Efficacy of plant essential oils against foodborne pathogens and spoilage bacteria associated with ready-to-eat vegetables: antimicrobial and sensory screening

The objectives of this study were to evaluate the antimicrobial activity of plant essential oils (EOs) against foodborne pathogens and key spoilage bacteria pertinent to ready-to-eat vegetables and to screen the selected EOs for sensory acceptability. The EOs basil, caraway, fennel, lemon balm, marjoram, nutmeg, oregano, parsley, rosemary, sage, and thyme were evaluated. The bacteria evaluated were Listeria spp., Staphylococcus aureus, Lactobacillus spp., Bacillus cereus, Salmonella, Enterobacter spp., Escherichia coli, and Pseudomonas spp. Quantitative antimicrobial analyses were performed using an absorbance-based microplate assay. Efficacy was compared using MIC, the half maximum inhibitory concentration, and the increase in lag phase. Generally, gram-positive bacteria were more sensitive to EOs than were gram-negative bacteria, and Listeria monocytogenes strains were among the most sensitive. Of the spoilage organisms, Pseudomonas spp. were the most resistant. Oregano and thyme EOs had the highest activity against all the tested bacteria. Marjoram and basil EOs had selectively high activity against B. cereus, Enterobacter aerogenes, E. coli, and Salmonella, and lemon balm and sage EOs had adequate activity against L. monocytogenes and S. aureus. Within bacterial species, EO efficacy was dependent on strain and in some cases the origin of the strain. On a carrot model product, basil, lemon balm, marjoram, oregano, and thyme EOs were deemed organoleptically acceptable, but only oregano and marjoram EOs were deemed acceptable for lettuce. Selected EOs may be useful as natural and safe additives for promoting the safety and quality of ready-to-eat vegetables.     

The antimicrobial efficacy of plant essential oil combinations and interactions with food ingredients

The objective of this study was to evaluate the efficacy of plant essential oils (EOs) in combination and to investigate the effect of food ingredients on their efficacy. The EOs assessed in combination included basil, lemon balm, marjoram, oregano, rosemary, sage and thyme. Combinations of EOs were initially screened against Bacillus cereus, Escherichia coli, Listeria monocytogenes and Pseudomonas aeruginosa using the spot-on-agar test. The influence of varying concentrations of EO combinations on efficacy was also monitored using E. coli. These preliminary studies showed promising results for oregano in combination with basil, thyme or marjoram. The checkerboard method was then used to quantify the efficacy of oregano, marjoram or thyme in combination with the remainder of selected EOs. Fractional inhibitory concentrations (FIC) were calculated and interpreted as synergy, addition, indifference or antagonism. All the oregano combinations showed additive efficacy against B. cereus, and oregano combined with marjoram, thyme or basil also had an additive effect against E. coli and P. aeruginosa. The mixtures of marjoram or thyme also displayed additive effects in combination with basil, rosemary or sage against L. monocytogenes. The effect of food ingredients and pH on the antimicrobial efficacy of oregano and thyme was assessed by monitoring the lag phase and the maximum specific growth rate of L. monocytogenes grown in model media. The model media included potato starch (0, 1, 5 or 10%), beef extract (1.5, 3, 6 or 12%), sunflower oil (0, 1, 5 or 10%) and TSB at pH levels of 4, 5, 6 or 7. The antimicrobial efficacy of EOs was found to be a function of ingredient manipulation. Starch and oils concentrations of 5% and 10% had a negative impact on the EO efficacy. On the contrary, the EOs were more effective at high concentrations of protein, and at pH 5, by comparison with pH 6 or 7. This study suggests that combinations of EOs could minimize application concentrations and consequently reduce any adverse sensory impact in food. However, their application for microbial control might be affected by food composition, therefore, careful selection of EOs appropriate to the sensory and compositional status of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to ready to use foods containing a high protein level at acidic pH, as well as lower levels of fats or carbohydrates.     

