Deep-Frying of Orange-Spotted Grouper Fillets in Olive, Corn, and Grape Seed Oils: Effects on nutritional quality indices, Lipid Oxidation, Minerals, and Vitamins composition

The aim of this study was to determine the nutritional quality indices , lipid oxidation, minerals, and vitamins composition of deep-fried orange-spotted grouper. Different vegetable oils (olive oil, grapeseed oil, and corn oil) were used for deep-frying. The results indicated that deep-frying significantly increased fat content and decreased moisture. The fatty acid profile of the fillets was markedly influenced by oil absorption. Corn oil-fried fillets exhibited the most favorable nutritional lipid indices, including the highest polyunsaturated-to-saturated fatty acid (PUFA/SFA) ratio (2.03) and hypocholesterolemic/hypercholesterolemic (HH) ratio, alongside the lowest atherogenic (AI) and thrombogenic (TI) indices. However, this was accompanied by a substantial reduction in beneficial long-chain omega-3 fatty acids (EPA+DHA), which decreased from 6.06% in raw fillets to 1.98%. Grape seed oil best preserved the EPA+DHA content among fried samples. Olive oil frying led to a significant increase in the arachidonic-to-eicosapentaenoic acid (ARA/EPA) ratio, indicating a potential negative impact on this sensitive nutritional index. Lipid oxidation analysis revealed no significant change in TBA values post-frying, possibly due to the volatility of malondialdehyde (MDA) or antioxidant effects from the oils. FFA content decreased significantly after frying, with olive oil-fried fillets showing the lowest value (1.42% oleic acid). Regarding vitamins, frying caused significant degradation of heat-sensitive vitamins B1 and B3, while vitamin A content increased, highest in corn oil-fried samples (8.36 mg/100g). Vitamin D levels varied, with olive oil-fried fillets retaining the highest content. Most minerals remained stable during frying, except for Cu, which decreased significantly. In summary, selecting a frying oil involves balancing distinct advantages and drawbacks: corn oil improves heart-healthy fatty acid ratios yet significantly reduces omega-3 content; olive oil better controls lipid hydrolysis and maintains higher vitamin D levels, but it negatively alters the ARA/EPA balance. Grape seed oil, meanwhile, is superior in preserving omega-3 fatty acids. Consequently, the optimal oil should be chosen based on the specific nutritional priorities for the end product.