Characterization of the physical properties and biological activity of chitosan films grafted with gallic acid and caffeic acid: A comparison study

In this study, chitosan (CS) was grafted with phenolic acids including gallic acid (GA-g-CS) and caffeic acid (CA-g-CS) through carbodiimide coupling. The conjugates were further developed into films by casting and were characterized in terms of appearance, structure, and mechanical and barrier properties, as well as antioxidant and antimicrobial activities; the purpose was to evaluate their potential application in food packaging. The results showed that the CA-g-CS film exhibited the highest tensile strength (10.67 +/- 0.47 MPa) and elongation at break and had desirable barrier properties against water vapour (0.70 +/- 0.02 g mm/m(2)h kPa) and oxygen (37.72 +/- 0.23 meq/kg). In addition, both the GA-g-CS and CA-g-CS films displayed higher antioxidant activity than the CS films, while CA-g-CS also exhibited a significantly stronger (p < 0.05) inhibitory effect on Bacillus subtilis (G(+)) and Staphylococcus aureus (G(+)). These findings will contribute to a theoretical basis for the development of the CA-g-CS film into food packaging.