| Abstract
| - To prepare composite films from biopolymers with anti-listerial activity and moisture barrier properties,the antimicrobial efficiency of chitosan−hydroxy propyl methyl cellulose (HPMC) films, chitosan−HPMC films associated with lipid, and chitosan−HPMC films chemically modified by cross-linkingwere evaluated. In addition, the physicochemical properties of composite films were evaluated todetermine their potential for food applications. The incorporation of stearic acid into the compositechitosan−HPMC film formulation decreased water sensitivity such as initial solubility in water andwater drop angle. Thus, cross-linking of composite chitosan−HPMC, using citric acid as the cross-linking agent, led to a 40% reduction in solubility in water. The water vapor transfer rate of HPMCfilm, ∼270 g·m-2·day-1·atm-1, was improved by incorporating chitosan and was further reduced 40%by the addition of stearic acid and/or cross-linking. Anti-listerial activity of films was determined onsolid medium by a numeration technique. Chitosan−HPMC-based films, with and without stearicacid, inhibited the growth of Listeria monocytogenes completely. On the other hand, a loss ofantimicrobial activity after chemical cross-linking modification was observed. FTIR and 13C NMRanalyses were then conducted in order to study a potential chemical modification of biopolymerssuch as a chemical reaction with the amino group of chitosan. To complete the study, the mechanicalproperties of composite films were determined from tensile strength assays. Keywords: Antimicrobial films; chitosan; cellulose derivatives; L. monocytogenes; cross-linking
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