Stability of chitosan powder during long-term storage at room temperature.

Physicochemical and functional properties of two chitosan products [low viscosity (LV) with 16.8 mPa s; high viscosity (HV) with 369.4 mPa s] were evaluated during 9-month storage at room temperature. As storage time increased, increased moisture content and DPPH radical scavenging activity and decreased viscosity and water binding capacity (WBC) were observed. The extent (%) of decreased viscosity and WBC and of increased DPPH radical scavenging activity during storage were more pronounced with the HV chitosan. Significant correlations were observed between WBC and viscosity (r = 0.88 for LV; r = 0.96 for HV) and between DPPH radical scavenging activity and viscosity (r = -0.79 for LV; r = -0.87 for HV). Although significant differences in L*a*b* values were observed during storage, color differences were not easily discerned visually. Antibacterial activity of the HV chitosan against two Gram-negative and two Gram-positive bacteria significantly increased with increasing storage time.