GENERATION OF LIPID-PEROXIDATION PRODUCTS IN CULINARY OILS AND FATS DURING EPISODES OF THERMAL STRESSING - A HIGH-FIELD H-1-NMR STUDY

The oxidative deterioration of glycerol-bound polyunsaturated fatty ac ids (PUFAs) in culinary oils and fats during episodes of heating assoc iated with normal usage (30-90 min at 180 degrees C) has been monitore d by high field H-1 NMR spectroscopy. Thermal stressing of PUFA-rich c ulinary oils generated high levels of n-alkanals, trans-2-alkenals, al ka-2,4-dienals and 4-hydroxy-trans-2-alkenals via decomposition of the ir conjugated hydroperoxydiene precursors, whereas only low concentrat ions of selected aldehydes were produced in oils with a low PUFA conte nt, lard and dripping when subjected to the above heating episodes. Sa mples of repeatedly used, PUFA-rich culinary oils obtained from restau rants also contained high levels of each class of aldehyde. The dietar y, physiological and toxicological ramifications of the results obtain ed are discussed.