An Optimization Method Of Increasingγ-Aminobutvric Acid In Tea Leaves And Its Application To Instant Tea Processing

y-Aminobutyric acid (GABA) is a kind of natural functional amino acids found in Animalia, Plantae and Microorganisms and it has strong physiological activities on mammal. In tea leaves, there is a trace amount of GABA, but it could be accumulated using biotechnues.In this study, tea shoots with a bud and two or three leaves were used as experimental materials, which were treated with exogenous amino acids and vacuum technique, and then processed into green tea or instant tea. HPLC method coupled with FDBN pre-column treatment was used to determine the contents of GABA and Glu in the samples. Effects of different processing methods and conditions on GABA content were studied and the optimum processing conditions for processing GABA green leaf tea and GABA instant tea were screened and the major results are as follows:1. There was no significant difference in GABA concentration of finished tea between leaf treatments with glutamic acid (Glu) and monosodium glutamate (MSG). MSG was recommended to be used in GABA tea enrichment since its solubility in water was higher than Glu.2. Treatment methods of MSG solution on fresh tea leaf affected the GABA concentration in made tea. At MSG concentration levels ranging0%to4%(W/V), spraying method was better than soaking method. After spraying MSG and then keeping under vacuum condition for12h, the GABA content in the dried tea leaves was more than1.5mg/g。3. When the tea leaves was soaked in MSG solution and then kept under vacuum condition, the leaf GABA was partially leaked into the solution, resulting in loss of GABA in made tea.4. Based on the studies on the effects of MAG concentration and vacuum time on the GABA content in made tea, the optimal conditions for processing GABA green tea were screened as:spraying with10%(W/V) MSG aqueous solution and keeping under vacuum for12h. GABA content in the made green tea was1.481±0.025mg/g.5. Based on the studies on the effects of spraying method and vacuum time on the GABA content in made tea, In the range of2%-10%and4-12h, the optimal conditions for processing GABA instant tea were screened as:fresh tea leaf being sprayed with10%(W/W) MSG solution and kept under vacuum for12h, in which the instant tea had a GABA concentration about3.8mg/g. If soaking method was used, the optimal conditions for processing GABA instant tea were screened as:fresh tea leaf being soaked in6%(W/V) MSG solution under vacuum condition for12h, in which the instant tea had a GABA concentration about3.4mg/g.