Quantitative quality tests for frozen fish: Soluble protein and free fatty acid content as quality criteria for hake (Merluccius capensis) stored at −18°C

Hake fillets and mince were frozen and stored at −18°C in four different tests. Samples were periodically withdrawn and analysed for total protein, protein soluble in aqueous salt solution, free fatty acid content and texture. Highly significant correlations were found between the texture and both the ratio of protein soluble in aqueous salt solution to total protein and the free fatty acid content. These correlations led to the formulation of quantitative quality criteria based on protein soluble in aqueous salt solution and free fatty acid content for frozen hake stored at −18°C.