Characterization Of Aroma Compositions Of Keemun Black Tea

This work investigated the aroma-active components of keemun black tea from different brands and species. Keemun black teas were analyzed by headspace-solid phase micro extraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O), electronic nose and statistical analysis.The extraction of volatile compounds by HS-SPME has been optimized and the optimized parameters were as followed: 50 μm of extraction fiber, 50℃ of extraction temperature, 50 min of extraction time, and 1.00 g of sodium chloride.A total of 67 volatile compounds were identified and quantified in different brands of keemun black tea, including five categories: alcohols (19), aldehydes (21), ketones (12),esters (9) and others (6), which all compounds showed significant difference (P<0.05).Through calculating the odor activity value (OAV) of volatile compounds, there were 22, 23 and 15 components (OAV>1) described the aroma-active components of keemun congou black tea, keemun maofeng black tea and keemun xiangluo black tea. A total of 42 aroma compounds in different brands of keemun black tea were identified by GC-O, and 1-heptanol,trans-linalool oxide, linalool, geraniol, isobutyraldehyde, 1-octanal,(E,E)-2,4-heptadienal,phenylacetaldehyde,(E,E)-2,4-nonadienal, 6-methyl-5-hepten-2-one, (E,E)-3,5-octadien-2-one,and cis-jasmone are common aroma-active components in different brands of keemun black tea. Through the analysis of the electronic nose technology (PCA and DFA), and combined with radar fingerprint, the results showed that electronic nose technology can well distinguished different brand of keemun black tea. A total of 67 volatile compounds were identified and quantified in different species of keemun black tea, including five categories:alcohols (19),aldehydes (21),ketones (12),esters (9) and others (6),which have 41 compounds showed significant difference (P<0.05). 52 volatile compounds were calculated by odor activity value (OAV), and 8 volatile compounds (geraniol, 2-methylbutyraldehyde,phenylacetaldehyde, (E,E)-2,4-nonadienal, (E,E)-2,4-decadienal, β-damascenone, β-ionone,methyl salicylate), which OAV>10, were potential contributors to the keemun black tea.Aroma-active compounds, which satisfied average OAV > 1 and average frequency≥3 of three specie keemun black tea, GC-MS quantitative data were analysis by principal component(PCA) and agglomerative hierarchical clustering (AHC), the results showed that PCA and AHC can well distinguished different specie keemun black tea.