Essential Oils In Vapour Phase Research Articles

Antimicrobial Activity of Essential Oils in Vapor Phase In Vitro and Its Application in Combination with Lactic Acid to Improve Chicken Breast Shelf Life.

The effect of essential oils (EOs) incorporated in their vapor phase combined with lactic acid immersion pretreatment was studied on fresh refrigerated chicken breast shelf life. Among the several EOs assayed, the in vitro results obtained from the vapor diffusion test allowed mustard, oregano, and garlic EOs to be selected due to their higher antimicrobial activity. In addition, it was possible to determine the EO minimum inhibitory concentrations against Pseudomonas aeruginosa and Escherichia coli and to identify EO binary mixtures showing synergistic or additive effects. Based on the obtained results, a ternary mixture constituted by 0.073, 0.292, and 0.146 µL/mL of headspace of mustard, oregano, and garlic, respectively, was proposed for its application to chicken breasts. The ternary mixture inhibitory action was confirmed in vitro against P. aeruginosa and E. coli. Furthermore, the presence of numerous compounds with recognized antimicrobial and antioxidant activity was found in its volatile phase through gas chromatography. When applying an EO mixture in its vapor phase in combination with 1.0% v/v of lactic acid immersion pretreatment on refrigerated chicken breast, a decrease in mesophilic microorganisms' growth rate as well as in lipid oxidation was observed. Moreover, in a preliminary sensory test, the treated chicken breast was found to be acceptable to consumers and showed no significant differences compared to untreated chicken. In conclusion, the combined use of lactic acid immersion and EOs in their vapor phase was an effective alternative to increase chicken breast shelf life.

Antifungal Activities of Essential Oils in Vapor Phase against Botrytis cinerea and Their Potential to Control Postharvest Strawberry Gray Mold.

Essential oils (EOs) from aromatic plants seem to have the potential to control several fungal pathogens and food contaminants. Botrytis cinerea is the main strawberry fruit contaminant causing high losses during storage. Here, thirteen EOs applied in the vapor phase were evaluated for their potential to inhibit the growth of three different strains of B. cinerea isolated from strawberry fruits. Eight EOs (lemongrass, litsea, lavender, peppermint, mint, petitgrain, sage, and thyme) were able to completely inhibit the growth of B. cinerea for 7 days when applied at a concentration of 625 μL·L−1. Four EOs with the lowest minimal inhibition concentrations (thyme, peppermint, lemongrass, and litsea) have been tested on strawberry fruits intentionally inoculated by B. cinerea. All four EOs showed high inhibition at a concentration of 250 or 500 μL·L−1, but only peppermint EO was able to completely inhibit B. cinerea lesion development at a concentration of 125 μL·L−1. The sensory evaluation of strawberries treated by EOs at a concentration 125 μL·L−1 resulted in a statistically significant decrease in taste, aftertaste, aroma, and overall quality. Lemongrass and litsea EOs scored better than thyme and peppermint ones, thus forming two viable methods for B. cinerea suppression and the extension of packed strawberries’ shelf life.

Essential oil in vapor phase in combination with Enterococcus mundtii STw38 to improve refrigerated hake fillets shelf-life

Essential oils (EOs) in vapor phase were applied together with the bacteriocinogenic strain E. mundtii STw38 to improve the shelf life of Argentinean hake -Merluccius hubbsi-. Evaluated EOs were oregano, thyme, rosemary, and lemongrass. In vitro results demonstrated their effectiveness against foodborne pathogen surrogate Listeria innocua, as well as against Lactobacillus plantarum, Shewanella putrefaciens, and fish indigenous biota. The most effective were oregano and lemongrass, showing the lowest minimal inhibitory concentration, and synergic activity when combined against L. innocua and S. putrefaciens. Furthermore, synergic mixtures promoted changes in target microorganisms cell wall. The composition of the volatile phase of a synergic EOs mixture showed a higher presence of oregano components. When applying the EOs alone in hake fillets, total bacteria count increased 3.3 log cycles whereas in the control system the increase was higher than 5 log cycles, and consumers evaluated similarly in taste and smell both the control and the EOs synergic mixtures. When adding the most concentrated synergic mixture (0.147 μL lemongrass/mL headspace and 0.195 μL oregano/mL headspace) together with the bioprotective culture, in 7 days total bacteria count only increased 3 log cycles, showing the effectiveness of the use of EOs together with E. mundtii STw38.

The Application of the Essential Oils of Thymus vulgaris L. and Crithmum maritimum L. as Biocidal on Two Tholu Bommalu Indian Leather Puppets.

