Upland rice vinegar vapor inhibits spore germination,hyphal growth and aflatoxin formation in Aspergillus flavus on maize grains

The efficacy of vapor-phase (VP) upland rice vinegar (URV) was investigated as a bio-fumigant for maize, to reduce consumer health risks associated with spore and toxin formation by Aspergillus flavus. Complete reduction of mycelial growth occurred with in vitro VP exposure to URV (containing 0.0017 mmol/L acetic acid) or with VP exposure to pure acetic acid (PAA) (containing 0.0023 mmol/L acetic acid). No significant differences were observed between the two materials after 90 min exposures. Using gas chromatography-mass spectrometry (GC-MS), URV vapor was shown to contain volatiles having antifungal activities. These are identified as isoamylalcohol, 1-butanol, 3-methyl-, acetate and β-phenylethyl acetate. It is suggested these volatiles increase the antifungal effectiveness of URV. Exposure to VP-URV (containing 0.0043 mmol/L AA) for 5 h completely eliminated viable spores of A. flavus on maize seeds (23% moisture content) previously inoculated with 4.43 ± 0.28 log spores/g). At the same time, aflatoxin production decreased, as VP-URV exposure increased. Hence, VP-URV is shown to be an effective control agent for A. flavus mycelial growth and aflatoxin formation on maize, so effectively reducing the potential for consumer health risks due to this widespread fungus.     

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.     

Combined analytical and microbiological tools to study the effect on Aspergillus flavus of cinnamon essential oil contained in food packaging

Cinnamon essential oil has been used for centuries to protect food from microbiological infection, and in the last ten years cinnamon essential oil is also incorporated into food packaging materials as antimicrobial agent. However, very little is known about the real effect that it has on the microorganism cells. This study combines analytical and microbiological tools to elucidate cell damage produced on Aspergillus flavus. First, antifungal activity of cinnamon essential oil was evaluated at 10³,10⁴, 10⁵ and 10⁶ CFU/mL. Minimal Inhibitory Concentration (MIC) and Minimal Fungicidal Concentration (MFC) were determined by macrodilution in direct contact with the mold. A strong activity was obtained, with a MIC of 0.05–0.1 mg/mL, and a MFC of 0.05–0.2 mg/mL, both ranges depending on the initial fungal suspensions.Polyethylene terephthalate films containing cinnamon essential oil were tested in vapor phase, without direct contact with the mold. Active PET started showing activity at 2% CIN EO load and produced total inhibition at 4% CIN EO. SEM and FTIR were used to study the cell damage on the mold exposed to the cinnamon essential oil. Evident damage and a strong decrease in sporulation were found by SEM, while biochemical changes in conidia could be suggested from the FTIR spectra analysis. Two deposition techniques were used to prepare the samples for FTIR. The results obtained are shown and discussed.     

Influence of pH and temperature variations on vapor phase action of an antifungal food packaging against five mold strains

An antifungal active food packaging containing cinnamon essential oil has been evaluated under different pH and temperature. Cinnamon essential oil was previously chosen among oregano, clove and their major components cinnamaldehyde, carvacrol and eugenol respectively. Minimal Inhibitory Concentration (MIC) and Minimal Fungicidal Concentration (MFC) were determined by macrodilution method against two strains of Aspergillus flavus as well as Aspergillus niger, Penicillium roqueforti and Penicillium expansum. Despite pH and temperature modified the growth rate of the molds, these variables did not affect the MIC and MFC values. The active food packaging, consisting of Polypropylene films coated with a formula containing 2%–6% cinnamon were produced and evaluated. The antifungal activity was studied against two A flavus, P roqueforti and P. expansum at different pH and temperature. The results highlighted the growth delay caused by the PP 2% in all cases. Total inhibition was obtained with higher amount of cinnamon. This fungicidal action was maintained beyond the 30 days of the experiments. Long-term properties were confirmed after 3 months. The fridge temperature did not hamper the antifungal action of the cinnamon volatile compounds. Finally, all these results demonstrated the high-performance of the antifungal packaging, what guarantee an efficient and durable antifungal protection.     

