Effect Of Oregano Essential Oil Research Articles

Effect of Oregano Essential Oil (Origanum vulgare subsp. hirtum) on the Storage Stability and Quality Parameters of Ground Chicken Breast Meat.

A study was conducted to investigate the effect of oregano essential oil on the oxidative stability and color of raw and cooked chicken breast meats. Five treatments, including (1) control (none added); (2) 100 ppm oregano essential oil; (3) 300 ppm oregano essential oil; (4) 400 ppm oregano essential oil; and (5) 5 ppm butylated hydroxyanisole (BHA), were prepared with ground boneless, skinless chicken breast meat and used for both raw and cooked meat studies. For raw meat study, samples were individually packaged in oxygen-permeable bags and stored in a cold room (4 °C) for 7 days. For cooked meat study, the raw meat samples were vacuum-packaged in oxygen-impermeable vacuum bags and then cooked in-bag to an internal temperature of 75 °C. After cooling to room temperature, the cooked meats were repackaged in new oxygen-permeable bags and then stored at 4 °C for 7 days. Both raw and cooked meats were analyzed for lipid and protein oxidation, volatiles, and color at 0, 3, and 7 days of storage. Oregano essential oil significantly reduced (p < 0.05) lipid and protein oxidation, and improved color stability of raw and cooked meat. However, oregano oil at 400 ppm showed the strongest effect for all these parameters. Hexanal was the major aldehyde, which was decreased significantly (p < 0.05) by oregano oil treatment, in cooked meat. Overall, oregano essential oil at 100–400 ppm levels could be a good preservative that can replace the synthetic antioxidant in chicken meat.

Synergistic and Additive Effect of Oregano Essential Oil and Biological Silver Nanoparticles against Multidrug-Resistant Bacterial Strains.

Bacterial resistance to conventional antibiotics has become a clinical and public health problem, making therapeutic decisions more challenging. Plant compounds and nanodrugs have been proposed as potential antimicrobial alternatives. Studies have shown that oregano (Origanum vulgare) essential oil (OEO) and silver nanoparticles have potent antibacterial activity, also against multidrug-resistant strains; however, the strong organoleptic characteristics of OEO and the development of resistance to these metal nanoparticles can limit their use. This study evaluated the antibacterial effect of a two-drug combination of biologically synthesized silver nanoparticles (bio-AgNP), produced by Fusarium oxysporum, and OEO against Gram-positive and Gram-negative bacteria, including multidrug-resistant strains. OEO and bio-AgNP showed bactericidal effects against all 17 strains tested, with minimal inhibitory concentrations (MIC) ranging from 0.298 to 1.193 mg/mL and 62.5 to 250 μM, respectively. Time-kill curves indicated that OEO acted rapidly (within 10 min), while the metallic nanoparticles took 4 h to kill Gram-negative bacteria and 24 h to kill Gram-positive bacteria. The combination of the two compounds resulted in a synergistic or additive effect, reducing their MIC values and reducing the time of action compared to bio-AgNP used alone, i.e., 20 min for Gram-negative bacteria and 7 h for Gram-positive bacteria. Scanning electron microscopy (SEM) revealed similar morphological alterations in Staphylococcus aureus (non-methicillin-resistant S. aureus, non-MRSA) cells exposed to three different treatments (OEO, bio-AgNP and combination of the two), which appeared cell surface blebbing. Individual and combined treatments showed reduction in cell density and decrease in exopolysaccharide matrix compared to untreated bacterial cells. It indicated that this composition have an antimicrobial activity against S. aureus by disrupting cells. Both compounds showed very low hemolytic activity, especially at MIC levels. This study describes for the first time the synergistic and additive interaction between OEO and bio-AgNP produced by F. oxysporum against multidrug-resistant bacteria, such as MRSA, and β-lactamase- and carbapenemase-producing Escherichia coli and Acinetobacter baumannii strains. These results indicated that this combination can be an alternative in the control of infections with few or no treatment options.

