| Beauty tea is a type of highly fermented oolong tea product,processed from fresh leaves sucked by small green leafhopper.It has a fruity honey aroma and unique quality.The planting area of the Tieguanyin variety in Datian County is relatively large,but the proportion of producing high-quality beauty tea is relatively low.Improving the quality of Tieguanyin beauty tea is beneficial for increasing the scale of beauty tea industry and the output value of beauty tea.This study compared the sensory quality differences between Tieguanyin beauty tea and suitable beauty tea varieties such as Qingxin Damao and Jinxuan through sensory evaluation and GC-MS techniques,and condensed the quality and aroma characteristics of Tieguanyin beauty tea;the quality differences of Tieguanyin beauty tea with different degree of puncturing were compared and analyzed by using UPLC-MS/MS,GC-MS,and sensory evaluation,thus the impact of fresh leaves puncturing on the quality of Tieguanyin beauty tea was analyzed;the dynamic changes of volatile compounds during the processing of Tieguanyin beauty tea was analyzed,the key processes for the formation of aroma quality during the processing of Tieguanyin beauty tea are revealed.The results of this study provides theoretical basis and practical guidance for establishing of high-quality fresh leaf picking standards for Tieguanyin beauty tea,optimizing the processing technology of Tieguanyin beauty tea,and assisting in the high-quality development of the beauty tea industry.The main results of this study are as follows:1.Quality characteristics of Tieguanyin beauty tea.Through the sensory evaluation and analysis of beauty tea made from a large number of different tea varieties and the analysis of the characteristics of some high-quality beauty tea,the quality characteristics of high-quality Tie Guanyin beauty tea were preliminarily clarified.The results showed that the yield rate of Tie Guanyin Beauty Tea was low,and only 7 of the 26 samples were of better quality,and the high-quality Tie Guan Yin Beauty Tea had fruity aroma,honey aroma and mellow taste.The soup color of Tie Guanyin is generally reddish;the quality of Qingxin Damao,Jinxuan,Jinmudan and other varieties beauty tea samples were better,with fruit and honey fragrance,and mellow and sweet taste.The aroma substances of Tieguanyin,Qingxin Damao,Jinxuan and Jinmudan beauty teas were mainly alcohols,hydrocarbons,esters and ketones,and the relative contents of aroma compounds such as linalool,phenethyl alcohol,benzyl alcohol,β-viologenone,methyl salicylate,trans-γ-stilbene and hexyl caproate were relatively higher.The high-quality Tieguanyin beauty tea had a relatively higher content of methyl salicylate,linalool,benzyl alcohol and other substances than that of low-quality Tieguanyin beauty tea,and exhibited honey aroma.2.Effects of different stinging degrees of small green leafhopper on the quality of Tie Guanyin beauty tea.The quality differences were analyzed by sensory evaluation,the differences of non-volatile metabolites between Tieguanyin fresh leaves and beauty tea were analyzed by UPLC-MS/MS,and the differences of volatile compounds were compared by GC-MS.The results showed that the quality of Tieguanyin beauty tea was the best in low puncturing,and the nectar fragrance was rich,sweet and refreshing;the quality of Tieguanyin beauty tea was the worst with heavy puncturing,and the quality of Tieguanyin beauty tea was promoted by low puncturing of small green leafhopper.Differences in non-volatile metabolites between Tieguanyin fresh leaves and beauty tea with different punturing degrees were obvious,and the difference substances were mainly catechins and their derivatives,flavonoids and flavonols and their glycosides,proanthocyanidins,sugars and glycoside derivatives.In the dried tea,with the increase of puncturing degree by small green leafhopper,the differential metabolites of polyphenols such as catechins and their derivatives,flavonoids or flavonols and their glycosides,phenolic acids,proanthocyanidins and tannins showed a decreasing trend,and the content of most sugars and their derivatives,linalool increased;this was consistent with the results of its sensory evaluation.The differential volatile compounds of Tieguanyin beauty tea with different stinging degrees were mainly esters,olefins,alcohols and aldehydes;nine volatile components with OAVs ≥ 1 were screened by OAV method,namely linalool,cis-linalool oxide,geraniol,β-cyclic citral,phenylethylaldehyde,methyl salicylate,decanal(fatty breath,sweet aroma),2-pentyl furan and cedarol;the study showed that the puncturing degree affects the content of linalool gly in fresh leaves of Tieguanyin,which in turn affects the content of cis-linalool oxide in dry tea.3.Aroma analysis of Tieguanyin beauty tea during processing.The aroma quality of Tieguanyin beauty tea processing was analyzed by using dynamic headspace collection method combined with gas chromatography,and the results showed that the water content of in-process leaves was significantly reduced during processing,and water stress may be an important factor in the formation of beauty tea aroma;the volatile compounds of in-process leaves in different processes were mainly alcohols,aldehydes,olefins and esters.18 kinds volatile components of dry tea in processing were generated.The number and relative contents of alcohols,aldehydes and esters of volatile components increased significantly in these stages.In conclusion,the quality of Tieguanyin tea differs greatly among different varieties of beauty tea;the moderate puncturing of small green leafhopper has a facilitating effect on the formation of good quality of Tieguanyin beauty tea,while heavy puncturing is not conducive to the formation of beauty tea quality;the processing process is crucial to the formation of beauty tea quality,and withering,making and stacking are the key processes for the formation of the aroma of Tieguanyin beauty tea.The results of this study will provide theoretical basis and practical guidance to improve the quality of Tieguanyin beauty tea. |
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