Iranian Journal of

Background and Objective: 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. 
Materials and Methods: 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.
Results: Physical examinations showed that thickness of resultant films significantly was increased (p<0.05) by addition of different concentrations of active agents. Additionally, the presence of them in the structure of films decreased the lightness and increased the redness and yellowness, simultaneously.  While none of the neat PLA film or films with just EEP had no antibacterial effect, all films containing higher percentages of OEO (5 and 10%) were effective against all four tested bacterial strains, and these effects were more significant in case of the gram-positive bacteria. The maximum inhibition zone was recorded for the film containing 10% of OEO and 2% of EEP, which the relevant values were 56.66, 45.46, 17.91 and 17.65 mm for Staphylococcus aureus, Listeria monocytogenes, Vibrio parahaemolyticus and Escherichia coli, respectively.
Conclusion: 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.
 

Background and Objective: Nowadays, the application of procedures to minimize oxidative and microbial spoilage in marine products is economically and hygienically important. This study was performed to determine the effect of free and nanoliposome forms of poneh (Mentha pulegium L.) essential oil to increase the shelf life and improve the sensory characteristics of silver carp minced fish (Hypophthalmichthys molitrix) during storage time.
Materials and Methods: In this study, the antibacterial properties of 1 and 2% essential oil and nanoliposomes form on the microbial population of minced silver carp fish inoculated with Bacillus cereus and Escherichia coli were measured. Also, chemical tests (DPPH (2,2-Diphenyl-1-picrylhydrazyl assay, measurement of iodine peroxide (PV), pH, total volatile nitrogen (TVB-N) and thiobarbituric acid (TBARs)) and sensory properties of minced silver carp were evaluated during 12 days of refrigerated storage.
Results: The results showed that the addition of poneh essential oil (free and nanoliposomes) according to the microbial results and the results of chemical experiments can effectively prevent microbial growth and chemical spoilage (p<0.05). Treatment containing 2% nano essential oil of poneh showed the greatest effect on the chemical, microbial and sensory properties of minced fish during the experimental period in comparison with control treatments, 1% poneh nanoliposomes essential oil and 2 and 1% free essential oils.
Conclusion: Therefore, the nanoliposomes form of 2% poneh essential oil can be used as a suitable additive to increase the shelf life of Silver carp fish in the fish industry.