Used frying fats and oils from several restaurants and fried food outlets in southern Spain were collected and 6 samples of olive and/or sunflower oils were selected for analysis. Mono-, di- and polymeric groups of altered fatty acids were quantified by high performance size exclusion chromatography, and monomeric fractions were further characterized by GLC-MS. Levels of polar compounds and altered fatty acids (total, oxidized monomers, nonpolar dimers, oxidized dimers and polymers) in the oils are tabulated. Levels and distributions of altered fatty acids depended largely on alteration levels and unsaturation degrees of fats and oils, although major monomeric compounds present (in all cases, aldehydes, epoxyacids, ketoacids and hydroxyacids) appeared generally independent of differences in variables in the frying process.

Trabajo presentado en el EURO FOOD CHEM VIII, celebrado en Viena (Austria) del 18 al 20 de septiembre de 1995.