A comparative study on the susceptibilities of soybean,sunflower and peanut oils to singlet molecular oxygen photooxidation

The susceptibilities of crude soybean, sunflower and peanut oils to singlet oxygen photooxidation were determined in a kinetic study. The accumulation of photosensitized hydroperoxides, determined spectroscopically, and the quenching of singlet molecular oxygen phosphorescence by the crude oils and their fatty acid methyl esters were compared. The relative tendency to photooxidation for the oils and the methyl esters was soybean ≫ sunflower > peanut. This trend was independent of the method employed in the determination of initial photodamaging. Soybean oil was demonstrated to be the most unstable product, not only due to the presence of highly unsaturated fatty acids, but also due to the absence of natural constituents, capable of providing a protective antioxidant effect. This protection was more effective in sunflower and peanut oils.