Occurrence, properties and biological significance of pyroglutamyl peptides derived from different food sources

Pyroglutamyl (pGlu) peptides are formed from intramolecular cyclization of glutamine or glutamic acid residue at the N-terminal position of peptides. This process can occur endogenously or during processing of foods containing the peptides. Some factors such as heat, high pressure and enzymatic modifications contribute to pGlu formation. pGlu peptides are thought to have different characteristics, especially bitter and umani tastes, and thus can affect the sensory properties of foods that contain them. Moreover, some health-promoting properties have been reported for pGlu peptides, including hepatoprotective, antidepressant and anti-inflammatory activities. However, the role of pGlu residue in the peptide bioactivity is not completely established, although the hydrophobic γ-lactam ring is thought to enhance the peptide stability against degradation by gastrointestinal proteases. This review discusses the occurrence and formation of pGlu peptides in foods, their quantification, sensory and biological properties, and prospects in food applications