Quality Chemistry Of Yin-flavor For Qingxiang Tieguanyin

Anxi Tieguanyin,with unique Yin-flavor quality,is a representative product of Minnan oolong tea.In order to explore the quality chemical composition of Yin-flavor of Qingxiang Tieguanyin,76 Qingxiang Tieguanyin tea samples were collected and used as the materials,aroma and taste flavor wheel for Qingxiang Tieguanyin in different producing areas were constructed through tea sensory evaluation method and quantitative descriptive analysis of sensory attributes;aroma and taste chemical composition of Qingxiang Tieguanyin were then detected by using gas chromatography-mass spectrometer（GC-MS）,ultra performance liquid chromatogram-mass spectrometer（UPLC-MS）,and other biochemical composition determination methods;main sensory attribute factors and aroma and taste components of the Qingxiang Tieguanyin Yin-flavor quality were selected out through correlation analysis,regression relationship analysis and verification analysis,which can provide scientific analysis for the chemical composition of Yin-flavor quality.The main results are as follows:1.The quality characteristics and regional differences of the Qingxiang Tieguan Yin-flavor.According to the results of sensory evaluation,the shape of Anxi Qingxiang Tieguanyin is tight and the color is forg skin alike green.The liquor color is mainly yellow,golden yellow,yellowish green and greenish yellow.The infused leaves are fat and thick,soft and bright.The aroma quality of Yin-flavor is mainly floral and fruity such as orchid aroma and ripe fruit aroma.The taste quality of Yin-flavor is fresh,mellow,sweet,refreshing and fragrance can be left in the soup.Based on the tea sensory evaluation,the aroma quality of Qingxiang Tieguanyin was divided into six sensory attributes:refreshing aroma,green aroma,floral aroma,sweet aroma,fruity aroma and tainted odour.The taste quality of Qingxiang Tieguanyin was divided into eleven sensory attributes:fresh,mellow,sweet after taste,brisk,sweet,fragrance left in the soup,thick,sour,bitter,astringent and tainted taste.Through the quantitative description analysis of sensory attributes,the aroma and taste flavor profiles of Qingxiang Tieguanyin in different producing areas were drawn,which explained the regional characteristics of the sensory quality of Yin-flavor in Qingxiang Tieguanyin.Gande Qingxiang Tieguanyin smells mainly floral,and tastes fresh and mellow.Longjuan Qingxiang Tieguanyin smells mainly ripe fruity,and tastes relatively thick and mellow.Xianghua Qingxiang Tieguanyin is mainly ripe fruity,and the taste is smooth,fragrance can be left in the soup.Xiping Qingxiang Tieguanyin smells obviously floral and fruity,and the taste is heavy and mellow,sweet after taste and brisk.2.Analysis of volatile components in Qingxiang Tieguanyin.The results of volatile metabolomics analysis showed that the aroma components of Qingxiang Tieguanyin were mainly terpenes,followed by esters,and the proportion of hydrocarbons,aromatic hydrocarbons,heterocyclic compounds and phenols also exceeded 4%,ketones and aldehydes accounted for more than 1%.The main aroma components of Qingxiang Tieguanyin different from Qingxiang Foshou tea are refreshing and floral-fruity components:（-）-verbenone,4-ethyl-benz Aldehyde,（E,Z）-6,10-dimethyl-3,5,9-undecatrien-2-one,2-（2-hexenyl）-cyclopentanone and 4,6-dimethyl-2,7-nonadien-5-one.The main aroma components of Qingxiang Tieguanyin different from Beauty tea are floral and fruity components:levomenol,1-heptadecene,cis-7-decenal andδ-decalactone（peach smell）.The contents of terpenes,esters,hydrocarbons,aromatic hydrocarbons,phenols,ketones and aldehydes volatiles were significantly different between Qingxiang Tieguanyin and Qingxiang Foshou tea.There was no significant difference in the content of terpenoids volatiles between Qingxiang Tieguanyin and Beauty tea.These nine classes of volatiles were the main aroma components of Qingxiang Tieguanyin Yin-flavor.3.Analysis of non-volatile components in Qingxiang Tieguanyin.Biochemical composition determination results showed that,water content,caffeine content and total tea polyphenol content of Qingxiang Tieguanyin in Anxi County were significantly higher than those in Datian County.There was no significant difference in water extract content,total free amino acid content,theaflavins,thearubigins and theabrownins content.There were some differences in the biochemical quality of Qingxiang Tieguanyin from different producing areas.Non-targeted determination of non-volatile components in Qingxiang Tieguanyin in different regions by ultra performance liquid chromatography-mass spectrometry showed that a total of 177 differential substances were screened and identified.The relative contents of amino acids and their derivatives and polyphenols in Longjuan Qingxiang Tieguanyin were significantly lower than other regions,and the contents of polyphenols and phenolic glycosides in Gande Qingxiang Tieguanyin were significantly higher.The relative contents of coumaric acid and its derivatives in Gande Qingxiang Tieguanyin and Longjuan Qingxiang Tieguanyin were significantly lower than those in Xianghua and Xiping.There was no significant difference in the relative content of glycosides,lipids,quinic acid and its derivatives in these different regions.4.Association analysis of Yin-flavor quality with aroma and taste components.Combined with the linear regression equation of sensory quality and aroma substances of Qingxiang Tieguanyin:S_{（aroma score）}=108.03-5566.27×X₁+185.22×X₂-60.62×X₃+5.00×X₄-56.22×X₅+197.93×X₆;and the correlation analysis results between their sensory quality and differential volatiles of Qingxiang Tieguanyin in Anxi and Datian County,the key aroma components of Yin-flavor identified as trans-geranic acid methyl ester,hotrienol and（E）-2-hexenal,which significantly positively affected the aroma score of Qingxiang Tieguanyin,and the upregulated differential volatiles of TGY-DT vs TGY-AX such as6-Undecanol,4-（1-methylethenyl）-1-cyclohexene-1-carboxaldehyde,isoamyl butyrate and 2,4-decadien-1-ol.Among them,trans-geranic acid methyl ester has the highest degree of influence.Correlation analysis showed that water content,the content of water extract,the total tea polyphenols and theaflavins content were determined as the main biochemical factors of the Yin-flavor quality of Qingxiang Tieguanyin.Linear regression analysis showed that phenolic glycosides,coumaric acid and their derivatives content,total free amino acids,quinic acid and its derivatives content significantly positively affected taste score,taste attributions sweet and strong.Coumarinic acid and its derivatives,phenolic glycosides,free amino acids and quinic acid and its derivatives are the key taste substances of Qingxiang Tieguanyin Yin-flavor quality.5.Preliminary verification of the effect of taste-related components on Yin-flavor quality attributes.The results of correlation verification experiment of taste-related components proved the correlation between theaflavins content,polyphenol ammonia ratio and the taste quality of Qingxiang Tieguanyin.Theaflavins significantly enhanced the thick intensity of taste and enhanced the umami,sweetness and aroma intensity of taste.The intensity of fragrance left in the soup was significantly enhanced with the increase of tea polyphenol content,while decreased with the increase of amino acid content,which was consistent with the significant positive effect of polyphenol ammonia ratio on the taste attribute,fragrance left in the soup.Using tea flavor quality evaluation technology combined with metrological statistical analysis methods,the research results of this paper constructed the aroma and taste flavor wheel of Tieguanyin in different regions,clarified the aroma and taste sensory attributes and contribution components of Yin-flavor quality,and comprehensively analyzed the quality chemical composition of Qingxiang Tieguanyin Yin-flavor quality.Which can provide scientific data for the high-quality development of Tieguanyin tea industry.