Study On The Release Mechanism Of Jasmine Flowers And The Change Of Volatile Constituents

Jasmine tea is popular in consumers because of its fragrant fragrance.At present,the change trend of volatile components and the mechanism of jasmine fragrance release haven't been clear.In this study,jasmine was firstly used as the material to observe the process of opening and releasing aroma.Then,the dynamic changes of volatile components in jasmine and green tea were studied by means of absolute quantitative analysis by GC-MS.Finally,molecular biological analysis was used to monitor the activity and gene expression of four enzymes(SAMT,HGMR,PAL and FPPS)related to aroma release.The following conclusions are drawn:1.This study observed the process of opening and aroma releasing of jasmine flowers in vitro under different temperature conditions,and analyzed the appropriate temperature for releasing aroma of jasmine flowers in vitro by integrating the opening rate,openness,color and freshness of jasmine flowers,as well as the indicators of fragrance type,concentration and freshness of flowers.The results show that 30 ? is the optimum temperature for jasmine to release aroma.Jasmine flowers at this temperature can keep fresh for a long time and release fresh and fragrant aroma.The results will provide temperature parameters for jasmine tea scenting system in the next step.2.GC-MS analysis technique was used to detect the dynamic changes of volatile components in the scenting process of scented tea.The results showed that a total of 78 active volatile compounds were detected from tea billets during scenting process,including 29 terpenes,6 alcohols,28 esters,8 nitrogenous compounds,1 aldehyde compound and 6 other compounds.A total of 71 active volatile components were detected in jasmine,including 24 terpenes,9 alcohols,6 hydrocarbons,24 esters,1 ketone,3 aldehydes,2 nitrogenous compounds and 2 oxygen-containing compounds.The JTF values in the new scenting process were higher than those of jasmine and green tea in the traditional scenting process at the same scenting time point.3.The absolute quantification results of volatile components showed that the total volatile components,terpenes,esters,alcohols,nitrogenous compounds and hydrocarbons in tea billets of different scenting processes tended to rise first and then fall.However,the oxygen-containing compounds showed a rising trend and then falling trend in the new scenting process,while the traditional scenting process showed a continuous declining trend.The content of alcohols and hydrocarbons in the new scenting process tea billets was lower than that in the traditional scenting process tea billets,and the other volatile components were higher than that in the traditional scenting process tea billets.The contents of terpenes,oxygen-containing compounds,esters,alcohols,nitrogenous compounds and hydrocarbons in jasmine flowers under different scenting processes showed a trend of increasing first and then decreasing.The content of alcohols and hydrocarbons was higher in jasmine than in the new scenting process,while the other volatile components were higher in the new scenting process than in the traditional scenting process.At the same scenting time point,the volatile components of green tea and fresh flowers under the new scenting process were much higher than those under the traditional scenting process.4.FPPS,HGMR,PAL and SAMT enzymes related to the release of fragrance from jasmine flowers were selected as research objects to analyze their activity changes during the scenting process.The results showed that the activity of HGMR decreased during the scenting process,while the activity of FPPS,PAL and SAMT increased first and then decreased.Except the activity of the traditional scenting process of scenting flowers is higher than that of the new scenting process of scenting flowers and in vitro jasmine flowers,the activity of HPL,SAMT and HGMR are the lowest among the three treatments.qPCR fluorescence quantitative analysis was conducted on rt HGMR,rt PAL,rt SAMT and rt FPPS genes in flowers treated with different treatments.The results showed that:during the process of gardening,the relative expression of rt HGMR gene in flowers showed a decreasing trend,while the relative expression of rt PAL,rt SAMT and rt FPPS genes increased first and then decreased.The correlation analysis between enzyme activity and gene expression showed that the expression levels of rt HGMR,rt PAL,rt SAMT and rt FPPS were positively correlated with their corresponding enzyme activities(p<0.05).Compared with scenting flowers by the traditional scenting process,scenting flowers by the new scenting process can improve the activity and gene expression of four enzymes related to the release of fragrance,which is beneficial to the release of fragrance substances of jasmine flowers and improve the aroma quality of scented tea.