Effect of selected oat sterols on the deterioration of heated soybean oil

Two sterol fractions of different purity, each containing both Δ⁵-avenasterol and β-sitosterol, were separated from oat oil, and their antioxidant effects studied in soybean oil at 180 C. Oil samples with added pure β-sitosterol and control samples (no added sterol) also were studied. Fatty acid changes, conjugated diene formation and polymerization were monitored in all samples. All heated oils with added oat-sterol fractions containing Δ⁵-avenasterol deteriorated more slowly than did the controls. Oil with added pure β-sitosterol was altered at a rate similar to that of the controls.