Selective Precipitation of Whey Proteins with Carboxymethylcellulose

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Abstract
Anionic hydrocolloids undergo pH- dependent interactions with whey proteins. A partial fractionation of carboxymethyl- cellulose/proteih complexes was achieved by selected conditions of pH, ionic strength, and ratio of carboxymethylcellulose to pro- tein. A rapid screening method determined the amount of carboxymethylcellulose re- quired, fl-Lactoglobulin and bovine serum albumin were complexed at pH 4 by add- ing a predetermined amount of carboxy- methylcellulose 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 super- natant to pH 3.2 and adding a controlled amount of carboxymethylcellulose at 2 C (yield: 0.7 gaiter of remaining super- natant, 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 am- monium sulfate precipitation at pH 6.6, a-lactalbumin and immunoglobulins were recovered free of carboxymethylcellulose.