Two apple skin extracts (ASE) prepared from "Northern Spy" cultivar were examined for their antioxidant properties to inhibit lipid oxidation in aqueous eicosapentaenoic acid (EPA) emulsions and bulk fish oil. The ASE were effective in reducing the oxidation induced by heat, UV light and peroxyl radical, when the extent of oxidation of the emulsions and bulk oil was measured by using the ferric thiocyanate test, the thiobarbituric acid reactive substances assay and Rancimat. On the basis of total phenolic concentration of extracts, removal of sugars and organic acids (ASE 2) from crude ethanol extract of apple skins (ASE 1) enhanced the antioxidant properties in both the emulsion and bulk fish oil systems. The average induction times of accelerated oxidation at 50 to 80 degrees C of fish oil incorporated with ASE 2 (400 microg/mL) was similar to that of alpha-tocopherol (400 microg/mL) and butylated hydroxytoluene (200 microg/mL).