Assessment of lipid oxidation in cottonseed oil treated with phytonutrients: Kinetic and thermodynamic studies

Cottonseed oil was oxidized under accelerated conditions at four different temperature values (110, 120, 130 and 140 degrees C) through Rancimat method. The temperature dependence of oxidation reaction was expressed by Arrhenius equation. Reaction rate constant (k), activation energy (Ea), activation enthalpy (Delta H++), activation entropy (Delta S++) and Gibbs free energy of activation (AG(++)) for the oxidative stability of the cottonseed oil were calculated according to both Arrhenius model and Eyring equation of activated complex approach. The relevant oil was also treated with gallic acid, rutin and carotenoid in order to improve the shelf -life of the product. Moreover, tertbutyl hydroquinone (TBHQ) was also applied into the oil as control. Furthermore, the quality parameters of the cottonseed oil was also evaluated with respect to phenolic (TP), flavonoid (TF) and carotenoid (TC) contents and free radical scavenging activity (FRSA). Fourier Transformed Infrared -Attenuated Total Reflectance (FIR-ATR) was also used to evaluate the functional groups of the oil. Depending on the fundamental thermodynamic parameters (Delta H++ > 0, Delta G(++) > 0 and Delta S++ 0), the nature of the oxidation reaction in the pure and treated cottonseed oils proves that it is an endothermic and non-spontaneous process. The predicted shelf-life of the oils ranged from 46 to 639 days at ambient conditions