AgroFOOD industry hi-tech - September/October 2012 - vol 23 n 5 55 Preservatives The precise targets of the antibacterial action of EOs and their components have not yet been fully established. Changes in the fatty acid composition of bacterial cell membranes (an increase in unsaturated fatty acids) have been observed when cells are exposed to sub-lethal concentrations of EO components (15). Carvacrol and thymol damage the outer membrane of gram-negative bacteria and increase the general permeability of the cytoplasmic membrane leading to leakage of ATP (16, 17). Carvacrol possesses ATPase inhibiting activity (16, 17), in any case it appears to dissipate the proton motive force (14, 16). p- Cymene has been shown to have lipolytic properties (13). The aim of this study was to investigate antibacterial effects of various concentrations of Origanum heracleoticum L. essential oil on the food-borne bacteria. MATERIALS AND METHODS Plant material Aerial parts of Origanum heracleoticum L. were collected during blooming stage (August 2009) from the locality Kamendol near Smederevo, Serbia. The plant material was dried under laboratory conditions (20-25ºC). Institute of Medicinal Plant Research Dr. Josif Panić identified the plants and voucher specimens were stored in the herbarium of the Institute of Medicinal Plant Research Dr. Josif Panić. Isolation of the essential oil The essential oil was isolated from dried plant material by hydro-distillation according to the standard procedure reported in the Sixth European Pharmacopeia (18). Distillation was performed using Clevenger type apparatus, for 2.5 hours. The resulting essential oil was dried over anhydrous sodium sulfate and stored at 4ºC. INTRODUCTION The modern trends in nutrition suggest the limitation of synthetic food additives or the substitution with natural ones. Aromatic herbs are probably the most important source of natural antimicrobial agents. Among the aromatic plant species from family Lamiaceae (Labiateae), genus Origanum occupies a special position. In Europe and, in general, all over the world, the most commonly found oregano species belong to the botanical genus Origanum. Within this genus, Ietswaart (1) recognised three groups, 10 sections, 38 species, 6 subspecies and 17 hybrids based on morphological criteria (2). Origanum heracleoticum L. (Origanum vulgare L. ssp. hirtum) is widely distributed in the Mediterranean basin and is used as a spicy herb under the name “Greek oregano”. It is generally accepted that Greek oregano is of the highest quality (3). Oregano is of great economic importance but this is not only related to its use as a spice. Chemical analysis of the oregano essential oil (EO) revealed the presence of several ingredients, most of which have important antioxidant, antibacterial and antifungal properties (4, 2, 5, 6). The major antibacterial components of these oils are carvacrol and its isomer thymol (7, 8). Both are approved food flavourings in the United States and Europe (9, 10) and have potential as antibacterial additives in food and feed (7, 11). A number of feed additives and food preservatives containing essential oils or carvacrol are already commercially available (12). p - Cymene is also a constituent of oregano but is less effective against food related pathogens (8, 13) and is thought to be a precursor to carvacrol and thymol in the plant (14). Antimicrobial activity of Origanum heracleoticum L. essential oil from Serbia IVANA ČABARKAPA 1 *, MARIJA ŠKRINJAR 2 , IVAN MILOVANOVIĆ 1 , DRAGANA PLAVŠIĆ 1 , DRAGAN PALIĆ 1 , BOJANA KOKIĆ 1 , IVANA ARSIĆ 3 *Corresponding author 1. University of Novi Sad Institute of Food Technology, Bulevar cara Lazara 1, Novi Sad, 21000, Serbia 2. University of Novi Sad Faculty of Technology, Bulevar cara Lazara 1, Novi Sad, 21000, Serbia 3. Institute for Medicinal Plant Research “Dr. Josif Panić“, Tadeuša Košćuška 1, Belgrade, 11000, Serbia KEYWORDS: Antimicrobial activity; essential oil Origanum heracleoticum L.; Origanum L. ABSTRACT: The modern trends in nutrition suggest the limitation of synthetic food additives or the substitution with natural ones. Aromatic herbs are probably the most important source of natural antimicrobial agents. The aim of this study was to investigate antibacterial effects of various concentrations of Origanum heracleoticum essential oil on the food-borne bacteria. The antimicrobial activity of Origanum heracleoticum essential oil was evaluated using laboratory control strains Escherichia coli ATCC /10536/, Salmonella choleraesuis ATCC /10708/, Salmonella enteritidis ATCC/13076/, Proteus mirabilis ATCC /12453/, Pseudomonas aeruginosa ATCC/10145/, Staphylococcus aureus ATCC /11632/, Bacillus cereus ATCC/10876/ and Enterococcus faecalis ATCC /14506/, obtained from the American Type Culture Collection. The antimicrobial activity was determined using disk diffusion method and more precise broth microdilution method. Using the broth microdilution method essential oil of Origanum heracleoticum L. showed antimicrobial activity against all tested strains of microorganisms with exception of the test strain of Pseudomonas aeruginosa. The tested oil had antibacterial effect on gram-positive bacteria in the range of MIC/MBC=0.2-0.39/0.78 l/ml. The essential oil was active in the range from MIC/MBC=0.39 to 50/0.78 to 50 l/ml against the tested gram-negative bacteria. P. aeruginosa ATCC/10145/ showed the lowest sensitivity of MIC/MBC=50/50 l/ml. Ivana Cabarkapa Peer-reviewed article