This is a different description of the course during the spray-drying process than the conventional, where low molecular weight solutes are described as migrating toward the interior of the droplets because of concentration gradients occurring during drying (30,31). However, these investigations were performed on solutions without any surface-active material (such as salt solutions), on relatively large droplets giving long drying times without the possibility to estimate the surface composition of the dry powders. Furthermore, the importance of surface activity on the formation of powder surfaces is emphasized by the fact that the domination of surface-active protein and absence of carbohydrate on spray-dried powder surfaces also occurs when lactose is changed for monosaccharides as well as high molecular weight polysaccharides (P.Faldt and B. Bergenstahl, unpublished results).