Oil-soluble Surfactants Have Little Effect on Competitive Adsorption of α-Lactalbumin and β-Lactoglobulin in Emulsions

Protein surface concentrations in emulsions stabilized by α-lactalbu-min (α-la), β-lactoglobulin (β-lg) and their mixture were studied with various amounts of oil-soluble surfactant present during homogenization. Three different surfactants were considered: diethyl glycol n-dodecyl ether (C12E2), sorbitan monooleate (Span 80), and glycerol monostearate (GMS). In n-tetradecane-in-water emulsions, low con-centrations of C12 E2or Span 80 resulted in a smaller average droplet size and a greater total protein surface coverage; we found the opposite effect at high surfactant concentrations. The effect of GMS in soybean oil-in-water emulsions was slight. In emulsions containing α-la+β-Ig, separate surface coverages of the whey proteins did not differ significantly. The competitive adsorption of milk proteins in food emulsions is unlikely to be affected by surface-active impurities present in typical food oils.