Esterification Deacidification Of High-Acid-Value Rice Bran Oil And Enzymatic Preparation Of Rice Bran Oil Rich In DAG

China is the world's largest rice producer and consumer countries,thus we have abundant resources of rice bran.Rice bran oil is a high-quality vegetable oil which was obtained by leaching or other methods and rice bran as raw material.Rice bran oil is rich in unsaturated fatty acids and its composition is reasonable.Due to the existence of lipase,it is easily to cause the high acid value during the processing of rice bran oil,which limits the production of rice bran oil.Diacylglycerol,which is generally recognized as safe(GRAS)dietary ingredient by FDA,is a natural minor component of rice bran oil.DAG exhibits multiples functions,such as lower blood lipids,prevent fatty liver,obesity,cardiovascular disease,etc.Therefore,the refining of rice bran oil using appropriate methods will greatly improve the comprehensive utilization of rice bran.In this paper,rice bran oil with high acid value was used as raw material.Chemical method and enzymatic method are used respectively on esterification deacidification in the solvent-free system.Furthermore,our aims also focused on enzymatic deacidification to prepare rice bran oil rich in DAG.The main conclusions of this experiment are as follows:(1)Chemical deacidification of high-acid-value rice bran oil by esterification:Effect of different chemical catalyst(such as ZnO,SnCl2·2H2O)to reduce the acid value of high-acid-value rice bran oil were compared.Results showed that ZnO as catalyst's deacidification rate is 83.39%,which is significantly higher than that of SnCl2·2H2O.Based on single factor tests,such as the catalysts addiction,reaction temperature,reaction time and the glycerol addiction,the optimum condition by response surface method is as follow:reaction time 4 h,reaction temperature 215?,catalyst addiction 0.3%,glycerol addition amount to 115%of theoretical glycerol.Under these parameters,the acid value of rice bran oil is 3.16 mg KOH/g,and the deacidification rate is 92.06%and oryzanol retention rate is 40.23%.(2)Enzymatic deacidification of high-acid-value rice bran oil by esterification:Effect of two catalysts(immobilized Lipozyme RMIM and Lipozyme 435)on the deacidification of high-acid-value rice bran oil in solvent-free system were compared.The results showed that Lipozyme 435 as catalyst's deacidification rate is 76.56%,which is better than that of Lipozyme RMIM.On the basis of single factor experiments,such as reaction temperature,reaction time,glycerol amount and enzyme amount on the esterification process,we use orthogonal experiment to optimize the high-acid-value rice bran oil process conditions.The optimum conditions are as follows:reaction temperature 70 ?,reaction time 10 h,catalyst dosage 3%,glycerol 250%.Under these conditions,that the acid value is reduced from 39.81 mg KOH/g to 1.86 mg KOH/g and the deacidification rate is 95.32%,remaining rate of oryzanol is 92.44%,remaining rate of VE is 77.94%.Moreover,we have the repeated utilization experiment.The results indicate that the enzyme is reused 10 times later,the deacidification rate is still above 85%.(3)Enzymatic production of rice bran oil rich in DAG:Rice bran oil and monoglycerid were used as raw material.On the basis of single factor,various factors are selected by Plackett-Burman test,such as types of enzymes,enzyme amount,the amount of substance ratio of rice bran oil to monoglycerid,reaction time and reaction temperature.The results showed that the reaction time,reaction temperature and enzyme dosage were clear the main influencing factors of enzymatic production of rice bran oil rich in DAG.The Box-Behnken response surface method was used to optimize the enzymatic production of rice bran oil rich in DAG process conditions,obtained the optimum conditions are as follows:reaction time 9.7h,reaction temperature 67 ? and enzyme dosage 3%.Under these parameters,DAG content can reach 46.68%in rice bran oil.At the same time,DAG-rich rice bran oil's composition of fatty acids and acid value were tested.Using Rancimat 892 oil oxidation stability tester tests show that DAG-rich rice bran oil's induction time was 8.56 h,and it was longer than the induction time of non-esterified rice bran oil by 8.86%.The results suggested that DAG-rich rice bran oil's oxidative stability was better than non-esterified rice bran oil.