PERFORMANCE OF POLYUNSATURATED OILS DURIN G FRYING OF POTATOES IN FAST-FOOD SHOPS - FORMATION OF NEW COMPOUNDS AND CORRELATIONS BETWEEN ANALYTICAL METHODS

In this study, different analytical methods, i.e. polar compounds, pol ar compound distribution, free fatty acids, peroxide value, conjugated dienes and trienes, oxidized fatty acids, viscosity and oxifrit-test, are applied to samples of both initial polyunsaturated oils and their counterparts after being used in the frying of potatoes in fast food shops. Two main objectives were established: the study of formation of new compounds during the frying process and the evaluation of possibi lities to substitute complex methodologies for simpler and more rapid techniques. Results indicated that, although new compounds comming fro m oxidation and polymerization stand out, 20% of the samples contained very high amounts of hyrdolytic products i.e. diglycerides and fatty acids, whose formation is difficult to explain. From the analysis of c orrelation coefficients between analytical methods, the utility of fre e fatty acids and conjugated dienes (or viscosity) to predict the amou nt of the main groups of new compounds in used polyunsaturated frying oils, was deduced.