Study on the conditions to brew rice vinegar with high content of γ-amino butyric acid by response surface methodology

In this study, rice vinegar with high content of γ-amino butyric acid (GABA) was prepared by using sprouted rice as raw material, supplemented with red yeast rice, glucoamylase preparation and raw starter complex during saccharification and alcohol fermentation, and the brewing conditions of the rice vinegar with high GABA content were studied. Through Plackett–Burman design, three factors (adding amounts of raw starter complex, red yeast rice and glucoamylase preparation) were identified as significant factors, which were subsequently optimized using Box–Benhnken center-united experiment design. At the optimal conditions, which were 500 g smashed sprouted rice, 4 g red yeast rice, 1.5 g raw starter complex, 1.6 mL glucoamylase preparation, 5 g sodium glutamate, 335 mL water, fermented at pH 6, 28 °C for 5 days, the estimated value of GABA was reached at 147.09 mg/100 mL fermenting mash, and the average experimental GABA value was 145.18 mg/100 mL. After that, the acetic acid fermentation in solid-state through adding wheat bran and chaff into the fermenting mash was carried on for 7 d before maturing for 8 d. In the end, the rice vinegar containing 100 mg/L GABA was prepared.