Freezing-Induced Exposure of Hydrophobic Amino Acid Residues from Actomyosin

Abstract

In order to clarify the mechanism of insolubilization of fish proteins induced by freezing, the surface hydrophobicity was compared between actomyosins (AM) before and after freezing. Ten ml of AM solution (0.45M KCl-phosphate buffer, pH 7.5) was frozen in a cellophane-tube at -20°C for two days. After thawing at 4°C, 1ml of 1% (w/v) sodium dodecyl sulfate (SDS) was added, shaken for 1 hr and dialyzed overnight against 20ml of water. The concentration of SDS diffused into the outer liquid was somewhat lowered on freezing for fish AM, while it was not for poultry AM. However, this lowering was depressed on the addition of cryoprotective substance such as sucrose or sodium glutamate.
From the above results, there arose a possibility that the hydrophobic interactions between AM molecules were responsible for the insolubilization of fish proteins induced by freezing.