Essential oils to control Alternaria alternata in vitro and in vivo

The inhibitory effects of five essential oils (thyme, sage, nutmeg, eucaptus and cassia) against Alternaria alternata were tested at different concentrations (100–500 ppm) in vitro. The cassia oil and thyme oil both exhibited antifungal activity against A. alternata. The cassia oil inhibited completely the growth of A. alternata at 300–500 ppm. The thyme oil exhibited a lower degree of inhibition 62.0% at 500 ppm. Spore germination and germ tube elongation of the pathogens in potato dextrose broth was strongly inhibited in the presence of 500 ppm cassia oil. Irreversible inhibition of fungal growth could be caused by exposure to 300 ppm and 400 ppm cassia oil for 6 days and 500 ppm cassia oil for 3 days. Cassia oil at 500 ppm reduced the percentage of decayed tomatoes. The experiments on reducing natural decay development of tomatoes gave similar results. Therefore, essential oils could be an alternative to chemicals for control of postharvest phytopathogenic fungi on fruits or vegetables.     

The in vitro antimicrobial and antioxidant activities of the essential oils and methanol extracts of endemic Thymus spathulifolius

The present study was conducted to evaluate the in vitro antimicrobial and antioxidant properties of essential oil and methanol extracts from a unique and endemic plant, Thymus spathulifolius (Hausskn. and Velen.). The antimicrobial test results showed that the essential oil of T. spathulifolius strongly inhibited the growth of test microorganisms studied, except for 4 fungi species while polar and non-polar subfractions of the methanol extract had moderate antibacterial, but not antifungal and anticandidal activity. The antioxidative potential of the samples was evaluated using two separate methods, inhibition of free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene–linoleic acid systems. The polar subfraction of the methanol extract was able to reduce the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) with an IC₅₀ of 16.15 ± 0.5 μg/ml, which was lower than that of synthetic antioxidant, BHT, (19.8 ± 0.5 μg/ml). Inhibition values of linoleic acid oxidation were calculated as 92% and 89% for the oil and the polar subfraction, respectively. Gallic acid equivalent total phenolic constituent of the polar subfraction was 141.00 ± 0.90 μg/mg (14.1%, w/w). The chemical composition of a hydrodistilled essential oil of T. spathulifolius was analyzed by a GC and GC/MS system. A total of 28 constituents representing 99.2% of the oil were identified; thymol (36.5%), carvacrol (29.8%), p-cymene (10.0%) and γ-terpinene (6.3%) were the main components comprising 82.6% of the oil. Results presented here may suggest that the essential oil and extracts of T. spathulifolius possess antimicrobial and antioxidant properties, and therefore, they can be used as a natural preservative ingredient in food and/or pharmaceutical industry.     

In vitro antioxidant and antibacterial activities of essentials oils obtained from Egyptian aromatic plants

The aim of this work was to (i) determine the chemical composition of the essential oils (EOs) of five spices widely cultivated in Egypt as: Fennel (Foeniculum vulgare), parsley (Petroselinum crispum), lavender (Lavandula officinalis), black cumin (Nigella sativa) and thyme (Thymus vulgaris); (ii) determine the total phenolic compound (TPC) content (iii) determine the antioxidant activity of the Egyptian essentials oils by means of three different antioxidant test and (iv) determine the effectiveness of the Egyptian essentials oils on the inhibition of the growth of some indicators of spoilage bacteria strains. There is a great variability in the chemical composition of EOs obtained from the five Egyptian aromatic plants. Thyme EO had the highest content of total phenols (913.17 mg GAE/L). Black cumin (highest % of inhibition of DPPH radical: 95.89% and highest FRAC values 3.33 mmol/L Trolox) and thyme (highest % of inhibition of TBARS: 80.76) essential oils presented the best antioxidant profile. Only the essential oil of thyme showed inhibitory effects on the three tested bacteria at all added doses.     

Flow cytometric assessment of the antimicrobial activity of essential oils against Listeria monocytogenes

Flow cytometry was applied to assess the antimicrobial activity of oregano, thyme and cinnamon essential oils against Listeria monocytogenes ATCC19114, using combined staining with propidium iodide (PI) for membrane damage evaluation and carboxyfluorescein diacetate (cFDA) for esterase activity detection. The antimicrobial activity of the essential oils was also tested at different NaCl concentrations.Significant differences were observed between plate count results and flow cytometric data, which suggested the presence of a sublethally stressed subpopulation, not able to form colonies on agar plates.Following treatments, flow cytometric assessment clearly discriminated three different subpopulations: viable, dead and injured cells. Cinnamon essential oil exerted a different impact on the cellular subpopulations, with a lower overall activity and a large percentage of cells having minimally damaged membranes. On the contrary, membrane disintegration seemed to be the primary inactivation mechanism of oregano and thyme essential oils.The antimicrobial activity of the essential oils increased with NaCl concentration increase, but higher NaCl concentrations were necessary following treatments with cinnamon essential oil.Our findings suggest differences in the mode of action of cinnamon essential oil against L. monocytogenes, in comparison with thyme and oregano essential oils.     

