Formation, Structure, and Functionality of Interfacial Layers in Food Emulsions

Emulsions, i.e., the dispersion of liquid droplets in a nonmiscible liquid phase, are overwhelmingly present in food products. In such systems, both liquid phases (generally, oil and water) are separated by a narrow region, the oil-water interface. Despite the fact that this interface is very thin (in the nanometer range), it represents a large surface area and controls to a great extent the physicochemical stability of emulsions. This review provides an overview of the aspects that govern the composition, structure, and mechanical properties of interfaces in food emulsions, taking into account the complexity of such systems (presence of numerous surface-active molecules, influence of processing steps, and dynamic evolution due to chemical changes). We also review methods that have conventionally, or recently, been used to study liquid-liquid interfaces at various scales. Finally, we focus on the link between interfacial properties and the physical, chemical, and digestive stability of emulsions at different levels and point out trends to control stability via interfacial engineering.