Essential Oil Emulsions Research Articles

Stability and antimicrobial activity of eucalyptus essential oil emulsions.

We evaluated various formulations of oil-in-water emulsions prepared from eucalyptus essential oil, for their stability and antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. These formulations were developed using a response surface experimental design and analyzed with Design-Expert® 10 software. The emulsions were prepared in a colloid mill, and emulsion characterization was performed using the zeta ( ζ)-potential, droplet size distribution, and phase separation. The antimicrobial effects were assessed by death kinetics. The droplet size and ζ-potential of the 16 emulsions ranged from 1.071 to 1.865 µm (based on Feret's diameter) and -34.8 to -24 mV, respectively. Three formulations (14, 15, and 16) demonstrated the highest stability parameters (no phase separation) during the 28 days of evaluation. Eucalyptus essential oil emulsions exhibited antimicrobial activity against E. coli, S. aureus, and P. aeruginosa in less than 1 min.

Preparation and in vitro diffusion study of essential oil Pickering emulsions stabilized by silica nanoparticles

AbstractIn the field of essential oil research, the low water solubility of essential oils (EOs) causes several problems, not only in pharmaceutical applications, but also in microbiological experiments. The aim of our work was to prepare Pickering emulsions with tea tree, thyme, and anise EOs stabilized with silica nanoparticles, in order to enhance their availability for microbiological tests. We have examined the influence of surface properties and concentration of silica nanoparticles and dispergation energy on emulsion stability and droplet size. In vitro diffusion experiments have been performed on model agar gel membranes, with the stable Pickering emulsions and conventional emulsions of EOs stabilized with Tween 80 surfactant. We have examined the influence of surface modifying group type, surface coverage of silica nanoparticles, and droplet size of the emulsions on the diffusion properties of the EOs. Our results show that highly stable Pickering emulsions can be prepared with silica nanoparticles of 20 nm diameter and 20% of surface covered with ethyl groups, in a wide EO concentration range. The cumulative amount of the EO was more effective in Pickering emulsions than in conventional emulsions for tea tree and thyme EOs, whereas the opposite case was true for anise EO. As the droplet size of the Pickering emulsion decreases, the cumulative concentration of the EO increases. In this work, we have shown that the Pickering emulsions of EOs are a suitable form for EO transport through complex membranes, and hopefully can be effectively applied in microbiological and pharmaceutical experiments.

Surfactant type affects the washing effect of cinnamon leaf essential oil emulsion on kale leaves

With increasing foodborne illness associated with fresh-cut produce, a chemical sanitizer to substitute chlorine is needed in the food industry. This study examined the washing effect of cinnamon leaf essential oil (CL-EO) emulsions on fresh-cut produce according to the ionic properties of surfactants. Washing effect of CL-EO emulsion (CLC) with cetylpyridinium chloride was the highest among all treatments on kale leaves. After CLC treatment, 1.83 and 1.54 log reductions against Listeria monocytogenes and Escherichia coli O157:H7 were achieved, respectively, compared to washing with distilled water, and had about 0.6 log-reductions higher than NaOCl treatment. CL-EO droplets in CLC had a positive ζ-potential (+55 mV) compared to other emulsions. These results indicate that ionic properties of surfactants are very important in the washing effect of CL-EO emulsion. Additionally, CLC treatment did not affect the quality of kale leaves during storage. Therefore, CLC can be an effective chemical sanitizer for washing kale leaves.

Different extraction methods for phenolic and volatile compounds recovery from Elsholtzia ciliata fresh and dried herbal materials