芳香精油在食品保藏中的应用性研究进展

芳香精油是重要的植物次生代谢物,药食应用历史悠久,因其多方面的生物活性,已引起人们对其在食品保藏领域替代化学防腐剂的极大兴趣。文中概述了芳香精油及其成分在采后果蔬、预切果蔬片、肉制品、乳制品和水产品等食品保鲜和贮藏领域中应用性和安全性研究的最新研究进展。许多研究表明,牛至、丁香、罗勒、胡荽、肉桂、百里香、薄荷、迷迭香、芥茉、芫荽、红根草等芳香精油以及丁子香酚、香芹酚、肉桂酸、己醛、草蒿脑、麝香草酚、香芹酮、肉桂醛、柠檬醛、香叶醇等单体成分具有优良的抗食源性腐败菌和致病菌活性。通过与食品生产前处理工艺、气调包装、配方优化等手段的结合,一些芳香精油及其成分显示出天然食品保藏剂良好的商用价值。     

Biodegradable gelatin–chitosan films incorporated with essential oils as antimicrobial agents for fish preservation

Essential oils of clove (Syzygium aromaticum L.), fennel (Foeniculum vulgare Miller), cypress (Cupressus sempervirens L.), lavender (Lavandula angustifolia), thyme (Thymus vulgaris L.), herb-of-the-cross (Verbena officinalis L.), pine (Pinus sylvestris) and rosemary (Rosmarinus officinalis) were tested for their antimicrobial activity on 18 genera of bacteria, which included some important food pathogen and spoilage bacteria. Clove essential oil showed the highest inhibitory effect, followed by rosemary and lavender. In an attempt to evaluate the usefulness of these essential oils as food preservatives, they were also tested on an extract made of fish, where clove and thyme essential oils were the most effective. Then, gelatin–chitosan-based edible films incorporated with clove essential oil were elaborated and their antimicrobial activity tested against six selected microorganisms: Pseudomonas fluorescens, Shewanella putrefaciens, Photobacterium phosphoreum, Listeria innocua, Escherichia coli and Lactobacillus acidophilus. The clove-containing films inhibited all these microorganisms irrespectively of the film matrix or type of microorganism. In a further experiment, when the complex gelatin–chitosan film incorporating clove essential oil was applied to fish during chilled storage, the growth of microorganisms was drastically reduced in gram-negative bacteria, especially enterobacteria, while lactic acid bacteria remained practically constant for much of the storage period. The effect on the microorganisms during this period was in accordance with biochemical indexes of quality, indicating the viability of these films for fish preservation.     

Antimicrobial effectiveness of oregano and sage essential oils incorporated into whey protein films or cellulose‐based filter paper

BACKGROUND: In this study the antimicrobial effectiveness of oregano and sage essential oils (EOs) incorporated into two different matrices, whey protein isolate (WPI) and cellulose‐based filter paper, was analysed. RESULTS: Antimicrobial properties of WPI‐based films containing oregano and sage EOs were tested against Listeria innocua, Staphylococcus aureus and Salmonella enteritidis. Oregano EO showed antimicrobial activity against all three micro‐organisms. The highest inhibition zones were against L. innocua. However, sage EO did not show antimicrobial activity against any of the micro‐organisms. Antimicrobial activity was confirmed for both EOs using cellulose‐based filter paper as supporting matrix, although it was significantly more intense for oregano EO. Inhibition surfaces were significantly greater when compared with those of the WPI films. This finding is likely due to the higher porosity and diffusivity of the active compounds in the filter paper. CONCLUSION: The interactions between the EOs and the films have a critical effect on the diffusivity of the active compounds and therefore on the final antimicrobial activity. As a result, to obtain active edible films, it is necessary to find the equilibrium point between the nature and concentration of the active compounds in the EO and the formulation of the film. Copyright © 2010 Society of Chemical Industry     

Effects of Allspice, Cinnamon, and Clove Bud Essential Oils in Edible Apple Films on Physical Properties and Antimicrobial Activities

