Optimization Of Rice Bran Stabilizing And Development Of Shelf-life Predicting Model

Rice bran,which contains about 80%of the nutrition of rice,is a kind of main by-product of brown rice milling and it is a cereal resource with great development potential.However,rice bran is rich in lipid and highly active lipase and lipoxidase resulting in rancidity of rice bran lipid and very short storage period,It is currently very important for rice bran to inhibit lipase activity and improve the stability of rice bran lipid during storage?also called stabilization of rice bran?in order to utilize and develop its valuable nutrition.The current stabilization methods reported include chemical treatments,biologicalpassivation?enzyme?,physicalinhibition?heating/extrusion/microwave,etc.?.In this paper,the enzymatic and microwave methods were studied and optimization of rice bran stabilizing were conducted with low damage to rice bran.Meanwhile,shelf-life prediction models were established under different storage temperature.The results showed as followings:1.Effects of five proteases?bromelain,papain,ficin,alkaline protease and neutral protease?on hydrolyzing lipase to make it inactivate to stabilize the rice bran were studied.Results showed that residual lipase activity values of five samples added proteases were only 2%⁶%lower than that of the original rice bran,and acid values of these five samples also had no significant difference with that of the original rice bran in accelerated storage experiment,neither of five proteases showed obvious stabilization effect on rice bran.2.Moisture regulation was investigated emphatically from the perspective of the process optimization of microwave.The results indicated that increasing the water content of rice bran had a reinforced effect on rice bran's stabilization along with microwave treatment.the order of three factors effects on residual lipase activity was as follows:moisture content>microwave power>microwave treatment time,and the optimum conditions of microwave processing was 23%of rice bran moisture content,795W of microwave power and 115s of microwave processing time.After Long-term storage experiment,the storage period of stabilized rice bran by optimal processing were1.5 times and 3.4 times respectively compared with both that of stabilized rice bran with original moisture content and that of original rice bran,demonstrating that the optimized microwave treatment based on moisture regulation was available for the stabilization of rice bran.3.During rice bran storage,smell and taste are the most significant factors for edible quality of rice bran,Acid value of rice bran during storage was determined regularly until the flavor deteriorated to unacceptable with the value of 23mg/g,which is called storage deadline.4.Both oxidation rates of original rice bran and microwave treated rice bran samples were developed with k _??=1670.20 exp?-3184.9/T? and k_???=577.96exp?-3282.7/T?respectively through accelerated storage experiment and the Arrhenius theory.The above equations showed that k_??was about 1/3 of k_??.Therefore,the stabilization method of modifying moisture combining with microwave treatment could obviously decrease the rate of oxidation of rice bran.5.The shelf-life prediction model of original rice bran and microwave treated rice bran were???and??? respectively during storage.The prediction model could precisely predict the shelf-life of microwave stabilized rice bran at different storage temperature and also provide theoretical basis for further developing rice bran products.