Effect of different vegetable oils on the nutritional properties of deep-fried orange-spotted grouper fillets

This study evaluated the nutritional quality indices, lipid oxidation, mineral composition, and vitamin profile of deep-fried orange-spotted grouper fillets prepared using olive, grapeseed, and corn oils. Deep-frying significantly increased fat content and decreased moisture content, while oil absorption altered the fatty acid profile. Corn oil-fried fillets exhibited the highest PUFA/SFA ratio (2.03) and hypocholesterolemic/hypercholesterolemic (HH) ratio, alongside the lowest atherogenic (AI) and thrombogenic (TI) indices. However, EPA+DHA content decreased from 6.06% in raw fillets to 1.98% after frying in corn oil. Grapeseed oil provided the highest EPA+DHA retention among fried samples, whereas olive oil significantly increased the ARA/EPA ratio. Thiobarbituric acid (TBA) values did not change significantly after frying, while free fatty acid (FFA) content decreased, reaching its lowest level (1.42% as oleic acid) in olive oil-fried fillets. Frying significantly reduced vitamins B1 and B3, whereas vitamin A increased, reaching 8.36 mg/100 g in corn oil-fried fillets. Olive oil-fried fillets retained the highest vitamin D content. Most minerals remained unchanged, although copper content decreased significantly. Overall, frying oil substantially influenced the nutritional characteristics of grouper fillets. Corn oil improved several lipid quality indices but caused greater EPA+DHA losses, grapeseed oil better preserved EPA+DHA, and olive oil reduced FFA levels and enhanced vitamin D retention but increased the ARA/EPA ratio. These findings demonstrate the importance of considering multiple nutritional indicators when selecting frying oils for fish processing.