Fish milt and roe-derived functional proteins and peptides: composition, bioactivities, and applications

An expanding list of marine species has been identified and evaluated for their potential bioactivity and nutritional values. Most attention is directed toward utilising protein-rich by-products of fish processing for their bioactive functionalities, which can aid in minimising waste and add value to underutilised resources. Milt and roe, the reproductive constituents of fish, are known to contain a high concentration of nutritional content. Bioactive peptides derived from these constituents have shown several biological activities including antihypertensive, antibacterial, anticoagulant, anti-inflammatory, anti-obesity, anti-cancer, and antioxidant activities. These peptides are commonly extracted by enzymatic hydrolysis and purified by different chromatographic methods according to their mass, molecular size, and composition. This review discusses the approaches to produce, purify, and characterise the protein hydrolysates from fish milt and roe and delves into the compositions of the nutraceutical compounds derived from milt and roe. The review also highlights the bioactive properties of the milt and roe-derived peptides that can have potential applications in the food, nutraceutical, pharmaceutical, and cosmeceutical industries.