Oxidative stability of seed oils extracted with supercritical carbon dioxide 1

Dry-milled corn germ, soybean and cottonseed flakes were extracted (at 70-90 C and 12,000 psi) with supercritical carbon dioxide (SC-CO₂) to yield crude oils. Oxidative stability of the crude oils was determined and compared to similar products obtained by conventional expeller and/or prepress solvent extraction. Under Schall oven storage conditions (60 C), SC-CO₂-extracted oils undergo rapid deterioration and fail to show the normal induction period observed with conventional expeller and solvent-extracted crude oils. The levels of tocopherols found in SC-CO₂-extracted oils are comparable to those obtained by expeller or solvent extraction, while phospholipids present in significant amounts in conventional crude oils are essentially absent from SC-CO₂-processed crudes. The addition of phosphatides to SC-CO₂-extracted crude oils improves oxidative stability, which suggests that both tocopherols and phospholipids are required to stabilize crude oils against autoxidation. Heating of SC-CO₂-extracted crude oils to deodorization temperatures improves oxidative stability. The destruction of fat hydroperoxides under these conditions probably accounts for improved oxidative stability. A combination of heat and the addition of citric acid and phenolic antioxidants resulted in further improvement of oxidative stability. Presented at the American Oil Chemists’ Society Annual Meeting in Philadelphia, PA, in May 1985.