Isoelectric precipitation of casein using high-pressure CO2

High-pressure CO2 was used as a recyclable add for the isoelectric precipit ation of casein. Measurement of the pH during the high-pressure process all owed the comparison of the process with conventional precipitation using su lfuric acid. A simple model was made up to calculate the pH in complex aque ous solutions pressurized with CO2. It was established that the isoelectric point (pH 4.6) could not be reached with CO2, unless the milk was diluted. Nevertheless, high precipitation yields could be obtained with this proces s. Still, it was found that the precipitation is mainly caused by the decre ase in pH. The removal of calcium phosphate appeared to be complicated, pro bably because of precipitation of calcium phosphate in the casein-free solu tions after the pressure is released.