Analysis of bovine whey proteins in soybean dairy-like products by capillary electrophoresis

The simultaneous separation of bovine whey proteins [alpha-lactalbumin and beta-lactoglobulin (AS-B)] and soybean proteins was performed, for the firs t time, by capillary electrophoresis. Different experimental conditions wer e tested. The most suitable consisted of 0.050 M phosphate buffer (pH 8) wi th 1 M urea and 1.2 mg/ml methylhydroxyethylcellulose, UV detection at 280 nm, 15 kV applied voltage, and 30 degrees C temperature. Quantitation of bo vine whey proteins in a commercial powdered soybean milk manufactured by ad ding bovine whey to its formulation was performed using the calibration met hod of the external standard. Direct injection of a solution of the powdere d soybean milk only enabled quantitation of alpha-lactalbumin in the commer cial sample. Detection of beta-lactoglobulin (A+B) required acid precipitat ion of the solution of the sample in order to concentrate bovine whey prote ins in the supernatant prior to the analysis of this protein in the whey ob tained. Since alpha-lactalbumin could also be quantitated from the injectio n of the whey, the simultaneous determination of alpha-lactalbumin and beta -lactoglobulin (A+B) was possible upon acid precipitation of the powdered s oybean milk solution. Detection limits obtained were 14 mu g/g sol. for alp ha-lactalbumin and 52 mu g/g sol. for beta-lactoglobulin (A+B) which repres ent protein concentrations about 60 mu g/100 g sample for alpha-lactalbumin and 100 mu g/100 g sample for beta-lactoglobulin (A+B). (C) 1999 Elsevier Science B.V. All rights reserved.