Biodegradable films based on thermoplastic starch and chitosan with antimicrobial activity employed as active packaging

One of the research lines related to active packaging takes into account the incorporation of antimicrobial agents such as chitosan, a polysaccharide derived from the crustaceans' exoskeleton. However, because of chitosan high molar mass, its diffusion from the package to the food surface is restricted, so the use of oligomers is an interesting but less investigated alternative. The purpose of this work was to obtain active films based on thermoplastic corn starch (TPS) by adding oligochitosans (OC, molar mass = 290 g mol(-1) and degree of polimerization = 2). Films were thermo-compressed in a hydraulic press. Diffusion assays of OC from TPS matrix to liquid medium with different acidity degree (pH = 3, 5, and 7) were performed. Liquid medium conditions were selected according to the acidity of a wide variety of foods. From these assays, oligomers diffusion capacity and the dependence with pH were demonstrated. The efficiency of OC incorporation in packaging material was compared to the corresponding to the conventional method by food spray with a solution of the active agent. The antimicrobial capacity of films and OC solutions was evaluated from the count of yeasts and molds, using fresh strawberries as food product. Obtained results from these experiments showed the active character of films based on TPS and OC, and a greater efficiency of antimicrobial active packaging compared to the conventional methods.