Studies confirming the antibacterial and antifungal properties of oregano oil as well as its effective use against food poisoning.
Antibacterial Effects of Allspice, Garlic, and Oregano Essential Oils in Tomato Films Determined by Overlay and Vapor-Phase Methods
Physical properties as well as antimicrobial activities againstEscherichia coliO157:H7,Salmonella enterica, andListeria monocytogenesof allspice, garlic, and oregano essential oils (EOs) in tomato puree film-forming solutions (TPFFS) formulated into edible films at 0.5% to 3% (w/w) concentrations were investigated in this study. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor-phase diffusion of the antimicrobial from the film to the bacteria. The results indicate that the antimicrobial activities against the 3 pathogens were in the following order: oregano oil > allspice oil > garlic oil.Listeria monocytogeneswas less resistant to EO vapors, whileE. coliO157:H7 was more resistant to EOs as determined by both overlay and vapor-phase diffusion tests. The presence of plant EO antimicrobials reduced the viscosity of TPFFS at the higher shear rates, but did not affect water vapor permeability of films. EOs increased elongation and darkened the color of films. The results of the present study show that the 3 plant-derived EOs can be used to prepare tomato-based antimicrobial edible films with good physical properties for food applications by both direct contact and indirectly by vapors emanating from the films.
From press release:
Oregano, allspice and garlic essential oils (EOs) can be effective, natural barriers against E. coli, Salmonella and Listeria, according to a study in the Journal of Food Science, published by the Institute of Food Technologists. The new study from government researchers revealed that oregano oil was found to be the most effective antimicrobial, followed by allspice and garlic.
Researchers at Processed Foods Research and Produce Safety and Microbiology units of Western Regional Research Center from the U.S. Department of Agriculture (USDA) investigated the effectiveness of the oils by incorporating them in thin, tomato-based antimicrobial coatings known as edible films. In addition to its flavor properties, tomatoes are reported to possess numerous beneficial nutritional and bioactive components that may benefit human health. Edible tomato films containing antimicrobials may protect food against contamination by pathogenic microorganisms.
Testing was done by laying the films on top of the bacteria and also by exposing the bacteria to the vapors arising from the film. According to researchers:
Edible films for fruits and vegetables can serve as carriers for food additives including plant-derived, safe antimicrobials. The increased interest in antimicrobial films is the result of increased consumption of contaminated fresh-cut produce.
In a related study from the same USDA research group, it was found that cinnamon, allspice and clove might have a new use in the kitchen. Essential oils (EOs) from these plants could be used to protect food from bacteria according to a study in the Journal of Food Science. They evaluated the physical and antimicrobial properties of allspice, cinnamon and clove bud oils in edible films of apple puree after 24 and 48 hours. Edible films and coatings on food products can serve as carriers for a wide range of beneficial food additives, including antimicrobials. The oils were incorporated into edible apple puree film at ranges of 0 to 3 percent. Researchers found:
The antimicrobial activity of cinnamon oil was significantly greater than allspice and clove bud oils against E. coli, Salmonella and Listeria.
Du, W-X, Olsen, Avena-Bustillos, McHugh, Levin, Mandrell, R. Friedman, Mendel. Antibacterial Effects of Allspice, Garlic, and Oregano Essential Oils in Tomato Films Determined by Overlay and Vapor-Phase Methods Journal of Food Science, 2009 September Volume 74, Number 7, pp. M390-M397(1).
Produce Safety and Microbiology, Western Regional Research Center, U.S. Dept. of Agriculture.
Antifungal and Antibacterial Effects of Oregano Oil
Growth inhibition of pathogenic bacteria and some yeasts by selected essential oils and survival of L. monocytogenes and C. albicans in apple-carrot juice.
Food safety is a fundamental concern of both consumers and the food industry. The increasing incidence of foodborne diseases increases the demand of using antimicrobials in foods. Spices and plants are rich in essential oils and show inhibition activity against microorganisms, which are composed of many compounds. In this research, effects of garlic, bay, black pepper, origanum, orange, thyme, tea tree, mint, clove, and cumin essential oils on Listeria monocytogenes AUFE 39237, Escherichia coli ATCC 25922, Salmonella enteritidis ATCC 13076, Proteus mirabilis AUFE 43566, Bacillus cereus AUFE 81154, Saccharomyces uvarum UUFE 16732, Kloeckera apiculata UUFE 10628, Candida albicans ATCC 10231, Candida oleophila UUPP 94365, and Metschnikowia fructicola UUPP 23067 and effects of thyme oil at a concentration of 0.5% on L. monocytogenes and C. albicans in apple-carrot juice during +4 degrees C storage (first to fifth day) were investigated. Strong antibacterial and antifungal activities of some essential oils were found. Thyme, origanum, clove, and orange essential oils were the most inhibitory against bacteria and yeasts. Cumin, tea tree, and mint oils inhibited the yeasts actively. It is concluded that some essential oils could be used as potential biopreservatives capable of controlling foodborne pathogens and food spoilage yeasts.
Irkin R, Korukluoglu M. Growth inhibition of pathogenic bacteria and some yeasts by selected essential oils and survival of L. monocytogenes and C. albicans in apple-carrot juice. Foodborne Pathog Dis. 2009 April 6(3):387-94.
Susurluk College, Balikesir University, Turkey.