This study was undertaken to determine the in vitro antimicrobial activities of 15 commercial essential oils and their main components in order to pre-select candidates for potential application in highly perishable food preservation. The antibacterial effects against food-borne pathogenic bacteria (Listeria monocytogenes, Salmonella Typhimurium, and enterohemorrhagic Escherichia coli O157:H7) and food spoilage bacteria (Brochothrix thermosphacta and Pseudomonas fluorescens) were tested using paper disk diffusion method, followed by determination of minimum inhibitory (MIC) and bactericidal (MBC) concentrations. Most of the tested essential oils exhibited antimicrobial activity against all tested bacteria, except galangal oil. The essential oils of cinnamon, oregano, and thyme showed strong antimicrobial activities with MIC ≥ 0.125 μL/mL and MBC ≥ 0.25 μL/mL. Among tested bacteria, P. fluorescens was the most resistant to selected essential oils with MICs and MBCs of 1 μL/mL. The results suggest that the activity of the essential oils of cinnamon, oregano, thyme, and clove can be attributed to the existence mostly of cinnamaldehyde, carvacrol, thymol, and eugenol, which appear to possess similar activities against all the tested bacteria. These materials could be served as an important natural alternative to prevent bacterial growth in food products.
Alex’s notes: Coming right off the heels of a SuppVersity post last week about essential oil alternatives to fluoride for oral hygiene, the study at hand sought to determine the antimicrobial properties of 15 essential oils for potential application to food preservation. It’s no surprise that bacteria shorten the “fresh period” of foodstuffs like meat and is one of the main reasons for the heavy use of preservatives in the food industry. These preservatives are usually synthetic, but not always. Natural preservatives such as rosemary and lactic acid have gained popularity among those wishing to avoid chemicals while still being able to consume their beloved bacon and sausages. And apparently, essential oils are another alternative. These secondary metabolites can be obtained from flowers, buds, seeds, leaves, bark, herbs, fruits, and roots of plants through expression, solvent extraction, steam or hydro distillation, and contain bioactive compounds with remarkably antioxidant activity.
All the bacteria tested against were strands commonly found in meat products, with the majority being pathogenic and a few the main cause of spoilage. Of all the oils, cinnamon, clove, oregano, and thyme showed consistently strong antimicrobial activity against all tested bacteria at different diluted concentrations (as low as 1/40). The effects are attributable to their bioactive constituents, and as the authors say, “these investigated essential oils and their main active components could be potential candidates to be used as natural alternatives for further application in food preservation.”
Now I still wouldn’t eat the food that preservatives are most commonly found in, even cured meats because frankly I prefer a fresh ground hamburger patty or steak. Nonetheless, it would be nice if the food industry made a shift in their chemical choices to safer and more effective alternatives.