Characterization of physical and antimicrobial properties of chitosan edible films containing Pistacia atlantica gum essence

The environmental effect of synthetic plastic wastes is of increasing global concern. There is an urgent need to develop and apply renewable biopolymer materials. Development of edible and biodegradable films can help solving the waste disposal problem by partially replacing synthetic plastics (Martins et al., 2012). Chitosan; a linear polysaccharide composed of (1, 4)-linked 2-amino-deoxy-b-d-glucan, is a deacetylated (to varying degrees) product of chitin, which is the second most abundant polymer found in nature after cellulose. It has been proved to be biodegradable, biofunctional, biocompatible, nontoxic and have strong antifungal and antimicrobial properties (Aider, 2010). Thus, this work was undertaken to investigate the physical, optical, barrier, mechanical, microstructural, and antimicrobial properties of chitosan films incorporated with PEO, to examine its potential applications as a packaging material.
The films were prepared according to the solvent casting technique reported by (Abdollahi et al., 2012) with some modifications. Tensile strenght (TS) and elongation at break (E) of the films were measured with texture analyzer according to Barzegar et al. (2014) method. Equilibrated film strips (at 53% RH for 48 h) were fixed between the grips with an initial separation of 50 mm and the cross-head speed was set at 50 mm/min. TS was calculated by dividing the maximum force by the initial area of the film and E% was calculated through dividing the extension at the moment of specimen rupture by the initial gauge length and multiplying by 100. The WVP of the films was determined at according to the Shojaee-Aliabadi et al. (2013). The test cups containing anhydrous calcium chloride (0% RH) were sealed by the test films, then were placed inside a desiccator containing sodium-chloride-saturated solution (75% RH). Weight gain of the cups along time were recorded periodically and plotted as a function of time. Antimicrobial properties of the films were assessed using the disc-diffusion method according to Dashipour et al. (2015). Four gram-positive or gram-negative bacteria, including B. cereus, S. aureus, E. coli and S. typhimurium were used for testing.
The influence of PEO incorporation on thickness, TS, EAB, WVP and water solubility of films can be seen in Table 1. The incorporation of PEO into the film-forming dispersion led to an increase in the thickness of the films, which varied between 0.131 mm and 0.185 mm. It could be due to the entrapment of PEO micro droplets by the polymer matrix (Dashipour et al. 2015). By increasing PEO concentration from 0.5 to 2 % in the film solutions, WS decreased markedly from 22.46 to 16.15 (P The results obtained in this study showed that the chitosan films incorporated with PEO has a good potential to being empolyed as an active film to preserve food products. Addition of PEO decreased water solubility and tensile strength, while increased the thickness, WVP and percent elongation of the films. Overall, this study demonstrates that PEO-containing films present a good potential for their application in the food industry.