Abstract:

The effect of ionic strength on the chain conformations of high (712.6 kD), medium (205.8 kD) and low (76.4 kD)
molecular weight chitosan was studied by intrinsic viscosity and static light scattering. Our results showed that the intrinsic
viscosities and mean square radiuses of the three samples decreased with increasing ionic strength. The chain stiffness of
chitosan became weak as the molecular weight increased. With an increase in ionic strength, the protonated amino groups
of chitosan chains were gradually screened by counter ions, which might account for the decrease in intrinsic viscosity and
mean square radius of gyration. This study indicated that the thickening effect of chitosan could be regulated by changing its
chain conformation through the adjustment of environment factors, which would be helpful for its application as a thickener
in food systems.

Key words: chitosan, ionic strength, chain stiffness, mean square radius of gyration, Zeta potential