QUANTITATIVE FRACTIONATION OF WHEY PROTEINS BY GEL-PERMEATION FPLC

Whey proteins were fractionated by gel permeation FPLC in tris-HCl buf fer at pH 7.0 and 20 degrees C on a column of Superdex 75 HR 10/30. Fo ur main fractions were identified by comparison of their elution posit ions with known standards, and by SDS-PAGE. On average, whey protein f rom the bulk milk of Friesian cows consisted of: (1) immunoglobulins, 9.8 %; (2) serum albumin and lactoferrin, 10.7 %; (3) beta-lactoglobul in, 61.4 %; (4) alpha-lactalbumin, 18.0 % of the total. The proteose-p eptone fraction had very low absorbance at 280 nm and was not determin ed along with the other column fractions, but could be detected at 214 nm after heat-denaturation and precipitation of the other whey protei ns. The FPLC method was used to measure the relative amounts of the in dividual whey proteins in acid filtrate and whey from raw and heated m ilk, and was suitable for measuring denaturation of whey proteins and the extent of their incorporation into the curd during cheese-making w ith heat-treated milk.