Physicochemical and antimicrobial properties of cassava starch films with ferulic or cinnamic acid

Plasticised cassava starch films with 1–2% ferulic or cinnamic acid were obtained by melt blending and compression moulding. Partial losses (about 40%) of the more thermo-sensitive ferulic acid occurred during processing. Incorporation of phenolic acids did not provoke remarkable changes in the oxygen and water vapour permeability of starch films, but these became less water soluble (13–25% reduction), more extensible and less resistant to break, especially with the highest concentration of ferulic acid. Films with 2% of either acid effectively inhibited the growth of E. coli and L. innocua in tests carried out in culture medium; being cinnamic acid more effective than ferulic and L. innocua more sensitive than E. coli; a Log CFU reduction, with respect to the control, higher than 6 was obtained for L. innocua with 2% of cinnamic acid in the films. The growth of both strains was also inhibited in chicken breast (log CFU reduction>2) with 2% of either acid. In fresh-cut melon, the L. innocua growth was significantly inhibited by films with 2% cinnamic acid, but lower growth inhibition of E. coli in fresh-cut melon was observed.