Study On The Variation Mechanism Of Volatile Components In Fresh Tea Leaves Caused By Ultra High Pressure

The volatile aroma components is one of the important factors determining the quality of tea, a lotof studies have reported that glycosidically bound aroma precursors are the basis of the volatilecomponents of tea, the contents of glycosidically bound aroma precursors are much higher than the freearoma components. Glycosidase is the hydrolysis catalyzer in the releasing of volatile aromacomponents, based on that, we could forsee that it is highly possible to improve the aroma of made teaas long as we take the appropriate processing methods. In order to find out the variation mechanism ofvolatile components in fresh tea leaves caused by ultra high pressure processing(UHPP), the effects ofultra high pressure processing on physical properties, glycosidase activity, volatile components andglycosidically bound aroma precursors of fresh tea leaves were studied, therefore, this study couldprovide a theoretical basis and technical support for using UHPP to improve the sensory quality of madetea. The main conclusions were as follows:At the cell level, fresh tea leaves cells were susceptible to UHPP,300MPa can change the cellshapes obviously, and result in the collapse of cell membrane and cellular organelle membrane by theobservation of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Theconductivity of the fresh tea leaves increased significantly, their hardness decreased significantly underUHPP treatment; when the pressure was more than300MPa, there was no significant changes.β-glucosidase and β-galactosidase activity in the fresh tea leaves did not change treated by lowerpressure (100MPa), on the other hand, its activity decreased with higer pressure (200-500MPa).Significant changes of volatile aroma components in fresh tea leaves appeared after UHPPtreatment. Treatment with300MPa showed greater changes of volatile components than100MPa,including the relative total content of alcoholic aromas increased much more, hydrocarbon aromasdecreased greater while withering, and the mass fraction of main aromatic compounds, such as geraniol,benzyl alcohol, phenylethyl alcohol, methyl salicylate, benzene acetaldehyde but β-linalool increasedmuch more within settled time.The total content of glycosidically aroma precursors in fresh tea leaves decreased during witheringafter UHPP treatment, in comparison with100MPa treatment, the total content of glycosidically aromaprecursors decreased much more in the300MPa treatment.