Structural changes of silver carp slide during frozen storage

To analyze the structural changes of silver carp slide during frozen storage,the salt extractable protein content,active sulfhydryl content and Ca²⁺ - ATPase activity were evaluated with circular dichroism spectra( CD),low- field nuclear magnetic resonance( LF- NMR) and scanning electron microscopy( SEM). The results indicated that these three indexes were decreased with the extension of storage time. The salt extractable protein content,active sulfhydryl content and Ca²⁺ - ATPase activity were decreased from 58.2 mg / g to 17.3 mg / g,0.598 mol /105 g to 0.204 mol /105 g and 0.214 μmol / min·g to 0.051 μmol / min·g respectively. CD analysis showed that α- helix transformed to β- sheet first during early period,then transformed to random coil.SEM results indicated that silver carp slide gel shrank due to dehydration gradually,which caused the reduction of surface smoothness and gelforming ability.The LF- NMR T₂ transverse relaxation time data demonstrated that the two bound water populations were T₂₁( 0.09~1 ms) and T₂₂( 1~10 ms).With the extension of frozen time,T₂₁ had no significant changes,while T₂₂ decreased on the whole,it indicated that the internal moisture binding force was enhanced. It provided biological evidences to discuss the changes of the quality of silver carp slide during frozen storage.