Antimicrobial activity and physical properties of chitosan–tapioca starch based edible films and coatings María B. Vásconez a , Silvia K. Flores b,c , Carmen A. Campos b,c, * , Juan Alvarado a , Lía N. Gerschenson b,c a Facultad de Ciencia e Ingeniería en Alimentos, Universidad Técnica de Ambato, Casilla 18-01-0334, Ambato, Ecuador b Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Aires, Pabellón de Industrias, Ciudad Universitaria, (1428) Buenos Aires, Argentina c Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) de la República, Argentina article info Article history: Received 19 May 2008 Accepted 22 February 2009 Keywords: Chitosan Starch Edible films and coatings abstract Antimicrobial activity of edible coating solutions based on chitosan and blends of chitosan–tapioca starch with or without potassium sorbate (KS) addition was studied. The agar well diffusion assay showed an antagonist effect on the efficiency of chitosan against Lactobacillus spp. when KS and/or tapioca starch were present. A salmon slice coating assay showed that the chitosan solution was the best coating since aerobic mesophilic and psychrophilic cell counts were reduced, pH and weight loss remained acceptable throughout refrigerated storage, extending global quality to 6-days. Chitosan–tapioca starch based films reduced Zygosaccharomyces bailii external spoilage in a semisolid product but were not effective against Lactobacillus spp. The results suggest that antibacterial action depended on the application technique, due to the fact that chitosan is more available in a coating solution than in a film matrix. Interactions between chitosan–starch and/or KS could affect film physical properties and the antimicrobial activity of chitosan. The addition of chitosan reduced water vapor permeability and solubility of starch films. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Over the last few years, considerable research has been con- ducted to develop and apply bio-based polymers made from a vari- ety of agricultural commodities and/or wastes of food product industrialization. Such biopolymers include starches, cellulose derivatives, chitosan/chitin, gums, proteins (animal or plant-based) and lipids (Cutter, 2006; Guilbert & Biquet, 1996). These materials present the possibility of obtaining thin films and coatings to cover fresh or further processed foods to extend their shelf life (Baldwin, 1994). Edible films and coatings offer some advantages such as edibil- ity, biocompatibility, aesthetic appearance, barrier properties, being non-toxic, non-polluting and having low cost (Han, 2000; Kester & Fennema, 1986; Krochta, Baldwin, & Nísperos-Carriedo, 1994). In addition, biofilms and coatings, by themselves or acting as carriers of foods additives (i.e.: antioxidants, antimicrobials), have been particularly considered in food preservation because of their ability to extend the shelf life (Franssen & Krochta, 2003; Franssen, Rumsey, & Krochta, 2002; Greener Donhowe & Fennema, 1994; Guilbert & Biquet, 1996). Starch based films have been particularly considered for the reason that they exhibit physical characteristics similar to syn- thetic polymers: transparent, odorless, tasteless, semi-permeable to CO 2 and resistant to O 2 passage (Nísperos-Carriedo, 1994). Stud- ies about the production and application of edible starch based films incorporating preservatives have confirmed their availability of the latter to extend the shelf life of fresh and minimal processed vegetables (Durango, Soares, & Andrade, 2006; Garcia, Martino, & Zaritzky, 1998). According to the Food and Agriculture Organiza- tion (FAO, 2004), one important source of starch in South America is tapioca. Therefore, the use of tapioca starch to develop edible films and coatings has been considered (Famá, Rojas, Goyanes, & Gerschenson, 2005; Flores, Famá, Rojas, Goyanes, & Gerschenson, 2007). In order to improve the physical and functional properties of starch films, blending with other biopolymers, hydrophobic sub- stances and/or antimicrobial compounds has been proposed (An- ker, Berntsen, Hermansson, & Stading, 2001; Ayranci & Tunc, 2003; Flores, Haedo, Campos, & Gerschenson, 2007; Garcia, Marti- no, & Zaritzky, 2000). Chitosan is a natural carbohydrate polymer obtained by the deacetylation of chitin [poly-b-(1?4)-N-acetyl- D-glucosamine], a major component of shells of crustaceans such as crab, shrimp and crawfish. Its obtention is a way to profit from seafood wastes. Today, chitosan is produced with different deacetylation degrees and molecular weights (No, Meyers, Prin- yawiwatkui, & Xu, 2007). This biopolymer has revealed to be useful for several applications such as metal chelation in wastewater 0963-9969/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2009.02.026 * Corresponding author. Address: Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Aires, Pabellón de Industrias, Ciudad Universitaria, (1428) Buenos Aires, Argentina. Tel./fax: +54 1145763366. E-mail address: carmen@di.fcen.uba.ar (C.A. Campos). Food Research International 42 (2009) 762–769 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres