Improved functionality and safety of peptides by the formation of peptide-polyphenol complexes

Peptides exhibit various functional properties and bioactivities, and have been widely investigated and used in food area. However, using peptides alone may show some drawbacks, such as the undesirable stability of peptide-stabilized emulsions during storage, and the diminished bioactivities and the occurrence of peptide-induced celiac disease during digestion. The addition of polyphenols may help to solve above issues by the formation of peptide-polyphenol complexes. This paper provides a comprehensive review of covalent and non-covalent interactions between peptides and polyphenols. The influence of such interactions in bioactivity, antimicrobial property, sensitivity (i.e., causing celiac disease), and emulsifying property of peptides is also discussed. Hydrophobic interactions, hydrogen bonds, electrostatic interaction, and van der Waals interactions are the main non-covalent bondings involving in the formation of peptide-polyphenol complexes. The properties of peptides and polyphenols, the ratio of peptide/polyphenol, and the environmental conditions are the main factors influencing such non-covalent interactions. Oxidized peptides or reactive peptide radicals can also interact with polyphenols trough covalent interactions, and the properties of peptides and polyphenols can influence these interactions. In addition, the presence of polyphenols in peptide-polyphenol complexes can show synergetic or subtractive effect on bioactive peptides through various mechanisms. In contrary, the inhibiting effect of polyphenols on the digestion, absorption and recognition of peptides can help to improve the safety of celiac disease-related peptides. Moreover, the formation of peptide-polyphenol complexes can also improve the physical and oxidative stability of peptide-stabilized emulsions.