Coalescence in Highly Concentrated Coarse Emulsions

Abstract

This study was focused on coalescence in highly concentrated emulsions stabilized by a whey protein isolate or by sodium dodecyl sulfate. For both stabilizers, coalescence of the emulsion at rest occurred below a critical concentration of the stabilizer. This concentration was related to full coverage of the droplet interface. Coalescence proceeded until the internal area of the emulsion was sufficiently reduced to obtain full coverage by the stabilizer. Above the critical stabilizer concentration, this mechanism of coalescence was almost completely inhibited. Coalescence could also be induced by subjecting the emulsion to external forces that made the emulsion flow. Coalescence induced by flow occurred much more readily for the protein-stabilized emulsion than for the surfactant-stabilized emulsion and also occurred above the critical stabilizer concentration. This demonstrated that coalescence induced by flow and coalescence at rest proceeded through different mechanisms.

Coalescence stability of emulsions containing globular milk proteins

“…Various experimental studies have shown that at low surfactant concentrations (in the so-called "surfactant-poor" regime [63]), the mean drop size rapidly decreases with the increase of the initial emulsifier concentration [4][5][6][7][8]63,64]. In contrast, at high surfactant concentrations (in the surfactant-rich regime), the mean drop size is independent of surfactant concentration.…”

“…At the same time, the adsorption may also increase with the emulsifier concentration [7,8,[84][85][86][87]. For this reason, the relative contributions of the effects of emulsifier adsorption and drop size on emulsion stability cannot be easily separated [64,83,87].…”

Crude Oil Emulsion Properties and Their Application to Heavy Oil Transportation

“…Concentrated protein emulsions are stable upon compression, but can collapse under the application of small shears, ultimately because of the fracture of the surface layers [23]. It is often stated and observed that protein-surfactant mixtures give more stable emulsions than proteins alone.…”

Effects of high pressure on functionality of whey protein concentrate and whey protein isolate

“…This general observation is quite consistent with the measured oil droplet range (for emulsions prepared with control WPC oil droplet diameter was in the range of 0.38-0.56 µm, while for emulsions stabilised with control WPI oil droplet diameter was in the range of 0.25-0.35 µm), since emulsions with smaller oil droplet size should be more stable than those with larger droplets. Generally speaking, emulsions that are stabilised solely by protein are very stable to coalescence, provided sufficient protein is available to fully cover the droplet surface [46]. The most important single property of a protein-stabilised emulsion is the maintenance of emulsion throughout the storage period of the product.…”