Physicochemical characteristics and functional properties of five commercially available chitins and five chitosans were investigated. Physicochemical characteristics (nitrogen, ash, degree of deacetylation, bulk density, and viscosity) differed with products. In functional properties, dye binding capacity differed depending on the products, although average binding capacity (63%) of chitosans was higher than that (54%) of chitins. Water binding capacity ranged from 381 to 673% for chitins and from 458 to 805% for chitosans. Fat binding capacities of chitins were mostly similar (316−320%) except for one product (563%), whereas chitosans showed dissimilar binding capacities from 314 to 535%. However, significant correlations were observed between water binding capacity and bulk density (r = −0.89, P < 0.01) and between fat binding capacity and viscosity (r = 0.72, P < 0.05) of chitin products. Both water and fat binding capacity of chitosan products were significantly correlated positively with ash (r = 0.81, 0.80) and negatively with bulk density (r = −0.98, −0.95). Emulsifying capacity of egg yolk increased by addition of chitosan compared with the control. No differences in emulsifying capacity of chitosan products were observed at each concentration tested. Keywords: Chitin; chitosan; physicochemical characteristics; functional properties

Deacetylation of chitin under autoclaving conditions (15 psi/121 degrees C) was evaluated for the preparation of chitosan under different NaOH concentrations and reaction times. Deacetylation was effectively achieved by treatment of chitin under elevated temperature and pressure with 45% NaOH for 30 min and a solids/solvent ratio of 1:15. Treated chitosan showed similar nitrogen content (7.42%), degree of deacetylation (90.4%), and molecular mass (1560 kDa) but significantly higher viscosity values (2025 cP) compared with those (7.40%, 87.6%, 1304 kDa, and 143 cP, respectively) of a commercial chitosan. Reduction of the solids/solvent ratio from 1:15 to 1:10 did not affect degree of deacetylation, viscosity, and molecular mass of chitosan.

Dye binding capacity of different commercial chitins was investigated with two commercial chitin products and two dyes (FD&C Red No. 3 and Yellow No. 5). Dye binding capacity of chitin increased with increasing dye concentrations and was dependent on the chitin products and the specific dyes used. A slight decrease in dye binding capacity was noted with reduction in chitin particle sizes. Within a pH range of 3−9, dye binding capacity was relatively stable. After 24 h of settling, no dye was released from dyed chitin at pH 2 and 3. Above this range, release of dye increased with pH, up to 1.1 and 5.8% of bound red and yellow dye, respectively, at pH 9. Dye release was less noticeable in 1 h of settling. Keywords: Chitin; dye; FD&C Red No. 3; FD&C Yellow No. 5