Effect of pH, Time and Temperature Affecting Gamma-Aminobutyric Acid (GABA) Content of Various Rice Varieties in Plantation Areas, Nakhon Sawan Province

Abstract

The objective of this research was to study the effect of pH, temperature, soaking time, and germination on the gamma-aminobutyric acid (GABA) content of 26 varieties of rice grown in Nakhon Sawan Province. The rice seeds of the Pathum Thani1 variety were soaked in various buffer solutions (pH4, pH5, pH6, pH7) and water at different temperatures (35, 40, and 45 °C) and for varying soaking times (3, 8, and 12 hours) and different germination times (24, 36, and 48 hours). Afterward, the rice was dried at a temperature of 50 °C until dry to stop the germination of rice. The results indicated that soaking the rice in a pH 5 buffer solution at 40°C for 8 hours led to the highest GABA content in rice grains and was significantly different (p <0.05). Additionally, the germinated rice condition with the highest GABA content was in the pH5 buffer solution at a temperature of 40°C for 36 hours and was also significantly different (p<0.05). Following this, all 26 rice varieties were tested using the Pathum Thani1 rice variety as a reference. Under these conditions, it was found that KDML105 had the highest GABA content during both the rice soaking period (12.79±0.12 ppm) and rice germination (20.47±0.35 ppm). In contrast, Jao Khao Jek rice had the lowest GABA content during rice soaking (10.17±0.15 ppm), and rice variety RD47 had the lowest GABA content during rice germination (11.58±0.15 ppm). In conclusion, the optimal conditions for rice to have the highest GABA content during germination were found to be in a pH 5 buffer solution at a temperature of 40°C for 36 hours and the difference was statistically significant at the 0.05 level.