rate on 87 tea samples with non-chestnut aroma was 100.00%, the results of cross-validation were consistent with those of canonical discrimination, the recognition performed a good effect.The results of discriminant analysis demonstrated that stepdisc process could filter interferential information and screened out effective information of identifying chestnut-like aroma from numerous aroma components, and that tea samples with chestnut-lke aroma and those with non-chestnut aroma could both be chemically recognized well by the established methods of Bayes discrimination and canonical discrimination based on the screened aroma components.3. The diverse aroma components of two types of teas produced from chestnut-like aroma transformation were screened; then, the distribution pattern of the teas and screened aroma components was inspected using principal components analysis. The results demonstrated that the divisive aroma components, which could distinguished 4 tea samples with chestnut-like aroma from those with non-chestnut aroma, were pentadecane,2-methyl-, nerolidol, phytol, heptadecane, 2,6-di-tert-butyl-p-benzoquinon,β-ionone, hexadecane,2,6,10-trimethyl-, nonanal and benzyl alcohol. In addition, according to the role of aroma components on the presentation and transformation of chestnut-like aroma, it could be concluded thatβ-ionone, 2,6-di-tert-butyl-p-benzoquinon, nerolidol, phytol and cis-jasmone were the principal aroma components of the presentation of chestnut-like aroma.
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