Physical and antimicrobial properties of chitosan film containing cinnamaldehyde

Abstract

This research aims to produce antimicrobial film by incorporating cinnamaldehyde into chitosan film. The films were prepared by dissolving chitosan powder (95% degree of deacetylation) into 1 %v/v acetic or lactic acid solution and blending with glycerol or sorbitol at different concentration (20, 40 and 60 %w/w of chitosan powder) as plasticizer. Physical properties including thickness, tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP) surface color and transparency were examined. Films from acetic acid and lactic acid solution showed similar visual appearance. However, chitosan film-forming solution from lactic acid was difficult to form into film, especially when the plasticizers were added, and thus physical property measurements were not possible. The results showed that an increase in amount of the plasticizers resulted in significant (p 0.05) increase in thickness, decrease in mechanical resistance (decrease in TS) and increase in extensibility (increase in EAB). TS decreased but EAB and WVP increased when the concentration of sorbitol and glycerol increased from 20 to 60 %w/w of chitosan powder. Moreover, film plasticized with sorbitol had lower WVP than those with glycerol at each concentration. The results suggested that 40 %w/w sorbitol was the optimum concentration of plasticizer for forming the chitosan film and thus used for further studies. In further studies, cinnamaldehyde was incorporated into chitosan film-forming solution (plasticized with sorbitol 40 % w/w) at different concentrations (50, 100 and 150 µl/g of chitosan powder). Addition of cinamaldehyde led to a significant increase in both TS and EAB, but a significant decrease in WVP of the films. Increasing of TS and EAB could be due to the interaction between fuctional group of chitosan and cinnamaldehyde. This could be proved by FT-IR spectra results. Antimicrobial property of chitosan film containing cinnamaldyhyde was tested against target microorganisms (S. aureus, B. lichenformis, B. subtilis, E. coli, P. aeruginosa and S. putrefaciens). The film was found to have small inhibition zone against S. aureus while inhibited other target microorganisms only on the contact surface. Addition of cinnamaldehyde could improve physical properties of chitosan film in terms of TS, EAB and WVP. However, only small amount can release from chitosan matrix due to the interaction between functional groups of chitosan and cinnamaldehyde.