Effect of frozen storage on thermal stability of sarcoplasmic protein and myofibrillar protein from common carp (Cyprinus carpio) muscle

Thermal stability of sarcoplasmic protein and myofibrillar protein extracted from fresh and frozen common carp was comparatively studied. Total sulphydryl content (SH) in sarcoplasmic protein solution from 5-month frozen carp decreased by 19.43% compared with fresh sample. The SDS-PAGE patterns showed that all the bands of sarcoplasmic protein from frozen-stored samples were almost invisible at 80 degrees C. Myofibrillar protein from fresh sample exhibited lower turbidity and surface hydrophobicity and higher Ca2+-ATPase activity and SH content than frozen-stored sample when heated from 20 to 80 degrees C. The Ca2+-ATPase activity from fresh (M0), 2 (M2)- and 5 (M5)-month frozen-stored carp was completely lost at 48, 46 and 46 degrees C, respectively. When heated to 80 degrees C, the SH content of myofibrillar solutions in M0, M2 and M5 decreased by 26%, 60% and 70%, respectively. Sarcoplasmic and myofibrillar proteins from frozen carp were more susceptible to aggregate during heating treatment.