Simple method for estimation of volatile carbonyl compounds in edible oils and fried potato chips

A simple and sensitive method has been devised to determine the amounts of volatile carbonyl compounds in vegetable oils and fried potato chips, using a chemical reaction trap and absorption spectrophotometry. A sample of oil or fried potato chips is heated and simultaneously purged with a flow of nitrogen gas which further bubbles through a tube (trap) containing a hydroxylamine hydrochloride solution. The volatile carbonyl compounds are removed from the sample with the purge gas and retained in the trapping solution as they react to form the less volatile oxime derivatives. These are subsequently estimated by ultraviolet absorption, at wavelength 212 nm for the total oximes and at 272 nm specifically for conjugated diene carbonyl oximes, including furfural if present. Volatile carbonyls can be determined by this method at levels as low as 0.1–0.5 ppm of the sample. The method has been applied to the analysis of samples of canola (low erucic acid rapeseed) oil, cottonseed oil, and potato chips, all before and after storage. The method should be suitable also for other types of fried food.