Competitive protein adsorption between bovine serum albumin and β-lactoglobulin during spray-drying

Competitive adsorption between bovine serum albumin (BSA) and β-lactoglobulin (β-Lg) during spray-drying was studied and the results were compared to the adsorption of single protein at the powder surface. The study was performed with a new method using fluorescence quenching of pyrene labelled proteins at the powder surface. Comparing the single adsorption of the two proteins during spray-drying showed a similar adsorption behaviour with little preferential adsorption of one protein over the other. Analysis of the powder surface after spray-drying a mixture of BSA and β-Lg in a dextran matrix indicated that β-Lg adsorbed to the surface in preference to BSA at lower concentrations, but at higher concentrations the effect was less pronounced. When one of the proteins was spray-dried in a surplus of the second protein the adsorbed amount of the protein studied showed a strong decrease in apparent surface load at higher concentrations. However, at lower concentrations the adsorption seemed to be independent of the other protein present. This was the case for both BSA and β-Lg. In the single adsorption study of β-Lg the apparent surface load of β-Lg was measured to be 1.1 mg/m2 at a concentration of 10% β-Lg in the powder.