Studies On Pretreatment Of Rice Bran By Explosion Puffing And Product Of Γ-Aminobutyric

Rice is one of the most common varieties of grain, and about200million tons of rice is produced annually in China. Rice bran is by-product of rice processing. It contains lipopolysaccharide, oryzanol, squalene, ceramide, tocopherols and many other natural antioxidants and bioactive substances, all of which have great significance on human health and disease prevention. Rice bran can be used as an inexpensive microbial fermentation material for the production of many biologically active substances which have a high added value, such as GABA and glutathione.In this research, rice bran was treated by explosion puffing followed by fermentation to produce the γ-aminobutyric acid (GABA) by Aspergillus oryzae. The main nutritional components of rice bran before and after explosion puffing were determined.Then, the effects of puffing parameters such as moisture content, puffing temperature, and heating time on the GABA content in the rice bran were investigated. A Box-Benhnken design was employed to the determine yield of GABA with different puffing parameters. At the optimal conditions, the moisture content, puffing temperature, and heating time were47%,74℃, and83min, respectively, and the estimated value of GABA content reached was149.1mg/100g.In order to improve further the GABA content in fermented rice bran, the effects of liquid fermentation conditions such as solid-liquid ratio, fermentation time, fermentation temperature, inoculum concentration and oxygen content on the GABA content in the rice bran were investigated. The optimal conditions is as follows:solid-liquid ratio was1:10, fermentation time was3d, fermentation temperature was28℃, inoculum concentration was5%and oxygen content was130r/min, and the GABA content in fermented rice bran was2.4times higher than initial value.At the same time, separation and purification of GABA in fermented rice bran were investigated preliminary. The ultrasonic extraction was used to separation GABA from rice bran and GABA purification was conducted by successive centrifugation, filtration, decoloration, desalination and ion-exchange chromatography (IEC). The recovery rate for the whole purification process was about45%. The purified product was characterized by HPLC, and its purity reached about73%.In addition, the antioxidant activity of the treated rice bran was studied.The result improved that the fermented rice bran has high ability of scavenge free radical and can be used as the materials of health foods in the further.