Physicochemical Aspects of an Emulsifier Functionality
The characteristic property of all emulsifiers is their surface activity. Surface activity is the ability to form a surface excess at interfaces. The formation of adsorbed layers at interfaces are displayed in a change of a range of easily observable and technically important properties.
The surface tension is reduced.
The lifetimes of bubbles are increased. (Only very pure water displays a very short lifetime, a few seconds, of bubbles created by shaking. Normal standard “pure water,” double distilled, usually displays a bubble lifetime of about 20–30 s.)
The emulsifiability of oils in water is enhanced. Smaller drops with a longer lifetime are formed with less stirring.
The aggregation rate of dispersed particles is changed. Surface-active additives may induce or prevent flocculation of disperions.
The sediment volume of settling particles is influenced. Surface additives inducing adhesive may create a loose or compact sediment.
Crystallization properties are changed. This may include crystallization rate and crystal shape.
This chapter aims to discuss the principal physical origin of the various functionalities of typical lipid food emulsifiers. Aspects on the functionality under very different conditions in various foods will be discussed. I will try to show how we may select emulsifiers on the basis of their fundamental properties.
KeywordsInterfacial Tension Emulsion Droplet Lamellar Phase Soybean Lecithin Food Emulsifier
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