EVALUATION OF ACTIVITIES OF ANTIOXIDANTS IN RAPESEED OIL MATRIX BY PRESSURE DIFFERENTIAL SCANNING CALORIMETRY

Samples of rapeseed oil and rapeseed oil inhibited with antioxidants were oxidized in the cell of a pressure differential scanning calorimeter (PDSC). The PDSC experiments were carried out under 1800 kPa oxygen pressure at temperatures in the range 131-156-degrees-C. The antioxidants used were 2-t-butyl-4-methoxyphenol (BHA), 2,6-di-t-butyl-4-methylphenol (BHT) and propyl gallate (PG). From resulting PDSC exotherms their extrapolated onset and peak maximum times were determined and used for the assessment of the oxidative stabilities of the samples. The efficiencies of antioxidants used for protection of rapeseed oil from oxidation can be ranked in the order BHT < BHA << PG, with PG the most and BHT the least efficient of the three. As PDSC exotherms were obtained at different temperatures the activation energies for oxidation of inhibited and uninhibited rapeseed oil samples have been calculated.