Effect Of Oregano Essential Oil Research Articles

The antimicrobial effect of oregano essential oil, nisin and their combination against Salmonella Enteritidis in minced sheep meat during refrigerated storage

The antimicrobial effect of oregano essential oil (EO) at 0.6 or 0.9%, nisin at 500 or 1000 IU/g, and their combination against Salmonella Enteritidis was studied in minced sheep meat during storage at 4° or 10 °C for 12 days. Sensory evaluation showed that the addition of oregano EO at 0.6 or 0.9% in minced sheep meat was organoleptically acceptable, and attribute scores were higher for the EO at 0.6 than 0.9%. According to compositional analysis of the oregano EO, the phenols carvacrol (80.15%) and thymol (4.82%) were the predominant components. Treatment of minced sheep meat with nisin at 500 or 1000 IU/g, proved insufficient to act against S. Enteritidis. The combination of the oregano EO at 0.6% with nisin at 500 IU/g showed stronger antimicrobial activity against S. Enteritidis than the oregano EO at 0.6% but lower than the combination with nisin at 1000 IU/g, which in turn was lower than that of the oregano EO at 0.9%. In its turn, oregano EO at 0.9% showed lower antimicrobial activity than its combinations with nisin at 500 or 1000 IU/g, which showed a bactericidal effect against the pathogen. The inhibition percentages of all treatments against S. Enteritidis at 10 °C were higher than those at 4 °C.

Chemical and sensory stability of fried‐salted peanuts flavored with oregano essential oil and olive oil

AbstractBACKGROUND: Synthetic antioxidants, such as BHA, BHT and PG, are used in many foods to prevent rancidity. However, their health safety is questioned. There is renewed interest in the increased use of naturally occurring antioxidants such as essential oils from aromatic plants. The objective of this work was to evaluate the effect of oregano essential oil and olive oil on the oxidative stability of fried‐salted peanuts.RESULTS: Fried‐salted peanuts (FP), fried‐salted peanuts with oregano essential oil (FP‐O) and fried‐salted peanuts with oregano essential oil and olive oil (FP‐OO) were prepared. Peroxide value (PV), p‐anisidine value (AV) and conjugated diene (CD) measurements, and descriptive analysis were analyzed on the products during 112 days of storage. FP‐OO showed higher stability during storage. PV and AV at the end of storage were lower in FP‐OO (57.70–7.77, respectively) followed by FP‐O (63.94–8.30) and FP (76.38–9.33, respectively). The oxidized and cardboard flavor intensities increased more in FP during storage than the other products while the roasted peanutty flavor also decreased more in FP.CONCLUSION: Oregano essential oil and olive oil showed protective effect against lipid oxidation in fried‐salted peanuts increasing the shelf‐life of this product. Copyright © 2009 Society of Chemical Industry

Effect of Oregano Essential Oil on Biofilms Formed By Staphylococci and Escherichia coli

Summary In the present study, it was aimed to investigate the effect of oregano (Origanum onites) essential oil (EO) on biofilm formation and established biofilm. Staphylococcus aureus (n=6), Staphylococcus lugdunensis (n=1), Staphylococcus haemolyticus (n=1), Staphylococcus sciuri (n=1) and Escherichia coli (n=1) were used as the test organisms. The crystal violet assay was used for assessing the growth of the biofilm on 96-well polystyrene microtitre plates. The minimum inhibitory concentration (MIC) was determined by broth dilution method as 0.05% (v/v) for staphylococci with the exception of Staph. sciuri (0.8%, v/v) and 0.1% (v/v) for E. coli. Oregano EO inhibited biofilm formation and eradicated established biofilm at MIC level. Subinhibitory concentrations of the EO reduced the level of biofilm formation of the test strains. Further investigations should be examined whether these observations extend to biofilms formed on other surfaces, particularly those found in food processing plants. The ability of biofilm-embedded microorganisms to resist clearance by antimicrobial agents points to the importance of a continuous search for novel agents. The use of oregano EO as a natural antimicrobial agent can be an effective alternative or a supplement for the control of microorganisms.

Antibacterial effect of oregano essential oil alone and in combination with antibiotics against extended-spectrum β-lactamase-producingEscherichia coli: Table 1

In this paper, we studied the antibacterial effects of oregano essential oil (OEO) both alone, using a twofold dilution method, and combined with antibiotics, using a checkerboard microtitre assay, against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. The result indicated that multiple drug-resistant E. coli was very sensitive to OEO and polymycin; their minimal inhibitory concentration values are 0.5 microL mL(-1) and 0.8 microg mL(-1). The antibacterial effects of OEO in combination with kanamycin were independent against E. coli, with fractional inhibitory concentration (FIC) indices of 1.5. The antibacterial effects of OEO combined with amoxicillin, polymycin, and lincomycin showed an additive effect against E. coli, with FIC indices in the range of 0.625-0.750. The antibacterial effects of OEO in combination with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol displayed synergism against E. coli, with FIC indices ranging from 0.375 to 0.500. The combination of OEO with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol to treat infections caused by ESBL-producing E. coli may lower, to a great extent, the effective dose of these antibiotics and thus minimize the side effects of antibiotics. This is the first report on OEO against ESBL-producing E. coli.

Effects of oregano, carvacrol and thymol on Staphylococcus aureus and Staphylococcus epidermidis biofilms

The aim of this study was to evaluate the effect of oregano essential oil, carvacrol and thymol on biofilm-grown Staphylococcus aureus and Staphylococcus epidermidis strains, as well as the effects of the oils on biofilm formation. For most of the S. aureus (n=6) and S. epidermidis (n=6) strains tested, the biofilm inhibitory concentration (0.125-0.500 %, v/v, for oregano, and 0.031-0.125 %, v/v, for carvacrol and thymol) and biofilm eradication concentration (0.25-1.0 %, v/v, for oregano and 0.125-0.500 %, v/v, for carvacrol and thymol) values were twofold or fourfold greater than the concentration required to inhibit planktonic growth. Subinhibitory concentrations of the oils attenuated biofilm formation of S. aureus and S. epidermidis strains on polystyrene microtitre plates.