Effects of oregano essential oil and attapulgite on growth performance, intestinal microbiota and morphometry in broilers

Two experiments were conducted to study the effects of a blend of oregano essential oil (OEO) (as a source of natural antibacterial growth-promoting substances) and attapulgite (as a source of toxin-binder and as an antidiarrhoeal agent) on growth performance, intestinal microbiota, and intestinal morphometry in broiler chickens (Ross-308). In the first trial, the control group was fed a basal diet without antibiotic growth promoters, and the experimental group was fed the basal diet supplemented with 5% OEO (OEO) (Ecodiar ® powder at 150 g/tn) and 80% attapulgite 80% (Ultrafed ® at 6 kg/tn) blend. In the second trial, the experimental group was given the basal diet supplemented with 5% OEO (Ecodiar ® powder at 300 g/tn) and 80% attapulgite (Ultrafed ® at 3 kg/tn) blend. Intestinal microbiota was enumerated by conventional techniques with selective agar media at the end of the trial at both ileum and caecum, and intestinal morphology was assessed in the duodenum, jejunum and ileum. Results showed that in the first trial, despite the positive impact on daily gain and feed-to-gain ratio, growth performance was not affected by the blend with OEO and attapulgite. Furthermore, no effect was found on intestinal morphometry. However, the counts of lactic acid bacteria were increased significantly, and coliforms were decreased in caecal contents. In the second trial, a positive impact was noticed on daily gain and feed-to-gain ratio by the high OEO and low attapulgite blend. Dietary supplementation of OEO and attapulgite increased ileal villus height and lactic acid bacteria significantly and reduced coliforms in ileal and caecal contents compared with the control group. In conclusion, the combination of OEO at 15 mg/kg and attapulgite at 2.4 g/kg exerted a positive effect on growth performance, ileal villus height and intestinal microbiota of broilers. Keywords: Gut microflora, intestinal architecture, magnesium aluminium silicate, oregano

Therapeutic effect of oregano essential oil on subclinical bovine mastitis caused by Staphylococcus aureus and Escherichia coli

Oregano (Origanum vulgare) is an aromatic herb belonging to the Lamiaceae family. This study evaluated the therapeutic effect of oregano essential oil (OEO) on clinical bovine mastitis caused by Staphylococcus (S.) aureus and/or Escherichia (E.) coli. Thirty-two quarters from 18 lactating cows with subclinical mastitis were selected from a dairy farm and were divided into 4 groups (8 quarters/group): negative control (CON), positive control (GEN) and two OEO-treated groups (OEO-1 and OEO-2). Each group was intramammarily treated with saline, 10 g/tube of gentamicin ointment, and single and double doses of 0.9 mL OEO ointment twice a day for three days, respectively. After the treatments, physical udder conditions were greatly improved in GEN and OEO groups. In CON group, somatic cell counts (SCCs), number of white blood cells (WBC) and bacteria were increased. However, in OEO groups, SCCs and number of WBC were significantly decreased and S. aureus and E. coli were not detected in milk as compared with those before the treatments as well as GEN group. These results suggest that OEO may be a useful alternative to antibiotics for the control of subclinical bovine mastitis caused by S. aureus and/or E. coli.

Ameliorative Effect of Oregano Essential Oil on Mycotoxins-Induced Immune Impairments in Growing Japanese Quail

Mycotoxins contaminated feed is one of the most serious problems in poultry and animal production sectors. Therefore, the current study aimed to investigate the effects of dietary oregano essential oil (OEO) for 4 weeks against the adverse effect of aflatoxins (AFs) on immunity, oxidative stress, Total and differential leucocytes counts (TLC and DLC), interleukin 1 (IL-1), nitric oxide (NO), lysozyme enzyme activity, serum malondialdehyde (MDA), catalase, superoxide dismutase (SOD) and reduced glutathione (GSH). Beside growth performance [Weekly body weight gain and feed conversion ratio (FCR)] were also determined. A total of 132 male, 2 weeks old Japanese quails chicks (Coturnix japonica) were used in this study and equally divided into 4 groups. Group I is considered as negative control at which birds fed only basal diet, group II served as positive control and were fed AFs 2.5 mg /Kg supplemented basal diet, Groups III and IV were fed basal diet with 2.5 mg AFs /Kg and treated with OEO at a rate of 200 and 400 mg/Kg , respectively. Regarding growth performance, there was a significant (P<0.05) reduction in weight gain and FCR at 4th week of the experiment in group II, additionally different pattern was noticed in group IV which represented a significant (P<0.05) improvement as compared to the other AFs treated groups and was nearly similar to that of group I. Concerning Lipid peroxidation, oxidative stress enzyme and immune parameters at 4th week of the experiment, MDA was significantly (P<0.05) increased in AFs treated quails (II and III) but when AFs co-administered with 400 mg OEO, MDA was nearly similar to that of group I. The SOD, catalase, and GSH were decreased significantly (P<0.05) in groups (II and III) and was remarkably improved in group IV. The NO level was increased significantly (P<0.05) while lysozyme activity was decreased significantly (P<0.05) in group II, while they were decreased and increased in group IV, respectively. IL-1 and globulin as well as TLC were declined significantly (P<0.05) in groups II and III and improved nearly similar to control one in group IV. In conclusion, OEO has a potential and a protective effect against AFs B1 immuno-deteriorating effect in Japanese quails especially at 400 mg/ kg dose.

