Alkali- or acid-induced changes in structure, moisture absorption ability and deacetylating reaction of 13-chitin extracted from jumbo squid (Dosidicus gigas) pens

Alkali- or acid-induced structural modifications in beta-chitin from squid (Dosidicus gigas, d'Orbigny, 1835) pens and their moisture absorption ability (MM) and deacetylating reaction were investigated and compared with alpha-chitin from shrimp shells. beta-Chitin was converted into the alpha-form after 3 h in 40% NaOH or 1-3 h-in 40% HCl solution, and alpha-chitin obtained from NaOH treatment had higher MM than had native alpha-chitin, due to polymorphic destructions. In contrast, induced beta-chitin from acid treatment of beta-chitin had few polymorphic modifications, showing no significant change (P > 0.05) in MM. beta-Chitin was more susceptible to alkali deacetylation than was alpha-chitin, and required a lower concentration of NaOH and shorter reaction time. These results demonstrate that alkali- or acid-treated beta-chitin retained high susceptibility toward solvents, which in turn resulted in good biological activity of beta-chitosan for use as a natural antioxidant and antimicrobial substance or application as edible coatings and films for various food applications. Published by Elsevier Ltd.