Current knowledge in the stabilization/destabilization of infant formula emulsions during processing as affected by formulations

Almost 60% of the infants are relying on infant formulas (IFs) in the world. There remain large differences in the fat composition and structure between IFs and breast milk, which significantly affects the gastrointestinal fate and biological functions of milk fat.This review mainly covers the recent progress and trends in emulsifying ingredients for the stabilization of IF emulsions. Depending on formulations, fat in IFs is stabilized with various emulsifying ingredients including milk proteins, plant proteins, protein hydrolysates, milk fat globule membrane (MFGM) enriched materials and commercial emulsifiers. The interfacial properties of each emulsifier and their interactions in different combinations at interface and in bulk were thoroughly discussed versus the interfacial structure, physicochemical stability and technological properties of IF emulsions under various processing conditions.Destabilization of IF emulsions during processing (high-pressure homogenization, heat treatment, spray-drying, salt supplementation and pH adjustment) mainly included creaming, coalescence, flocculation and coagulation which significantly affected the powder quality of spray-dried IFs and the physical stability of liquid formulas. The stability of IF emulsions was mainly determined by the intermolecular interactions at interfaces and in bulk plus the inter-droplet interactions and interface-bulk exchange which were closely related to the physicochemical properties (including multicomponent composition, solubility, charge and surface hydrophobicity) of emulsifying ingredients in different formulations. Limited/selective hydrolysis and protein blends could effectively improve the performance of plant proteins in IFs. Of note: bio-functional MFGM materials are promising emulsifying ingredients to improve the lipid composition and structure of IFs.