analyze emulsion droplets which are charged and have a significant density difference compared to the surrounding liquid, and therefore they have limited application to many food systems.
The use of electroacoustics for measuring the zeta potential of droplets in concentrated emulsions is illustrated in Figure 10.28. When calcium ions are added to a 20% oil-in-water emulsion stabilized by lecithin, they "bind" to the surface of the negatively charged droplets and reduce the zeta potential. Above a certain concentration, they actually cause the sign of the droplet charge to become reversed. One would therefore expect low concentrations of calcium to reduce the electrostatic repulsion between droplets, which may lead to flocculation (Chapters 3 and 7).
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