The aim of this study was to determine main chemical compounds in Elsholtzia ciliata and increase the efficiency of their extraction from herbal materials. To our knowledge, this is the first research comparing different extraction methods and conditions of the E. ciliata extracts production. Extracts were obtained by ultrasound-assisted (UAE), heat-reflux (HRE), continuous stirring (CSE), maceration (ME), percolation (PE), and ultrasound assisted with percolation (UAE with PE) extraction methods In this study, 13 phenolic compounds were determined for the first time in E. ciliata extracts (quinic acid, neochlorogenic acid, chlorogenic acid, p-coumaric acid, vitexin, ferulic acid, luteolin-7-rutinoside, luteolin-7-glucoside, procyanidin B, apigenin-7-glucoside, naringenin, diosmetin, and chrysin) and six volatile compounds in essential oil (EO) (ethylfuran, shisofuran, methyl nerate, 4-vinyl guaiacol, cis-alpha-bergamotene and phytone). The lowest contents of polyphenols and ketones were obtained by PE. The optimal method for the chemical compounds recovery was UAE with the solvent 70% ethanol and 30 min extraction time. For the first time was investigated E. ciliata EO emulsion relaxation effect of rat mesenteric blood vessels. Emulsion showed a weak vasorelaxing ability.

Effect of emulsifier HLB and stabilizer addition on the physical stability of thyme essential oil emulsions

ABSTRACTThe objective of this work was to formulate and to further improve the stability of emulsions based on thyme essential oil. Several nonionic surfactants of different nature and with different hydrophilic−lipophilic balance (HLB) values were investigated. The surfactant with optimal HLB found for the thyme essential oil was Appyclean 6548 (HLB: 9-9.5). Afterwards, stabilizing biopolymers were added in order to improve emulsion stability. Properties of emulsions were evaluated in terms of droplet size and physical stability. Thyme essential oil/W emulsions formulated with a new biodegradable emulsifier (alkyl polypentoside) and welan gum as stabilizer were obtained with high shelf-life.

Antibacterial Activity of Emulsified Pomelo (Citrus grandis Osbeck) Peel Oil and Water-Soluble Chitosan on Staphylococcus aureus and Escherichia coli.

This study utilized pomelo steam distillation to isolate pomelo peel essential oil. The constituents were then analyzed through gas chromatography-mass spectrometry (GC-MS), and the antibacterial activity of the essential oil emulsions at different homogenizer speed conditions and concentrations of water-soluble chitosan (degree of acetylation, DA = 54.8%) against S. aureus and E. coli was examined. Analysis of the essential oil composition identified a total of 33 compounds with the main constituent, limonene accounting for 87.5% (940.07 mg/g) of the total. The pomelo peel oil was emulsified through homogenization at 24,000 rpm, resulting in a minimal inhibitory concentration (MIC) for E. coli that was 1.9 times lower than that of the essential oil without homogenization. In addition, a mixture of 0.4% essential oil emulsion and 0.03% water-soluble chitosan had the strongest synergetic antibacterial effect on S. aureus and E. coli at pH 7.4. In comparison with chitosan alone, the MIC value of this mixture was significantly 2.4 and 2.5 times lower. Hence, this study suggests using a mixture of emulsified pomelo peel oil and water-soluble chitosan to develop a novel natural food preservative, and that the processability of food, as well as the economic value of the byproducts of the Taiwan Matou pomelo and chitosan, could be increased.

Lippia gracilis Schauer essential oil nanoformulation prototype for the control of Thielaviopis paradoxa

The goal of the study was to evaluate the antifugal effect of essentials oils from the Lippia gracilis genotypes with main components of thymol and carvacrol and essential oil emulsions on Thielaviopis paradoxa. The essential oil was extracted from the genotypes by hydrodistillation. The nanoemulsions were obtained from the spontaneous emulsification technique. The nanoemulsions obtained where characterized by particle size, zeta potential and polydispersity. For the fungal activity bioasssays in vitro, the essential oils, majority components and nanoemulsions in different concentrations were added to potato-dextrose-agar (PDA) medium. Each plate was inoculated placing at the center a 7 mm disk containing T. paradoxa mycelium. For the in vivo assay, for the plant infections a 2 × 106 CFU (colony forming unit) suspension in was use in PDA medium. After 7 days, the emulsions were pulverized with minimal inhibitory concentrations and testemonies. The ecophysiology parameters (photosynthesis; stomatal conductance, transpiration and vapor pressure deficit between plant and air) in 30 coconut trees inoculated with T. paradoxa was analyzed. The L. gracilis essential oil has antifungal potential for the control of coconut tree stem-bleeding, since the T. paradoxa was inhibited in all concentrations used. The genotype LGRA109 essential oil presented MIC of 0.23 mg/mL, while the LGRA106 presented MIC of 0.82 mg/mL. The essential oil nanoemulsions presented high efficiency in disease control (MIC 0.6 mg/mL) and low phytotoxicity; therefore representing a good alternative for the efficient control of T. paradoxa in coconut tree.

