Peptide/protein hydrolysate and their derivatives: Their role as emulsifying agents for enhancement of physical and oxidative stability of emulsions

Studies on peptide-based emulsifiers in the field of foods have progressed rapidly in the last decade, due to the higher anti-oxidative activity, faster adsorption to the interfaces, reduced allergenicity and higher nutritional values, compared to proteins used as emulsifiers. Peptides therefore have the potential for broader applications in emulsion-based foods. This paper provides an update on the current knowledge of the surface behavior of surface-active peptides and peptide assemblies. Factors affecting physical and oxidative stability of peptide-stabilized emulsions and the fabrication and utilization of peptide-associated conjugates in emulsions have also been summarized. The potential applications of peptide-stabilized emulsions in the food industry are finally discussed. Peptides with different primary and secondary structures show different surface behavior. Surface-active peptides with facial amphiphilicity can orient horizontally at the interfaces, while those with half hydrophobic-half hydrophilic residues orient perpendicularly at the interfaces. In addition, peptide assemblies with supermolecular structures can embed in the oil-water interfaces. The long-chain peptides with molecular weights of higher than 5 kDa usually exhibit better emulsifying capacity than short-chain peptides, and many factors (e.g., pH, temperature and ionic strength) can influence the physical stability of peptide-stabilized emulsions. Moreover, the presence of peptides can improve the oxidative stability of emulsions by repulsing or chelating metals. The fabrication of peptides into conjugates with polysaccharides, flavonoids, or phenols can further improve their emulsifying capacity. Finally, peptide-stabilized emulsions have been reported to be used as encapsulation materials or stabilizers/antioxidants in real emulsion-based food systems. • Protein hydrolysis is the mostly used method to prepare emulsifying peptide. • Primary and secondary structures of peptide affect their orientation at interfaces. • Environmental conditions influence the physical and oxidative stability of peptide-stabilized emulsions. • The stability of peptide-stabilized emulsions can be improved by using peptide conjugates. • Peptide-based emulsions can be used in delivery systems and real food systems.