Dietary oregano essential oil alleviates experimentally induced coccidiosis in broilers

An experiment was conducted to determine the effects of oregano essential oil on growth performance and coccidiosis prevention in mild challenged broilers. A total of 250 1-d-old chicks were used in a completely randomized design with 5 treatments and 5 replicates with 10 birds in each replication. Experimental treatments included: (1) negative control (NC; unchallenged), (2) positive control (PC; challenged with sporulated oocysts of Eimeria), (3) PC fed 200ppm Diclazuril in diet, (4) PC fed 300ppm oregano oil in diet, and (5) PC fed 500ppm oregano oil in diet. At 22 d of age, all the experimental groups except for NC were challenged with 50-fold dose of Livacox T as a trivalent live attenuated coccidiosis vaccine. On d 28, two birds were slaughtered and intestinal coccidiosis lesions were scored 0–4. Moreover, dropping was scored in the scale of 0–3, and oocysts per gram feces (OPG) were measured. Oregano oil at either supplementation rate increased body weight gain (P=0.039) and improved feed conversion ratio (P=0.010) from d 22 to 28, when compared with PC group. Using 500ppm oregano oil in challenged broilers diet increased European efficiency factor than PC group (P=0.020). Moreover, challenged broilers fed 500ppm oregano oil or Diclazuril in diets displayed lower coccidiosis lesions scores in upper (P=0.003) and middle (P=0.018) regions of intestine than PC group, with the effect being similar to unchallenged birds. In general, challenged birds fed 500ppm oregano oil or Diclazuril in diets had lower OPG (P=0.001), dropping scores (P=0.001), litter scores (P=0.001), and pH of litter (P=0.001) than PC group. It could be concluded that supplementation of oregano oil at the dose of 500ppm in diet may have beneficial effect on prevention of coccidiosis in broilers.

Oregano essential oil decreased susceptibility to oxidative stress-induced dysfunction of intestinal epithelial barrier in rats

The protective effects of oregano essential oils (OEO) against oxidative stress in intestine of rats were investigated. The results showed that rats orally treated with 5 or 20 mg/kg BW with OEO abolished diquat-induced oxidative stress in jejunum, thereby maintaining jejunal architecture. The protective effect of OEO might cause modification of selected intestinal microbiota, inhibition of inflammatory cytokine expression and subsequent increased occludin expression in jejunum by enhancement of antioxidative capacity. These results revealed that OEO exerted a protective effect against diquat-induced oxidative injury in intestine of rats.

The Effect of Oregano Essential Oil in Post-Harvest Quality of Minimally Processed Radish

The Effect of Oregano Essential Oil in Post-Harvest Quality of Minimally Processed Radish

The impact of oregano (Origanum heracleoticum) essential oil and carvacrol on virulence gene transcription by Escherichia coli O157:H7.

The aim of the current study was to determine, via reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis, the effect of oregano essential oil (Origanum heracleoticum) and carvacrol, its major component, on the expression of virulence-associated genes in enterohaemorrhagic Escherichia coli (EHEC) O157:H7 ATCC strain 35150. Both oregano oil and carvacrol demonstrated their efficacy firstly, by inhibiting the transcription of the ler gene involved in upregulation of the LEE2, LEE3 and LEE4 promoters and of attaching and effacing lesions and secondly by decreasing both Shiga toxin and fliC genes expression. In addition, a decrease in luxS gene transcription involved in quorum sensing was observed. These results were dose dependent and showed a specific effect of O. heracleoticum and carvacrol in downregulating the expression of virulence genes in EHEC O157:H7. These findings suggest that oregano oil and carvacrol have the potential to mitigate the adverse health effects caused by virulence gene expression in EHEC O157:H7, through the use of these substances as natural antibacterial additives in foods or as an alternative to antibiotics.