Optimizing Production of Mentha longifolia Essential Oil Emulsion Loaded with Omega 3 Fatty Acids by Nano-Fiber/Gas Chromatography

The main aim of this study is providing of Mentha longifolia L essential oil emulsion loaded with omega 3 fatty acids and optimization by polyaniline (PANI) nano-fiber/gas chromatography (PANI-F/GC). The head space solid phase microextraction (HS-SPME) method by polyaniline nanofibers was used to extract released essential oils of emulsion. The effects of four factors, including omega 3 percent, surfactant-to-oil ratio (SOR%), surfactant type (TWEEN 20, 80 and caseinate sodium) and storage time on the encapsulation efficiency, and essential oil chromatographic characteristics including total peak number, total peak area and total peak height were studied. The Central Composite Design (CCD) was used to design experiments and study the effects of four factors on the responses and P-value of <0.05 was considered statistically significant. Desirability function (D) was used for determination of optimum condition. Results showed that all four factors affected GC profile, essential oil release and encapsulation efficiency. According to the results the emulsion has the best release power on the condition: Omega 3 (%); 25, Storage Time (day); 60, SOR (%); 193.33 and Surfactant type; T80 where the total peak number was 3, total peak area: 407, total peak height: 77 and encapsulation efficiency was 75%.

ANTIFUNGAL ACTIVITY OF SOME ESSENTIAL OIL EMULSIONS AND NANOEMULSIONS AGAINST FUSARIUM OXYSPORUM PATHOGEN AFFECTING CUMIN AND GERANIUM PLANTS

In the present investigation, the antifungal activity of essential oil emulsions and nanoemulsions of sweet basil (Ocimum basilicum L.), marjoram (Majorana hortensis Moench), peppermint (Mentha piperita L.), spearmint (Mentha spicata L.) and thyme (Thymus vulgaris L.) were evaluated against Fusarium oxysporum isolated from infested cumin and geranium plants. Essential oils were obtained by hydrodistillation and analyzed by gas chromatography. The nanoemulsion was formulated using the essential oils, non-ionic surfactant (Tween 80) and water by ultrasonication method for 30 min and characterized by particle size analyzer and transmission electron microscope. Essential oil emulsions were prepared as mentioned above without sonication. The transmission electron micrograph showed that the essential oil nanoemulsions were spherical in shape and moderately mono or di-dispersed. The droplet size was correlated well with the results obtained from droplet size analysis showing that droplets are present in the nanometer range, with particle size of less than 100 nm and were stable after 3 months of storage under room temperature (27 °C). Four concentrations of the emulsions and nanoemulsions were used to evaluate the anti-fusarium activity in vitro. The results showed that maximum inhibition against Fusarium oxysporum. f.sp. cumini was resulted by thyme essential oil nanoemulsion and emulsion at 2000 ppm and sweet basil essential oil nanoemulsion at 4000 ppm. Also, maximum inhibition against Fusarium oxysporum isolated from geranium plant resulted by thyme essential oil nanoemulsion and emulsion at 2000 ppm. All essential oil nanoemulsions exhibited higher activities compared to emulsions against fungal growth at all concentrations. Treating cumin seeds with each of the concentrations of essential oil emulsions did not affect germination, while seed germination percentage sharply decreased at high concentrations of nanoemulsions treatments. The results suggest the potential effects of thyme and sweet basil essential oil nanoemulsions as novel fungicide agents against Fusarium spp.

