Study of the formation of carbonyl compounds in edible oils and fats by H-1-NMR and FTIR

Oils and fats start decomposing from the moment they are isolated from thei r natural environment. Heating accelerates oxidative rancidity and frying a t high temperatures produces thermal degradation with the formation of deco mposition products, such as aldehydes, ketones, free acids and hydroxilic c ompounds that in high levels can be harmful to human health. The decomposit ion products formed up to 300 degrees C were determined by means of H-1-NMR spectroscopy and an FTIR spectroscopic method was developed for the quanti fication of carbonyl compounds generated during heating. The results show t hat there is a formation of carbonyl compounds starting at 150 degrees C an d when the sample was heated at 300 degrees C for 40 min, the following con tents (expressed as butyraldehyde mass fraction) were found: olive oil 10.5 %, sunflower oil 11.3%, corn oil 3.0%, seeds oil (sunflower, safflower and canola seed) 6.6% and lard 3.5%. (C) 1999 Elsevier Science B.V. All rights reserved.