ENZYMATIC AND AUTOXIDATION OF LIPIDS IN LOW-FAT FOODS - MODEL OF LINOLEIC-ACID IN EMULSIFIED TRIOLEIN AND VEGETABLE-OILS

To evaluate problems in novel foods with reduced fat content the linol eic 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 alpha-tocopherol. Initial rates of oxygen uptake b y enzymic oxidation depended on the emulsion concentrations and not on their fatty acid compositions. Using static headspace gas chromatogra phy a significant difference in the release of hexanal was detected be tween emulsions rich in either linoleate or oleate. The higher the lin oleate content of the emulsion, the higher the conjugated diene absorb ance and the amounts of hexanal produced. In the presence of alpha-toc opherol the diene absorbance was increased and the hexanal yields decr eased, indicating that alpha-tocopherol retarded the decomposition of hydroperoxides. On the other hand, the antioxidant effects of alpha-to copherol were gradually lost during autoxidation tests at 60 degrees C . Therefore, large differences were observed in the amounts and compos itions of volatile compounds between emulsions rich in either oleate o r linoleate. Lipid concentration, type of lipids and presence of antio xidants are important factors in the oxidative formation of volatile c ompounds in our models. These factors are expected to impact on the fl avour of low fat foods.