Antibacterial activities of a cinnamon essential oil with cetylpyridinium chloride emulsion against Escherichia coli O157:H7 and Salmonella Typhimurium in basil leaves.

This study examined the antibacterial activities of two different cinnamon essential oil emulsions against Escherichia coli O157:H7 and Salmonella Typhimurium on basil leaves. Cinnamon oil (0.25%) treatments containing CPC (0.05%) exhibited greater effects on the pathogenic bacteria than cinnamon oil treatment without this emulsifier (p<0.05). Treatment with cinnamon bark and leaf oil emulsions (CBE and CLE, respectively) reduced the populations of E. coli O157:H7 by 4.10 and 5.10 log CFU/g, and S. Typhimurium by 2.71 and 2.82 log CFU/g, respectively. Scanning electron micrographs showed morphological changes in the two pathogenic bacteria following emulsion treatment. In addition, there was no difference in the color or ascorbic acid content of the basil leaves by the emulsion treatment. These results suggest that CBE or CLE treatment can be an effective way to ensure the microbial safety of minimally processed vegetables and a good alternative to chlorination treatment in the fresh produce industry.

Modeling phase separation and droplet size of W/O emulsions with oregano essential oil as a function of its formulation and homogenization conditions

ABSTRACTOregano essential oil emulsions (W/O) were prepared using different emulsifiers’ blend concentrations of Tween 80/Span 20, to study their phase separation during storage and to optimize the homogenization processing parameters by minimizing the droplet size of emulsions. Phase separation followed a second-order kinetic model, and relationships between the kinetic parameters and the blend concentrations of emulsifiers were established for determining the best emulsion formulations. The instability mechanism of emulsions demonstrated to be Ostwald ripening; therefore, by means of surface response methodology, mechanical homogenization parameters (11,700 rpm for 12 minutes at 1°C) were specified in order to minimize the droplet size of emulsions (1.02 ± 0.12 µm).

Shelf-life extension of refrigerated rainbow trout fillets using total Farsi gum-based coatings containing clove and thyme essential oils emulsions

In this study, total (non-fractionated) Farsi gumbased coatings (FGC) incorporated with clove (CEO) and Shirazi thyme (SEO) essential oils emulsions were utilized to extend the shelf-life of refrigerated rainbow trout fillets. Sonication decreased the amount of water insoluble fraction of FGC. Physicochemical, microbial and sensory characteristics of coated fillets were evaluated during 16 days. The results showed that incorporating CEO and SEO into FGC could significantly (p < 0.05) improve the quality of fish fillets. During storage, the increase in the amounts of peroxide value (PV), thiobarbituric acid reactive substances (TBARS), and total volatile basic-nitrogen (TVB-N) followed this order: CEO-SEO loaded FGC < FGC < uncoated (control). Regarding color parameters including L* and b* increased; whereas, a* decreased. Texture, odor, color and overall acceptability of coated fillets were significantly (p < 0.05) better than those of uncoated ones. A significant (p < 0.05) improvement in the microbial quality (total viable count (TVC), psychrophilic and lactic acid bacteria counts) was observed in the presence of essential oil-loaded coatings. Interestingly, an obvious synergistic effect was observed between CEO and SEO. The increase (>6 days) in the shelf-life was attributed to the antioxidant and antimicrobial characteristics of CEO and SEO.

Citrus peel essential oil nanoformulations to control the tomato borer, Tuta absoluta: chemical properties and biological activity

The repeated use of conventional synthetic pesticides in crop protection leads to resistance development by pests along with a negative impact on the environment, particularly non-target arthropods. Plant-derived active compounds, such as essential oils (EOs), play a key role in sustainably controlling pests. The lethal and sublethal activity of citrus peel EOs as emulsions and included in polyethylene glycol (PEG) nanoparticles (EO-NPs) was determined against the invasive tomato pest Tuta absoluta. Their effects on the plants were also assessed. The results showed an overall good insecticidal activity of the compounds tested, with a higher mortality through contact on eggs and larvae by EO emulsions and through ingestion on larvae by EO-NPs. The nanoformulation also significantly reduced the visible toxic effects on the plants. The data collected suggest that these natural compounds, especially when nanoformulated, could be successfully used in integrated pest management programs for T. absoluta.

