Antioxidant activity of Para-hydroxybenzoic acid and its methyl ester in triacylglycerols of Kilka fish oil and its oil-in-water emulsion

Medical benefits of Omega 3 fatty acids have appealeda lot of research to be done on of fish oil. Among marine fish, kilka has the most industrial application. Kilka oil contains significant amount of omega-3 fatty acids. In this study, physiochemical properties, fatty acid composition and stabilization of kilka oil were investigated. p- hydroxy benzoic asid, its methyl ester and alpha-tocopherol as control were compared to each other.
Crude Kilka fish oil was supplied by Khazarcompany (Babolsar, Iran). All chemicals and solvents used in this study were of analytical reagent grade and purchased from Merck (Darmstadt, Germany) and Sigma–Aldrich (St. Louis, MO). 200 ppm of the mentioned antioxidants was added to the purified oil and kinetic regime of oxidation at temperatures of 35, 45 and 55°C was prepared. After monitoring theoxidation over time using peroxide test, graph of peroxide changes over time was plotted and induction period and kinetic parameters (F, ORR and A) were calculated. In order to compare the performance of antioxidants in oil and water, 10% emulsion of Kilka oil-in-water was prepared and 200 ppm of antioxidant was added to it and its oxidation process was monitored at 55°C.
Results showed that the fatty acid composition of this oil contains a variety of unsaturated fatty acids, saturated and polyunsaturated (mainly linoleic, eicosapentaenoic and docosahexaenoic acids). Temperature had significant effect on oxidation. p-hydroxymethylbenzoate, a little more than p-hydroxybenzoic asid, could increase oxidative stability of oil. Alpha-tocopherol had better performance as compared with other antioxidants. Performance of methylp-hydroxybenzoatewas better in emulsion than oil. In general, the emulsifier and emulsion preparation as compared with antioxidant had a more prominent role in the oxidative stability of Kilka oil.