KINETICS PARAMETERS DETERMINATION OF REFINED AND COLD–PRESSED RAPESEED OILS AFTER OXIDATION BY RANCIMAT

This works summarizes results of quality assessment of five refined and five cold-pressed rapeseed oils. The analyzed oils were characterized by a good quality that meet requirements of the Codex Alimentarius standard. Oxidative stability of the oils was determined in Rancimat test at five temperatures (90, 100, 110, 120, 130 oC). The oxidation rate constant (k) was observed to increase along with increasing process temperature. The Arrhenius equation and active complex theory were used to compute the exponential factor (Z), activation energy (Ea), reaction rate constant at various process temperatures (k) as well as enthalpy (ΔH++) and entropy (ΔS++) of the oxidation reaction of the analyzed oils. The Ea, ΔH++and ΔS++ values ranged from 76.43 to 82.44 kJ/mol, from 72.12 to 79.26 kJ/mol and from –48.35 to –68.45 J/molK for the refined oils as well from 74.24 to 77.56 kJ/mol, from 71.04 to 75.47 kJ/mol and from –56.40 to –69.99 J/molK for the cold-pressed oils, respectively.