Stability of lime essential oil emulsion prepared using biopolymers and ultrasound treatment

ABSTRACTThe objective of this study was to investigate the kinetic stability of lime essential oil emulsion using gum arabic (GA) and whey protein isolate (WPI) biopolymers as emulsifiers and stabilizers. Different solid compositions were evaluated: GA, GA/WPI (1:1) and WPI, as well as oil concentration (5.0, 7.5 and 10% w/w). Emulsions were prepared using an ultrasonic homogenizer. Viscosity, oil droplet size, zeta potential, pH and conductivity were measured to predict the emulsion stability over a period of 4 h (estimated time until complete drying in microencapsulation processes). Emulsion rheological behaviour and microstructure were characterized. All emulsions were stable during the time period analysed, and no destabilization characteristic was observed. The pH, conductivity and viscosity showed no significant difference (p > 0.05) over the 4-h period. Emulsions with WPI showed higher zeta potential values, confirming the biopolymer electrosteric stabilization. The combination of wall materials (GA/WPI) and the oil concentration increased the average droplet size. The results of the apparent viscosity at shear rate of 100 s−1 confirmed the emulsions stability. These values did not change significantly considering the fresh emulsions and emulsions after 4 h of preparation. The emulsifying biopolymers showed to be excellent natural stabilizers for lime essential oil emulsions, highlighting the results using WPI.

Characterization of Portuguese Thymbra capitata, Thymus caespititius and Myrtus communis essential oils in topical formulations

AbstractAs the personal care industry evolves, formulators are seeking innovative solutions for their formulations' needs, and for ingredients that can offer multiple functions within formulations. Considering that essential oils (EOs) may present a wide spectrum of biological activities, the composition, antimicrobial and antioxidant activity of Portuguese Thymbra capitata, Thymus caespititius and Myrtus communis EOs were assessed in order to evaluate them as preservatives and antioxidants in topical emulsions. The in vivo safety application of some emulsions was also tested. T. capitata EO was mainly constituted by carvacrol (73%), whereas α‐terpineol (27%), p‐cymene (14%) and carvacrol (10%) dominated Th. caespititius EO, and 1,8‐cineole (37%) was dominant in M. communis EO. The minimum inhibitory concentration of T. capitata, Th. caespititius and M. communis EOs was 0.4 μg/mL against C. albicans and ranged between 0.4 and 30.7 μg/mL against A. brasiliensis. Gram‐positive bacteria were more susceptible to each EO than Gram‐negative bacteria. T. capitata EO showed significantly higher antioxidant activity than Th. caespititius and M. communis EOs. EOs incorporated in emulsions showed preservative activity against all microorganisms tested and T. capitata EO emulsions showed powerful reactive oxygen species (ROS) scavenging effects. A safety evaluation study was performed with 0.10% and 0.01% T. capitata EO emulsions according to the Human Repeat Insult Patch Test (HRIPT). All emulsions were considered safe for topical application. T. capitata, Th. caespititius and M. communis significantly improved the microbiological quality of the prepared emulsions and may constitute a powerful alternative to the current preservatives and antioxidants for use in topical formulations.

Emulsions of essential oils and aloe polysaccharides: Antimicrobial activity and resistance inducer potential against Xanthomonas fragariae

Bacterial angular leaf spot disease (Xanthomonas fragariae) is an important strawberry disease and responsible for significant yield losses. The efficacy of emulsions containing tea tree or palmarosa essential oils (EO) against angular leaf spot, seeking to elucidate their mode of action, was evaluated in this study. Tea tree or palmarosa EO were added in an aqueous suspension of aloe polysaccharide (AP) and tea tree EO emulsion (TAP) and palmarosa EO microemulsion (PAP) were obtained. The antimicrobial potential of AP, TAP and PAP were evaluated in plants of two cultivars (Albion and San Andreas). The ability of these preparations to reduce disease severity and to activate plant defenses were evaluated. AP, TAP and PAP reduced X. fragariae growth by up to 44.0%, 94.4% and 86.1%, respectively. In addition, TAP and PAP suppressed completely the symptoms in both cultivars. Increased activities of superoxide dismutase, dismutase, catalase and peroxidase were observed in the more susceptible cultivar (Albion) treated with the emulsions, while a higher concentration of total phenolic compounds was verified in the less susceptible cultivar (San Andreas). Thus, emulsions with EO and AP can be used to control angular leaf spot by activating latent defense mechanisms in strawberry.

