| The high content of omega-3 fatty acid glyceride type fish oil has becoming a trend in the development of fish oil processing and production due to its high digestibility,bioavailability and safety.In this study,30.02%triglyceride-type fish oil and 74.38%ethyl ester-type fish oil were used as the transesterification reaction substrate with different omega-3 fatty acid content.Different kinds of lipase were added to the substrate,and the content of Omega-3 fatty acids in triglyceride was determined by gas chromatography,to investigate the effect of different lipases.The effects of ionic liquids on the content of ?-3 fatty acids in the triglycerides of the enzymatic transesterification products were investigated.The reaction conditions were optimized by the five-factor and three-level response surface test.The composition of fatty acids and the kinetics of thermal oxidation were analyzed under the optimal reaction conditions.The results showed that the best lipase was Lipozyme TL IM,and the total amount of EPA and DHA in the product triglyceride was 51.86%,followed by porcine pancreatase,Novozyme435 and self-enzyme B(Self-developed marine salt-resistant lipase from Aspergillus niger).Lipozyme TL IM,porcine pancreatase and self-enzyme B were compounded in view of the synergistic effect between lipases and the economics of industrial production.The results showed that the total content of EPA and DHA in the product triglyceride was 58.63%when the proportion of the three enzymes was 29.94%,35.98%and 34.08%,respectively.The results showed that[BMIM][BF4],[BMIM][PF6]and[BMIM][Tf2N]could improve the transesterification activity of the three lipases.The three kinds of ionic liquids were added to the fish oil for different enzymatic transesterification reaction.It was found that the addition of ionic liquid resulted in a significant increase in the total content of EPA and DHA in the product triglyceride fish oil.Among them,when the amount of[BMIM][Tf2N]was 4%,the total content of EPA and DHA in triglyceride catalyzed by Lipozyme TL IM was 63.65%,which was 11.79%higher than that without adding ionic liquid.The[BMIM][PF6]and[BMIM][Tf2N]have similar effect,but[BMIM][Tf2N]is more expensive,so[BMIM][PF6]is selected as the reaction medium for fish oil transesterification.Based on the single factor test,the optimum reaction conditions were as follows:the amount of added enzyme was 2.14%and substrate mass ratio was 19:40,reaction time was 18h,reaction temperature was 57.7 ?,ionic liquid addition amount was 5.64%.The optimized conditions were tested and the total content of EPA and DHA in the triglyceride was 65.40%.The thermal oxidation kinetics of the optimal product triglyceride fish oil was studied by differential scanning calorimetry(DSC).The results showed that the thermal oxidation process was closely related to its fatty acid composition.The kinetics of the thermal oxidation process analyzed by Flynn-Wall-Ozawa method and Kissiger method Parameters was consistent. |
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