Inhibition of food poisoning and pathogenic bacteria by Lactobacillus plantarum strain 2.9 isolated from ben saalga, both in a culture medium and in food

The bacteriocinogenic strain Lactobacillus plantarum 2.9 isolated from the traditional pearl millet-based African fermented food ben saalga was tested for inhibition of food poisoning and pathogenic bacteria in MRS broth and in a malted millet flour slurry. In MRS broth, strain 2.9 completely eliminated Bacillus cereus, Escherichia coli O157:H7 and Salmonella enterica cells within 48 h incubation at 22–30 °C. A much lower inhibition was observed at 15 °C. The inhibitory effect of strain 2.9 on the above-mentioned target bacteria was corroborated in the malted millet flour slurry, reducing viable cell counts below detection levels after 8 h storage for B. cereus or after 24 h for S. enterica and 48 h for E. coli. An Enterobacter aerogenes strain was only moderately inhibited in the slurry. Results from the present study suggest that strain 2.9 could be used as starter culture to improve the microbiological safety of fermented ben saalga.     

Thyme oil to control Alternaria alternata in vitro and in vivo as fumigant and contact treatments

This study was conducted to evaluate the efficacy of thyme oil in suppressing Alternaria alternata (Fr.:Fr.) Keissl in vitro and in vivo as fumigant and contact treatments. Thyme oil possessed great fumigant and contact toxicity against A. alternata at different concentrations in vitro. Irreversible inhibition of fungal growth could be caused by exposure to 500 μL/L thyme oil as a fumigant for 6 and 12 days. The spores of A. alternata were completely suppressed 6 h after incubation in potato dextrose broth (PDB) by 2000 μL/L of thyme oil. The thyme oil as a fumigant at 66.7 μL/L showed a significant inhibition effect on A. alternata of cherry tomatoes stored at 25 °C for 5 days. Thyme oil at 500 μL/L showed a significant contact inhibition effect on A. alternata of cherry tomatoes stored at 25 °C for 3 days.     

Reducing nitrite content in hot dogs by hurdle technology

The objective of the present study was to reduce nitrite content in hot dogs using hurdle technology without sacrificing product safety and quality. In the present study, the water activity of the hot dog was adjusted to 0.95 by the addition of humectants. Although the pH at the hot dog was adjusted with Glocono-delta-lacton to 5.4, the product had (p > 0.05) the least acceptance on account of the organoleptic changes (sour taste). Moreover, the temperature of 80 ± 1 °C for an hour with the aim of achieving an internal temperature of 75 °C was applied. Subsequently, the temperature of the hot dog samples reduced to around 5–6 °C within 40–45 min, and afterwards the sausages were kept at chilled temperature (>3 °C but 10 °C) throughout their shelf life. There was a decrease in total aerobic counts in hurdle treated hot dogs (with 50 ppm nitrite), compared to the control (with 120 ppm nitrite), whereas Clostridium perfringens counts and Clostridium botulinum detection were the same (p < 0.05) in both hurdle treated and control samples. The obtained results of present study clearly showed that both hurdle treated sample and control had the same (p < 0.05) overall acceptability and sensory attributes.     

Organic thyme oil emulsion as an alternative washing solution to enhance the microbial safety of organic cantaloupes

Emulsions of organic essential oils may be used as postharvest alternative washing solutions in fresh produce production. In the present study, organic thyme oil was emulsified with whey protein concentrate, gum arabic, lecithin, or their equal mass mixtures without using specialized equipment. The stability of these emulsions was monitored by measuring hydrodynamic diameter during ambient storage up to 7 days. The antimicrobial activity of these emulsions against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes was evaluated by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). All emulsions had lower MIC and MBC than free thyme oil pre-dissolved in ethanol. Thyme oil emulsified with gum arabic had the smallest and most stable hydrodynamic diameter (156–239 nm) and was chosen as the washing solution to evaluate its efficacy in reducing pathogens on organic cantaloupes. Cantaloupes inoculated with pathogens were immersed in 0.1%, 0.2%, or 0.5% emulsified or free thyme oil for 2 min. The counts of the three cultures inoculated on cantaloupes were reduced by either 0.2% or 0.5% thyme oil and the emulsions were more effective than free thyme oil (P < 0.05). Organic load (2% or 5%) had no effect on their antimicrobial efficacy (P > 0.05). During ambient storage (21 °C) up to 10 days, the counts for all three bacteria gradually declined for all treatments and the emulsion treatment had consistently lower populations than unwashed and water-washed treatments. Therefore, emulsions of organic essential oils have potential applications as postharvest washing solutions to improve the microbiological safety of organic fresh produce.     

