Natural antioxidants in the stability of ray liver oil

The effect of the addition of natural antioxidants on oxidative stability of ray (Rhinoptera bonasus) liver oil was evaluated. Different concentrations of rosemary extract, γ-tocopherol, and caffeic acid (w/w) were added to the oil. Afterwards, concentration of each antioxidant that gave the highest stability was used in an accelerated stability test (Schaal method). The protective effect was established by the retention in the oil of fatty acids eicosapentaenoic (EPA) and docosahexaenoic (DHA), and concentration of volatile compounds. The best concentrations were: 2.5% of rosemary extract, 0.5% of γ-tocopherol, and 0.06% of caffeic acid. Rosemary extract showed to be the product with the greatest ability to retard oxidation, followed by γ-tocopherol, and caffeic acid. A high correlation between the peroxide value and the concentration of the 2-decenal, 1-penten-3-ol, and 2-octenal, was reported, suggesting that this can be used to assess the development of oxidative rancidity in the ray liver oil.