Effect of purification methods on functional properties of sardine oil ethyl esters

Abstract

In this study, four methods including urea complexation (UC), molecular distillation (MD), low-temperature crystallization (LTC), and Ag+ bonded to mercaptopropyl silica gel column chromatography (AgMSG-CC) were adopted to purify eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from sardine oil ethyl esters (SOEEs). These methods were systematically compared in terms of physicochemical properties, fatty acid (FA) compositions, and volatile flavor compounds to evaluate the performance and find the superior among them. The AgMSG-CC method was superior in enhancing iodine value (IV) and reducing peroxide value (PV), enriching EPA and DHA from 31.63% to 92.19% and removing undesirable volatiles. Its mild experimental conditions could avoid the degradation and geometrical isomerization of lipids, and the packed AgMSG column could be reused. Multivariate data analysis was applied to provide an integrated and holistic view of correlation coefficients between the samples and FA species. The results supported the critical role of AgMSG-CC method in purifying EPA and DHA. Finally, this method was validated to be accurate and sensitive in the purification of EPA and DHA from SOEEs. Practical applications High quality of fish oil is related to its high content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and friendly aroma. However, enrichment methods about purifying fish oil affect the percentages of EPA and DHA, physicochemical indexes and the volatile flavor. In this study, the results demonstrated that Ag+ bonded to mercaptopropyl silica gel column chromatography was the most effective to purify EPA and DHA as well as remove the undesirable odor volatiles.