Separation And Enrichment Technologies For EPA And DHA From Anchovy Oil’s Soapstock

Anchovy (Engraulis japonicus) is one of the most abundant resources of small fish in the ocean. Due to the anchovy is rich in endogenous enzymes, it’s easily autolyzed rot and mainly used to extract fish oil and other deep-processing. The total content of EPA and DHA account for more than20%in the extracted anchovy crude oil which is an ideal raw material for preparing refined fish oil. Fish oil soapstock is produced in alkaline deacidification process which is one step of fish oil refining process, and accounts for5～6%of the refined oil production. There are40%～60%of total fatty acid in fish oil soapstock, which have a great of recycling value, especially the high content of EPA and DHA in total fatty acids.This thesis took anchovy oil’s soapstock as the experimental materials.Firstly, determine the content of its main component. Secondly, convert the soap into fatty acids through the acidification process.Thirdly, through esterification and transesterification reaction with ethanol generates fatty acid ethyl ester. Fourthly, enrichment EPA and DHA from bleached fish oil ethyl ester by molecular distillation. Finally, analyze the fatty acid composition and volatile flavor components of the refined fish oil riched EPA and DHA, and identify its quality. The main results obtained in this thesis were as follows:The experimental tests showed that the content of water, soap, neutral oil in the experimental materials were69.73%,5.12%,23.89%. And the experimental materials was the oil-rich soapstock, which contained78.92%of the neutral oil in dried condition and had a great of recycling value. In the acidification process of anchovy oil soapstock, the conversion rate was the examining indexes. The effects of liquid to solid ratio, H2SO4content, reaction temperature and reaction time on the conversion rate of soap were systemically investigated. Through response surface methodology the optimum reaction parameters of the acidification process were obtained:the H2SO4content of4.18mL, the reaction temperature of71℃, the reaction time of60min. The conversion rate of soap was99.92%and the extraction yield of oil was25.27%in three verified experiments.In the esterification process of crude oil with high acid value, the esterification rate was the examining indexes. The effects of concentrated sulfuric acid content, anhydrous ethanol content, reaction time and reaction temperature on the esterification rate were systemically investigated. Through response surface methodology the optimum reaction parameters of the esterification process were obtained:the concentrated sulfuric acid content of9mL, the anhydrous ethanol content of90mL, the reaction temperature of78℃, the reaction time of3.0h. The esterification rate was97.56%and the recovery rate was83.80%in three verified experiments. And the results indicated the order of effect factor is:reaction time> reaction temperature> anhydrous ethanol content> concentrated sulfuric acid content. Variance analysis showed that the four factors all have very significant impact on the esterification rate.The enrichment of EPA and DHA from fish oil ethyl ester was carried out by molecular distillation. The effects of distillation pressure and distillation temperature on the enrichment of EPA and DHA were systemically investigated. The results showed that the distillation pressure and distillation temperature all have very significant impact on the heavy component yield and the purity of EPA and DHA, lower distillation temperatures can help to improve the heavy component yield. The multistage molecular distillation can ensure high purity of EPA, DHA and improve the heavy component yield. The total purity of EPA and DHA was60.50%and the heavy component yield was62.79%in five stages molecular distillation process designed in the experiment.Finally, the fatty acid composition and volatile flavor components of the refined fish oil were analyzed, and its quality was identified. The results showed that there are18Kinds of fatty acids in refined fish oil with8kinds of SFA,4kinds of MUFA and6kinds of PUFA, and the content of SFA, MUFA, PUFA occupied21.26%,14.77%,62.29%respectively of the total fatty acids. The refined fish oil had7kinds of main fragrance compounds, including3,6-Nonadienal,2,4-Decadienal, Octanoic acid ethyl ester, Hexanoic acid ethyl ester,2-Propenal,2-Decenal,4-Heptenal. Combined effect of a variety of flavoring substances made the refined fish oil smell fishy. The physical and chemical indexes of refined fish oil can achieved to the first refined fish oil demand for SC/T3502-2000standard.