Repeating treatment of anaerobic and aerobic incubation increases the amount of gamma-aminobutyric acid in tea shoots

gamma-Aminobutyric acid (GABA), a hypotensive compound, is formed from glut amic acid by glutamate decarboxylase under anaerobic conditions in tea shoo ts. In the first three hours of anaerobic incubation, glutamate was remarka bly decreased and GABA was considerably increased. But under continuous ana erobic incubation, those of amino acids remained almost constant. After thr ee hours of anaerobic incubation, when tea leaves were placed under aerobic condition, glutamate increased rapidly up to its original amount. But GABA didn't decrease. After one hour of aerobic incubation, tea leaves were giv en three hours of anaerobic incubation again, and then accumulated glutamat e changed to GABA. As a result of this treatment, the amount of formed GABA increased over 1.5 times more than that under usual continuous anaerobic i ncubation. By four times repetition, GABA in tea leaves was formed 2.3 time s as much as that under usual anaerobic incubation in the third crop of tea . By this new method, the level of GABA in tea leaves of the third crop rea ched to the same level as tea leaves of the first crop treated by the previ ous method.