Several studies have focused on the characterization of different fish collagens. Most fish collagens
consist of two α-chain variants, which are normally known as α1 and α2. In addition to differences in molecular
types, fish collagens have been shown to vary widely in their amino acid composition. In particular, the
physical properties of the protein and the quantity of the amino acids, proline and hydroxyproline, vary
significantly among fish species, and this is strictly correlated with the outside temperature of the animal’s
environment [8, 9].