Enzymatic Methylesterification And Purification Of V_E From Soybean Oil Deodorized Distillate

In this paper,intermittent and continuous enzymatic processes of methyl esterification on soybean oil deodorized distillate(SODD)as raw materials,using lipase Novoyme 435 as a catalyst were studied,and the mechanism of the the reaction kinetics was also investigated.After methyl esterification and molecular distillation,we enriched and refined high-purity vitamin E, and studied the process of separating and refining plants sterol from the methyl esterifing production.We also test the antioxidant effect of the vitamin E in the fish oil.Firstly,on the composition of raw materials(SODD) were determined,and the dehydration test was done.The moisture content decreased from 1.3g/kg to 0.3g/kg.The single factors test which impact the conversion of fatty acids to methyl ester was carried out.Through orthogonal process optimization experiments,we found that the main factors affecting the conversion were the enzyme dosage and reaction time,and that temperature and substrate ratio were of secondary interest.Using the extreme analysis and comprehensive analysis,we obtained the best combination of four factors.They are the acid conditions of methanol molar ratio of 1:1.5;the enzyme dosage 60 plu/g;the reaction temperature 55℃;and the reaction time 8 hours.The conversion rate under the conditions was 95.86%.The TLC analysis verified that most of the fatty acids from the SODD converted into fatty acid methyl ester,but that triglyceride did not change.The purity of sterol which was crystallized at 20℃,from the product of methyl esterification and separated by filtration was 54.01%,the preserving rate was 74.32%.The content of V_E in SODD was 10.07%and the preserving rate of vitamin E was 98.35%after removing sterols.After the methanol,sterols and moisture were removed,the total preserving rate of vitamin E was 95.86%.The reaction kinetics of lipase catalysis of SODD and methanol synthesis was studied.First of all,the studies of the influence of different enzyme dosage to the initial velocity showed that the initial velocity of the reaction linearly increased with the enzyme dosage increase,and esterification reaction was controlled by its kinetic.Secondly,with the inference of the reaction mechanism,the analysis showed that the reaction of methyl esterification conformed to accord with ping pong response mechanisms.Their initial velocity of the kinetic equations was derived. It was found that after fitting and of trending the parameters of the equation the calculated values were in agreement with the experimental data,reaction mechanism and model inferred is reasonable assumptions.The continuous process of methyl esterification of SODD was investigated by using fill-bed reactor.The conversion of fatty acids to methyl esters was optimized by using a statistical design.Through the single factor experimental and the orthogonal experiment,each influence factor(under experimental condition which the influence order in this experiment applies) to the response was:the substrate ratio＞the reaction temperature＞the input speed ratio. The optimum methyl esterification response conditions were:substrate ratio:1:2,temperature: 55℃,the input speed 0.075ml/min·cm.The obtained conversion rate was 90.87%.Under the optimum condition,the half-life of the Novoyme 435 is 45 hours.Secondly,by using sodium methoxide in the SODD that had been methyl esterficated and separated sterols,triglyceride and methanol were reacted.The reaction conditions were the 0.5% (W/W oil-based) sodium methoxide,0.7:1(V/W) methanol,temperature 70℃,the reaction time 1h.Glycerol analysis showed trilyceride components had been better conversion.The purity of vitamin E was 10.14%,the preserving rate was 96.27%.The kinematic viscosity of esterification product which had been crystallized under different temperature and separated sterols was analysed,and the sterol purity and the recovery rate were analyzed,then 5℃was determined to be the temperature of crystallization of esterification.Application of the molecular distillation process to enrich vitamin E of SODD was studied. It was tested that was first distillation temperature,second distillation temperature,feed rate, distillation pressure,speed scraping rate and times of distillation which impact the purity and recovery rate of the vitamin E.Through response surface analysis,the effects of second distillation temperature,feed rate,scraping speed on vitamin E content were set up in the regression equation,and the optimum experimental condition was identified:first distillation temperature of 110℃,the second distillation temperature of 151～152℃,press 0.1Pa,feed speed 98～99 ml/h,scraping speed 156.0～157.0r/min.Under the best conditions,the content of vitamin E was up to 50.98%,and the recovery rate reached to 60.21%.The times of distillation was studied,the content of vitamin E was 73.31%,and the recovery rate was 50.25%by three times distillation;the content of vitamin E was 85.35%,and the recovery rate only was 45.62%by four times distillation.Solvent extraction method was used to refine sterols.Through sterol purity and obtaining ratio and economic analysis,hexane was chosen as a washing decolorization agent for the raw sterols;Through the single factor experiments and response surface analysis,a regression equation was set up,and a significant test was done,the optimum conditions were determined: hexane to material 16.7:1,temperature 30℃,and time 10min.The confirmation test results verified that sterol purity was up to 85.10%,the recovery rate was 77.51%under the optimum conditions.The sterol purity was 95.34%,but the obtaining ratio was only 49.47%after 3 times of hexane extractions.Natural vitamin E is a better antioxidant in fish oil.Using glyceride fish oil and ethyl fish oil as raw materials,through heat-resistant test we found that vitamin E can indeed prevent fish oil from automatic oxidation.Compared to adding 0.12%mass fraction of the natural vitamin E, the oil containing 30%EPA and DHA which was added 0.1%mass fraction of the natural vitamin E had better antioxidant effect.The shelf-life can be extended to 144 days.For the fish oil containing 80%EPA and DHA with the addition of 0.12%natural vitamin E,its antioxidant effect was better.