Analysis of the Major Characteristic Aroma Compounds in Different Grades of Jingshan Tea
To characterize the difference of odorants among different grades of Jingshan tea,we investigated the super grade,the first grade,the second grade and the third grade of Jingshan tea by stir bar sorptive extraction gas chromatography-mass spectrometry(SBSE-GC-MS),headspace solid-phase microextraction gas chromatography-mass spectrometry(HS-SPME-GC-MS)and gas chromatography-olfactometry(GC-O)analysis.Herein,we detected and identified 161 volatile organic compounds.The differences between the four grades of Jingshan tea were revealed by principal component analysis(PCA)and hierarchical cluster analysis(HCA).The variable importance in projection(VIP)of the orthogonal partial least squares discriminant analysis(OPLS-DA)was used to determine candidate differential volatile compounds among tea samples of different grades and further screening of differential compounds was carried out through analysis of relative odor activity value(ROAV)and GC-O analysis.A total of 18 volatile compounds were identified as key odorants for the discrimination of different grades of Jingshan tea,including linalool,geraniol,indole,(Z)-jasmone,dimethyl sulfide,etc.Among them,the contents of hoterienol,methyl jasmonate,and indole in the super grade Jingshan tea were significantly higher than those in other grades,and together with(Z)-jasmone,δ-decalactone,and 1-octen-3-ol and other aroma-active compounds constitute the characteristic floral aroma of super grade Jingshan tea samples.This study revealed significant differences in the characteristic volatile compounds among different grades of Jingshan tea,providing a reference for distinguishing the grades of green teas by chemometrics combined with multivariate statistical analysis.
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