Effect of protein hydrolysate of pearl oyster [Pinctada fucata] meat on the state of water and denaturation of fish myofibrils during frozen storage

From the point of view of high utilization of pearl oyster meat, shellfish protein hydrolysates (SPH) were prepared from pearl oyster meat and three other species of shellfish meat by enzymic treatment using proteases. SPH prepared from each meat was added to lizard fish myofibrils and the changes in the amount of unfrozen water in myofibrils associated with freezing were analyzed by a differential scanning calorimetry. ATPase activity was simultaneously measured. The amount of unfrozen water increased by the addition of each SPH. When SPH was not added to myofibrils, the amount of unfrozen water rapidly decreased during frozen storage, whereas the decrease was moderate in myofibrils with SPH. Meanwhile, the decrease in ATPase activity during frozen storage was a similar tendency to that of the amount of unfrozen water, indicating a close correlation between ATPase activity and the amount of unfrozen water. The present study suggests that the denaturation of myofibrils might be suppressed by the addition of SPH, since SPH constructed the water molecules resulting in an increase in the amount of unfrozen water.