Whitefly attraction to rosemary (Rosmarinus officinialis L.) is associated with volatile composition and quantity.

Whitefly (Bemisia tabaci) is an important insect pest, causing severe damage to agricultural crops. The pest was recorded in a commercial rosemary (Rosmarinus officinalis, Lamiaceae) field, colonizing rosemary variety (var.) '2', but not '11'. A series of field and controlled laboratory choice bioassays confirmed the observed phenomenon. Mature potted plants of the two varieties were randomly organized in a lemon verbena (Lippia citrodora) and lemon grass (Cymbopogon spp.) fields. Seven days later var. '2' was significantly more colonized by whiteflies than var. '11'. Under lab conditions, whiteflies were significantly more attracted to var. '2' plantlets than to var. '11' following choice bioassays. Furthermore, cotton plants dipped in an essential oil emulsion of var. '2' had significantly greater colonization than cotton plants dipped in the essential oil emulsion of var. '11'. Similar results were obtained in 'plant-plant', 'plant-no plant' as well as, 'essential oil—essential oil' choice bioassay designs. Analyses of the essential oils of the two varieties identified a set of common and unique volatiles in each variety. Among these volatiles were β-caryophyllene and limonene, two compounds known to be associated with plant-insect interactions. The attraction of B. tabaci to pure (>95%) β-caryophyllene and limonene using a range of concentrations was examined in vitro by choice bioassays. The compounds were attractive to the insect at moderate concentration, but not at the lowest or highest concentrations used, where the insect was not attracted or repelled, respectively. Limonene attracted the insects at rates that were 10-fold lower than β-caryophyllene. The results emphasized the role of host plant volatiles in shaping the structure of B. tabaci populations in nature and in agricultural systems, and provided insights into the factors that contribute to the development of insect populations with unique characteristics. The results could also serve for future development of bio-pesticides and in breeding programs.

Influence of non-ionic surfactant type on the salt sensitivity of oregano oil-in-water emulsions

During the last decade, there has been a growing interest for more “label-friendly” ingredients in food industry, as well as in pharmaceuticals, and cosmetics. Thus, a lot of research has been developed to the antimicrobial and/or antioxidant characteristics of essential oils. We, therefore, examined the influence of environmental stress conditions (i.e. salt addition and acidification) on the stability of oregano essential oil emulsions that were stabilized by either Tween 80 or Inutec SP1. Whereas Tween 80 is a non-ionic, food-grade ethoxylated sorbitan ester, Inutec SP1 is a biodegradable and renewable hydrophobically modified inulin. Whereas the emulsions prepared with Tween 80 exhibited phase separation (oiling off) at all salt concentrations studied, the emulsions stabilized with Inutec SP1 remained stable for several days; pH variation on the other hand exhibited no significant effect on the stability. Diffusion ordered spectroscopy measurements by nuclear magnetic resonance (DOSY NMR) as well as viscosity measurements suggested the dehydration of the polyoxyethylene (POE) head groups of Tween 80 upon NaCl addition. Measurements by a Quartz crystal microbalance with dissipation, on the other hand, presented no NaCl effect on the thickness of the adsorbed Tween 80 layer to a hydrophobic surface. Besides the effect of NaCl addition or pH variation, the influence of the ripening inhibitor concentration in the lipid phase and/or temperature variation on the Ostwald ripening levels were also investigated. Emulsions containing a 50:50 ratio of oregano essential oil to sunflower oil stored at 4°C exhibited a significant reduction in Ostwald ripening rate. This study has implications for the development of essential oil emulsions to be used as antimicrobial agent when exposed to environmental stress conditions.