Investigations on the essential oil of Lippia rugosa from Cameroon for its potential use as antifungal agent against Aspergillus flavus Link ex. Fries

Lippia rugosa essential oil was tested for its effectiveness against Aspergillus flavus on artificial growth media. The chemical composition of the oil was determined by gas chromatography–mass spectrometry (GC–MS). Geraniol (51.5%), nerol (18.6%) and geranial (10.4%) were the main components of Lippia oil. After 8 days of incubation on essential oil supplemented medium, mycelium growth of A. flavus was totally inhibited by 1000 mg l^?1 of L. rugosa essential oil. The effect of essential oil on aflatoxin B₁ synthesis was evaluated in SMKY broth. The medium supplemented with different essential oil concentrations, was inoculated with A. flavus mycelium and incubated at 25 °C. After 2, 4, 6 and 8 days, aflatoxin B₁ (AFB₁) was quantified in the supernatant using Enzyme Linked Immuno-Sorbent Assay (ELISA). Results showed that aflatoxin B₁ synthesis was inhibited by 1000 mg l^?1 of L. rugosa essential oil after 8 days of incubation. The effect of the EO on the H⁺-ATPase pumping membrane was also evaluated in the presence of several concentrations of oil (200–2000 mg l^?1) by monitoring glucose-induced acidification of the external medium. L. rugosa essential oil at the concentration of 2000 mg l^?1 completely inhibited the activity of this enzyme. These data suggest that the essential oil of L. rugosa is a fungicidal for A. flavus and its possible cellular target include the H⁺-ATPase.Results obtained in the present study indicate the possibility of exploiting Lippia rugosa essential oil in the fight against strains of A. flavus responsible for biodeterioration of stored foods products.     

Antifungal, aflatoxin inhibition and antioxidant activity of Callistemon lanceolatus (Sm.) Sweet essential oil and its major component 1,8-cineole against fungal isolates from chickpea seeds

The present investigation reports the extent of molds and aflatoxin contamination to Avarodhi, Kabuli, Pusa 256, Radha and Samrat varieties of chickpea seeds. The study also examines the chemical composition of Callistemon lanceolatus (Sm.) Sweet essential oil and its antifungal, antiaflatoxin and antioxidant activity. During standardization of chemical profile, a total of 8 compounds constituting 0.862 mg/mL of oil composition were analyzed by GC-MS analysis where 1,8-cineole was recorded as a major component (0.56 mg/mL). The antifungal activity of EO and 1,8-cineole was evaluated by contact assay on Czapek’s dox agar. The EO (0.227-0.908 mg/mL) and 1,8-cineole (0.918 mg/mL) showed remarkable antifungal effect against all the fungal isolates of chickpea. Their minimal inhibitory (MIC) and fungicidal (MFC) concentrations for Aspergillus flavus were lower than those of the prevalent systemic fungicide Nystatin. Aflatoxin B₁ (AFB₁) production by NKD-208 isolates of A. flavus was strongly inhibited even at the lower fungistatic concentration of EO and 1,8-cineole.There was no adverse effect of EO treatment on chickpea seed germination suggesting its non-phytotoxic nature. Based on the findings of present investigation, C. lanceolatus essential oil may be recommended as botanical preservative for the enhancement of shelf life of food items in- view of the adverse effect of synthetic preservatives and its strong antifungal, aflatoxin inhibition and antioxidant activity.     

Influence of emulsifier type on the antifungal activity of cinnamon leaf,lemon and bergamot oil nanoemulsions against Aspergillus niger

Only exiguous data are currently available on the antifungal properties of essential oil (EO) nanoemulsions against spore-forming microorganisms. The aim of this work is to develop physically stable nanoemulsion-based delivery systems for different EOs (cinnamon leaf, lemon, and bergamot), to exploit their antifungal properties against Aspergillus niger. The inhibition of mycelial radial growth and spore germination were used as indicators of antifungal activity of the nanoemulsions, which were prepared at 3 wt% EO, using non-ionic Tween 80 (T80) or anionic whey protein isolate (WPI) (1 wt%) as emulsifiers, and sunflower oil (1 wt%) as ripening inhibitor. The nanoemulsions were physically stable over seven days of accelerated aging at 35 °C.The minimal inhibitory concentration of free cinnamon leaf and of both citrus EOs were 0.35 and 5.50 μg/g, respectively. The encapsulation of cinnamon leaf EO in nanoemulsions significantly enhanced the inhibiting effect against A. niger mycelial growth and spore germination, with respect to the free EO. In contrast, for citrus EOs, the encapsulation in nanoemulsions generally decreased the antifungal activity, likely because of the nanoemulsion acting as a hydrophobic sink for the main constituents of citrus EOs. The emulsifier played a fundamental role in the resulting antifungal activity, with WPI-based nanoemulsions being more effective in inhibiting the mycelial growth and the spore germination of A. niger than T80-based ones. The antifungal action was correlated to the morphological alterations observed in A. niger, such as the loss of cytoplasm in fungal hyphae and hyphal tip. The results of this study show the importance of nanoemulsions design in the development of efficient and stable natural antifungal agents for food applications.     

