Decoloration of chitosan by UV irradiation

Decoloration of chitosan by UV irradiation, which was used to replace a bleaching step during chitosan preparation, was evaluated under four separate treatments (effect of irradiation time, chitosan/water ratio, stirring speed, and UV light source). The optimal decoloration condition was defined as that producing white chitosan with higher viscosity. Decoloration of chitosan could be achieved effectively using a UV-C light by stirring unbleached chitosan in water (1:8, w/v) for 5 min at 120 rpm. UV irradiation applied under the optimal conditions could be used to produce chitosan with desirable white color (L∗ = 76.95, a∗ = −0.37, and b∗ = 14.04) and high viscosity (1301.7 mPa s at 0.5% w/v in 1.0% v/v acetic acid).