**4.1 Chitosan bio-based films**

One of the properties of major importance of chitosan is its filmogenic capacity. The films can be prepared from moderately concentrated polymer solutions, in general at 3 % (w/w). Chitosan films possess acceptable mechanical and permeability properties, good adherence to different surfaces, are flexible, resistant to water and show excellent barrier properties against gases (O2, CO2, water vapor), that allows its application in the development of food packing materials (Agulló et al., 2004; Plascencia-Jatomea et al., 2010; Tharanathan et al., 2002).

There are different methods for the productions of chitosan films, as the evaporation of solvents (Casting) -the first developed and more used at present- and the extrusion with some polyesters, olefins or carbohydrates. The last one is the most used for the industrial production of polymeric materials (Bhattacharya et al., 2005; Pelissari et al., 2009). With regard to the edible covered films, these are obtained by direct application (spraying, immersion) of chitosan solutions on the food surface or in the medicine's tablets, forming a thin layer that covers and protects the product of the environment (Janjarasskul & Krochta, 2010). Nowadays, most of the films and chitosan composites are prepared by this method, changing the solvent and the component's concentration of the blends, according to the application. Recently, it has been reported that the electrospinning technique allows the preparation of ultrathin chitosan nanofibers with unusually high porosity in their nanometer scale architecture and large surface area (Chen, Z. et al., 2009; Martínez-Camacho et al., 2011; Ohkawa et al., 2004). As particular interests have been addressed in the tissue engineering, great efforts have been made to study electrospinning of biodegradable polymers (Schauer & Schiffman, 2008).

Due to its abundance in the nature and to its biocompatibility, chitosan is considered to be a promising polymer for the development of functional materials (Ohkawa et al., 2004; Westbroek et al., 2007). In contrast to other materials, it has been demonstrated that chitosan films possess antifungal properties (Martínez-Camacho et al., 2011; Plascencia-Jatomea et al., 2010), that make it a good alternative for food protection and food shelf life extension (Chien et al., 2007b; Chien et al., 2007a; Coma et al., 2003; El Ghaouth et al., 1992; Fornes et al., 2005; Li & Yu, 2001; No et al., 2007; Schnepf et al., 2000). In general terms, although the materials prepared with conventional synthetic polymers are functional, of easy production, and low cost, they hardly are degradable, which strongly impacts the environment (Tharanathan & Srinivasa, 2007). Nevertheless, the use of these biopolymers is limited due to problems related to its deficient mechanical properties (fragility, poor barriers against gases and moisture) and cost (De Azeredo, 2009).

The incorporation of natural compounds has allowed the appearance of new materials with good mechanical properties, which overcome those that possess the individual materials. Most of these films are prepared mainly thinking about its use as food packing and tissue engineering materials (Tharanathan & Srinivasa, 2007). Additionally, to improve chitosan blends elasticity a biodegradable materials might be added (Butler et al., 1996).

#### **4.2 Chitosan films and bio-plasticizer**

Plasticizers are additives used to increase the flexibility or plasticity of polymers (Daniels, 1989). The most studied plasticizing agent in chitosan films has been glycerol and polyols and its efficacy in improving the properties of films has been well-documented (Table 4).


Table 4. Plasticizer effect on the properties of chitosan films.

Recently, the potential action of acid soluble collagen from jumbo squid (ASC) as a plasticizer in chitosan films was evaluated (Uriarte-Montoya et al., 2010; Arias-Moscoso et al., 2011). In general, the use of acid soluble collagen from jumbo squid by-products, in amounts equal or lower than 50 % in the production of chitosan biocomposites, produces films with reasonable tensile properties (Arias-Moscoso et al., 2011). More details about it will discuss in the following subsections.
