Enzymic and autoxidation of lipids in low fat foods: model of linoleic acid in emulsified triolein and vegetable oils

Abstract

To evaluate problems in novel foods with reduced fat content the linoleic acid model systems used in our previous study were applied to high oleic sunflower oil, triolein and stripped corn oil, in the presence or absence of added α-tocopherol. Initial rates of oxygen uptake by enzymic oxidation depended on the emulsion concentrations and not on their fatty acid compositions. Using static headspace gas chromatography a significant difference in the release of hexanal was detected between emulsions rich in either linoleate or oleate. The higher the linoleate content of the emulsion, the higher the conjugated diene absorbance and the amounts of hexanal produced. In the presence of α-tocopherol the diene absorbance was increased and the hexanal yields decreased, indicating that α-tocopherol retarded the decomposition of hydroperoxides. On the other hand, the antioxidant effects of α-tocopherol were gradually lost during autoxidation tests at 60°C. Therefore, large differences were observed in the amounts and compositions of volatile compounds between emulsions rich in either oleate or linoleate. Lipid concentration, type of lipids and presence of antioxidants are important factors in the oxidative formation of volatile compounds in our models. These factors are expected to impact on the flavour of low fat foods.