Differential Contribution Of Jasmine Floral Volatiles To The Aroma Of Scented Green Tea

Aroma is important for tea quality.Teas contain numerous volatile compounds.So far,more than 700 kinds of volatile compounds have been identified from fresh tea leaves and made teas,including those derived from carotenoids and lipid oxidation degradation,Maillard reaction,and the hydrolysis of glycosidically bound precursors.Many factors such as breeding,cultivation techniques,picking and processing procedure influence tea aroma composition and quality.Improvement of tea aroma has always been a hot and complex issue in academia and industry.Using fresh flowers of jasmine,rose and osmanthus to scent green tea for the enhancement of tea aroma has a long history in China,which is simple and effective.Jasmine tea is the mostly common scented tea.Although many previous studies have reported the composition of jasmine tea aroma,however,none of the studies has focused on the dynamic adsorption and desorption of jasmine floral volatiles and their differential contributions to the aroma quality of the scented green tea.The adsorption and retention of volatile compounds during tea processing are poorly understood.Therefore,in order to improve the effect of scenting system and promote the quality of tea aroma,this study focused on the difference of aroma components between fresh jasmine flowers,scented green tea,and non-scented tea control so that differential contributions of jasmine floral volatiles to the aroma quality of the scented green tea can be elucidated.Volatile profiles of non-scented green tea,scented tea and fresh jasmine flowers were analyzed.Meanwhile,the difference between green tea and jasmine tea before and after heat treatment,which mimic heat treatment during scenting process,had also been examined.The main findings are listed as follows:1.Comparing the volatile compounds of green tea and jasmine tea,the contents of 34 volatile compounds from jasmine tea were found significantly higher than that from green tea.Obviously,mostly part of these compounds were directly from jasmine flowers or sequentially transformation through adsorption,a small number of them came from thermal degradation.2.Out of the 34 enhanced volatiles from the scented tea,?-ionone,?-linalool,indole,and methyl anthranilate were the most potent odorants with 5.1-45.2-fold higher odor activity values than the corresponding compound from the non-scented green tea.3.Through analysis of the physical and chemical properties of these volatile compounds,the selective effect of scenting efficiencies may be influenced by its volatility and water solubility.4.Moreover,due to additional rounds of heat treatment for scented green tea manufacturing,some volatiles such as carotenoid-derived geraniol and ?-ionone and lipid-derived(Z)-jasmone were heat-enhanced and others such as nonanal were heat-desorbed in the scented green tea.5.The thermal degradation of compounds in the heating process will accelerate the evaporation,however,because of their different volatilities,the final retention amount may also be different,as found in this study.Our study revealed that dynamic volatile absorption and desorption collectively determined tea volatile retention and tea aroma.It have great significance to further study the aroma mechanism of tea.