In vitro and in vivo antifungal activity of chitosan-essential oils against pomegranate fruit pathogens

This study investigated the effect of chitosan combined with essential oils (cinnamon, lemon, and oregano, respectively) as edible films against the growth of three important disease-causing pathogens of pomegranate (Botrytis sp., Penicillium sp., and Pilidiella granati). Essential oils (EOs) were characterised by gas chromatography analysis and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). In vitro antifungal activity of the EOs against Botrytis sp., Penicillium sp., and Pillidiella granati was conducted on agar media inoculated with fungal spores using the inverted lid and direct contact with agar techniques. Cast films were prepared from chitosan of different (low, medium, and high) molecular weights (Mw), and assessed for use as biodegradable packaging material. Thereafter, chitosan films (medium Mw) were used in combination with 0, 10, 50 or 100gL−1 concentrations of EOs (cinnamon, lemon, and oregano) for in vitro investigation. The use of ATR-FTIR effectively discriminated the EOs based on the energy levels of the atomic bond vibrations present, as indicated by their characteristic absorption peaks. Based on GC–MS analysis of the selected EOs, 35 volatile compounds belonging to eight different chemical classes were tentatively identified. In addition, differences in chitosan Mw were found to have significant influence on the film functional properties such as colour, thickness, contact angle, and tensile strength. Based on in vitro investigation, chitosan-oregano or −cinnamon EO films with the concentration of 10gL−1 exhibited complete inhibitory effect against all three pathogens. Maximum inhibitory effects of chitosan-lemongrass films was dependent on EO concentration, with P. granati, Botrytis sp., and Penicillium sp. inhibited completely at 10, 50, and 50gL−1, respectively. Antifungal in vivo study on pomegranate fruit artificially inoculated with Botrytis sp. and treated with chitosan-oregano EO (emulsions and films), showed that both treatment methods inhibited Botrytis sp. growth. However, the inhibitory effect was higher for fruit directly dipped into the chitosan-EO emulsions as opposed to samples exposed to vapour contact via the films. This study showed that chitosan-EOs applied as edible coatings or casted films can be used to control postharvest fungal pathogens associated with pomegranate fruit.

Antimicrobial activity of essential oils and fruits supplement in reduced nitrite salts condition

Because of the growing negative perception of consumers related to the use of meat products produced by conventional curing methods, organic and natural products are increasingly accepted by consumers. Such products contain a large number of natural products derived from plants, spices, as well as their derivatives in form of essential oils, extracts, concentrates, and so on. These derivatives contain large number of active substances which are known to inhibit the metabolic processes of bacteria, yeasts and molds. Therefore, the goal of this paper was to investigate the synergistic antimicrobial activity of the models with a reduced presence of nitrite salt in aqueous solution, emulsions of essential oils in varying concentrations in vivo via antibiogram tests on pathogenic microorganisms. The effect of the six model groups was analyzed. Two groups were fruit powder solutions in concentrations of 0.2% to 1.2% (Acerola powder and fruit powder mix), while the other four groups were models of aqueous emulsion of essential oil in concentrations ranging from 0.05% to 1.2% (tea tree, clove, oregano, and cinnamon essential oils). In all models reduced amount of the sodium salt of 1.80%, 0.0075% nitrite salt and the liquid derivative as a natural source of the nitrate salt of 3% were used. Antibiogram tests were performed on five pathogenic bacteria (C. perfringens, E. coli, S. enterica, L. monocytogenes, and S. aureus). All antibiogram tests were performed according to Kirby-Bauer disk diffusion protocol. Results of antibiograms showed that without the presence of additional antimicrobial agents, in model systems with reduced content of salts, inhibition zones were not detected. Additionally, models with essential oils of tea tree oil and oregano had the widest inhibition zone diameters, ranging from 17.76?0.48mm for E. coli up to 42.50?0.13mm for S. aureus.