Effects of Different Pretreatments on the GABA Content of Germinated Brown Rice

Brown rice germination increases γ-aminobutyric acid (GABA) levels and enhances its antioxidant activity. In this study, Kaohsiung 145 brown rice was used as the raw material, and soaked in various solutions for 6 h before being processed with either high-pressure processing (HPP) or ultrasonic treatment to increase the GABA content. The GABA and antioxidant components of brown rice were analyzed after 42 h of germination and subsequent air-drying to obtain a moisture content of 14%. The results showed that non-germinated brown rice had GABA at 7.10 mg/100 g and treatment with various soaking solutions (0.1% CaCl2, 0.1% Glu, 0.2% CaCl2, and 0.2% Glu) increased GABA contents. Specifically, 0.1% CaCl2 and 0.1% Glu exhibited higher GABA content, at 42.51 and 44.64 mg/100 g. Furthermore, the GABA content increased synergistically when combined with HPP (100 MPa, 10 min) and ultrasonic (20 min) treatments after soaking. The results showed that the GABA contents in germinated rice were the greatest after ultrasonic treatment, followed by HPP treatment, and the least with only soaking treatment. The treatments with 0.1% CaCl2 and 0.2% Glu combined with ultrasonic processing for 20 min resulted in the highest GABA content at 102.38 and 110.88 mg/100 g, respectively. Finally, 0.1% CaCl2 with ultrasonic treatment for 20 min was chosen, as it demonstrated a considerable improvement in total polyphenols content and DPPH scavenging abilities, as seen by improved scores in subsequent taste evaluations.