Activation and Tempering on Γ-Aminobutyric Acid Accumulation and Distribution in Brown Rice

Abstract

Brown rice absorbing water slowly under atomization environment, its endogenous enzymes could be activated and the activated brown rice was formed. At the same time, functional components such as γ-aminobutyric acid (GABA) could be accumulated in the activated brown rice. In this study, brown rice was activated through raising temperature in gradient and then tempering for several hours. Results showed that raising temperature as 30-50-70C got higher GABA content. After activation under 30-50-70C, tempering at 40C for 10 h and dried to moisture content of 15%, GABA content in activated brown rice and its 15 s milled rice were 24.77 and 21.24 mg/100g DW, respectively, which were 3.99- and 8.63-fold of those in raw brown rice and 15 s milled rice, respectively. During 10 h of tempering, GABA transferred from aleurone layer to endosperm, and the activated brown rice got the relative lower broken ratio after milling. Practical Applications Based on slowly absorbing water, endogenous enzymes in brown rice are activated within the short time. So that GABA accumulated and crack ratio decreased. Tempering resulted in the transfer of GABA from aleurone layer to endosperm. As a result, white rice with higher GABA content could be obtained after milling.