| Chungui is a new shrub-type,small-leaf and late-growing variety bred from the natural hybrid offspring of Huangdan.The fragrance of Minnan oolong tea is rich and has obvious quality characteristics of jasmine fragrance.The Chungui varieties have been popularized in Minbei oolong tea areas,but there are few studies on Chungui Minbei oolong tea.In order to explore the characteristic quality and flavor of Chungui Minbei oolong tea,the Chungui varieties were used as experimental materials in this study.Non-targeted and targeted metabolomics methods such as sensory evaluation,ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry(UPLC-Qq Q-MS),headspace solid-phase microextraction combined with gas chromatography-time of flight mass spectrometry(HS-SPME-GC-TOF-MS)were used to explore the key processing technology of turning over and baking degree and characteristic quality of Chungui Minbei oolong tea.Compared with the tea of Rougui,Shuixian and Huangguanyin.By analyzing and comparing the taste contribution value(TAV)and aroma contribution value(OAV)of four varieties,the characteristic quality components of Chungui Minbei oolong tea were determined,which provided theoretical and application basis for the matching processing technology of Chungui Minbei oolong tea.The main results are as follows :1.Effects of turning over intensity on the quality of Chungui Minbei Oolong teaThe analysis of biochemical components of Chungui tea with different turning over intensity showed that the contents of thearubigins and theaflavins increased with the increase of turning over degree,and there were significant differences in the contents of thearubigins and theaflavins.With the increase of the intensity of turning over,the water extract,tea polyphenols,amino acids,caffeine and theabrownin showed a downward trend,among which the water extract,tea polyphenols and theabrownin were significantly different,and the amino acid content was significantly different.The results of UPLC-Qq Q-MS targeted metabolomics showed that the total amount of catechins and amino acids decreased significantly with the increase of turning over intensity.The total amount of catechins was 40.54 mg/g and 29.05 mg/g,respectively.The contents of EGCG,ECG and EGCG3’ ME were significantly different.Non-ester catechins EC,C,GC and EGC showed significant differences.The total amino acid content of light turning over of Chungui was 12.44 mg/g,and the total amino acid content of heavy turning over was 9.85 mg/g.There were significant differences in sweet amino acids.Using HS-SPME-GC-TOF-MS metabolomics analysis method,it was found that the main volatile substances of Chungui tea were nerolidol,indole,geraniol,jasmine lactone,phenethyl alcohol,α-farnesene,caproate,dehydrolinalool,the relative content was about 44 % ～ 50 % of the total volatile substances,and both samples showed obvious floral aroma.The relative contents of indole(11.98%),jasmine lactone(6.4 %),α-farnesene(5.36 %)and phenylethyl alcohol(4.29 %)in light turning over of Chungui tea were higher,and the aroma type was fresh flower and fruit aroma.The relative content of aroma components in heavy turning over intensity of Chungui such as nerolidol(11.61 %),geraniol(5.53 %),and acetate leaf alcohol ester(3.63 %)was high,and the relative content of ester aroma components was high,and the aroma type was fragrant.2.Effects of different baking degrees on the quality of ’Chungui’Oolong teaThe light baking degree and medium baking degree were made from Chungui tea with different turning over intensity,which were recorded as QQ(light turning over intensity and light baking degree),ZQ((heavy turning over intensity and light baking degree),QZ(light turning over intensity and medium baking degree)and ZZ(heavy turning over intensity and medium baking degree).Analysis of biochemical components of different baking degrees of Chungui: The contents of water extracts,amino acids and thearubigins in light-baking Chungui Oolong tea were higher than those in medium-baking Chungui,and the content of amino acids was significantly different.The contents of tea polyphenols,flavonoids,theaflavins,theabrownins and phenol-ammonia ratio in light baking degree of Chungui were lower than those in medium baking degree,and there were significant differences in theaflavins,theabrownins and phenol-ammonia ratio.The UPLC-Qq Q-MS targeted metabolomics was used to analyze the catechins and amino acids of different baking degrees of Chungui.The results showed that the increase of baking degree could significantly reduce the content of catechins in tea soup,among which the content of ester catechins was significantly reduced,and the content of caffeine had no significant