Effect of frozen storage on the chemical and physical properties of black and silver scabbardfish

Black scabbardfish (Aphanopus carbo) and silver scabbardfish (Lepidopus caudatus) were frozen and stored at −18°C for 8 weeks. Samples were withdrawn weekly and analysed for protein insolubilisation, electrophoretic profile, texture and colour. A considerable decrease in the percentage of protein nitrogen extractable in 50 g litre−1 sodium chloride was observed in both species during frozen storage, which was also reflected in the decrease of sarcoplasmic and myofibrillar fractions. On the other hand, the alkali‐soluble and stroma fractions tended to increase. This behaviour was considered as an indicator of protein denaturation. The analysts of the electrophoretic profiles only showed slight differences either between species or during frozen storage. A highly significant correlation (P < 0.05) was found between soluble protein and texture parameters. This correlation allowed the derivation of a statistical expression which permits the prediction of textural quality during frozen storage of both scabbardfish species from the soluble protein content.