Preparation of β‐Lactoglobulin and p‐Lactoglobulin‐Free Proteins from Whey Retentate by NaCI Salting Out at Low pH

Solubility of the main proteins in 10 x acid and rennet whey retentates was studied in the pH range 2.0 to 4.0 in the presence of NaCI from 2 to 15% (w/v) final concentration, at 20°C to find fractionation conditions suitable for preparing pure β‐lactoglobulin and β‐lactoglobu‐lin‐free whey proteins and scaling up. At pH 2.0, 7% NaCI, 20 min holding time, nearly all (3‐lactoglobulin remained soluble while a precipitate (PI) containing all other proteins was formed. Pure p‐lacto‐globulin was quantitatively recovered by salting‐out the centrifugation supernatant at 30% NaCI (w/v) final concentration. PI, insoluble at pHs lower than 4.0, was made soluble at any pH by dissolving at pH 9.0, dialyzing against 50 mM formic acid (pH 3.0) and freeze‐drying.