Hydrocarbon Group Analysis of Arabian Crude Oils TBP-Fractions

Experimental studies have been carried out on hydrocarbon group analysis of commercial Arabian crude oil fractions corresponding to the true boiling point ranges or 200-400 ast;F, 400-500 *F 500-650 *F, 650-850 *F, and 850 *F-K The crude oils included Arab heavy (API* = 28·0), Arab medium (API* = 30·0), Arab light (API* = 33·3), and Arab Berry extra light (API* = 36*9). Waters Hydrocabon Group Analyzer (HGA) system interfaced with model 730 Data Module has been used to obtain the compositional analysis in terms of saturates, neutral aromatics, polar aromatics and asphaltcnes.     

Effect of nisin on the storage of sous vide processed Korean seasoned beef

Seasoned beef called Jangzorim in Korea is produced by boiling in soy sauce, and is a popular food in Korea. The aim of this study is to evaluate the microbial safety and physical qualities of sous vide processed seasoned beef, and the effect of nisin during storage. Sous vide processed packages with or without nisin (100 IU or 500 IU) were stored at 4 °C or 25 °C for 60 days, and samples measured for quality at regular intervals throughout this storage period. In the case of 25 °C storage, the number of mesophilic microorganisms in seasoned beef packages without nisin increased markedly, but with nisin there was no observed increase. Psychrotrophic microorganisms, anaerobic microorganisms, and B. cereus cells showed similar trends, although C. perfringens was not detected in all samples. At 25 °C storage, changes in the cutting force of packages containing nisin showed no significant change, packages without nisin decreased markedly. The colour of packages without nisin showed a drastic decrease in lightness (‘L’) while no changes were observed in packages with nisin.     

Antibacterial activity of plant essential oils and extracts: The role of thyme essential oil,nisin, and their combination to control Listeria monocytogenes inoculated in minced fish meat

Food poisoning caused by Listeria monocytogenes leads to a 30% rate of mortality among patients. The antibacterial activity of cinnamon, thyme, and rosemary essential oils (EOs) and shallot and turmeric extracts was tested against L. monocytogenes using agar well and disc diffusion techniques. Results showed that thyme EO had the highest antimicrobial activity, followed by cinnamon and rosemary EOs, respectively. The antilisterial activity of thyme EO at 0.4%, 0.8%, and 1.2% levels, nisin at 500 or 1000 IU/g level, and their combination against L. monocytogenes was examined in minced fish samples. The antilisterial properties of nisin were also investigated in cooked minced fish treatments. Nisin at 500 or 1000 IU/g in the minced fish meat demonstrated bacteriostatic activity against L. monocytogenes. The use of thyme EO at 0.8% and 1.2% reduced the L. monocytogenes viable count below 2 log cfu/g after 6 days. Furthermore, simultaneous use of thyme EO at 0.8% and 1.2%, and nisin at 500 or 1000 IU/g level, reduced the L. monocytogenes viable count below 2 log cfu/g after the second day of storage. The antilisterial activity of nisin in the cooked minced fish samples was slightly stronger than that of the raw group.     

Effects of exposure to biocides on susceptibility to essential oils and chemical preservatives in bacteria from organic foods

A collection of 38 biocide-adapted strains with significant increases in their tolerance to biocides after step-wise exposure to these compounds were screened for sensitivity to essential oils and chemical preservatives. Several strains adapted to quaternary ammonium compounds (benzalkonium chloride, hexadecylpyridinium chloride or cetrimide) showed a generalized increase in the sensitivity to preservatives. Similar results were found among hexachlorophene- or chlorhexidine-adapted strains. Moreover, tolerance to hexadecylpyridinium chloride showed a very strong positive correlation with 4-hydroxybenzoic acid, thyme oil and sodium nitrite increased sensitivity, as well as a strong correlation with clove oil, potassium sorbate and potassium nitrate increased sensitivity. On the contrary, an increase in tolerance to preservatives was detected among triclosan-adapted strains. Results from this study suggest that exposure of bacteria from foods to biocides is not always associated with co-selection for other antimicrobial resistances, especially against essential oils or chemical preservatives used in the food industry.     

