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S. H. YOON, Food Chemistry and Biotechnology Division, Korea Food Research Institute, PO Box 2, Bundang, Seongnamsi, Kyeonggido, 463-420, South Korea

Oxidative stability of soybean oils obtained by several extraction methods and/or from different stages of refining processes were determined by gas chromatography. Soybean oil samples were shown to contain various kinds of non-triglycerides components at different levels depending upon the extraction methods and the stages of refining process. Extraction methods employed were aqueous extraction, enzymatic extraction, and supercritical fluid extraction. Phospholipids contents in oil samples were substantially changed according to extraction methods and oxidative stability of oil samples were greatly influenced by the contents of phospholipids. Phospholipids showed anti- or pro-oxidant activity depending on the oil sample systems. Deacidification of oils were performed by conventional caustic refining, solvent refining, steam refining, enzymatic and microbial refining methods. The contents of phospholipids, chlorophylls, tocopherols and metal ions that affected oxidative stability of oils prudentially changed as refining processes proceeded. For the determination of oxidative stability of oils, several analytical methods such as volatile compounds evolution, headspace oxygen disappearance, weight gain, peroxide value were used, and new method detecting molecular hydrogen gas evolution was developed and compared with other methods. Hydrogen evolution method showed high correlation coefficient (r2>0.95) with total volatile compounds evolution method.