Old products, new applications? Considering the multiple bioactivities of plastein in peptide-based functional food design

• Plastein is a high-molecular size protease-induced peptide aggregation product.
• Plastein reaction has resulted in enhancement of bioactivities of protein hydrolysates.
• Proposed peptide rearrangement in plastein can result in new bioactive sequences.
• Migration of hydrophobic peptides into plastein core can also mask peptide bitterness.
• Plastein is susceptible to endogenous proteolysis, limiting its use in functional food.

For over a century, plastein has remained mostly cryptic with inconclusive proof of their formation mechanisms. Although initial interest in the nutritional application of plastein decreased by the mid-1980s, the last decade has seen a reemergence of plastein as bioactive agents. It is thought that sequence variations due to protease-induced peptide modification during plastein formation are associated with the enhancement of bioactivities such as angiotensin converting enzyme inhibition (antihypertensive), calcium-chelating (anticoagulation), antioxidant and cytoprotective activities. Moreover, the clustering of hydrophobic residues during peptide aggregation has enabled exploration of plastein as peptide debittering agents, and as a bile acid sequestrant with potential endogenous cholesterol-reducing role. This article presents plastein from different perspectives with emphasis on their chemistry, bioactivity and prospective functional food applications.