MECHANISM FOR STABILIZATION OF FISH ACTOMYOSIN BY SODIUM LACTATE

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. Rela tively high intrinsic viscosity [eta] and Huggins factor (k') values s howed SL is an effective water structure-maker. Thermal aggregation st udies showed that AM stability increased up to 15% SL; higher concentr ations of SL destabilized the AM. Surface tension and water activity m easurements indicated that the transition from stabilization to destab ilization and from increasing to decreasing surface tension coincided with a change in molecular species in the SL solutions. The decrease i n surface tension (and ARI 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 expec ted to preferentially absorb at an interface (with for example air or protein) and thus lower surface tension.