| Wuyi rock tea has fruit flavor aroma and unique "Yan flavor",previous studies on aroma of Wuyi rock tea mainly foucus on the detection of aroma components.In this study we analyzed aroma during the processing of Shuixian and Rougui;explored the effect of β-glucosidase activity on the formation of alcoholic aroma;analyzed glycosidic aroma precursor’s change in proccessing;research the differences temporal expression of β-primeverosidase and β-glucosidase gene and find correlation among glycosidic aroma precursors,aroma,enzymes activity and gene expression,aiming to reveal the mechanism of Wuyi Shuixian and Rougui aroma formation and find differences and similarities between them.The results are as follows:1 Aroma changes in processing of Wuyi rock teaAroma change during the processing of Wuyi rock tea:(1)The total amount of aroma show that:Shuixian<Rougui,the change rate in processing of Shuixian(72.23%)was more than Rougui(33.38%);(2)The content of aroma components show that:Esters,alkenes,alkanes,ketones and nitrogen compounds in Shuixian were higher than Rougui,alcohols,aldehydes aroma in Rougui were higher than Shuixian,the aroma components shared by both were alcohols,esters and ally]based compound;(3)The total amount in the sun-withering stage and the shaking leaves stage of Shuixian and Rougui showed a rising trend,the total amount in the rolling and dring stages continued to increase in Shuixian while decreased significantly in Rougui.The differences of aroma in Wuyi Shuixian and Rougui:Wuyi Shuixian and Rougui have common characteristic aroma components,including nerolidol,geraniol,linalool,leaf acid ester,butyl lactate,cis-3-hexenyl acetate butyrate,methyl salicylate,a-farnesene,β-ocimene and indole,unique aroma components in Shuixian were acid hexyl acrylate,cedrene,what unique in Rougui were phytol,caryophyllene.Different varieties of Wuyi rock tea have diverse characteristic aroma composition content,nerolidol and geraniol content in Rougui is higher than Shuixian,other ingredients in Shu ixian is higher than Rougui.2 Variation of β-glucosidase activity in Wuyi rock teaThe changes of β-glucosidase activity in Wuyi rock tea:(1)Overall average activity ofβ-glucosidase:Shuixian(2.37U/g)<Rougui(4.15U/g),β-glucosidase activity of Rougui is 1.06-2.26 times Shuixian;(2)The change range of β-glucosidase activity:Shuixian(32.11%)>Rougui(14.76%),variation width of Shuixian is 1.21 times Rougui;(3)In both varieties of Wuyi rock tea β-glucosidase activity showed a general downward trend,and reached the highest value in the end of the sun-withering stage.β-glucosidase activity in fresh leaves of Shuixian and Rougui rised extremely significantly,but the β-glucosidase activity of them have not reached significant level,and the differences of β-glucosidase activity in Shuixian and Rougui rised extremely significantly level in the shaking leaves stage.Correlation between Wuyi rock tea β-glucosidase activity and aroma show that:(1)Aroma and enzyme activity in Shuixian were lower than Rougui,but the change rate during processing is higher than Rougui;(2)In Shuixian,enzyme activity increased in the sun-withering stage which was corresponding to increase in total amounts of aroma,alcoholic aroma and the content of main alcoholic aroma components,in shaking leaves stage,with the decrease of the enzyme activity,total amounts of aroma,alcoholic aroma and main alcoholic aroma components degraded accordingly;(3)Rougui enzyme activity increased in the sun-withering stage,total amounts of aroma,alcohol aroma and nerolidol,geraniol content increased and linalool and its oxides decrease,with the decrease of the enzyme activity,total amounts of aroma,alcoholic aroma and main alcoholic aroma components content decrease in shaking leaves stage;(4)β-glucosidase activity in Shuixian showed height index negative correlation with aroma,nerolidol and geraniol,the correlation coefficient was 0.931,0.973,0.999 respectively;show height index of positive correlation with linalyl,high index of positive correlation with cedrol,the correlation coefficient was 0.947,0.872 respectively;β-glucosidase activity in Rougui showed high index of negative correlation with aroma,nerolidol,geraniol and linalool oxides I,the correlation coefficient was 0.897,0.888,0.869,0.882 respectively.3 The changes of glycosides aroma precursors in Wuyi rock teaThere are 5 kinds of main aroma precursors in Wuyi Shuixian and Rougui,including