Survival and growth of Listeria monocytogenes on sausage formulated with inoculated and stored rework product

To assess the effect of including contaminated rework on survival and growth of Listeria monocytogenes, two sausage formulations (one American, Bologna sausage; and one Bulgarian, Stranja sausage) were inoculated with the pathogen and stored for 4 days at 10 °C plus 15 h at 30 °C. After storage, both rework types were included (at 20% and 40%) in corresponding fresh sausage emulsions and heated to 68, 70 and 71.7 °C; fresh Bologna and Stranja emulsions served as controls and were inoculated with 24 h broth cultures of the same 10-strain mixture of L. monocytogenes and thermally treated to the same temperatures. The results showed that heating to 68 and 70 °C inactivated 3–4 log CFU/g of the initial concentration of L. monocytogenes cells (>7 log CFU/g), while heat treatment to 71.7 °C in the center of experimental samples reduced counts by 6 log CFU/g. Survival of L. monocytogenes in samples heated to 68 and 70 °C was higher in controls. Control samples of Stranja emulsion heated to 71.7 °C allowed higher growth (P < 0.05) during storage (5 days at 10 °C) as compared to other control and experimental rework samples. The Stranja emulsion had a higher fat content (20.2%) compared to the Bologna emulsion (11%). This study provides evidence about the possible danger when potentially contaminated rework is stored and then introduced into fresh product formulations.     

Plant essential oils and components on growth of spoilage yeasts in microbiological media and a model salad dressing

Essential oils (EOs) and EO components have been widely tested for their antimicrobial properties against microorganisms. However, less is known about the inhibitory properties of essential oil components against microorganisms in foods and, more specifically, spoilage yeasts in a food matrix. Clove bud, cinnamon bark, and thyme oils, and the EO components, trans-cinnamaldehyde, cinnamic acid, eugenol, carvacrol, and thymol first were evaluated for their antimicrobial activity against yeasts in microbiological media. The yeasts tested included Torulaspora delbrueckii, Candida krusei, Schizosaccharomyces pombe, and Zygosaccharomyces bailii. The most efficacious EO components in media were applied to a model mayonnaise-based salad dressing as a food model to determine the effect on spoilage yeast growth. Trans-cinnamaldehyde and cinnamon bark oil were the most effective against yeasts in microbiological media among the compounds tested with minimum inhibitory concentrations (MICs) of 50 mg/L. Thymol and carvacrol had the next most inhibitory activity against yeasts with MICs of 200 mg/L. In a model salad dressing at pH 4.2, trans-cinnamaldehyde at 500 mg/L was most effective among the EO components inhibiting S. pombe and Z. bailii during 4- and 5-day storage, respectively, at 22 °C.     

A Comprehensive Evaluation of High Viscous Crude Oil from Shuguang No. 1 Zone of Liaohe Oil Field

The high viscous crude oil from Shuguang No. 1 zone of Liaohe oil field has the characteristics of high density (ρ₂₀ = 0.9977 g cm^-3), great viscosity (ν₁₀₀ = 1223.9 mm² s^-1) and high pour point (48°C), which are similar to those of the residue distillation of general crude oils. It contains no gasoline distillation and the diesel oil fraction yield is just 7.19%. It is often used as fuels after emulsification. But this oil is so vicious that it cannot be atomized uniformly and burned fully. In order to make full use of it, this kind of high viscous crude oil has been evaluated comprehensively and the properties of its various distillations are analyzed respectively. The results indicate that this crude oil contains less wax, but more resins and asphaltene, which belongs to low-sulfur naphthene-base crude oils and it is the suitable material to produce high-quality paving asphalt. Based on its characteristics, the optimum processing scheme is put forward and the high-quality paving asphalt is produced by using the distillation higher than 350°C.     

