Comparative Analysis of Physicochemical and Thermophysical Properties of Palm Kernel Oil Extracted by Cold Press and Solvent Methods

This study presents a comparative evaluation of the physicochemical and thermophysical properties of palm kernel oil (PKO) extracted via cold pressing (Sample C) and solvent extraction (Sample D), with all analyses conducted in triplicate (n = 3). Key parameters, including acid value, iodine value, peroxide value, saponification value, density, viscosity, refractive index, and thermal conductivity, were measured alongside GC-MS-based fatty acid profiling. The top three fatty acids identified in both samples were lauric acid (C12:0), myristic acid (C14:0), and oleic acid (C18:1), with respective percentages in cold-pressed oil (Sample C) being 48.6%, 16.3%, and 15.4%, and in solvent-extracted oil (Sample D) being 47.1%, 15.8%, and 16.0%. While the fatty acid distribution remained consistent, the solvent-extracted oil exhibited a more complex chromatographic fingerprint, containing additional volatiles, such as δ-dodecalactone, and exogenous contaminants, like bis(2-ethylhexyl) phthalate. Statistically significant differences (p < 0.05) were observed in oxidative stability, with peroxide values of 2.2 meq O₂/kg for Sample C and 3.0 meq O₂/kg for Sample D, indicating a higher susceptibility to lipid peroxidation in the latter. Thermal conductivity also differed significantly between the two samples, with values of 0.192 W/m·K for the cold-pressed oil and 0.187 W/m·K for the solvent-extracted oil. In summary, although solvent extraction enhanced yield and recovery of minor compounds, cold pressing yielded a purer oil with lower oxidative degradation and better thermal performance. Thus, extraction method selection should be tailored to the oil's end-use, favoring cold pressing for nutritional and cosmetic applications where purity and stability are paramount.