ABSTRACT:  Essential oils (EOs) derived from plants are rich sources of volatile terpenoids and phenolic compounds. Such compounds have the potential to inactivate pathogenic bacteria on contact and in the vapor phase. Edible films made from fruits or vegetables containing EOs can be used commercially to protect food against contamination by pathogenic bacteria. EOs from cinnamon, allspice, and clove bud plants are compatible with the sensory characteristics of apple-based edible films. These films could extend product shelf life and reduce risk of pathogen growth on food surfaces. This study evaluated physical properties (water vapor permeability, color, tensile properties) and antimicrobial activities against  Escherichia coli  O157:H7,  Salmonella enterica,  and  Listeria monocytogenes  of allspice, cinnamon, and clove bud oils in apple puree film-forming solutions formulated into edible films at 0.5% to 3% (w/w) concentrations. 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 antimicrobial activities against the 3 pathogens were in the following order: cinnamon oil > clove bud oil > allspice oil. The antimicrobial films were more effective against  L. monocytogenes  than against the  S. enterica . The oils reduced the viscosity of the apple solutions and increased elongation and darkened the colors of the films. They did not affect water vapor permeability. The results show that apple-based films with allspice, cinnamon, or clove bud oils were active against 3 foodborne pathogens by both direct contact with the bacteria and indirectly by vapors emanating from the films.     

Antimicrobial activity of plant essential oils using food model media: Efficacy,synergistic potential and interactions with food components

The aim of this study was to optimise the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria spp. and spoilage bacteria using food model media based on lettuce, meat and milk. The EOs evaluated were lemon balm, marjoram, oregano and thyme and their minimum inhibitory concentrations (MIC) were determined against Enterobacter spp., Listeria spp., Lactobacillus spp., and Pseudomonas spp. using the agar dilution method and/or the absorbance based microplate assay. MICs were significantly lower in lettuce and beef media than in TSB. Listeria strains were more sensitive than spoilage bacteria, and oregano and thyme were the most active EOs. EO combinations were investigated using the checkerboard method and Oregano combined with thyme had additive effects against spoilage organisms. Combining lemon balm with thyme yielded additive activity against Listeria strains. The effect of simple sugars and pH on antimicrobial efficacy of oregano and thyme was assessed in a beef extract and tomato serum model media. EOs retained greater efficacy at pH 5 and 2.32% sugar, but sugar concentrations above 5% did not negatively impact EO efficacy. In addition to proven antimicrobial efficacy, careful selection and investigation of EOs appropriate to the sensory profile of foods and composition of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to foods containing a high protein level at acidic pH, as well as moderate levels of simple sugars.     

STABILIZATION OF MEAT LIPIDS WITH GROUND SPICES

The antioxidant efficacy of ground clove, ginger, oregano, rosemary, sage, and thyme was investigated in comminuted pork systems. Spices at 200–2000 ppm levels of addition inhibited the formation of the 2-thiobarbituric acid (TBA) reactive substances (TBARS) by 12–96% over 21-days of storage at 4C. The anti-oxidative effect of spices was concentration-dependent; but close followed by sage and then rosemary was most effective. Ginger and thyme exerted the least effect in prevention of oxidation of meat lipids.     

Antibacterial Effects of Allspice, Garlic, and Oregano Essential Oils in Tomato Films Determined by Overlay and Vapor-Phase Methods

ABSTRACT:  Physical properties as well as antimicrobial activities against  Escherichia coli  O157:H7,  Salmonella enterica , and  Listeria monocytogenes  of 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 monocytogenes  was less resistant to EO vapors, while  E. coli  O157: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.     

Antibacterial activity of 11 essential oils against Bacillus cereus in tyndallized carrot broth

The antibacterial activity of 11 essential oils from aromatic plants against the strain INRA L2104 of the foodborne pathogen Bacillus cereus grown in carrot broth at 16 degrees C was studied. The quantity needed by the essential oils of nutmeg, mint, clove, oregano, cinnamon, sassafras, sage, thyme or rosemary to produce 14-1110% relative extension of the lag phase was determined. Total growth inhibition of bacterial spores was observed for some of the antimicrobial agents assayed. The addition of 5 microl cinnamon essential oil per 100 ml of broth in combination with refrigeration temperatures of 相似文献   

Influence of Some Spice Essential Oils on Aspergillus Parasiticus Growth and Production of Aflatoxins in a Synthetic Medium

Gas-liquid chromatography was used to determine the essential oil compositions of thyme, cumin, clove, caraway, rosemary, and sage. The basic components of these oils were thymol, cumin aldehyde, eugenol, carvonc, borneol and thujonc, respectively. The antifungal potential of the oils against Aspergillus parasiticus were investigated. The essential oils caused complete inhibition of both mycelial growth and aflatoxin production. The effectiveness followed the sequence: thyme > cumin > clove > caraway > rosemary > sage. The major components of the essential oils produced an inhibitory effect at minimum inhibitory concentrations equal to those obtained with the oils.     