Effects of some Chinese medicinal plant extracts on five different fungi

Chinese medicinal plant extracts were screened against some fungal strains, such as Aspergillus niger, Botrytis cinerea, Fusarium moniliforme, Glomerella cingulata, and Phyllosticta caricae. Plants were extracted with hot water, 80% methanol or acetone. Aliquots of the extracts at variable concentrations were then incubated with different fungal strains, and the minimum inhibitory concentrations (MICs) of each plant extract determined. In this study, the methanol extracts of Cinnamomum cassia had MIC values of 13.3 mg ml⁻¹, when tested against F. moniliforme and P. caricae. The acetone extracts of C. cassia had MIC values of 8.3 mg ml⁻¹ and 10 mg ml⁻¹ respectively, when tested against B. cinerea and G. cingulata. The hot water extracts of C. cassia inhibited significantly the growth of A. niger, B. cinerea, F. moniliforme, and P. caricae with MIC values at 10, 11.7, 5, and 6.7 mg ml⁻¹ respectively. The acetone extracts of Curcuma longa inhibited effectively P. caricae with the MIC value at 6.7 mg ml⁻¹. To determine the stability, various plant extracts were stored at 4 and 25 °C over a period of one month and their effects on fungal growth examined. Results show that the acetone extracts of Cu. longa and Coptidis rhizoma maintained their activity against fungal strains when stored at 4 °C, but not at 25 °C. The methanol extracts of C. cassia lost a great portion of inhibitory activities but not all, after stored at 4 °C and 25 °C for one month. The effect of various combinations of these extracts on antimicrobial activity has also been examined. The combinations of herb extracts showed higher inhibitory effect towards tested fungi than that of individual extract. Results from these findings suggest that these herbal extracts may be used as natural antifungal agents to inhibit growth of foodborne pathogen.     

Characteristic Properties of a Locally Produced Paraffinic Oil and Its Suitability as a Heat-Transfer Fluid

The thermo-physical properties of a paraffinic mineral oil produced in a local refinery were experimentally determined over a wide temperature range of 30-360°C to determine its suitability for use as a heat-transfer fluid. The effect of temperature on the physical characteristics of the oil and two synthetic organic heat transfer fluids was evaluated at high temperatures (180-360°C). Comparison of the main properties of the mineral oil with other heating fluids revealed its compatibility with synthetic organic fluids, some other paraffinic and mineral oils employed as heat-transfer fluids. The study further confirmed that the investigated mineral oil which was produced locally can be used to replace the imported synthetic oils in heat transfer systems operating at a maximum application temperature of 310°C, as indicated by the thermal stability test.     

陆相原油、生油岩、油页岩和煤等卟啉化合物的分离鉴定和对比

本文试图采用溶剂抽提、柱层析、旋转离心薄层层析、紫外可见分光、萤光分光、液相色谱、色谱-质谱等手段,对我国胜利、冀中、辽河、江汉等油田的原油及抚顺、茂名的油页岩、煤炭等样品中的卟啉化合物进行分析鉴定和研究,找出他们之间的特性和共性,以探讨原始有机质的演化及其地球化学环境.      

Addition of phytochemical-rich plant extracts mitigate the antimicrobial activity of essential oil/wine mixtures against Escherichia coli O157:H7 but not against Salmonella enterica

Marinades for preparing raw meats for cooking are frequently made of wine and herbs. We simulated several formulations of potential antimicrobial marinades with these components and other food compatible/food derived extracts. Red wine formulations containing essential oils from oregano or thyme, or their primary active components carvacrol and thymol, respectively, and a mixture of plant extract powders from phytochemical-rich apple skin, green tea, and olive, were evaluated for inhibitory activity against the foodborne pathogens Escherichia coli O157:H7 and Salmonella enterica. Red wine alone exhibited low activity, as did the plant extract suspended in the wine. Surprisingly, the high activity of oregano or thyme essential oils in red wine was reduced in E. coli, but not in Salmonella, by addition of the plant extract. This study shows that essential oils in red wine can be an effective antimicrobial in food, however the possibility exists that phytochemicals, added to the treatment solution or natively present in the food itself, could adversely impact the antimicrobial activity and should be addressed with future studies.     

Flow Enhancement of Medium-Viscosity Crude Oil

This study investigated the different alternatives to enhance the flowability of crude oil with medium viscosity. These alternatives include the addition of water into crude oil to form water-in-oil emulsion, the addition of light petroleum product, the addition of flow improver, and a preheating technique. Temperature range of 10-50°C, water concentration range of 0-50% by volume, flow improver concentration range of 0-5000 ppm, and kerosene concentration range of 0-50% by volume were investigated in the flowability enhancement study of crude oil with medium viscosity. The flowability enhancement in terms of viscosity reduction was investigated using RheoStress RS100 from Haake. A cone-plate sensor was used with a cone angle of °4, cone diameter of 35 mm, and 0.137-mm gap at the cone tip. The addition of kerosene to crude oil improves the flowability much better than any other investigated technique.