Formation of Emulsions

Emulsions are formed either by (1) beating/mixing a mixture, or by (2) the process of homogenization.

1. Beating/Mixing A classic example of food emulsion is the preparation of homemade mayonnaise. As an emulsion, mayonnaise consists of a liquid dispersed into another liquid, with emulsifiers added for stability.

Begin by mixing egg yolk, sugar, paprika and vinegar. These ingredients form the liquid phase of mayonnaise. To prepare the emulsion, add oil to the mixture drop by drop. Whether the emulsion becomes thick and white, or oily and yellow, will depend on the temperature of all the ingredients as well as the rate of mixing and dropping. A stable mixture will result in a thick, white emulsion, with emulsifiers surrounding each small drop of oil. The emulsifiers (comprised of egg yolk, paprika, vinegar and sugar) add a charged, protective layer due to their hydrophilic nature.

There are many other emulsions in foods. For example, through creaming and mixing, a shortened cake mixture disperses fat as a liquid emulsion; this dispersion is integral to the quality of the final product. As a general rule, the greater the emulsification (created by beating the batter), the finer the cake structure. Classic research on cake batter structure was conducted by Martha Jooste at Oregon State University. Click on the Research button for more information, or click on Continue.