Antimicrobial activity of poly lactic acid films incorporated with Trachyspermum ammi essential oil and ethanolic extract of propolis on the growth of some bacterial foodborne pathogens

Background and Aim: Using active antimicrobial packaging reduce the risks of growth of pathogenic or spoilage microorganisms in foods. In this study, antimicrobial activity of poly lactic acid (PLA) films containing different concentrations (0, 0.5, 1 and 1.5%) of Trachyspermum ammi essential oil and ethanolic extract of propolis (0, 1 and 2%) was evaluated against Listeria monocytogenes, Staphylococcus aureus, Escherichia coli O157:H7 and vibrio parahaemolyticus by using disk diffusion assay. Materials and Methods: Circular discs of poly lactic acid films incorporated by essential oil and ethanolic extract of propolis, prepared by casting method on glass petri dishes, were placed on Muller-Hinton agar plates that previously inoculated by tested bacteria. Diameters of inhibition zones were measured after 24 h incubation of plates at 35o C, by using Digital Caliper and Digimizer software. Results: Result of this study showed that the inhibition zone was increased with increasing concentration of essential oil for all tested bacteria. Also, gram positive bacteria were more sensitive to the poly lactic acid films containing essential oil than gram negative bacteria. The results revealed that L. monocytogenes was the most sensitive bacteria against films containing Trachyspermum ammi essential oil alone or in combination by ethanolic extract of propolis. Also, poly lactic acid films containing ethanolic extract of propolis showed no inhibitory effects against all tested bacteria. Conclusions: Poly lactic acid films containing Trachyspermum ammi essential oil have a high potential for antimicrobial food packaging applications to enhance the safety of food products

Evaluation of the antimicrobial effect of chitosan and whey proteins isolate films containing free and nanoliposomal garlic essential oils against Listeria monocytegenes, E.coli O157:H7 and Staphylococcus aureus

Background and Aim: Active antimicrobial packaging is an innovative technique that can enhance safety and shelf life of foods. In this study antimicrobial activity of chitosan and whey protein isolate (WPI) films incorporated with free and nano-liposomal garlic essential oil was investigated against Listeria monocytogenes, Escherichia coli O157:H7 and Staphylococcus aureus. Materials and Methods: This study was done in 2015 and disk diffusion method was applied to determine antimicrobial effect of films. Films were cut into circular disks with 9 mm diameter and put on the inoculated BHI agar plates with tested microorganisms. Then plates incubated for 24 h at 37oC. The diameter of inhibition zone was measured by digital caliper. The statistical analysis was done by one-way analysis of variance (ANOVA) followed by Tukey's test. Results: The results of this study revealed pure chitosan and WPI films alone or incorporated with nano-liposomal garlic essential oil did not show any inhibitory effects on tested microorganisms. Incorporation of 2% or higher concentrations of garlic essential oil to the chitosan solution showed the antibacterial activity of films against all tested microorganisms, whereas when the WPI solution incorporated with 3% or higher concentrations of garlic essential oil the antibacterial activity films was seen against all tested microorganisms. Also the results revealed that S. aureus and L. monocytogenes were more sensitive to chitosan and WPI films incorporated with garlic essential oil. Conclusions: Our results declared that the films incorporated with garlic essential oil have the potential to be used as an active antimicrobial packaging