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

Competitive adsorption between bovine serum albumin (BSA) and beta-lactoglo bulin (beta-Lg) during spray-drying was studied and the results were compar ed to the adsorption of single protein at the powder surface. The study was performed with a new method using fluorescence quenching of pyrene labelle d proteins at the powder surface. Comparing the single adsorption of the tw o proteins during spray-drying showed a similar adsorption behaviour with l ittle preferential adsorption of one protein over the other. Analysis of th e powder surface after spray-drying a mixture of BSA and beta-Lg in a dextr an matrix indicated that beta-Lg adsorbed to the surface in preference to B SA at lower concentrations, but at higher concentrations the effect was les s 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 d ecrease in apparent surface load at higher concentrations. However, at lowe r concentrations the adsorption seemed to be independent of the other prote in present. This was the case for both BSA and beta-Lg. In the single adsor ption study of beta-Lg the apparent surface load of beta-Lg was measured to be 1.1 mg/m(2) at a concentration of 10% beta-Lg in the powder. (C) 2000 E lsevier Science Ltd. All rights reserved.