change.There were significant differences between EGCG and ECGC3’ ME in ester catechins.There were significant differences between GC and EGC in non-ester catechins.The amino acid content of light baking degree of Chungui is significantly higher than that of medium baking degree.Partial least squares discriminant analysis was performed on Chungui tea with different baking degrees.The four amino acid components of theanine,aspartic acid,glutamic acid and glycine were significantly different in Chungui tea with different baking degrees,and increasing the baking degree could reduce the bitterness and astringency of the tea broth.The volatile components of Chungui tea with different baking degrees were determined and analyzed.The results showed that the baking process had significant effects on alcohol compounds,lactone compounds,aldehyde compounds,alkane compounds,nitrogencontaining compounds and other compounds.Among the volatile substances with special odors in Chungui Minbei oolong tea,the substances with significantly increased baking degree were phenylacetonitrile,hexyl benzoate,phenylethyl butyrate,indole,dehydrolinalool,nerolidol,geraniol,benzyl alcohol,benzoic acid ester,α-farnesene,hexanoic acid ester,phenylethyl alcohol,cis-jasmone,methyl salicylate,trans-linalool oxide;the volatile substances with significantly increased content were phenylacetaldehyde,furfural,dihydroactinidiolide,geranylacetone,(E,E)-2,4-heptadienal,5-methylfuranaldehyde,hexanal,2-acetylfuran,benzaldehyde,tea pyrrole,dehydro-β-ionone,2-acetylpyrrole.In summary,the aroma of QQ is characterized by high floral aroma,the ZQ aroma type is characterized by rich and lasting floral aroma,the QZ aroma type is floral fragrance,and the ZZ aroma is characterized by rich floral aroma.The results of this chapter show that the Chungui Minbei oolong tea is suitable for the medium baking degree process.Its taste is mellow and strong,and the aroma type is floral and fragrant,and the comprehensive quality is better.3.Quality characteristics and flavor analysis of Chungui Minbei Oolong teaIn order to find out the quality difference between the Chungui varieties and the main tea varieties in Wuyishan,the Minbei Oolong tea made of Chungui,Rougui,Shuixian and Huangguanyin was selected.The results showed that the content of medium ester catechins in Chungui was higher,but the content of methylated catechin EGCG3’ Me was relatively low.The total amount of amino acids in Chungui was significantly higher than that in Rougui,Shuixian and Huangguanyin.The taste distribution of amino acids in the four varieties was bitter amino acids > umami amino acids > sweet amino acids,but the content was significantly different.The differential amino acid components of the four varieties were Arg,Cys,Asn,Asp,Met,Theanine,GABA,Trp and Tyr.TAV value method was used to analyze the contribution rate of amino acid components to taste.It was found that the taste amino acids Theanine,Glu,Phe,Cys,Val and His,which contributed more to the taste of Chungui(TAV > 1),formed the mellow and fresh taste of Chungui under the combined action of amino acid components with high content and high taste intensity and catechin components.The relative contents of alcohols,olefins and other compounds in the volatile substances of Chungui were significantly higher than those of Rougui,Shuixian and Huangguanyin,and the contents of esters were significantly higher than those of Shuixian and Huangguanyin.The contents of nerolidol,α-farnesene,hexanoic acid leaf alcohol ester,indole,phenylethyl alcohol,jasmine lactone and dehydrolinalool were higher,and the content of indole was significantly higher than that of the other three varieties,which may be an important component of the characteristic aroma of Chungui.The contribution of the different volatile substances of the four samples to the overall aroma of the tea was analyzed by the OAV value method.The results showed that the main aroma contribution(OAV > 10)of the volatile substances in the Chungui were caproic acid leaf alcohol ester,indole,α-ocimene,dehydro-β-ionone,nerolidol,cis-jasmone,and the aroma type was floral.Other(OAV > 1)volatile substances such as α-farnesene,trans-α-ionone,phenylethanol,2-n-pentylfuran,dehydrolinalool,tea pyrrole,the aroma type is mainly flower and fruit aroma,and with baking aroma,so that the aroma of Chungui Minbei Oolong tea is mainly elegant floral aroma.In summary,the appearance of Chungui Minbei oolong tea is heavy and tight,the taste is mellow and fresh with floral aroma,the soup color is orange and bright,the aroma floral fragrance is long-lasting,the leaf base is thick and soft. |
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