The chemical profile of the Thymus vulgaris (Lamiaceae) essential oil (EO) was investigated in order to evaluate its biological properties against microorganisms affecting two Tholu Bommalu, typical Indian leather puppets stored at the International Puppets Museum “Antonio Pasqualino” of Palermo, Italy. A GC–MS analysis, using both polar and apolar columns, was used to determine the chemical composition of the essential oil. The aim of this study was to evaluate the antimicrobial effectiveness of the Thymus vulgaris and Crithmum maritimum essential oils in vapor phase to disinfect heritage leather puppets. Pieces of leather artifacts that were affected by different bacterial colonies were exposed to EO under vacuum and static evaporation conditions. The results presented showed that the vaporization of essential oil was an efficient method in the disinfection of natural skins, eradicating microorganism in short times. T. vulgaris EO in the 50% solution showed excellent inhibitory activity against isolated bacteria with both methods, but the obtained results suggest that the vacuum method allowed for faster exposition of the artifacts to the biocide. Furthermore, the biocidal properties of the essential oil of a Sicilian accession of Crithmum maritimum (Apiaceae) aerial parts were compared and investigated. The results of the latter essential oil showed a poor activity against the isolated micro-organisms.

Effect of essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris), orange (Citrus sinensis var. Valencia) in the vapor phase on the antimicrobial and sensory properties of a meat emulsion inoculated with Salmonella enterica

The demand for healthier meat products is increasing remarkably and natural antimicrobial agents such as essential oils (EOs) are required, which can be applied in the vapor phase. For this experiment, the effectiveness of essential oils of oregano, thyme, and orange in the vapor phase on the microbiological and sensory characteristics of sausages inoculated with Salmonella enterica and stored at 4°C during 72 hrs and 144 hrs, were studied. Oregano EO with 2000 ppm was the most effective treatment against Salmonella enterica with a logarithmic reduction of 1.97 Log10 CFU/g compared to thyme 1.36 Log10 CFU/g and orange 1 Log10 CFU/g) after 144 hrs. In relation to the general acceptance level, the meat product exposed to the orange EO in vapor phase presented the highest approval by the judges nevertheless, however, were the ones that showed the least reduction in the microbial population. Finally, the results showed that the addition of essential oil in the vapor phase to meat products exerted a bactericidal effect with higher EOs concentrations and some also caused alterations in the sensorial properties of the product.

The in vitro and in situ effect of selected essential oils in vapour phase against bread spoilage toxicogenic aspergilli

The major objective of this study was to determine the antifungal, anti-toxicogenic and anti-sporulation effect of selected essential oils in the control growth of Aspergillus spp. by contact vapour method in in vitro and in situ condition. In continue, the effect of the essential oils treatment on the sensory profile of the bread was evaluated. In this study, ten essential oils (EOs), namely: thyme, clove, laveder, cumin, oregano, cinnamon, basil, rosemary, sage and lemongrass were tested against four strains of Aspergillus [Aspergillus flavus (SLO-B-201), Aspergillus parasiticus (SLO-B-219), Aspergillus ochraceus (SLO-B-245) and Aspergillus westerdijkiae (SLO-B-249)] isolated from bread samples. The Aspergillus strains were tested for potential production of mycotoxins by thin layer chromatography (TLC). The chemical composition of all tested EOs was identified by GC-MS and by gas chromatography with flame ionization detector (GC-FID). The antifungal activity, the minimum inhibitory doses (MIDs), anti-toxicogenic and antisporulation effect of the selected EOs were investigated by gas diffusion method in both, in vitro and in situ analyses. The results indicated that the thyme, clove, oregano, cinnamon and lemongrass were highly effective against tested toxigenic Aspergillus species in vapour phase. A treated bread sample with EOs does not have negative effect on the sensory properties of the breads, with exception of oregano and lemongrass. In this context, application EOs in vapour phase seems to be an effective, sustainable and safe method and promising alternative to the use of chemical inhibitors for bread preservation.

