Cooking–freezing–reheating (CFR) of sardine (Sardina pilchardus) fillets. Effect of different cooking and reheating procedures on the proximate and fatty acid compositions

The sequential cooking–freezing–reheating (CFR) method was studied. Sardine (Sardina pilchardus Walb) fillets were cooked by frying, oven-baking or grilling, frozen, and then reheated using conventional or microwave ovens in order to study changes occurring in the proximate and fatty acid compositions. Both cooking and freezing–reheating affected (P<0.001) the proximate composition. Frying produced the highest water loss and fat gain, followed by grilling, and then by oven-baking. Microwave oven-reheating (MR) induced higher dehydration than conventional oven-reheating (OR), with grilled–frozen–MR samples also loosing fat and ash. Frying significantly (P<0.001) affects the fatty acid composition of sardine, increasing oleic and linoleic acids and decreasing eicosapentaenoic and docosahexaenoic acids. Oven-baking and grilling minimally affected the fatty acid content. Freezing–reheating significantly affected (P<0.001) the fatty acid composition with the content of oleic acid increasing and those of the ω-3 fatty acids, decreasing more in MR than in OR. Thus, according to the positive effect attributed to ω-3 fatty acids, cooked samples with no further treatment would be preferred to their respective CFR counterparts. However, OR should be used instead of MR when the CFR system is performed.