Oxidation Rates of Triacylglycerol and Ethyl Ester Fish Oils

Abstract Fish oil is available primarily as triacylglycerols (TAG) or ethyl esters (EE). Anecdotal evidence suggests that TAG have superior bioavailability and oxidative stability compared to EE. In this work, peroxide value (PV) and p ‐anisidine value (AV) were used to monitor oxidation in commercially available TAG and EE fish oils incubated at temperatures from 5 to 60 °C. Pseudo first‐order kinetics were assumed and rate constants were calculated for each temperature. At all temperatures, the rates of oxidation were higher for EE oils than TAG oils. For PV and AV measured in both oils, non‐linear Arrhenius models were plotted, generating activation energies that ranged from 7 to 103 and 2 to 159 kJ/mol for PV and AV, respectively. Although TAG were more resistant to oxidation than EE, they had lower activation energies ( E a ) at ≤15 °C for reactions measured with PV and AV. The E a for EE was negative at temperatures ≥45 °C, indicating that reaction rate was influenced by factors in addition to temperature.