Emulsion partial coalescence

Emulsion Partial Coalescence and Structure Formation in Dairy Systems... 

Separation of two liquid phases, immiscible or partially miscible liquids, is a common requirement in the process industries. For example, in the unit operation of liquid-liquid extraction the liquid contacting step must be followed by a separation stage (Chapter 11, Section 11.16). It is also frequently necessary to separate small quantities of entrained water from process streams. The simplest form of equipment used to separate liquid phases is the gravity settling tank, the decanter. Various proprietary equipment is also used to promote coalescence and improve separation in difficult systems, or where emulsions are likely to form. Centrifugal separators are also used. 

A typical characteristic of many food products is that these are multi-phase products. The arrangement of the different phases leads to a microstructure that determines the properties of the product. Mayonnaise, for example, is an emulsion of about 80% oil in water, stabilized by egg yolk protein. The size of the oil droplets determines the rheology of the mayonnaise, and hence, the mouthfeel and the consumer liking. Ice cream is a product that consists of four phases. Figure 1 shows this structure schematically. Air bubbles are dispersed in a water matrix containing sugar molecules and ice crystals. The air bubbles are stabilized by partial coalesced fat droplets. The mouthfeel of ice cream is determined by a combination of the air bubble size, the fat droplet size and the ice crystal size. 

Altering the Ratio of Solvents Coalescence of an emulsion may also be achieved either by altering the ratio of the prevailing dispersed phase or even by partial evaporation of the solvent,... 

Partial Coalescence in Emulsions Comprising Partially Crystallized Droplets 167... 

K. Boode and P. Walstra Partial Coalescence in Oil-in-Water Emulsions 1 Nature of the Aggregation. Colloids and Surfaces A Physicochem. Eng. Aspects 81, 121 (1993). 

H. D. Goff Instability and Partial Coalescence in Whippable Dairy Emulsions. J. Dairy Sci. 80, 2620 (1997). 

Partial coalescence and phase inversion. Partial coalescence and phase inversion are additional mechanisms that can destabilize an emulsion (Dickinson, 1992 Friberg and Kars-son, 1997 McClements, 1999). Partial coalescence occurs when emulsion droplets are cooled below the melting point of the dispersed... 

Flocculation. Flocculation means an aggregation of emulsion droplets but, in contrast to coalescence, the films of the continuous phase between the droplets survive. Hence, the process may be partially reversible. Both processes, flocculation and coalescence, speed up the creaming of an emulsion due to the increase of the drop size. The process of flocculation is even more important for dispersions of solids than for emulsions because in this case a coalescence is not possible. 

Boode, K., Walstra, P. 1993. Partial coalescence of oil-in-water emulsions. 1. Nature of aggregation. Coll. Surf. A. 81, 121-137... 

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