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Background: Food spoilage and foodborne diseases are two important problems in the food industry. On the other hand, consumers’ tendency to use natural additives is increasing. Hence, plant essential oils (EOs) can be safe alternatives in this regard. Objective: The objectives were to determine the chemical composition and to evaluate the antimicrobial activity of Cymbopogon citratus EO against some foodborne bacteria alone and in combination with Origanum majorana and Caryophyllus aromaticus EOs. Materials and Methods: Chemical composition of C. citratus EO was analyzed by gas chromatography-mass spectrometry. Further, antibacterial activity of the EO against foodborne bacteria was assessed using disk diffusion method. In addition, the minimum inhibitory concentration of the EO was determined by microdilution broth method and then the minimum bactericidal concentration value was determined. Checkerboard synergy testing was also performed to determine the fractional inhibitory concentration index. Finally, time-kill curves were drawn based on the bacterial population (CFU/mL) against time (h). Results: The major compounds of C. citratus EO were isothymol, thymol, trans-caryophyllene, and cymene. The most and the least sensitive foodborne bacteria to C. citratus EO were Staphylococcus aureus and Bacillus subtilis, respectively. The minimum inhibitory concentration (MIC) values of C. citratus EO against all the evaluated bacteria were 0.1% and The minimum bactericidal concentration (MBC) values ranged between 0.1 and >2% (v/v). The combination of C. citratus and O. majorana EOs showed a synergistic activity against Salmonella typhimurium and partial synergism against B. subtilis, Escherichia coli O157:H7, S. aureus, and Listeria monocytogenes. Moreover, the combination of C. citratus and C. aromaticus EOs demonstrated partial synergism against S. aureus and L. monocytogenes, and additive interaction against S. typhimurium; however, the combination was indifferent against E. coli O157:H7 and B. subtilis. Furthermore, C. citratus plus O. majorana EOs and C. citratus plus C. aromaticus EOs showed a bactericidal effect against S. typhimurium after 24 hours in the time-kill assay. Conclusion: In general, the synergism, partial synergism, and additive effects of C. citratus in combination with C. aromaticus and O. majorana EOs strengthen the antimicrobial activity, expand the spectrum of activity, reduce the concentrations required, decrease the side effects, and prevent the alteration of organoleptic properties of food.

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Background: Active packaging is one of the new packaging technologies which causes interaction between packaging material and food with the aim of food shelf life extension while maintaining food safety and quality. Biodegradable films like polylactic acid (PLA) can be good alternatives to non-biodegradable plastics because of environmental pollution and concerns about the limitations of petroleum resources. Objective: This study was conducted to evaluate the efficacy of PLA film incorporated with marjoram and clove essential oils (EOs) (0.5 and 1% v/v) in maintaining the microbial and chemical quality of minced beef during refrigerated storage. Materials and Methods: Minced beef was packaged with PLA film incorporated with marjoram and clove EOs (0.5 and 1% v/v) alone and in combination and stored at refrigerator temperature for 10 days. Then, microbiological and chemical analyses were done at 0, 2, 4, 7 and 10 days of examination. Results: A reduction of 1 log CFU/g in total count was observed between groups with simultaneous use of EOs and control group (P<0.05) at day 7; however, there was not any significant difference between the mentioned groups at day 10. Active packaging with marjoram and clove EOs decreased the number of psychrotrophs in comparison to the control group and it was more evident at days 7 and 10. The number of Enterobacteriaceae in control and 1% clove EO/1% marjoram EO groups showed a difference of 3 log units at day 10. TVB-N of 1% clove EO/1% marjoram EO and 0.5% clove EO/1% marjoram EO showed significant differences from control at day 10 (P<0.05). Conclusion: The results of the current study have shown that the active PLA films can be a promising approach in order to maintain microbial and chemical quality of minced beef at refrigerator temperature for 10 days.