Chitin is a naturally occurring polymer. It is found in crustaceans, mollusks, marine benthic organisms and krill fish. Chitin is also present in some fungi. The commercial utility of chitin and chitosans is well defined in prior art patents and other literature.
Extraction of chitin and chitosans is generally through a process of grinding and demineralization with different acid solutions, such as hydrochloric, sulfurous and acetic acids.
Derivatives of chitin, such as chitin sulfate, chitin xanthate and cyanoethylated chitosans have been prepared for use for a broad range of applications ranging from adsorbers to wound healing.
The present invention involves the separation of the protein fraction from the natural (active) chitin fraction of selected shellfish wastes in a sequence of drying, crushing, grinding, air classifying and screening operations, all mechanical steps, carried out without chemicals. The chemical processes of the known prior art are more expensive and more complicated and less easy to control.
The shellfish waste material from crabs, lobsters, shrimps, crayfish, king crabs, etc. obtained from a shellfish meat packing plant is dried to a suitable moisture content in a dried, such as a tray drier, rotary drier or fluid bed drier. The dried material is then ground in a ball, hammer or blade mill into groups of particle sizes that range between 10 microns and 400 microns. The grinding process fractures the dried waste material and results in fractionating the protein, chitin and calcium base materials. The ground fractionated material is then subjected to air classification. In this process, the lighter fraction blown from the top of the air classifier consists mainly of active chitin and some calcium salts. The heavier fraction falling to the bottom of the air classifier consists mainly of protein and calcium salts. The top fraction can be further subjected to screening to eliminate most of the calcium salts from the active chitin. Since the recovered chitin is produced in an essentially mechanical process without relying on chemicals, there are no chemical residues in the material which is essentially natural or active.
The differences between mechanically processed protein and active chitin and chemically prepared protein and chitin include the following. The chemically obtained chitin, during acid degradation, has some of its properties modified permanently. Such properties include optical activity, solubility, molecular weight, and conformation. There is also a degradation of some of the associated carotenoid pigments, viz. astaxanthin and astaxanthin ester.
Active chitin obtained by the mechanical process will retain the unique properties of the natural material including optical activity, molecular weight, acetyl values and molecular configuration. Chitin in its natural form consists of multiple units of .beta. glycosidic linkages and is naturally levorotatory. Also, active chitin has different biological activity from that which is produced from customary chemical treatments. These factors combine to make the natural product produced by the invention more useful for such things as chelation, flocculation, co-ordination, etc.
In addition to retaining all of the natural properties of chitin, the protein recovered by mechanical separation still contains the carotenoid pigments, astaxanthin and astaxanthin ester and the removal of some of its calcium salts along with chitin improves its carbon to nitrogen ratio and thus its food value. These properties make for a better quality and enhanced protein meal in comparison to the meal customarily produced from drying and direct grinding of shellfish wastes.
The recovered active chitin should serve as a better performing and more cost effective starting material for the manufacture of chemically produced chitin and chitosans, such as for biomedical applications, than the ground raw waste material presently used for chemically producing chitin and chitosans.