Study On New Technologies In Brown Rice Stabilization

Brown rice contains a variety of potentially protective substances, which have been found to help reduce the risk of certain diseases. As a more economical way of grain circulation, storage of brown rice in recent years has attracted more attention. However, the rancidity of brown rice not only limits its comprehensive utilization, but also restricts the grain storage system based on stabilization brown rice. Thus the research of brown rice stabilization is practical necessary. The present study investigated the effect of microwave as well as the ultrasonic-assisted microwave process (UAMP) on the residual lipase activity in brown rice. The treating conditions and the physical, nutritional properties of brown rice treated with microwave, UAMP were also in consideration.In conclusion, microwave could significantly inhibit lipase activity, meanwhile lead to quality deterioration of rice. To get an optimum process for brown rice with lowest lipase activity and retained quality of rice, the technological parameters were optimized through the responsive surfaces analysis of 3 factors based on the residual lipase activity and rice broken rate. The results showed that the optimal condition was power 700W, time 100s and moisture content 21%. The lipase activity and rice broken rate were minimizing with estimated value were 15.66μmol/(g·h) and 18.92%, and verified value were 16.25μmol/(g·h) and 17.33%, respectively.UAMP could also significantly inhibit the activity of lipase. It was found that after soaking in for 480 s with a simultaneous ultrasonic power of 50 W and a microwave power of 300 W, and then following two stages of microwave drying, the final lipase activity decreased to about 1% of the initial activity. However, 5% ethanol or 1.2% citric acid replacing water as soaking media took little effect on enhancing lipase inactivation in UAMP. Furthermore, the ultrasonic and microwave in UAMP were revealed to have synergic action on inactivating lipase. The rice kernels from brown rice treated with UAMP gained the same head rice yield but higher white belly compared with raw rice.The FFA contents of microwave, UAMP treated brown rice and raw brown rice were finally 24.84, 19.99, 46.04mgKOH/100g after 10 weeks storage, which proved microwave, UAMP treatment could improve stabilization of brown rice. The drop in the viscosity, enthalpy of gelatinization and gelatinization temperature range of rice were observed after microwave, UAMP treating, but the digestibility of rice was improved by these treatments. The microwave treated rice had a better sensory property while UAMP had no effect on it. Data showed that microwave,UAMP treatment had the higher value in water holding capacity and oil holding capacity,lower value in foaming capacity and foaming stability of rice bran .In addition, microwave treatment had negative effect on antioxidant activity of rice bran.