Selective Precipitation of Whey Proteins with Carboxymethylcellulose

Anionic hydrocolloids undergo pHdependent interactions with whey proteins.A partial fractionation of carboxymethylcellulose/proteih complexes was achieved by selected conditions of pH, ionic strength, and ratio of carboxymethylcellulose to protein.A rapid screening method determined the amount of carboxymethylcellulose required, fl-Lactoglobulin and bovine serum albumin were complexed at pH 4 by adding a predetermined amount of carboxymethylcellulose solution to whey, cooling the mixture to 2 C and collecting the precipitate by centrifugation (yield: 5.1 g/liter, CMC/protein ratio : 0.2S).A second complex containing a-lactalbumin was precipitated by adjusting the supernatant to pH 3.2 and adding a controlled amount of carboxymethylcellulose at 2 C (yield: 0.7 gaiter of remaining supernatant, CMC/protein ratio: 0.48).After removal of this complex by centrifugation the supernatant was adjusted to pH 7.5 which eoprecipitated proteins (apparently proteose-peptones) along with calcium phosphate salts (yield of freeze-dried, dialyzed product: 0.1 gaiter, CMC/protein ratio: 0.05).With a combination of CMC treatment of whey at pit 4.0 and ammonium sulfate precipitation at pH 6.6, a-lactalbumin and immunoglobulins were recovered free of carboxymethylcellulose.