Journal of Thermal Analysis, Vol. 45 (1995) 741-750 DYNAMIC AND ISOTHERMAL DSC INVF_SrIGATION OF THE KINETICS OF THERMOOXIDATIVE DECOM] SITION OF SOME EDIBLE OILS G. Litwinienko, T. Kasprzycka-Guttman and M. Jarosz-Jarszewska Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland Abstract The kinetics of thermooxidation of edible oils: soybean oil, rapeseed oil, corn and peanut oil was investigated in two ways. The DSC and its pressure version (PDSC) were used for measure- merits under the isothermal and non-isothermal conditions in atmosphere of oxygen. Comparing these two methods for each oil the differences between the values of activation energies were ob- served. However, mechanism of oxidation in both method was different. Keywords: DSC, isothermal method, non-isothermal method, thermooxidation of edible oils InWoduction Experimental techniques as thermogravimetry (TG), differential scanning calorimetry (DSC) and its pressure version (PDSC) are being used increasingly for the identification and characterization of chemical substances and also for determining the kinetic parameters of simple and complex reactions. Both isothermal and non-isothermal DSC techniques can be used for such exothermal reactions as thermal oxidative decomposition of oils and fats. These kinds of substance are mixtures of triacylglycerols of saturated, unsaturated, polyunsaturated acids, tocopherols and other organic compounds. Due to that complicated composition, the oils are treated as homogeneous material in TA experiments what is right for assessment of their quality and thermal stability. The aim of this research is to compare the dynamic and isothermal method of investigating of the kinetic behaviour of oils. Special accent was put on activa- tion energy and kinetic parameters obtained independently from those different experiments. In the thermal analysis experiments the rate of conversion (dec/d0 is de- scribed by basic kinetic equation: an dt =k~) (1) 0368--4466/95/$ 4.00 9 1995 Akad~miai Kiad6, Budapest John Wiley & Sons, Limited Chlehester