An emulsion is a mixture of two fluids such as oil and water that is achieved by breaking up the molecules in both substances into very fine, small droplets in order to keep the combination from separating. In the August issue of Food Technology magazine published by the Institute of Food Technologists (IFT) Contributing Editor, J. Peter Clark breaks down what emulsifiers are and how they are used in familiar foods.
There are several common foods that are considered emulsions: milk, margarine, ice cream, mayonnaise, salad dressings, sausages, and sauces like béarnaise and hollandaise. When packaged and manufactured on a larger scale, most of these foods need emulsifiers to stabilize the mixture and keep the different ingredients from becoming separated. Lecithin is a common emulsifier that is naturally found in soy oil. Egg yolks are another example of an emulsifier; they contain lecithin and cholesterol, which makes them a great binder for sauces like mayonnaise.
The way emulsifiers work is by coating the molecules of a certain fluid, making it easier to mix with the other ingredients, and also keeping the mixture together over a longer period of time without separating. In the kitchen this can be achieved by vigorous beating or whisking, or using a hand mixer. Using an emulsifier correctly in a sauce or mixture requires adding the ingredients in the proper order, and often at a specific temperature.
Other common emulsifiers in foods include proteins, gums, and various fatty acids. The same elements that are often good emulsifiers also are used in other ways in foods, such as keeping bread from going stale, reducing the amount of cocoa butter in chocolate which also reduces calories, and can help cakes stick less to the side of the pan.