Optimization of γ-aminobutyric acid in germinated brown rice using a controlled temperature-humidity method and its effects on the volatile profile

• Using constant temperature and humidity to accurately control the germination conditions of brown rice and optimize them. • Constant temperature and humidity can increase the GABA content of germinated brown rice to more than twice that of non-germinated brown rice. • The aroma of germinated brown rice changes compared to non-germinated rice. To increase the γ-aminobutyric acid (GABA) content of germinated brown rice, a method involving constant temperature and humidity was studied, which was different from the traditional soaking method. Firstly, the effects on GABA accumulation in germinated brown rice were studied by means of a single-factor experiment, that considered the following variables: germination time, germination temperature, germination humidity and drying time. Secondly, Box-Behnken design was used to optimize the optimization by response surface methodology. The optimum conditions for GABA accumulation were as follows: germination time of 60 h, germination temperature of 35°C, germination humidity of 70%, drying temperature of 45°C. The GABA content was 49.12 mg/100 g DW, which was 2.23 times higher than that before germination. Additionally, 44 aroma compounds were identified before and after germination. There was an increase in alcohols and acids, and a slight decrease in esters and aldehydes/ketones. The results could provide reference for the application of germinated brown rice with high GABA content.