Antifungal activity of thyme, summer savory and clove essential oils against Aspergillus flavus in liquid medium and tomato paste

Antifungal activity of essential oils of thyme, summer savory and clove were evaluated in culture medium and tomato paste. Aspergillus flavus were inoculated in Sabouraud Dextrose Broth and tomato paste and then 0, 50, 200, 350 and 500 ppm of essential oils were added to each sample and then kept at 25 ± 0.5 °C for 2 months. Results showed that all essential oils could inhibit the growth of A. flavus and the thyme oil and summer savory, showed the strongest inhibition at 350 ppm and 500 ppm, respectively. Taste panel evaluations were carried out in a tomato ketchup base, and the percent of inhibition of each essential oil in tomato paste was lower than culture medium. Taste panel was carried out and sample with 500 ppm thyme oil was accepted by panelists.     

Effects of cooking and freezing practices on the distribution of cadmium in different tissues of the brown crab (Cancer pagurus)

Increased cadmium concentrations in claw meat were demonstrated after cooking and freezing practices of whole brown crabs. This was investigated in crabs from two different locations along the Norwegian coast, one with normal and one with high cadmium concentration. For both locations, in whole crabs, samples of fresh raw claw meat showed lowest values followed by raw-boiled and frozen-thawed-boiled. Cadmium levels in separately cooked claws were comparable to the low values in claws from raw whole crab. Claws taken from frozen crabs before thawing had low values compared to claws taken off the carapace after thawing. This clearly indicates a transfer from hepatopancreas to claw meat, which potentially induces biases when measuring and monitoring Cd levels in crabs. Further, different cooking and storing practices might have profound effects on cadmium intake from eating crabs since concentrations above regulatory limits were found following common household and commercial practices.     

Effect of water activity and temperature on the growth of Aspergillus flavus,the expression of aflatoxin biosynthetic genes and aflatoxin production in shelled peanuts

The contamination of peanuts with Aspergillus flavus and subsequent aflatoxins is considered to be one of the most serious safety problems in the world. Water activity (a_w) and temperature are limiting factors for fungal growth and aflatoxins production during storage. To optimize the practical storage parameter, the effect of a_w (0.85–0.99) and temperature (15–42 °C) on fungal growth, aflatoxin production and the expression of aflatoxin biosynthetic and regulatory genes in shelled peanuts was investigated. A. flavus grew at a lower rate when temperature ≤20 °C or a_w ≤ 0.85. For the growth of A. flavus in shelled peanuts, the optimum conditions were a_w was 0.98, and the optimum temperature was 37 °C. The maximum amount of AFB₁ in peanuts was obtained at 28 °C and a_w 0.96. Real-time analysis showed that 16 of 25 genes had highest expression levels at 28 °C under a_w 0.92, while 9 genes had highest expression levels at 37 °C under a_w 0.92. Compared with 37 °C, all aflatoxin biosynthetic pathway genes were down-regulated at 42 °C. All the pathway genes and laeA were up-expressed at a_w of 0.96 under 28 °C, compared to a_w 0.99. Furthermore, there was a good positive correlation between the ratio of aflS/aflR and AFB₁ production. The expression of laeA was also positively correlated with AFB₁ production while the expression of brlA was correlated with the A. flavus growth. The results of this study suggest that AFB₁ production in peanut kernels can occur over a wider range of a_w × temperatures levels compared to formula media and peanut media. Previous studies have showed that AFB₁ could not be produced on formula media at 37 °C without the expression of most aflatoxin structural genes. But, in the un-autoclaved shelled peanuts, high concentration of AFB₁ was produced at 37 °C with up-regulation of some aflatoxin biosynthetic genes. From a food safety point of view, the results can be used to optimize certain food technological processes and develop prevention strategies to control such carcinogenic natural metabolites in grains (such as peanuts, maize and rice) and derived products.     

