Coalescence Mechanisms in Protein-Stabilized Emulsions

Abstract

Coalescence of emulsified oil may be defined as any physical process that leads to the merging of the oil droplets into a larger droplet. Coalescence is desired in some cases—for example, during butter manufacture, where churning of cream leads to the separation of butter granules through a phase-inversion process that involves coalescence of milk fat globules (1). Another example is during whipping of cream (2), where coalescence leads to the formation of a network of partially coalesced fat globules, which stabilizes the air bubbles in the cream (1,3). A final example is a limited amount of coalescence in the mouth, which may lead to the release of some oil that may coat the oral tissues and provide oily lubriciy (4) and enhance the release of fat-soluble flavours (5). However, usually coalescence is undesired, such as during emulsion formation by homogenisation, where the occurrence of coalescence of newly formed droplets reduces the efficiency of the homogenizer (6), and during storage, where coalescence leads to the formation of larger droplets with an increased creaming rate or even a visible oil layer on top of the emulsion.