Effect of Adding Oregano Essential Oil, Garlic and Tomato Preparations Separately and in Combination on the Stability of Vacuum-Packed Minced Pork During Storage

Abstract This paper investigates the effect of adding oregano essential oil (0.02% v/w), freeze-dried garlic (1%), tomato concentrate (15%) and a combination of all three (in the same concentrations) on the shelf life of minced pork meat. Vacuum-packed samples with additives and a control were stored at 6±1°C for 16 days. Sensory, microbiological and biochemical changes were analysed over the whole storage period. The beneficial effect of oregano essential oil was generally to inhibit lipid oxidation, although its effect on bacterial growth was very weak. Adding tomato concentrate, combined with other additives, slowed the rate of microbiological and sensory changes, but had a marked effect on changes in proteins (SDS-PAGE analysis) and the proportion of meat pigments. The addition of freeze-dried garlic did not cause a substantial reduction of detectable bacteria count. Adding a combination of all three additives resulted in a product with a distinctly longer shelf life.

Cytotoxicity and morphological effects induced by carvacrol and thymol on the human cell line Caco-2

Essential oils used as additives in the food industry due to its flavour, antimicrobial and antioxidant properties. Therefore, human can be exposed orally to these compounds through the ingestion of foods. In this sense, the present work aims to assess toxicological effects of oregano essential oil on the digestive tract. In concrete, the cytotoxic effects of two components of the oregano essential oils, carvacrol and thymol, and their mixture, on the intestinal cells line Caco-2 after 24 and 48h of exposure are studied. The basal cytotoxicity endpoints assayed (total protein content, neutral red uptake and the tetrazolium salt reduction) and the annexin/propidium iodide staining indicated that carvacrol and the mixture carvacrol/thymol induced toxic effects. Moreover, a morphological study was performed in order to determine the ultrastructural cellular damages caused by these substances. The main morphological alterations were vacuolated cytoplasm, altered organelles and finally cell death. In addition, although no cytotoxic effects were recorded for thymol at any concentration and time of exposure, ultrastructural changes evidenced cellular damage such as lipid degeneration, mitochondrial damage, nucleolar segregation and apoptosis.

Effect of oregano essential oil on the engraftment and development of Lewis carcinoma in F1 DBA C57 black hybrid mice

Effect of oregano essential oil on the engraftment and development of Lewis carcinoma in F1 DBA C57 black hybrid mice

Combined antimicrobial effect of oregano essential oil and caprylic acid in minced beef

Oregano essential oil (OEO) and caprylic acid (CA) are highly aromatic natural antimicrobials with limited individual application in food. We proved their combined additive effect when used in meat. Application of 0.5% CA and 0.2% OEO (v/w) with 0.1% of citric acid in vacuum packed minced beef inoculated with Listeria monocytogenes at a concentration of 5log cells/g reduced counts of lactic acid bacteria by 1.5log CFU/g and counts of psychrotrophic bacteria and L. monocytogenes by more than 2.5log CFU/g at the end of storage at 3°C for 10days. In sensory evaluation the samples with OEO showed during the whole experiment statistically better scores than control, whereas the samples treated with CA showed worse colour attributes.

Effect of oregano essential oils on lipid oxidation in storage eggs enriched with dietary omega‐3 fatty acids

Oregano plants produce secondary metabolites, which they are utilized by the plant for growth and reproduction, but they are useful as functional additives in animal feeding systems because their intrinsic bioactivities properties. Oregano antioxidant property is attributed to thymol and carvacrol that react with lipid and hydroxyl radicals converting them into stable products. The aim of this study was to evaluate the effect of oregano essential oils (OEO) on lipid oxidation of n‐3 PUFA‐enriched fresh eggs and storage at 4 ºC y −10 ºC during six months. A total of 160 laying hens 40 wk old were placed in 80 cages and were randomly assigned to one of the 8 experimental diets: palm oil and fish oil (n‐3 PUFA source), with and without supplementation of OEO at 4 qualitative thymol levels. Results showed that lipid oxidation was greater in eggs storage at 4ºC (3.09 mg MDA/g). In n‐3 PUFA‐enriched fresh eggs the lowest lipid oxidation was shown by the group supplemented with OEO low thymol (1.27 mg MDA/g). Lipid oxidation increased in n‐3 PUFA‐enriched eggs stored at 4ºC and −10ºC compared to fresh eggs (P&lt;0.001). At 4ºC greater lipid oxidation was shown in enriched eggs without OEO (5.6 mg MDA/g), but OEO supplementation lowered lipid oxidation around 48%. In the present study, dietary OEO supplementation positively influenced by retarding lipid oxidation in eggs enriched with dietary omega‐3 fatty acids during storage.