Vortex-assisted dispersive liquid-liquid microextraction for the analysis of major Aspergillus and Penicillium mycotoxins in rice wine by liquid chromatography-tandem mass spectrometry

The presence of Aspergillus and Penicillium species during the fermentation process of rice wine is inevitable. The toxic secondary metabolites produced by the two fungi need to be practically monitored for rice wine safety. In this study, we developed a fast and simple vortex-assisted dispersive liquid-liquid microextraction (VADLLME) for the extraction and preconcentration of major Aspergillus and Penicillium mycotoxins (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, ochratoxin A, mycophenolic acid, sterigmatocystin and verruculogen) in rice wine. The key parameters affecting the extraction efficiency of VADLLME procedure (pH value, type and volume of extraction and dispersive solvents) were optimized by response surface methodology (RSM) combined with Box-Behnken design (BBD) and desirability function. Target compounds were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Under the optimum conditions, good linearity (R²>0.99) was achieved for all the analytes in the concentration range of 0.5–100 μg/L. The recoveries for spiked samples at three concentration levels were between 84.5% and 111.2%, with the relative standard deviations (RSD) lower than 20%. The limits of detection (LOD) and quantification (LOQ) ranged from 0.05 to 0.5 μg/L and from 0.1 to 1.0 μg/L, respectively. Simplicity in operation, low cost and low usage of organic solvents were the major advantages of the developed method. The method was successfully applied to the analysis of rice wine samples. It was found that mycophenolic acid had high incidence rate in rice wine, which needed to be continuously monitored.     

氮气对塔河油田原油轻质组分抽提作用实验与评价

采用塔河油田缝洞型油藏稀油和常规稠油两种代表性油样,通过开展向前多次接触相平衡实验模拟蒸发气驱过程、向后多次接触相平衡实验模拟凝析气驱过程,研究了氮气与塔河油田原油在高温高压条件下的相态变化,明确了氮气与地层原油充分接触混合后地层流体的气液组分变化规律,提出了抽提指数的计算表达式,定量评价了氮气在高温高压条件下对原油轻...     

Evaluation of Zataria multiflora Boiss. essential oil activity against Escherichia coli O157:H7, Salmonella enterica and Listeria monocytogenes by propidium monoazide quantitative PCR in vegetables

Essential oils (EOs) have long been applied as flavoring agents in foods, and due to their content in antimicrobial compounds, they have potential as natural agents for food preservation. Recently, real-time PCR in combination with PMA has successfully been applied to discriminate between live Escherichia coli O157:H7 and dead bacteria killed by cumin, clove, oregano and cinnamon EOs. In this study, initial experiments were performed in order to elucidate the minimum bactericidal concentration of Zataria multiflora EOs on E. coli O157:H7, Salmonella enterica and Listeria monocytogenes. Thereafter PMA-qPCR was applied in order to selectively quantify life cells within a bacterial population treated with Z. multiflora EO. Inactivation was obtained at EO concentrations of 0.02, 0.035, 0.045 for L. monocytogenes, E. coli O157:H7 and S. enterica, respectively. L. monocytogenes were totally killed in 30 min while it took 1 h 30 min for the gram negative pathogens. As a conclusion Z. multiflora EO has potential as natural food additive or biopreservative since it was able to irreversibly inactivate the three pathogens tested, at lower concentrations than other EOs and short exposition times. In addition, the PMA-qPCR approach proved efficient to selectively detect live pathogenic bacteria in vegetables following inactivation with Z. multiflora EO.     

