Phospholipids as natural emulsifiers in foods and beverages: Structure, interfacial properties, and applications

Lecithin is widely used in the food industry as a natural emulsifier, but its functional performance in foods and beverages is highly variable and strongly food-matrix dependent. This variability is mainly a result of the intrinsic molecular heterogeneity of industrial lecithin ingredients, and limited understanding of the link between phospholipid structure, food matrix effects, interfacial properties, and functional performance. In this review, we present a mechanism-driven framework that links phospholipid structure, interfacial behavior, and functional performance in a diverse range of food matrices. Initially, the main structural features of food-grade phospholipids are summarized, including their headgroup and tail group characteristics, as these determine their molecular geometry, packing, and self-assembly behavior. We then discuss how these molecular features influence adsorption kinetics, interfacial structure, interfacial rheology, and emulsion stability under processing-relevant conditions. Specifically, the impacts of changes in pH, ionic strength, temperature, and shearing on lecithin performance are reviewed. Lecithin performance is then evaluated in representative food applications, including colloidal delivery systems, beverages, chocolate, bakery products, and fat-structured foods. Overall, this review highlights the importance of establishing structure-function relationships for lecithin-based ingredients. This knowledge can then be used to rationally guide the design and production of robust, clean-label emulsified foods and beverages. In particular, products can be created with improved resistance to environmental stresses, as well as extended shelf lives and enhanced performances.