Effect of Heat on the Proteins of Milk as Revealed by Gel and Immunoelectrophoresis

Summary Four different milk proteins (serum albumin, beta-lactoglobulin, casein, and immune globulin) were separated by gel electrophoresis. Further definition was accomplished with immunoelectrophoresis, a combination of gel electrophoresis and antigen-antibody precipitation. With this sensitive technique, the four electrophoretic fractions and alpha-lactalbumin formed precipitation arcs when reacted with their antisera. Beta-lactoglobulin and alpha-lactalbumin had weak antibody stimulating properties. Casein existed as a homogeneous substance rather than as several components which was observed when it was subjected to various separation techniques. A complex existed between beta-lactoglobulin and casein in raw skimmilk. Effect of heat on stability in increasing order was immune globulin, alpha-lactalbumin, serum albumin, beta-lactoglobulin and casein. Immunoelectrophoretic patterns of acid precipitated casein reacted against various antisera showed a complex was formed between beta-lactoglobulin and casein, and between casein and serum albumin.