Effects of Turkish spice extracts at various concentrations on the growth of Escherichia coli O157:H7

The antimicrobial activities of the extracts of seven spices (cumin, Helichrysum compactum Boiss (HC), laurel, myrtle, oregano, sage and thyme) were examined in their capacity to inhibit the growth of Escherichia coli O157:H7. Spices were fractionated by the extraction method to obtain a methanolic fraction. Of the spices tested, thyme showed promising results by inhibiting growth both in paper disc assay and agitated liquid culture assay. Antibacterial effects of tested spices extracts vary related to concentrations. Thyme and oregano showed higher activity than the others. It was also found that laurel and HC markedly stimulated the growth of E. coli O157:H7. Statistically, important variations were found among the inhibitory effects of spice extracts. This study has shown that E. coli O157:H7 inhibition by spice extracts may be of use in the field of food preservation.     

Antibacterial activity of soy edible coatings incorporated with thyme and oregano essential oils on beef against pathogenic bacteria

Food Science and Biotechnology - Inhibitory effects of soy-protein edible coatings incorporated with 1, 2, or 3% of thyme or oregano essential oils (EOs) were determined against Escherichia coli...     

Inhibition of Lactic Acid Bacteria by Herbs

Increasing concentrations (0.5–8g/liter) of oregano, rosemary, sage, and thyme progressively delayed growth and acid production by Lactobacillus plantarum and Pediococcus acidilactici in a liquid medium. After the bacteriostatic activity was overcome, all four herbs strongly stimulated acid production. The relative inhibitory effect of the herbs toward both microorganisms was oregano ? rosemary = sage gt; thyme. L. plantarum was more resistant than P. acidilactici to the toxic effect of the herbs. Organisms from cultures exhibiting delayed fermentation in the presence of sublethal concentrations of an herb, when subcultured into fresh media containing identical herb concentrations, initiated fermentation without delay, indicating development of resistance to the herb's effect. Moreover, bacteria which had acquired a resistance to one herb were also resistant to the other three herbs.     

Heavy metals in spices commonly consumed in Republic of Korea

Levels of lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) were evaluated in 359 samples of commonly consumed spices (cinnamon, parsley, basil, oregano, coriander seed, nutmeg, cumin, bay leaf, fenugreek, rosemary, thyme, fennel, sage, clove, marjoram, tarragon, caraway, dill seed, pepper, and turmeric) from the market in the Republic of Korea. The content of Pb, Cd, and As was assessed by acid wet digestion using a microwave oven and inductively coupled plasma mass spectrometry (ICP-MS). The content of Hg was analysed using a direct mercury analyzer (DMA). Pb, Cd, As, and Hg mean content in spices ranged from 0.039–0.972 mg kg^?1, 0.013–0.315 mg kg^?1, 0.121–0.861 mg kg^?1, and 0.001–0.025 mg kg^?1, respectively.     

肉桂精油-玉米淀粉基抗菌膜的制备及其性能

为研究新型抗菌降解包装材料,筛选肉桂精油等4?种植物精油,以玉米淀粉、壳聚糖和魔芋葡甘露聚糖为成膜基质,甘油为增塑剂,吐温-80为表面活性剂,研究肉桂精油添加对复合膜机械性能、光学性能、阻水性能和抑菌性能的影响。结果表明：4?种精油对金黄色葡萄球菌、大肠杆菌和沙门菌的抗菌活性依次为肉桂精油＞牛至精油＞百里香精油＞迷迭香精油。随着肉桂精油质量浓度增加,复合膜的抗拉强度和水蒸气透过系数降低,断裂伸长率和不透明度升高。当肉桂精油质量浓度在15.0～20.0?g/L时,复合膜色泽指数a*值无明显差异（P＞0.05）,L*值显著降低,b*值和ΔE值显著增加（P＜0.05）。添加肉桂精油显著提高了玉米淀粉基膜的抗菌能力（P＜0.05）,精油与吐温-80相互作用对革兰氏阴性的大肠杆菌具有协同作用,而对革兰氏阳性的金黄色葡萄球菌具有拮抗作用。当肉桂精油质量浓度为20.0?g/L时,膜具有较好的物理性能和抗菌效果。本研究可为肉桂精油-玉米淀粉基可降解抗菌膜生产工艺参数的进一步优化提供参考。     

