Emulsions are smooth mixtures of water and oils, so emulsifier molecules need to have parts that attract water and other parts that attract oils. Different emulsifiers have different molecular structures, and therefore are highly targeted for specific applications.

Emulsifiers also have other important functions in food. They interact with fats, modifying their crystal structure and reducing viscosity in chocolate, or increase the amount of air in products such as whipped cream. They interact with starch to reduce stickiness, for example in potato granules, and also make bread go hard and stale more slowly. They also interact with gluten, improving the baking quality of wheat flour, giving packed goods a better texture and volume.