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

Chitin and chitosan are known to possess multiple functional properties. Chitin 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 physiological functional foods. However, chitin and chitosan oligomers are not only water-soluble and their solutions have low viscosity values, but they may also be absorbed in the human intestine. They may have much physiological functionality in the in vivo systems. This review demonstrates that chitin and chitosan oligomers can be prepared by chemical and enzymatic hydrolyses and that the oligomers with high degrees of polymerization, especially those with six residues or more, show strong physiological activities.