Fatty Acid Profile and Lipid Quality Indices of Refined Palm Oil Versus Palm Kernel Oil: A Comparative Fame–Gc-Fid Analysis of Major Brands Marketed in Rivers State, Nigeria

The fatty acid composition of refined vegetable oils is a primary determinant of their nutritional value, technological functionality, and health implications. Palm oil (PO) and palm kernel oil (PKO) are two chemically distinct products derived from anatomically separate fractions of the oil palm fruit (Elaeis guineensis Jacq.), yet they are frequently perceived interchangeably in Nigerian consumer practice. This study conducted a rigorous comparative fatty acid methyl ester (FAME) analysis using gas chromatography with flame ionization detection (GC-FID) on commercially refined PO, PKO, groundnut oil (GNO), soybean oil (SBO), and sunflower oil (SFO) brands purchased from major markets in Port Harcourt, Rivers State, Nigeria. Eight brands were analysed for complete fatty acid profiles, fatty acid class distributions, atherogenicity index (AI), thrombogenicity index (TI), hypocholesterolaemic-to-hypercholesterolaemic fatty acid ratio (h/H), polyunsaturated-to-saturated fatty acid ratio (PUFA/SFA), and omega-6/omega-3 ratio. Physicochemical quality parameters including peroxide value (PV), acid value (AV), free fatty acid content (FFA), iodine value (IV), saponification value (SV), refractive index (RI), and specific gravity were determined by standard AOCS and AOAC methods. Refined PKO was dominated by lauric acid (C12:0, 45.8–47.2%) and myristic acid (C14:0, 15.6–16.4%), yielding a combined saturated fatty acid (SFA) fraction of 82.9–86.4%. Refined PO was predominantly composed of palmitic acid (C16:0, 42.6–44.8%) and oleic acid (C18:1, 37.4–39.2%), with SFA content of 48.5–51.1%. GNO exhibited the highest monounsaturated fatty acid (MUFA) content (49.70%), while SFO recorded the highest polyunsaturated fatty acid (PUFA) proportion (58.54%). Atherogenicity and thrombogenicity indices were highest for PKO (AI: 8.42–8.86; TI: 4.22–4.68) and lowest for SFO (AI: 0.18–0.22; TI: 0.22–0.28). SBO demonstrated the most nutritionally balanced omega-6/omega-3 ratio (7.7:1), closest to the WHO-recommended range. All brands met CODEX Alimentarius physicochemical quality benchmarks. These findings provide the first comprehensive FAME–GC-FID comparative characterisation of refined vegetable oil brands in the Rivers State market and underscore the urgent public health need for mandatory fatty acid disclosure on Nigerian vegetable oil labels.