Detection of adulteration of cottonseed oil by gas chromatography

To detect adulterant vegetable oils in cottonseed oil, soybean, rapeseed, and ricebran oils were mixed into cottonseed oil extracted experimentally from seeds. These adulterated oils and the component oils were analyzed for sterols, fatty acids, and triglycerides by gas chromatography. In sterol analysis, stigmasterol was determined for adulteration with soybean and ricebran oils. Brassicasterol content seemed to be reliable as the indicator of adulteration for rapeseed oil. In fatty acid analysis, erucic acid for rapeseed oil and linolenic acid for soybean and ricebran oils were proof of adulteration. Triglyceride analysis was not so reliable as sterol analysis for detecting contamination, except that triglycerides with carbon-58, 60, and 62 indicate adulteration with rapeseed oil. Rapeseed oil (5%) and soybean and ricebran oils (10%) were the limits of detection for adulteration in cottonseed oil. Analysis of cottonseed oil from six refineries did not show positive indications of adulteration.