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

Abstract

The simultaneous separation of bovine whey proteins [a-lactalbumin and b-lactoglobulin (A1B)] and soybean proteins was performed, for the first time, by capillary electrophoresis. Different experimental conditions were tested. The most suitable consisted of 0.050 M phosphate buffer (pH 8) with 1 M urea and 1.2 mg/ml methylhydroxyethylcellulose, UV detection at 280 nm, 15 kV applied voltage, and 308C temperature. Quantitation of bovine whey proteins in a commercial powdered soybean milk manufactured by adding bovine whey to its formulation was performed using the calibration method of the external standard. Direct injection of a solution of the powdered soybean milk only enabled quantitation of a-lactalbumin in the commercial sample. Detection of b-lactoglobulin (A1B) required acid precipitation of the solution of the sample in order to concentrate bovine whey proteins in the supernatant prior to the analysis of this protein in the whey obtained. Since a-lactalbumin could also be quantitated from the injection of the whey, the simultaneous determination of a-lactalbumin and b-lactoglobulin (A1B) was possible upon acid precipitation of the powdered soybean milk solution. Detection limits obtained were 14 mg/g sol. for a-lactalbumin and 52 mg/g sol. for b-lactoglobulin (A1B) which represent protein concentrations about 60 mg/100 g sample for a-lactalbumin and 100 mg/100 g sample for b-lactoglobulin (A1B).  1999 Elsevier Science B.V. All rights reserved.