Kinetic studies of the effect of muscle fiber type and tripolyphosphate on the aggregation of porcine salt-soluble proteins

The kinetics of thermal aggregation of salt-soluble proteins (SSP) isolated from porcine Longissimus dorsi (75% white fiber, Serratus ventralis (43% red fiber, and Vastus intermedius (76% red fiber) muscles were studied in the presence of sodium tripolyphosphate (TPP). SSP solutions containing 0-2·0% TPP were heated at constant temperatures between 40° and 70°C, and protein aggregation was monitored using turbidity measurements. SSP aggregation followed first-order kinetics, and the rate and extent of aggregation increased with the red fiber content. Addition of TPP generally increased the aggregation temperature for both white and red muscle SSP, but the changes in the aggregation rate varied depending on the specific temperature and muscle type. Arrhenius plots revealed 10·2-11·5% reduction in the activation energy for SSP aggregation caused by 0·5% TPP. These results indicate that SSPs from red and white muscle types differ in thermal properties and response to phosphate treatments.