Beans germination as a potential tool for GABA-enriched tofu production

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that can be found in many plants, especially beans. Beans are normally used for producing vegetarian foods, such as bean milks, bean sprouts, and tofu. Thus, the aims of this study were to determine the GABA content in various germinated beans (yellow beans, black beans, green beans, and red beans) as well in tofu products made from different types of germinated beans. The results showed that soaking and germination significantly contributed to an increase in GABA production. The GABA content increased to a maximum value of 0.89, 3.09, 3.93 and 4.78 mg/g in yellow beans, red beans, green beans, and black beans, respectively. Moreover, due to the bean characteristics, green beans, red beans, and black beans were collected at 6 h after germination while yellow beans were collected at 0 h after germination. As a result, only yellow bean sprouts could be used for tofu production since they are composed of a high amount of proteins and a low amount of carbohydrates. The GABA content in tofu was 0.55 mg/g, which was lower than that in soybean milk (0.65 mg/g), likely due to the filtration and pressing processes of tofu production.