Chemical Modifications of Peptides and Their Impact on Food Properties (original) (raw)

|Chem. Rev. 2011, 111, 7876-7903 Chemical Reviews REVIEW free amino group positioned on the left. 2 The amino acids of the chain ends are denoted as N-terminal and C-terminal amino acids. This notation will also be used throughout this review. In addition, chirality of the molecules is not represented in the schemes and figures because, first, in many cases the chirality of the starting products was not specified in the corresponding publications and, second, the chirality of the starting products might not be conserved due to high processing temperatures. Because of the rather innovativeness of the subject, this review mainly covers literature from the last two decades. 2. IMPORTANCE OF PEPTIDES IN FOOD Initially, the discovery of oligopeptides as products of protein hydrolysis did not draw much attention. However, nowadays, peptides are highly valued in food because they influence the functional properties, affect the product taste, and exhibit biological activity. 1 Functional properties of peptides include solubilizing, emulsifying, gelling, and foaming properties. 5 Concerning taste properties, bitter-tasting peptides are described most extensively, while in fact, peptides may reveal all kinds of taste. Sweet, sour, salty, and umami tastes have also been reported. 1,5,6 Besides these five basic tastes, Japanese distinguish "kokumi", which has been described as continuity, mounthfulness, and thickness of taste. According to Ueda et al., 7 the peptide glutathione increases the kokumi flavor of umami solutions and a model beef extract. In addition, interaction of these different tastes can result in the formation of typical food flavors. For instance, the dry-cured ham flavor is very characteristic and, besides volatile compounds and amino acids, also peptides have been shown to contribute to this specific flavor. 8À10 The biological activity of peptides has been the subject of many studies, which have been compiled in multiple reviews. Biological activities include antimicrobial, 3,5,11,12 antioxidant, 3,12À15 antihypertensive (angiotensin converting enzyme [ACE] inhibitory), 3,12,13,16 antithrombotic, 3,13 hypocholesterolemic and hypotriglyceridemic, 3,13 antiobesity, 13 opioid agonist or antagonist, 3,5,12 immunomodulating, 3,5,12 cytomodulating, 3 mineral sequestering, 3,12 cytotoxic, 4 and allergenic 4,5 properties. Some peptides are multifunctional and can exert more than one of the effects mentioned. 3,13 Although most of the food peptides are degraded by the host during ingestion, digestion, and absorption, Sato et al. 17 demonstrated that some unmodified food-derived peptides are present in human blood.