Study On The Activity Of Glutamic Acid Dicarboxylase And The Accumulation γ-Aminobutyric Acid In White Tea

Research and development of GABA tea has been becoming hot subjects because of the various health caring function at home and abroad in recent years ,such as regulating the function of neurological , decreasing blood pressure , anti-aging , improving the function of liver , activating the function of renal and so on . The health caring function of white tea that made only in Fujian is better than other tea . So it is the urgent demand of development of white tea that the exploration of GABA white tea .Glutamic acid dicarboxylase is the enzyme that transforms Glutamic acid intoγ-aminobutyric acid , so it is very important in theoretical and practical for accumulating GABA in white tea ,it also very important for the quality of GABA tea by regulating GAD activity in white tea .The GAD activity of tea fresh leaves in different tenderness was determined, and the GAD activity of different varieties, including Fuyun6,Fuandabai Tea,Fudingdahao Tea and Fuyun595 were compared. And the dynamic change of the GAD activity in the process of natural withering and warm withering was determined too. The process and techniques of preparing the GABA white tea was researched in this paper. The results are as follows:There is very significant difference in different varieties on the GAD activity , but not significant difference in different tenderness . The interaction effect of varieties and tenderness on the GAD activity is very significant difference . By comprehensive consideration of variety , tenderness , source of raw materials and so on , two leaves and a bud of Fuyun 6 and Fuyun 595 are the best materials for processing the GABA white tea.The change tendency of GAD activity in the natural withering is basically identical in Fuyun 6 and Fuyun 595 , the GAD activity gradually increases on the early stagy of withering , and decreases on the middle stage . But there is little difference on the last stage , Fuyun 6 first increases and then decreases on the stage , Fuandabai Tea decreases continually on the stage . The GAD activity of two varieties in the process of warm withering both experienced"increase to decrease to increase", the last increase is very little .Only four samples conform to standard of GABA tea in the twelve experimental samples in the initial process, they are sample 2(25℃,vacuum two times) ,sample 3 (25℃,vacuum three times),sample 9(40℃,vacuum three times),sample 12(4℃→40℃, vacuum three times). The result of sensory evaluation for the three samples is not good because of peculiar smell , so the process of preparing GABA white tea must be improved , firstly , advancing the time when the withering leaves are vacuumed ; secondly , reducing the hours of vacuum each time.Four samples conform to standard of GABA tea in the six experimental samples in the improved process , they are sample 2(25℃, vacuum three times),sample 3(25℃,vacuum four times),sample 5(4℃→25℃,vacuum three times),and sample 6(4℃→25℃,vacuum four times) . The content of GABA in sample 3 is 200.41 mg/100g , and 201.45 mg/100g in sample 6 . Compared with the made tea from the initial process , the quality of the made tea from the improved process is better . The tea not only have health caring function of GABA tea , and also its quality conform to the requirements of middle class Baimudan tea . Because the content of GABA in sample 3 and in sample 6 is similar ,but sample3'quality is better than sample6', so the process of preparing sample 3 tea is the best process of GABA white tea according to this paper.