Antifungal activity of essential oils of clove ( Syzygium aromaticum ) and/or mustard ( Brassica nigra ) in vapor phase against gray mold ( Botrytis cinerea ) in strawberries

The search for new alternatives to preserve foods is a growing research field that is of great interest to the food industry. In this study, the inhibitory effect of clove and/or mustard essential oils in vapor phase was evaluated in vitro and in vivo (strawberries) against Botrytis cinerea, a mold highly detrimental to fruits and vegetables. In vitro and in vivo minimum inhibitory concentration (MIC) for clove essential oil was 92.56 μL/Lair, while for mustard, essential oil was 15.42 μL/Lair. As for the combination of tested essential oils the MIC was 46.28 μL/Lair of clove essential oil and 1.93 μL/Lair of mustard essential oil for the in vitro tests, while 11.57 μL/Lair of clove essential oil and 1.93 μL/Lair of mustard essential oil for the in vivo tests. Furthermore, the observed inhibitory effect is due to a synergism of tested essential oils in most of the assessed combinations. Effectiveness of vapors of clove and/or mustard essential oils against B. cinerea was demonstrated. The inhibitory activity exhibited by essential oils vapors can be attributed to the major compounds identified in clove and mustard essential oils, inhibiting B. cinerea growth in vitro and in vivo (strawberries). Combinations of clove and mustard essential oils had a synergistic antifungal effect, confirming that the combined use of volatile compounds from essential oils is more effective than its individual application.

Preservative effectiveness of essential oils in vapor phase combined with modified atmosphere packaging against spoilage bacteria on fresh cabbage

This study was conducted to investigate the antibacterial effects of various essential oils (EOs) against pathogens using the disc volatilization method. Also, combined effects of EOs in vapor phase and MAP were evaluated for reducing levels of total mesophilic microorganisms on fresh cabbage. The vapor phase activities of EOs (thyme-1, oregano-1, lemongrass-1, and lemongrass-2 oils) observed strong inhibitory effects. The MAP results showed that 100% CO2 gas packaging reduced significantly levels of total mesophilic microorganisms on cabbage and radish sprouts, and their reduction level was 1.55 and 2.26 log10 CFU/g compared to control after 21 days of storage (p ≤ 0.05). Based on previous results, combined effects of EOs in vapor phase and MAP (100% CO2) showed that lemongrass-2 oil with 20 discs showed complete inactivation by <1.0 log10 CFU/g after 14 days of storage. These results could provide useful information for developing alternative preservation method to improve the freshness and shelf-life of fresh produce using natural antimicrobials.

Morphological changes in Enterococcus faecium on exposure to Citrus essential oils in vapor phase as determined by TEM, SEM and AFM

The antimicrobial effects of essential oils in vapor phase have been previously reported although the mechanism whereby they bring about their effect continues to be investigated. Morphological changes give some indication of the extent of the damage to cells brought about by exposure to essential oils and may provide a means of substantiating the physiological and biochemical changes that are integral to the antimicrobial effect. In this study, the morphological changes that occur during exposure of Enterococcus faecium to a Citrus essential oil in vapor phase has been investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). TEM shows membrane damage, vacuole formation and leakage of cytoplasmic material, SEM shows deformation of shape, whereas AFM, which gives the most information, confirms the deformation, which could be seen even after 15 minutes exposure using this method.

Fast screening method for assessment of antimicrobial activity of essential oils in vapor phase

Among promising alternative methods to control food spoilage much attention is being paid to the use of essential oils (EOs), and lately also to their activity in vapor phase. Until now, no standard assay exists, and there are many methods used by different authors, but any of them is suitably adapted for fast screening of large quantities of samples. We have modified most commonly used disc volatilization method by using four-section Petri dish (PD, 90mm diameter), large filter paper disc (85mm diameter) evenly impregnated with EO and medium containing lid. In comparison to normal disc volatilization method, labor and material needed are several times reduced, while the composition of headspace is more uniform than in case of 6mm disc, where different volatility of particular compounds could influence the results. Sixty nine EOs were tested for its antimicrobial activity against three bacteria (Staphylococcus aureus, Salmonella enteritidis, Pseudomonas aeruginosa) and three fungi (Alternaria alternata, Aspergillus niger, Penicillium digitatum). Thirty nine EOs inhibited at least one microorganism, Armoracia rusticana and Cinnamomum zeylanicum being the most active, followed by EOs of Eugenia caryophyllata, Origanum compactum, Origanum vulgare, Pimenta racemosa, Thymus serpyllum and Thymus vulgaris inhibiting all six or five microorganisms, respectively. According to our opinion, this method is suitable for screening of large quantities of samples for antimicrobial activity in vapor phase.

