ASSESSMENT OF OXIDATION IN HEATED SAFFLOWER OIL BY PHYSICAL, CHEMICAL AND SPECTROSCOPIC METHODS

Safflower oil was heated at 180C by static heating in an open pan or in an oven, or by heating through intermittent heating-cooling cycles (as in frying) over a period of 8 h. The extent of deterioration of the oil was followed by measurement of physical characteristics such as color and viscosity and the chemical indices such as free fatty acid, peroxide, iodine, conjugated diene and triene values, unsaponifiable matter and oxidized fatty acids. The extent of oxidation was also assessed by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopic techniques through analysis of oxidized fatty acids. The results indicated that heating in open pan caused deterioration in oil faster than in other treatments. Furthermore, the IR, and NMR studies of the oil heated in an open pan indicated cross polymerization while during oven heating and frying cross polymerization was not observed.