Influence of calcium, magnesium, or potassium ions on the formation and stability of emulsions prepared using highly hydrolyzed whey proteins

Oil-in-water emulsions (4 wt % soy oil) containing 4 wt % whey protein hydr olysate (WPH) (27% degree of hydrolysis) and different levels of calcium, m agnesium, or potassium chloride were prepared in a two-stage homogenizer. O ther emulsions containing 4 wt % WPH but including 0.35 wt % hydroxylated l ecithin and different levels of the above minerals were similarly prepared. The formation and stability of these emulsions were determined by measurin g oil droplet size distributions using laser light scattering and by confoc al scanning laser microscopy and a gravity creaming test. Both lecithin-fre e and lecithin-containing emulsions showed no change in droplet size distri butions with increasing concentration of potassium in the range 0-37.5 mM. In contrast, the diameter of emulsion droplets increased with increasing ca lcium or magnesium concentration > 12.5 mM. Emulsions containing hydroxylat ed lecithin were more sensitive to the addition of calcium or magnesium tha n the lecithin-free emulsions. Storage of emulsions at 20 degrees C for 24 h further increased the diameter of droplets and resulted in extensive crea ming in emulsions containing > 25 mM calcium or magnesium. It appears that both flocculation and coalescence processes were involved in the destabiliz ation of emulsions induced by the addition of divalent cations.