Effects of dietary oregano essential oil and vitamin E on the lipid oxidation stability of cooked chicken breast meat

The antioxidant effect of oregano essential oil and vitamin E was evaluated in cooked chicken breast meat. In total, 480 broilers were randomly assigned to 6 treatments and 4 replications. Broilers were raised with a corn-soybean meal diet including either crude soybean oil or acidulated soybean oil soapstock, each supplemented with vitamin E at 10 or 100 mg or oregano essential oil at 100 mg/kg of feed. At 42 d, broilers were slaughtered and their breast meat was prepared into strips (1.5 × 10 cm) or patties (150 g). Fatty acid composition of the muscle was determined. For lipid oxidation stability, both meat strips and patties were cooked to an internal temperature of 74°C and malonaldehyde contents were assessed during 0, 3, 6, and 9 d of storage at 4°C. Each storage day had 4 replications per treatment. The meat lipid oxidative stability was estimated by content of malonaldehyde values. Results showed that feed consumption, weight gain, and feed conversion were not affected by the dietary oils or antioxidants, except for the mortality in acidulated soybean oil soapstock with the 10-mg vitamin E treatment. The fatty acid composition of the meat was similar between the 2 diets given the same antioxidant supplement. The oxidation stability of meat lipids in both types of meats showed a significant (P < 0.05) interaction between oils, antioxidants, and storage time. In the crude soybean oil oil diet, the malonaldehyde value in the 10-mg vitamin E treatment was the highest, followed by oregano essential oil, and then the 100-mg vitamin E treatment at 9 d of storage, whereas the value of oregano essential oil in the acidulated soybean oil soapstock diet was the highest, followed by the 10-mg vitamin E, and then the 100-mg vitamin E treatment during the 9 d of storage. In conclusion, the dietary oils and antioxidants used can be included in broiler diets without negative effects on their productivity. The antioxidant effect of vitamin E was higher with a higher supplementation level, regardless of the oil treatment, whereas the antioxidant effect of oregano essential oil was better in crude soybean oil than in the acidulated soybean oil soapstock diet.

The antimicrobial effect of Origanum compactum essential oil, nisin and their combination against Escherichia coli in tryptic soy broth (TSB) and in sheep natural sausage casings during storage at 25 and 7°C

The aim of this study was to investigate the antimicrobial effect of oregano essential oil (EO) at 0.015, 0.03 or 0.06%, nisin at 800 or 1600 IU/g, and their combination on Escherichia coli in tryptic soy broth (TSB) and in sheep natural sausage casings. At 0.015%, EO presented a weak antibacterial activity against the pathogen in TSB. Consequently, only the levels of 0.03 and 0.06% were examined in casings. EO at 0.03 or 0.06% showed an inhibitory activity against E. coli O157:H7, E. coli ATCC 25922 and E. coli cocktail during storage at 25°C and at 7° C in casings. Treatment of casings or in TSB with nisin at 800 or 1600 IU/g did not show any antibacterial activity against E. coli strains. Synergy between EO and nisin was observed in both TSB and natural casings. The combination of EO at 0.03 or 0.06% and nisin at 800 or 1600 IU/g presented an additive effect against the pathogen, during storage at 25°C and at 7°C. Key words : Oregano essential oil, nisin, natural casings, biopreservative, Escherichia coli

Influence of oregano extract on the intestine, some plasma parameters and growth performance in chickens

The effect of oregano essential oil on growth performance, intestinal alkaline phosphatase (IAP) level, enterocyte proliferative ability, plasma proteins, and plasma minerals (calcium and magnesium) were studied in 1 day-old Ross 308 hybrid broiler chickens under commercial conditions during 42 experiment. Chickens fed oregano oil supplemented diet (0.707 g.kg-1) had significantly higher body weight gain (BWG) in the grower (19-29 d) and finisher (30-42 d) periods. Total plasma immunoglobulin levels were lower while mineral levels were higher during the finisher period. Significant decrease of IAP activity was demonstrated in animals fed oregano oil supplemented diet on 29, and 42 days of the experiment. Proliferative activity of enterocytes significantly increased in the finisher period along duodenal villi in animals treated with essential oil extracted from oregano. We suppose that higher body performance was probably the result of higher digestibility in the digestive tract. It is suggested that the antibacterial effect of carvacrol caused a lower number of intestinal bacteria, decrease of immunoglobulins and increase of investigated plasma proteins.

