Authenticity and safety assessment of canned sardine oil bases in Abuja, Nigeria: GC-MS fatty acid profiling and heavy metal contamination

Abstract

Canned sardines are a widely consumed and affordable source of protein and omega-3 fatty acids in Nigeria, with the surrounding oil base significantly influencing product quality and safety. This study evaluated the quality, safety, and authenticity of oil bases extracted from four commercial canned sardine brands marketed in Abuja, representing vegetable, sunflower, soybean, and olive oils. Proximate composition, physicochemical parameters, heavy metal concentrations (Hg, As, Al, Cu), and fatty acid profiles were determined using standard analytical methods (AOAC), atomic absorption spectrophotometry, and gas chromatography-mass spectrometry (GC-MS). Results were compared with Codex Alimentarius standards. Proximate analysis revealed high lipid content (89.10–90.19%) across all samples, confirming energy density, though moisture levels (2.78–4.26%) exceeded typical refined oil standards due to fish-oil interactions during canning. Soybean oil exhibited the highest vitamin E content (43.70 µg/ml), indicating superior antioxidant potential. Most physicochemical parameters complied with Codex standards; however, soybean oil marginally exceeded the acid value limit (0.62 mg KOH/g), and iodine values (10.62–17.17 mg I₂/100g) were substantially reduced, indicating thermal modification during processing. Critically, heavy metal analysis revealed universal exceedance of Codex limits: mercury (0.53–0.57 mg/kg), approximately five times the permissible limit, arsenic (0.08–0.28 mg/kg) exceeding in all four samples, and aluminium (0.16–0.32 mg/kg) and copper (0.17–0.44 mg/kg) uniformly above standards. GC-MS analysis confirmed the authenticity of the oils, with fatty acid profiles consistent with the declared oil types: oleic acid dominance in olive oil and linoleic acid predominance in sunflower and soybean oils. Detection of marine-derived eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in all samples confirmed lipid exchange between fish tissue and oil during canning, enhancing nutritional value. The findings reveal a trade-off between nutritional richness (PUFA content) and oxidative stability among oil bases, with olive oil demonstrating superior stability but lower vitamin E content. However, widespread heavy metal contamination raises significant public health concerns and underscores the need for urgent regulatory intervention by National agency for food drug administration (NAFDAC) and Standard organization of Nigeria (SON) to ensure consumer safety.