Inhibition of the Oxidation of Corn Oil Stripped of Tocopherols and Refined Olive Oil by Thiols

The ability of N-acetyl-cysteine and glutathione to inhibit the oxidation of corn oil stripped of tocopherols and refined olive oil was examined. The oxidative stability of corn oil stripped of tocopherols at 50 o C, 120 o C and 180 o C was evaluated. The absorbances at 234 nm and 270 nm, and p-anisidine value were monitored. N-acetyl-cysteine and glutathione inhibited the oxidation of oil, N-acetyl-cysteine at a higher degree. In comparison to BHA at 200 mg/L, both thiols at 20-40 mg/L exhibited lower (50 o C and 120 o C) or similar (180 o C) antioxidant activities. Compounds similar to the two thiols but not containing –SH group, N-acetyl-serine and oxidized glutathione, exhibited very low or no antioxidant activities. The oxidative stability of refined olive oil at 20 o C was determined by monitoring the peroxide value. N-acetyl-cysteine and glutathione at 20 mg/L exhibited antioxidant activities comparable to that of BHA at 200 mg/L. Present results show the ability of N-acetyl-cysteine and glutathione to inhibit the oxidation of corn oil stripped of tocopherols and refined olive oil indicating that thiols can inhibit the oxidation of any oil.