Mechanism for Stabilization of Fish Actomyosin by Sodium Lactate

Abstract

The mechanism for stabilization of actomyosin (AM) by sodium lactate (SL) was studied by comparing physical properties (viscosity, density, surface tension, and water activity) of SL and sucrose solutions. Relatively high intrinsic viscosity [η] and Huggins factor (k‘) values showed SL is an effective water structure-maker. Thermal aggregation studies showed that AM stability increased up to 15% SL; higher concentrations of SL destabilized the AM. Surface tension and water activity measurements indicated that the transition from stabilization to destabilization and from increasing to decreasing surface tension coincided with a change in molecular species in the SL solutions. The decrease in surface tension (and AM stability) with increasing SL concentration above the optimum is presented to be due to formation of the lactate dimer lactoyl lactate. This molecule is amphiphilic and would be expected to preferentially absorb at an interface (with for example air or protein) and thus lower surface tension. Keywords: Fish; protein; aggregation; amphiphilic; surface tension; water activity.