Physico-chemical changes occurring in clean label fish burgers during frozen storage

Two ‘clean label’ formulations for fish burgers made with mechanically separated fish meat were chemically and physically characterised during 90 days of frozen storage (T90). The formulations differed in the ratios of European sea bass to rainbow trout (50:50, R1; 30:70, R2). The formulations were added with lemon, salt, water, and potato flakes to obtain products contained 72% of water. The protein and lipid contents were not affected by the presence of the different amount of fish species. Overall, even the fatty acid composition of R1 and R2 was slight affected. The sum of the polyunsaturated (PUFA) ω6 fatty acids was higher in R2 than in R1 (18.99 vs 18.57g/100g of total fatty acids) while no differences in the sum of PUFA ω3 emerged. The high amount of trout in R2 seemed to better preserve the product from lipid oxidation, as revealed from the lower content of secondary oxidative products (thiobarbituric acid reactive substances, TBARS) found in the R2 than in the R1, being 0.81 and 0.98mg MDA/kg sample, respectively. The high amount of trout in R2 significantly increased the shear stress of the fish burgers being 4.09 and 4.99N, in R1 and R2 respectively. Frozen storage showed to be a good way for food preservation. Indeed, proximate and fatty acid composition of fish burger were not altered for 90 days. A low oxidative profile of fish burgers emerged by evaluating both conjugated dienes (CD) and TBARS content in the products immediately prepared (T0) and after 90 days of storage. On the other hand, the recipes showed a dramatic decrease in their shear stress during the storage, being 7.62N at T0 and 3.30N at T90. In conclusion, the recipe with more trout, R2, showed less changes in physical quality and had more oxidative stability during frozen storage.