Antibacterial properties of certain essential oils against different strains of Staphylococcus aureus

Antibiotics introduce very narrow group of substances. On the other hand natural active substances are chemically very diverse [1]. There have been more and more bacteria which are resistant against same type of antibiotics, for example the large problem introduce Methicillin-resistant Staphylococcus aureus (MRSA) in hospitals [2]. The aim of this study was to identify antimicrobial properties of the 7 essential oils (EOs) in vapour phase against 2 collection strains of MSSA, 1 collection strains of MRSA and 6 clinical isolates of S. aureus, obtained from two hospitals. All these strains have been tested against 10 species of antibiotics in standard doses. Tested EOs were obtained by hydro-distillation and tests of their antimicrobial properties were carried out by the modified diffusion method for testing of EOs in vapour phase [3] in concentrations 0.0083–0.53µl/cm3 of air. The ampicillin and erythromycin were tested as reference antibiotics by standard diffusion method in direct contact. The best MICs were shown by Armoracia rusticana (0.0083–0.017µl/cm3), followed by Majorana syriaca (0.0083–0.13µl/cm3) &gt;Allium sativum (0.0083–0.26µl/cm3) &gt;Satureja hortensis (0.017–0.13µl/cm3) &gt;Satureja montana (0.033–0.26µl/cm3) &gt;Thymus vulgaris (0.033–0.26µl/cm3) &gt;Thymus serpyllum (0.033–0.53µl/cm3). Based on the results, EOs mentioned above could be considered as effective anti-Staphylococcal natural products.

Activity of essential oils in vapour phase against Paenibacillus larvae

Paenibacillus larvae subspecies larvae, a Gram-positive, spore-forming bacterium, is the causative agent of the American foulbrood (AFB), one of the most serious and destructive brood diseases of honeybees. AFB is a problem for beekeepers world-wide [1]. Thus, in this study we have tested eight essential oils from aromatic plants against two strains of P. larvae, one wild strain isolated from infected honeybee colony (15/08f4) and one standard strain (ATCC 9545). For the tests we have used disc volatilization method, as the application of chemicals in vapour phase in the beehives is simple and common. In addition, several products containing thymol against parasitic mite Varroa destructor are commercially available. Four essential oils were active in the range of tested concentrations (from 1 to 256 nl/ml). The most active was EO from Armoracia rusticana (MICs 16 nl/ml) followed by Thymus vulgaris (MIC 64 nl/ml), Mentha spicata var. crispa (MICs 64 and 128 nl/l against wild and standard strain, respectively) and Satureja hortensis (MICs 128 and 256 nl/ml, respectively). The results are quite promising, the toxicity of active EO against honeybees and possible organoleptic changes of bee products will be checked in the next phase.

Antimicrobial properties of selected essential oils in vapour phase against foodborne bacteria

The aim of this study was to identify antimicrobial properties of essential oils in vapour phase. In vitro antibacterial activity against five foodborne bacteria ( Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella enteritidis, Staphylococcus aureus) was evaluated by disc volatilization method. The results were expressed as minimum inhibitory concentrations (MIC) in μl/cm 3 of air. Thirteen of the 27 essential oils were active at least against one bacterial strain in the range of tested concentrations (0.0083–0.53 μl/cm 3). The best results were shown by Armoracia rusticana (MIC 0.0083 μl/cm 3) against all of the strains, followed by Allium sativum > Origanum vulgare > Thymus vulgaris > Satureja montana, Thymus pulegioides > Thymus serpyllum > Origanum majorana > Caryopteris x clandonensis, Hyssopus officinalis, Mentha villosa, Nepeta x faassenii, Ocimum basilicum var. grant verte. In conclusion, certain essential oils are highly effective in vapour phase and could be used in control of foodborne bacterial pathogens.

Antifungal activity of essential oils against filamentous fungi determined by broth microdilution and vapour contact methods

The in vitro activity of some essential oils (EO) (thyme red, fennel, clove, pine, sage, lemon balm and lavender) against clinical and environmental fungal strains was determined. The minimal inhibitory concentrations were determined by a microdilution method in RPMI 1640 and by a vapour contact assay. The composition of oils was analysed by gas chromatography (GC) and GC/mass spectrometry. The results indicated that the oils antifungal activity depended on the experimental assay used. The inhibiting effects of EO in vapour phase were generally higher than those in liquid state. According to both methods thyme red and clove were found to be the oils with the widest spectrum of activity against all fungi tested. Despite the differences between the two methods, our results demonstrate that some EO are very active on dermatophytes and dematiaceous fungi. However, more data will be necessary to confirm this good in vitro efficacy. This study could identify candidates of EO for developing alternative methods to control environmental and clinically undesirable filamentous fungi.