In vitro combined effect of oregano essential oil and caprylic acid against Salmonella serovars, Escherichia coli O157:H7, Staphylococcus aureus and Listeria monocytogenes

In vitro inhibition of foodborne pathogens via action of natural antimicrobials – caprylic acid (CA) and essential oil from Origanum vulgare L. (OEO) with high carvacrol content (72%) was evaluated. For 15 Salmonella strains the minimum inhibitory concentration (MIC) determined by broth microdilution method ranged between 3.67–4.33 μl·ml-1 for CA and between 0.48–0.57 μl·ml-1 for OEO. For 7 Listeria monocytogenes strains the MIC ranged between 2.17–2.83 μl·ml-1 for CA and between 0.52–0.58 μl·ml-1 for OEO. Type strains of Escherichia coli O157:H7 and Staphylococcus aureus were tested, too, with MIC of CA 3.60 μl·ml-1 and 3.20 μl·ml-1 and MIC of OEO 0.51 μl·ml-1 and 0.48 μl·ml-1, respectively. Furthermore, it was found that the MIC of CA can be decreased by even low addition (0.05%) of citric or acetic acid and to a lesser extent by lactic acid, whereas the MICs of OEO did not notably decrease. Combined application of CA and OEO determined by FIC index led only to an additive effect (0.5 ≤ FIC ≤ 1). Combination of natural additives OEO, CA and eventually acetic or citric acid seems to have the potential to be an effective mixture for inhibition of foodborne pathogens, predominantly Salmonella spp. and L. monocytogenes, even in only slightly acidic food.

Quality Assessment of Salted, Modified Atmosphere Packaged Rainbow Trout under Treatment with Oregano Essential Oil

The present study evaluated the effect of oregano essential oil (EO) on fresh salted, packaged (45%CO(2)/5%O(2)/50%N(2)) rainbow trout fillets and stored for a period of 21 d at 4 °C. Treatments included the following: M1 (control without added EO), M2 (EO 0.2%, v/w), and M3 (0.4%, v/w). Populations of lactic acid bacteria (LAB), H(2)S-producing bacteria (including Shewanella putrefaciens), Enterobacteriaceae, and Pseudomonas spp. reached higher final numbers in control (M1) than for M2 and M3 samples. Under treatments M2 and M3, total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) values were lower than for M1 samples, whereas lipid oxidation, as judged by determination of thiobarbituric acid values (TBA), did not occur during the refrigerated storage period. Interestingly, treatment M2 resulted in a shelf-life extension of 7 to 8 d for the fresh trout fillets, whereas treatment M3 proved unsuitable (due to strong odor) for trout fillet preservation, as determined by sensory evaluation. The use of an essential oil such as oregano oil in fresh fish preservation may be considered an alternative "natural" additive, enhancing the sensory characteristics and extending the shelf life of the product.

Electronic paramagnetic resonance investigation of the activity of Origanum vulgare L. essential oil on the Listeria monocytogenes membrane

To evaluate the effect of oregano essential oil on Listeria monocytogenes cytoplasmic membrane. Nitroxide free-radical Electron Paramagnetic Resonance was applied on L. monocytogenes after 30 min exposure to oregano essential oil concentrations ranging from 0 to 1.25%. The impact of essential oil on the number of viable cells was evaluated by plate count. Growth dynamics of survivors in BHI and TSB were evaluated by turbidometry. After exposure to essential oil concentrations up to 0.50%, the membrane fluidity was changed and its order increased. When L. monocytogenes was exposed to higher concentrations, membrane order parameters slightly returned to the values of untreated cells. However, when the cells were exposed to EO in the presence of sodium azide, which impairs energy metabolism, the membrane fluidity was progressively enhanced, even at the lowest EO concentration (0.25%). Microbiological analyses confirmed a progressive reduction of viable count, at increasing essential oil concentrations. Both in BHI and TSB, the Lag phase length increased in treated cells with respect to controls, suggesting a cell damage recovery. The combined approach including microbiological and EPR analyses provided relevant information on membrane modification and cell response to essential oils. EPR approach was demonstrated to be an effective and helpful tool to comprehend the modifications exerted by essential oil on the bacterial membrane.