Insights into Polymerization of Vegetable Oil: Oligomerization of Oleic Acid

Viscous gel-like species form in vegetable oils during frying. After fatty acid formation, thermal oxidation of unsaturated chains causes polymerization. Heat treatment of oleic acid was employed to produce and identify the initial polymerization products. Spectroscopic studies revealed that heating oleic acid (210 degrees C, open to air) causes the formation of oligomers cross-linked by ester groups. The absence of esters, before thermal treatment, facilitated observation of cross-links (ester groups) that propagate to produce heavier insoluble products.