Viscosity-Temperature Stability, Chemical Characterization, and Fatty Acid Profiles of some Brands of Refined Vegetable Oil

Abstract

Oils of vegetable origin are of great importance in food, soap, and cosmetic industries and they may also be used as lubricants and raw materials for biodiesel production depending on their viscosity and thermal stability. This work provides insight into the fatty acid components, physicochemical properties and thermal stability of some refined vegetable oils. The Saponification values, peroxide values, acid values, iodine values and refractive index of these oils range from 185.38 to 209.26 mg/g KOH, 2.00 to 37.00 meq O2/ kg, 2.50 to 5.50 mg KOH/ g, 31.09 to 89.46 g / 100g and 1.441 to 1.488 respectively The activation energies obtained from Arrhenius-type equation range from 11.32 to 3.85 kJ mol-1, while the enthalpy (∆H҂) and entropy (∆S҂) of activation obtained from Eyring-type equation range from 6.852 to 14.317 kJ mol-1 and -31.85 to -29.06 J mol-1 K-1 respectively. The Gibbs free energy of activation (∆G҂) ranges from 15.51 to 23.81 k J mol-1. The Pw oil brand has the highest thermal stability and resistance to shear stress due to its high activation energy and a low degree of unsaturation. The heat was absorbed during the process, the reaction mechanism was associative and the entire process was non-spontaneous.