Cryoprotective effects of shrimp head protein hydrolysate on gel forming ability and protein denaturation of lizardfish surimi during frozen storage

The effects of shrimp head protein hydrolysate (SHPH) from three species of shrimp (northern pink shrimp [Pandalus eous], endeavour shrimp [Metapenaeus endeavour], black tiger shrimp [Penaeus monodon]) on gel forming ability and protein denaturation of lizardfish surimi during frozen storage at -25 degrees C were evaluated. The quality of lizardfish surimi with 5% (dried matter) of any of the three SHPH or sodium glutamate (Na-Glu) was examined in terms of gel strength, whiteness, Ca-ATPase activity and the amount of unfrozen water, comparing with those of surimi without additive as the control. The residual Ca-ATPase activity and gel strength of surimi with SHPH were higher than those of the control throughout 180 days of frozen storage, regardless of shrimp species. The highest effect was found in surimi with Na-Glu. The gel strength and Ca-ATPase activity found a high positive correlation. The addition of SHPH to surimi also increased the amount of unfrozen water by approximately 1.29-1.36 fold higher than the control, however kamaboko gels of the control was significantly whiter. From these results, freeze-induced denaturation of lizardfish muscle protein could be lessened by the addition of SHPH, resulting in a high gel strength and Ca-ATPase activity.