Food protein-based nanoemulsions: A comprehensive review with an emphasis on strategies to facilitate the formation and stabilization

Nanoemulsions contain tiny droplets (d < 200nm) that endow them with better characteristics than macroemulsions such as higher physical stability, high optical clarity, and increased bioavailability of lipophilic components, therefore imparting them with promising applications in a variety of food, cosmetics, and pharmaceutical fields. Accumulating evidence indicates the great potential of many food proteins for the fabrication of food-grade nanoemulsions as replacements for synthetic surfactants. However, the effectiveness of proteins in the fabrication of nanoemulsions has not reached a consensus mainly because of their inferior emulsifying capacity than surfactants that would readily lead to large droplet size, droplet flocculation, even “over-processing” during high energy homogenization. Therefore, improvement of protein emulsifying performance would be a key to facilitate the formation and stabilization of nanoemulsions. In this review, recent advances in the formation and characteristics of protein-based nanoemulsions are summarized with a focus on their advantages and limitations. More emphasis is given to potential strategies to facilitate the formation and stabilization of protein-based nanoemulsions, including protein modification, complexation with polysaccharides, glycation, and incorporation of polyols, which can be beneficial for novel applications of protein-formulated nanoemulsions in the food and drug sectors. As food-grade nanoemulsions are appealing, this review is of crucial importance for guiding the development and application of food-grade nanoemulsions using proteins as natural emulsifiers.