| Abstract: | Samples of cod, whiting, herring, lemon sole and skate muscle were frozen and stored at ? 8°C for up to 20 months. Samples of cod muscle were also stored at ? 30°C. During storage at ?8°C the decrease in the solubility of the muscle proteins in 5% NaCl (denaturation) was most rapid in whiting followed in order by skate, cod, herring and lemon sole. Little change was detected in the NaCl solubility of cod muscle protein stored at ? 30°C. An increase in the pH was found to occur in all the species examined. The relationship between these changes and the toughening that occurs in fish muscle during frozen storage is considered. No nutritionally significant decrease in the lysine availability or the in vitro digestibility of the muscle proteins was found to occur in any of the species examined. In whiting, lemon sole and skate very small, statistically significant, increases in the available lysine content were detected after 7 months of storage at ?8°C and this may indicate that unfolding of the protein chains had occurred. |