cis-3-hexyl alcohol,linalool,geraniol,methyl salicylate,benzyl alcohol glycosidic aroma precursors,the maximum content among them is geraniol.Precursors in Wuyi Shuixian and Rougui was different,the result show that:Shuixian(22.15μg/g)<Rougui(27.66μg/g),each ingredients of Shuixian performance:Geraniol glycosides(13.9μg/g)>benzyl alcohol glycosides(3.3μg/g)>methyl salicylate glycosides(2.93μg/g)>linalool glycoside(1.94μg/g)>cis-3-hexyl alcohol glycosides(0.31 μg/g),each ingredients of Rougui performance:Geraniol glycosides(15.69μg/g)>benzyl alcohol glycosides(5.35μg/g)>linalool glycoside(3.31 μg/g)>methyl salicylate glycosides(2.24μg/g)>cis-3-hexyl alcohol glycosides(1.3μg/g)The same variation of Wuyi Shuixian and Rougui glycosidic aroma precursors performance:In the sun-withering stage,glycosidic aroma precursors increased significantly,the glycosidic aroma precursors decreased compared with withering leaves in shaking leaves stage.Correlation of Wuyi rock tea aroma and glycosidic aroma show that:Different varieties of Wuyi rock tea aroma components and their corresponding glycoside formed coordinate dynamic equilibrium,aroma and glycosidic aroma precursors have consistent changes in the sun-withering and shaking leaves stages.4 Differential gene expression analysis of β-primeverosidase and β-glucosidase genes of Wuyi rock teaDifferential gene expression of β-primeverosidase and β-glucosidase gene in Wuyi rock tea:(1)Gene expression of β-primeverosidase and β-glucosidase rised significantly compared with fresh leaves in the end of sun-withering of Shuixian,not reach significant level in the shaking leaves stage,gene expression of β-primeverosidase(1.1)is inferior to β-glucosidase(1.9)on average in Shuixian,the average rate(60.53%)is more than β-glucosidase(44.22%);(2)Gene expression of β-primeverosidase and β-glucosidase in Rougui compared with fresh leaves have not reached significant level,bue rised significantly in the end of shaking leaves stage.Gene expression of β-primeverosidase(0.54)is inferior to β-glucosidase(0.76)on average in Rougui,the average rate(42.64%)is inferior to β-glucosidase(52.43%);(3)Gene expression ofβ-primeverosidase in Shuixian is higher than Rougui,and the average change rate is greater than the Rougui.Gene expression of β-glucosidase in Shuixian is generally higher than Rougui,but the average change rate is less than Rougui.5 Correlations among glycosidic aroma precursors,aroma,gene expression ofβ-primeverosidase and β-glucosidase in Wuyi rock teaThe correlation between gene expression of β-primeverosidase and β-glucosidase in Wuyi rock tea and aroma:Gene expression of and β-glucosidase,aroma peak area,alcoholic aroma of Shuixian all decrease in sun-withering stage,gene expression ofβ-primeverosiase and β-glucosidase decrease while aroma peak area,alcoholic aroma increased.Gene expression of β-glucosidase,aroma peak area,alcoholic aroma of Rougui increase while gene expression of β-primeverosidase decrease in sun-withering stage,gene expression ofβ-primeverosidase and β-glucosidase decrease while aroma peak area,alcoholic aroma increase in shaking leaves stage.The correlation between gene expression of β-primeverosidase and fi-glucosidase in Wuyi rock tea and enzyme activity:Gene expression of β-glucosidase and enzyme activity of Shuixian have same changing trend in the sun-withing and the earlier shaking leaves stages.In the medium shaking leaves stage,gene expression of β-glucosidase decrease while enzyme activity increase,both of them decreased in later shaking leaves stage.Gene expression of and enzyme activity of Rougui have a shift change trend in sun-withing and the earlier shaking leaves stages,in later shaking leaves stage,gene expression of β-glucosidase and enzyme activity have same change trend.The correlation between gene expression of β-primeverosidase and β-glucosidase in Wuyi rock tea and glycosidic aroma precursors:The change of gene expression of β-primeverosidase and β-glucosidase in processing of Shuixian have same trend with glycosidic aroma precursors,the change of gene expression of β-glucosidase in processing of Rougui have same trend with glycosidic aroma precursors,gene expression of β-glucosidase decrease while glycosidic aroma precursors content increase in sun-withering stage of Rougui,gene expression and glycosidic aroma precursors have the same change trend in shaking leaves stage. |
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