Antibacterial activity of different essential oils obtained from spices widely used in Mediterranean diet

Raw and processed foods are open to contamination during their production, sale and distribution. At present, therefore, a wide variety of chemical preservatives are used throughout the food industry to prevent the growth of food spoiling bacteria. However health and economic considerations have led to a search for alternatives, such as essentials oils that can safely be used as substitutes for fungicides and bactericides to partially or completely inhibit the growth of fungi and bacteria. The aim of this work was to determine the effectiveness of the essentials oils from oregano (Origanum vulgare), thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), sage (Salvia officinalis), cumin (Cuminum cyminum) and clove (Syzygium aromaticum) on the growth of some bacteria commonly used in the food industry, Lactobacillus curvatus, Lactobacillus sakei, Staphylococcus carnosus and Staphylococcus xylosus or related to food spoilage Enterobacter gergoviae, Enterobacter amnigenus. The agar disc diffusion method was used to determine the antibacterial activities of the oils. All six essential oils analysed had an inhibitory effect on the six tested bacteria. Oregano essential oil showed the highest inhibition effect followed by cumin and clove.     

Comparative evaluation of antioxidant and anti food-borne bacterial activities of essential oils from some spices commonly consumed in Iran

The antioxidant potency, anti food borne bacterial activity, and total phenolic contents of essential oils (EOs) from avishane shirazi (Zataria multiflora), clove (Syzgium aromaticum), cinnamon (Cinnamomum zeylanicum), cumin (Cuminum cyminum), black cumin (Bunium persicum), spearmint (Mentha spicata), horsemint (Mentha longifolia), coriander (Coriandrum sativum), sage (Salvia officinalis), and ginger (Zingiber officinale) were evaluated. In 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, free radical scavenging activities of clove and avishane shirazi EOs were 90.69% and 88.63%, respectively. In reducing power assay, the EO of clove showed the highest reducing capacity. The highest concentrations of total phenolics (66.01 mg and 44.81 mg GAE/gram sample) were also detected for the EOs of clove and avishane shirazi, respectively. The results of disc diffusion assay showed that the EOs of avishane shirazi, cinnamon, and clove strongly inhibited growth of the tested bacteria. The EO of cinnamon had the lowest minimal inhibitory concentration (MIC) (0.312 mg/mL).     

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.     

Antimicrobial activity of whey protein based edible films incorporated with oregano,rosemary and garlic essential oils

The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging. Antimicrobial properties of spice extracts are well known, however their application to edible films is limited. In this study, antimicrobial properties of whey protein isolate (WPI) films containing 1.0–4.0% (wt/vol) ratios of oregano, rosemary and garlic essential oils were tested against Escherichia coli O157:H7 (ATCC 35218), Staphylococcus aureus (ATCC 43300), Salmonella enteritidis (ATCC 13076), Listeria monocytogenes (NCTC 2167) and Lactobacillus plantarum (DSM 20174). Ten millilitres of molten hard agar was inoculated by 200 μl of bacterial cultures (colony count of 1 × 10⁸ CFU/ml) grown overnight in appropriate medium. Circular discs of WPI films containing spice extracts, prepared by casting method, were placed on a bacterial lawn. Zones of inhibition were measured after an incubation period. The film containing oregano essential oil was the most effective against these bacteria at 2% level than those containing garlic and rosemary extracts (P < 0.05). The use of rosemary essential oil incorporated into WPI films did not exhibit any antimicrobial activity whereas inhibitory effect of WPI film containing garlic essential oil was observed only at 3% and 4% level (P < 0.05). The results of this study suggested that the antimicrobial activity of some spice extracts were expressed in a WPI based edible film.