Mechanical and antimicrobial properties of corn starch-carboxymethyl cellulose films incorporated with Zataria multiflora and Rosmarinus officinalis

Edible films and coatings containing antimicrobial ingredients as a type of active packing mode help the improvement of food preservation during storage. In this paper, the mechanical and antimicrobial properties of the films made of corn starch and carboxymethyl cellulose (CMC) incorporated with Zataria multiflora and Rosemarinus officinalis(Rosemary) were studied. The films made of starch and CMC containing 0,0.1,0.3,0.5,1,3 and 5 percent of Zataria multiflora and Rosemary essential oils were produced by casting method. By examining the mechanical properties, it was demonstrated that young modulus(E), tensile strength(TS) and elongation at break(%EB) will be reduced by the increase of essential oils quantity (p<0.05). The antimicrobial effect of the films on two bacteria, Escherichia coli(ATCC 8739) and Staphylococcus aureus( ATCC 2538) was examined by Agar diffusion method. The results showed that the films containing Zataria multiflora essential oil by two level of concentration (3 and 5 percent) have good preventive impact on the bacterial growth. Zones of inhibition on the film containing 3% of Zataria multiflora is 32.76 mm for E.coli and 42.11 mm for St.aureus . The films were more active on gram positive bacteria than gram negative ones (p<0.05). However, the Rosemary essential oil used in the films showed no preventive effect in any concentration level.