Chitosan formed covalent complex with chlorogenic acid (CA).
Chitosan–CA covalent complex had as high as 276.5 ± 6.2 mg CA/g complex.
Covalent complexation induced a larger change of physical structure.
Chitosan–CA covalent complex was more thermally stable in terms of antioxidant activity.
The viscosity of chitosan was significantly increased by covalent modification.