Coalescence is the process whereby two or more liquid droplets merge together to form a single larger droplet (Figure 7.16). It is the principal mechanism by which an emulsion moves toward its most thermodynamically stable state because it involves a decrease in the contact area between the oil and water phases (Section 7.2). Coalescence causes emulsion droplets to cream or sediment more rapidly because of the increase in their size. In oil-in-water
emulsions, coalescence eventually leads to the formation of a layer of oil on top of the material, which is referred to as oiling off. In water-in-oil emulsions, it leads to the accumulation of water at the bottom of the material. For these reasons, an understanding of the factors which influence coalescence is important to food manufacturers attempting to create products with extended shelf lives.
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