Whey Protein Fractionation with Polyethylene Glycol

Abstract

Fractionation of whey proteins with polyethylene glycols 1,450, 6,000, and 20,000 was studied at pH 4.6, 6.0, and 7.0 and at 4 and 23C. Whey proteins were most susceptible to precipitation by polyethylene glycols at pH 4.6 and most resistant to precipitation at pH 6.0. At pH 4.6, 6,000 and 20,000 were more effective precipitation agents than 1,450. Temperature did not affect precipitation ability at any pH. The order of precipitation of individual whey proteins from whey was dependent on glycol concentration and protein molecular weight. The concentration required to precipitate each whey protein was inversely related to protein molecular weight, e.g., immunoglobulins, bovine serum albumin, β-lactoglobulin, and α-lactalbumin were selectively precipitated from pH 4.6 whey at 2 to 14, 12 to 25, 12 to 30, and 25 to 50% polyethylene glycol 6,000, respectively. Factors that affect physical properties of whey proteins apparently determine their susceptibility to precipitation by the glycols.