Methods for increasing γ-aminobutyric acid (GABA) in potato tubers

Abstract

Previously, we reported that potato tubers and common potato snack products contain GABA, and oral administration of certain types of potato snack products currently on the market reduced blood pressure in spontaneously hypertensive rats. In this study, we examined methods to increase the GABA content of "TOYOSHIRO" potato tubers, as measured by HPLC. Treatments used to increase GABA levels were sprouting, anoxic conditions (nitrogen displacement, soaking in various solutions), freezing and GABA substrate coenzyme addition. Sprouting treatment increased GABA levels by approximately 1.3 times. In the anoxic conditions, GABA increased over three times after three days exposure to a nitrogen atmosphere, during which time glutamic acid in the tubers was converted into GABA, but only about two times after soaking in various solutions (water, salt solution, citrate solution, ethanol) for two days. GABA levels increased 3 times after freezing treatment, 2 times by trituration treatment at 35°C, and over 3 times by co-treatment with glutamic acid, a substrate of GABA, and coenzyme pyridoxal 5′-phosphoric acid. These results indicate that GABA content of potato tubers was increased 2-3 times by several anoxic conditions, freezing, and trituration treatment.