Figure 2 Spray-dried emulsions with constant oil content but different ratios of lactose to whey protein. (e) The composition of the spray-dried emulsion (% of dry weight) before spray-drying; (0) the surface composition of the spray-dried powders before storage; (0) the surface composition of the spray-dried powders after storage in a humid atmosphere (4 days, RH 75%).
These findings are somewhat contrary to earlier conclusions drawn from scanning electron microscopic investigations of similar whey protein-containing particles (13-15). These investigations state, on the basis of scanning electron micrographs, that the ability of whey protein to encapsulate milk fat is high when whey protein-stabilized emulsions are spray-dried. However, with ESCA, direct information of powder chemical surface composition is obtained. ESCA measurement clearly shows that a rather large part of the whey protein/fat/lactose powder surface is covered by fat. This is not evident from scanning electron micrographs.