Separation of collagen from fish scales by treatment of dilute hydrochloric acid aqueous solution

Fish scales are mainly composed of collagen and hydroxyapatite (HAp). Since HAp is solubilized in a dil. hydrochloric acid aq. soln., crude collagen could be separated from carp (Cyprinus carpio Linnaeus) scales by a HCl treatment. The optimal conditions for the HCl treatment were examined and compared to those applied for sardine (Sardinops melanostictus Temminck et Schlegel) scales, reported previously. The utilization of the separated collagen is discussed on the basis of the contents of heavy metals in the ash obtained by asking of the scales at 1000°C. The determination of hydroxyproline, which is a kind of characteristic amino acid for collagen, and SDS-PAGE analysis show that the crude collagen obtained is Type-I collagen.