Comparative Thermal Oxidative Stability of Refined Palm Oil , Palm Kernel Oil and Groundnut Oil Under Deep -Frying Condition

Publication Details

Publication Date

10/07/2026

Volume / Issue

Vol 1, Issue 2 (2026)

Article No.

033

Journal

British Journal of Contemporary Research

Received

16 Jun 2026

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2

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0

Abstract

Repeated deep-frying is the most thermally demanding application of edible oils in Nigerian cooking, and a principal driver of lipid oxidative deterioration and toxic compound formation. This study comparatively evaluated the thermal oxidative stability of refined palm oil (PO), palm kernel oil (PKO), and groundnut oil (GNO) brands marketed in Port Harcourt, Rivers State, Nigeria, under standardized simulated deep-frying conditions (180 ± 5°C; 0, 2, 4, 6, and 8 cumulative frying hours). Six brands were tested (two per oil type). The primary analytical endpoints were total polar compounds (TPC), measured by column chromatography as the gold-standard indicator of frying oil quality; polymer content (PC), quantified gravimetrically; and a comprehensive panel of secondary quality indices including peroxide value (PV), p-anisidine value (p-AV), total oxidation value (TOTOX), free fatty acid content (FFA), viscosity, colour (Gardner scale), and specific extinction coefficients (K232, K270). Results demonstrated that refined PO brands exhibited the greatest thermal oxidative stability, with TPC values reaching 22.4–24.6% after 8 hours of frying—below the internationally recognized discard threshold of 25% TPC. Refined PKO brands showed intermediate stability (TPC: 18.8–21.4% at 8 h), benefiting from their high saturated fatty acid content despite being primarily composed of medium-chain fatty acids more susceptible to hydrolytic breakdown. Refined GNO brands demonstrated the least thermal stability among the three oil types, with TPC values of 28.6–31.4% at 8 h, exceeding the 25% discard threshold between 6 and 8 hours of continuous frying. Polymer accumulation followed the same rank order: GNO > PO > PKO at equivalent frying durations. Viscosity increased 2.1- to 3.4-fold across all oil types following 8 hours of frying, with the greatest increase observed in GNO. These findings provide the first brand-specific, comparative thermal stability dataset for the three major domestic cooking oils in Rivers State, Nigeria, and support evidence-based regulatory thresholds for frying oil replacement in the Nigerian food industry and domestic cooking context.

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This article is published under the Creative Commons Attribution 4.0 International License . Free to read, share, and adapt with attribution.