Microwave Irradiation
Shiraki107 investigated the accumulation of GABA in fresh tea leaves by means of microwave and infrared irradiation It was found that the amount of GABA in the semifermented tea with fresh tea leaves irradiated both by microwave and infrared was higher than that in the ordinary green tea. Microwave irradiation caused the amount (167-202 mg/100 g) of GABA and alanine to increase, while the amount of aspartic and glutamic acids decreased in the resultant tea There was a tendency for the amount of GABA and alanine to increase by microwave irradiation In addition, the amount of theaflavins also increased at the levels of 3 .57-11 . 8 mg/100 g, but the theanine did not differ from the amount in green tea The study pointed out that the optimum generating power of microwave irradiation was 0 3 kw, and the optimum time for microwave irradiation was 20 min . The results indicate that it is possible to increase the amount of GABA in tea by microwave irradiation without using anaerobic treatment Shiraki pointed out that the increase of amount of GABA was due to the rise of glutamate decarboxylase activity.
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