Evaluation of synergistic antibacterial and antioxidant efficacy of essential oils against food borne pathogens

Abstract

Abstract newlineDeterioration of food can be caused by various factors such as physical, chemical, enzymatic or microbiological. Due to increasing side effect of chemicals in food, consumers demand for some natural alternative to these chemical preservatives. One of these alternatives is use of plant essential oils. This study investigated the possible synergistic interactions on antibacterial efficacy of essential oils studied (rosemary, eucalyptus, cinnamon, clove and lemon grass) in combination. The antibacterial potential of the plant essential oils was evaluated against food borne bacteria, isolated from twenty spoiled food samples of different categories. Results demonstrated that eight bacteria were responsible for spoilage of food samples (Salmonella, Pseudomonas, Escherichia, Staphylococcus, Lactobacillus, Klebsiella, Bacillus, Micrococcus sp.). Best antibacterial results were shown by cinnamon oil followed by rosemary oil and least activity was shown by lemon grass oil. Pseudomonas was least sensitive bacterium out of all tested bacteria. All the tested essential oils exhibited maximum antibacterial activity against E. coli (gram negative) and Micrococcus (gram positive). So these two bacteria were selected for further studies. Combination of Rosemary/eucalyptus oil depicted synergistic effects and was chosen for further studies. Among all the combinations studied best antioxidant activity was shown by rosemary/eucalyptus oil combination (91.97%), least antioxidant activity was observed for eucalyptus/cinnamon oil combination (10.70%). Viability assay performed on both selected bacteria demonstrated that at MIC concentration the viability of both bacteria decreased with the increase in interval of treatment. The assays performed to study the effect of combination of oil on cell membrane of both selected bacteria exhibited that the combination at MIC concentration damaged the cell membrane of both bacteria. The rosemary/eucalyptus oil combination was found to exhibit no cytoxicity effect at MIC concentrations. These results provide the useful information that the rosemary /eucalyptus oil combination might be used as efficient and safe natural antimicrobial agent in food industry. newline