Study of effect of oregano essential oil and ethanolic extract of propolis on antibacterial properties and some physical characteristics of biodegradable poly-lactic acid films

Natural antimicrobial compounds have a valuable capacity to be used in a variety of foods to inhibit growth of foodborne pathogens and spoilage bacteria. The aims of this study were to produce active biodegradable films by incorporation of different percentage of oregano essential oil (OEO) and ethanolic extract of propolis (EEP) into poly-lactic acid (PLA) films, and to evaluate physical and antimicrobial properties of the resulting films.
The active films were produced by solvent casting method, and their thickness and major color parameters were measured using a digital micrometer and a colorimeter instrument, respectively. Afterwards, antibacterial effects of the films were assessed against four common foodborne pathogens, including Staphylococcus aureus, Escherichia coli, Vibrio parahaemolyticus and Listeria monocytogenes, by means of disk diffusion test.
Physical examinations showed that thickness of resultant films significantly was increased (p Based on the findings of this study, the presence of just EEP in the initial formulation of poly-lactic acid films was not effective against the four tested foodborne pathogens, while the addition of this compound to the films containing OEO increased the effective antibacterial properties of the resulting films. As a result, the simultaneous use of these two compounds in the structure of hydrophobic films, such as poly-lactic acid film, can be used to produce active food packaging films.