Electrophoresis of Milk Proteins. I. Some Comparisons of Salt-Acid and Salt-Lyophilized Whey Fractions,

There are several known methods used for the isolation of whey proteins from milk. ttarland and Ashworth (3) have outlined a salt-acid method which is perhaps one of the simplest and easiest. Their procedure involves the precipitation of casein by saturation of skim milk with NaC1 followed by precipitation of the whey proteins upon addition of HC1 to the resulting filtrate. Harland and Ashworth claimed that whey proteins prepared by this method were "relatively undenatured." However, it is possible that addition of HC1 to the noncasein filtrate might change the characteristics of the original whey proteins. Such changes in these protein fractions have been suggested by Whitnah et aI. (13) in their studies of the surface tension of milk. Differences between the electrophoretic patterns for ttarland and Ashworth whey proteins and for those obtained from whey proteins isolated by other methods should show possible changes in the whey proteins due to the effect of the precipitating reagents. The usual procedure employed in the preparation of whey proteins for electrophoretic studies involves the precipitation of casein from skim milk by acid (Smith, 10) or rennet (Deutsch, 2), followed by the concentration of the casein-~ree proteins by lyophilization2