Preparation of chitin and chitosan oligomers amd their applications in physiological functional foods

Chitin and chitosan are known to possess multiple functional properties. Ch itin is insoluble in any common solvent containing organic or mineral acid as well as water. Chitosan is water-insoluble and highly viscous in dilute acidic solutions. These solubility problems may restrict their use in physi ological functional foods. However, chitin and chitosan oligomers are not o nly water-soluble and their solutions have low viscosity values, but they m ay also be absorbed in the human intestine. They may have much physiologica l functionality in the in vivo systems. This review demonstrates that chiti n and chitosan oligomers can be prepared by chemical and enzymatic hydrolys es and that the oligomers with high degrees of polymerization, especially t hose with six residues or more, show strong physiological activities.