Apparent chemical composition of nine commercial or semi-commercial whey protein concentrates, isolates and fractions

Analytical results are given for whey powders prepared on a commercial or s emi-commercial scale by three companies. Altogether, five preparations enri ched in beta-lactoglobulin, four whey protein isolates and a fraction enric hed in alpha-lactalbumin were analyzed for protein composition, including % beta-lactoglobulin, alpha-lactalbumin, bovine serum albumin, casein (glyco ) macropeptide and the main triglycerides. Protein composition was determin ed by high pressure gel permeation and reversed phase liquid chromatography and by capillary zone electrophoresis. The extent of modification of the n ative beta-lactoglobulin structure was also measured through the degree of lactosylation and the fraction of accessible free sulphydryl groups. One si gnificant finding was that the calculated recovery of protein following qua ntitation of the chromatogram or electropherogram was seldom above 90% and occasionally below 60% of that loaded onto the column or capillary, raising doubts as to the reliability of the analytical results. Extrapolation by l inear regression to 100% recovery allowed estimates to be made of the true beta-lactoglobulin composition of the samples. The nine samples could be pl aced into three distinct groups with estimated true beta-lactoglobulin weig ht % of 70.9 +/- 1.1, 62.0 +/- 3.4 and 39.5 +/- 4.9. Physico-chemical prope rties of the group of samples are reported elsewhere (Holt et al., 1999).