Optimization of centrifugal separation of alpha-lactalbumin and beta-lactoglobulin

Whey proteins, which are mainly composed of beta-lactoglobulin (beta-lg) and alpha-lactalbumin (alpha-la), account for about 20% of the proteins of bovine milk. In this study we investigated the effect of pH, dry matter content, concentration factor, heat treatment and centrifugation on the separation of alpha-la from beta-lg using clarified whey as raw material. alpha-la precipitation was highest, 23.3%, when the dry matter content ranged from 5.8% to 25.7%. The optimum pH of alpha-la precipitation depended on the dry matter content. The separation efficiency increased when the concentration factor and heat treatment time at 55 degrees C increased. A longer centrifugation time and higher separation speed did not have a marked effect on the separation efficiency. Separation was more efficient with a higher centrifugation speed at concentration levels 30 X and 60 X. The separation efficiency did not improve when the temperature was raised from 55 degrees C to 65 degrees C but it was better at a concentration level 120 X than at 60 X and 30 X, and also at concentration level 60 X than with 30 X.