Structural and Functional Properties of Sarcoplasmic Proteins from Silver Carp Surimi Wash Water Recovered by Different Methods

In this study, the effects of different recovery methods on the structure and functional properties of sarcoplasmic proteins from silver carp surimi wash water were analyzed. The results showed that acidic pH-shifting and heat treatment had a great effect on the degree of conversion of –SH groups to disulfide bonds, surface hydrophobicity, intrinsic tryptophan fluorescence intensity, solubility and foamability of sarcoplasmic proteins. Secondary structure analysis showed that freeze drying and heat treatment gave rise to a higher relative content of β-sheet; isoelectric point precipitation, acidic pHshifting alone and in combination with chitosan flocculation resulted in a higher relative content of random coil; chitosan flocculation led to a higher relative content of β-turn. These methods consistently yielded a lower relative content of α-helix, and caused the secondary structure of sarcoplasmic proteins to transform from an ordered to a disordered state. In addition, chitosan could bind to sarcoplasmic proteins to form large molecular mass complexes, whereas acidic pH-shifting caused partial decomposition of sarcoplasmic proteins. The structural changes cause by the different recovery methods affected the functional properties of sarcoplasmic proteins. The sarcoplasmic proteins prepared by acidic pH-shifting coupled with chitosan flocculation had much higher surface hydrophobicity and consequently poorer emulsifying properties, while those obtained by freeze drying, isoelectric point precipitation, and chitosan flocculation had stronger emulsifying properties. Notably, chitosan treatment significantly improved the emulsifying properties of sarcoplasmic proteins.