Combined effect of oregano essential oil and modified atmosphere packaging on shelf-life extension of fresh chicken breast meat, stored at 4 °C

The combined effect of oregano essential oil (0.1% and 1% w/w) and modified atmosphere packaging (MAP) (30% CO 2/70% N 2 and 70% CO 2/30% N 2) on shelf-life extension of fresh chicken meat stored at 4 °C was investigated. The parameters that were monitored were: microbiological (TVC, Pseudomonas spp., lactic acid bacteria (LAB), yeasts, Brochothrix thermosphacta and Enterobacteriaceae), physico-chemical (pH, TBA, color) and sensory (odor and taste) attributes. Microbial populations were reduced by 1–5 log cfu/g for a given sampling day, with the more pronounced effect being achieved by the combination of MAP and oregano essential oil. TBA values for all treatments remained lower than 1 mg malondialdehyde (MDA) kg −1 throughout the 25-day storage period. pH values varied between 6.4 (day 0) and 5.9 (day 25). The values of the color parameters L*, a* and b* were not considerably affected by oregano oil or by MAP. Finally, sensory analysis showed that oregano oil at a concentration of 1% imparted a very strong taste to the product for which reason these lots of samples were not scored. On the basis of sensory evaluation a shelf-life extension of breast chicken meat by ca. 3–4 days for samples containing 0.1% oregano oil, 2–3 days for samples under MAP and 5–6 days for samples under MAP containing 0.1% of oregano oil was attained. Thus oregano oil and MAP exhibited an additive preservation effect.

Effect of oregano essential oil on chicken lactobacilli andE. coli

The effect of the oregano essential oil (EO) on lactobacilli and E. coli isolated from chicken was showed in the series of in vitro and in vivo experiments. Minimum inhibitory concentrations of amikacin, apramycin, streptomycin, neomycin against E. coli strains increased after oral application of EO.

The effect of oregano essential oil on survival/death of Salmonella typhimurium in meat stored at 5°C under aerobic, VP/MAP conditions

The effect of oregano essential oil and film permeability on the behaviour of Salmonella typhimurium in sterile and naturally contaminated beef fillets stored under aerobic, modified atmosphere consisting of 40% CO2 /30% O2 /30% N2 (MAP) and a vacuum packaged (VP) environment was studied during storage at 5°C. In samples without oregano essential oil, the pathogen survived under all storage conditions. Addition of oregano essential oil at a concentration of 0·8% v/w resulted in an initial reduction of 1–2 log10 cfu g−1 of the majority of the microbial population of meat with lactic acid bacteria and S. typhimurium showing the greatest reductions in all gaseous environments regardless of film permeability. The use of VP/MAP at chill temperatures in conjunction with oregano essential oil as a means of controlling spoilage and safety of meat is discussed.

Effect of oregano essential oil on microbiological and physico-chemical attributes of minced meat stored in air and modified atmospheres.

This study aimed to determine the combined effect of packaging (air, modified atmosphere) with or without the addition of essential oil not only on the selection of microbial association of meat but also to determine any significant difference in microbial metabolites produced from the prevailing bacteria. Samples of minced meat were mixed with different concentration of oregano essential oil (0, 0.05, 0.5 and 1% v/w) and packed under aerobic or with modified atmosphere (Mixed Gas Modified Atmosphere--MGMA, 40% CO2/30% N2/30% O2; or CO2 Modified Atmosphere--COMA, 100% CO2) and stored at 5 degrees C. In all packaging conditions, only concentrations of 0.5% and 1% oregano oil were effective. Inhibition was evident in the order air < MGMA < COMA. Oregano essential oil delayed glucose and lactate consumption aerobically as well as under MGMA. pH changes were also evident. Furthermore, proteolysis was significantly inhibited in aerobically stored samples, and so was the production of acetate under MAP. Similar results were obtained for the other organic acids eluted from HPLC column. Oregano essential oil delayed microbial growth and suppressed the final counts of the spoilage micro-organisms. It also caused a pronounced alteration in the physico-chemical properties of the minced meat. Microbial analysis alone as spoilage index may misrepresent the effect of a hurdle such as essential oils on spoilage.

Impedance measurements to study the antimicrobial activity of essential oils from Lamiaceae and Compositae

A wide range of essential oils from sage, mint, hyssop, camomile and oregano were tested for their inhibitory effects against nine strains of Gram-negative bacteria and six strains of Gram-positive bacteria. Three principles were used in describing the antimicrobial effects of the essential oils: the overall antimicrobial activity determined by use of an impedometric method, the bactericidal effect determined as colony forming units after exposure to the essential oils, and the number of apparent dead cells determined after further enrichment. The data obtained indicate that while the essential oils of sage, mint, hyssop and camomile had generally a bacteriostatic activity, the essential oil from oregano appeared to be bactericidal at concentrations above 400 ppm, probably because of high contents in phenolic compounds. For the other essential oils, the chemical analysis was unable to explain the antimicrobial effect. The bacteriostatic activity was more marked against Gram-positive bacteria; in contrast, the bactericidal activity was greatest against Gram-negative bacteria. The most sensitive strain was Escherichia coli O157:H7 and, of the Gram-positive species even at the lowest oil concentrations, Listeria innocua was the most sensitive. The data obtained from the study of the bactericidal effect of oregano essential oil indicated that the major part of the species was irreversibly inactivated, i.e. they could not be revived by enrichment.