Valorisation of viscera from fish processing for food industry utilizations

Fish viscera is a valuable source of functional materials for the food industry, such as protein, oil, enzymes, protein hydrolysate, peptones, sterols, producing biodiesel, and other oleochemical industries. The major components of fish viscera are oil and protein, and their quantity depends on the fish habitats. Viscera oil from fish contains appreciable amounts of omega-3 fatty acids. The protein of fish viscera is a raw material for protein concentrates, hydrolysate, and bioactive peptides. All are valuable ingredients in food processing and product formulation. Most viscera are fish digestive tracts and organs responsible for producing enzymes, and several enzymes are found in high activity, such as lipases and proteases. The extraction of lipases and proteases from fish viscera and their utilizations have been intensively studied. Currently, the isolation of each major component from fish viscera is conducted separately. Therefore, it is challenging to obtain all valuable components from fish viscera to have a zero-waste process. This article reviews the separation of major components of fish viscera by conventional and emerging technology and the proposed simultaneous and integrative separation of all valuable major components.