Characterization of used frying oils. Part 1: Isolation and identification of compound classes

In this study, an analytical scheme is presented for detailed qualitative comparisons between heated and unheated oils. This scheme is less subject to loss or alteration of sample components when compared with methods that characterize the distillable non‐urea adducting portion of heated oils. In this work, oils were first converted to their corresponding fatty acid methyl esters (FAMEs) by transesterification. These FAMEs were then separated by degree of polarity by means of adsorption chromatography and solid‐phase extraction. High‐resolution capillary gas and liquid chromatography were used to profile isolated fractions. Mass spectrometric and infrared analyses of major chromatographic features were used to identify the presence of aldehydes, epoxides, ketones, alcohols, phytosterols and dimer methyl esters down to 5 ppm in the original sample.