Changes in firmness and thermal behavior of ice-stored muscle of jumbo squid (Dosidicus gigas)

Changes in firmness, muscle total protease activity, and the thermal behavior of jumbo squid (Dosidicus gigas) were measured throughout 15 days of ice-storage. A significant decrease (p<0.05) in the shear force of raw mantle muscle was observed after 7-days ice-storage. The highest total protease activity detected was 1.24 U/g mantle. The thermograms obtained at day zero showed four transition states. The first three transition states were endothermic and correspond to myosin (50 degrees C), sarcoplasmic proteins (69 degrees C), and actin (79 degrees C). The fourth transition state was exothermic at 107 degrees C, and was probably associated with protein aggregation. The thermal behavior of the muscle showed a decreasing trend in temperature and enthalpy of transition for myosin, sarcoplasmic proteins, and actin with storage time. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed a change in the myofibrillar protein pattern, which with the shear force, and differential scanning calorimetry data, suggests a partial denaturation of that protein fraction during ice-storage.