Comparative study on chemical and gel-forming properties of surimi from freshwater and marine fish during frozen storage

Abstract

Consumption of surimi based-products has been increasing, while marine raw materials, particularly tropical fish, continuously decrease due to overexploitation of fishing resources. Freshwater fish have been shown to provide good surimi gel. However, intrinsic properties of freshwater and marine surimi have not been fully realized. This study aimed at comparing the frozen stability of surimi produced from freshwater and marine fish. Surimi from three freshwater fish species including silver carp (Hypophthalmichthys molitrix), rohu (Labeo rohita), tilapia (Oreochromis niloticus) and marine fish, threadfin bream (Nemipterus spp.), were produced at a commercial surimi plant. Samples were kept at -20°C and analyzed at various time intervals of 0, 3, 6 and 9 months. All surimi samples were prepared without addition of egg white powder. The results showed that protein solubility of all samples decreased continuously throughout the frozen storage. After 9 months of frozen storage, solubility of surimi made from freshwater fish decreased by 52-57%, while only 30% reduction was observed in threadfin bream. Silver carp surimi showed the highest gel-forming ability as compared to other freshwater species studied. Gel quality from all freshwater fish surimi decreased throughout 9-month storage with a 30 and 20% decrease in breaking force and deformation, respectively. Breaking force of threadfin bream surimi only decreased by 9% after 9 months without a significant change of deformation. No marked change in whiteness of all species during frozen storage. In addition, actomyosin conformation of all fish species slightly changed during frozen storage. Changes of reactive sulfhydryl group contents and surface hydrophobicity indicated that muscle proteins of freshwater fish were sensitive to frozen denaturation to a greater extent than that of threadfin bream surimi.