Effects Of The Aroma Related Enzyme On Congou Black Tea LED Yellow Withering

In the withering process of tea,?-glucosidase and ?-primeverosidase play important roles in the metabolism of terpene alcohol aroma components.In this study,we screened the withering optimal light(yellow light)by comparing the qualities of Congou black teas,which were illuminated by using different Light Emitting Diode(LED)at the withering process.;in order to evaluate the effects of LED yellow light on the quality of tea,the aroma components of Congou black tea were detected by GC-MS,and the sensory evaluation was conducted,the results imply that withering by LED yellow light can significantly improve the aroma of Congou black tea.In order to reveal the physiological and molecular mechanism of improving the aroma of tea by LED yellow light,Camellia sinensis cv.Zhenghedabaicha were divided into two groups,one group withering by LED yellow light,the other group as the control(CK)withering under indoor condition,and then the process of rolling,fermentation and drying were carried out,enzyme related genes(?-glucosidase and ?-primeverosidase)were cloned,and we analysized the expression level of the aroma related genes,the activity of(3-glucosidase during Congou black tea withering and the tea aroma components.The main results were followed:(1)The biochemical components of tea were significantly different due to the withering using white,red,orange,yellow,purple and blue light,respectively.The result showed that the content of free amino acids of tea withering by LED yellow light was the highest,and tea polyphenols were the lowest.The results of sensory evaluation showed that the quelity of tea withering by LED yellow tea was the best,whose aroma score was 9.5 points higher than CK,and which was the only treatment group with the floral aroma.(2)LED yellow light had a positive influence on the composition and content of the volatile aroma components in the withered leaves and raw teas.Yellow light withering can promote the accumulation of linalool,geraniol and other terpene alcohols,it could effectively improve the aroma of Congou black tea.(3)From Zhenghedabaicha,we successfully cloned two ?-glucosidase genes(CsBG1,CsBG2),and one ?-primeverosidase gene(CsBP);CsBP belong to the family of glycosyl hydrolase 1.The nucleic acid sequence length of CsBG1 is 377bp,coded 60 amino acids;the nucleic acid sequence length of CsBG2 is 1232bp,coded 409 amino acids;the nucleic acid sequence length of CsBP in 844 bp,coded 202 amino acids.Compared with the corresponding glycosidases in Theobroma cacao,Vitis vinifera,Ricinus communis and Viburnum furcatum,three aroma related enzyme genes were highly homologous.(4)According to the sequences of CsBG1,CsBG2 and CsBP gene,primers were designed,and the 18SrRNA as reference gene,withering process of aroma related enzyme genetic expression was detected by qRT-PCR technique.In the LED yellow withering 6h,CsBGI.CsBG2 genes were highest,significantly higher than the control group.CsBP gene was up-regulated expressed in withering process.(5)We determined ?-glucosidase activity in withering by spectrophotometer,the result showed that ?-glucosidase activity was highest in the withering of 12h,which was significantly higher than that of the control group.we analysised the correlation of activity and genetic expression,the result showed that the expression of CsBG2 gene has the positive correlation with the activity of ?-glucosidase.The rise of genetic expression is started from the early LED withering stage,and The activity of enzyme increased in the later period of withering,which positively promoted the development of sweet and floral aroma of Congou black tea and finally the quality was improved.This study provides theoretical support for the physiological and molecular mechanism of tea aroma improving.