Increase of phytase activity in brown rice treated by heat shock and germinated in citric acid medium

Brown rice were treated by short-time heat-shock and germinated in acidic medium to investigate changes of endogenous phytase activities, and the experiments were performed to optimize conditions of heat shock by using response surface design. The results showed that activity of phytase increased with increasing heat-shock duration, then declined after reaching peak value. The conditions of heat shock treatment and soaking time, which were optimized and validated by using central composite response surface design, were heat-shock temperature of 50℃, heat shock time of 30min, and soaking time of 6h. As the germination time extension, phytase activities of brown rice germinated in citrate buffer (2mmol/L, pH5.2) increased, and reached maximum value after 3 days (241.27U/kg) , which were higher than of raw brown rice (115.57U/kg) . In summary, this study achieved a novel technology to activate endogenous phytase activity of germinated brown rice to reduce phytic acid, which provided basic technical data for maintaining their nutritional value.