水平井油水两相产液剖面解释方法探讨

水平井中因重力差异普遍存在层流,且流型受井斜角度影响变得复杂,致使测量仪器及测量参数发生变化,传统的滑脱模型已不适用于水平井产液剖面解释。文中分析了水平井油水两相流流型特点,探讨了水平井集成化测量仪器油水两相产液剖面解释方法,并对某井进行了实例分析。     

The effect of waterflooding on the occurrence of alkyl naphthalenes and phenanthrenes in crude oil

Using GC and GC-MS, the occurrence of alkyl naphthalenes and alkyl phenanthrenes in 36 waterflooded oils in the Qu9 reservoir was investigated. Compared with the early waterflooded oils, the later ones feature a loss of aromatics but a gain of saturates. Possibly due to their much lower solubility and stronger resistance to biodegradation, the alkyl naphthalenes with three or more alkyl substituent–related parameters are substantially unaltered in values, the same as the alkyl phenanthrene–related parameters with the advance of waterflooding. The random changes of alkyl naphthalenes with two or less alkyl substituent–related parameters during waterflooding are possibly the mixed results of water washing and biodegradation.     

论三角洲对南海海相油气田分布的控制作用

南海是全球重要的油气富集区之一,在新生界已发现约340个油气田,原油可采储量达17.6×10⁸t,天然气可采储量为5.0×10¹²m³,油气主要富集于渐新世以来三角洲—海相沉积体系中,三角洲对南海含油气盆地成烃、成储和成藏具有重要的控制作用。海陆过渡相烃源岩是南海含油气盆地的重要烃源岩,三角洲体系是煤系烃源岩发育的重要场所,河流—三角洲体系所携带的陆生高等植物有机质有利于陆源海相泥质烃源岩的发育。三角洲体系发育的碎屑岩储层厚度大、分布广、物性好,与海相泥岩构成良好的储盖组合。三角洲是南海油气富集的重要场所,三角洲对南海海相油气田的形成和分布具有重要的控制作用。     

塔里木盆地热液特点及其对碳酸盐岩储层的改造作用

塔里木盆地热液活动普遍,为弄清其对该区下古生界碳酸盐岩储层的影响,分析了该盆地碳酸盐岩中热液活动产物的岩石学、地球化学特征,发现该区热液普遍具有贫镁离子、富含CO_2的特点。进一步探讨了该区热液活动对储层的改造作用,发现热液流体成分是这一改造作用的决定性因素。研究结果表明:①热液流体富含CO_2,沿断裂带通道附近溶蚀作用强烈,发育大小不等的溶蚀孔洞,形成规模较小但孔渗性很好的优质储层;②热液流体自身镁离子含量很少,虽然通过溶蚀寒武系白云岩能获得部分镁离子,但热液白云石化作用规模较小;③富含CO_2的热液流体溶蚀围岩形成优质的溶蚀孔洞型储层,其分布明显受到断裂的控制;④热液白云石化作用主要表现为鞍形白云石充填溶蚀孔洞,以及在断裂附近热液活动导致白云石晶体重结晶或过度生长,堵塞已有的孔隙,总体而言是一种破坏性成岩作用。该成果可以为该盆地深部碳酸盐岩储层预测提供帮助。     

Investigation and quantifying effect of dispersion on oil recovery in the process of viscoelastic polymer flooding using numerical method

In this study an existent mathematical model was implemented to investigate the effect of dispersion on oil recovery of core-flood experiments in process of viscoelastic polymer flooding as a tertiary stage of enhanced oil recovery. Discretized forms of equations of pressure, saturation, and concentrations were obtained and solved by implicit in pressure and explicit in saturation and concentrations with considering effect of time step on solution. Furthermore, a new procedure was presented to solve polymer concentration equation by trial and error. The results showed that dispersion phenomenon reduces displacement efficiency of viscoelastic polymer flooding.     

陆相沉积油层水平井水平段轨迹对产能及采收率影响的研究

我国油田多属陆相沉积,油层内或多或少地存在着薄厚不等的夹层或隔层,而且分布不均。对于无气顶底水的这类油层,研究了有隔层水平井产能下降的幅度,研究了与油层相交贯穿油层上下的大斜度水平井和平行油层水平井的产能和采收率。计算分析结果表明：①存在夹层、隔层的油层不适合打平行油层的水平井;②对含有夹层、隔层的油层,选择与油层相交贯穿油层上下的大斜度水平井,可有效地降低夹层、隔层对产能和采收率的负面影响;③当相交油层的水平井长度为平行油层水平井长度的１．１５倍时,无论油层有无夹层、隔层,其产能要大于或等于相应平行油层水平井的产能,而且采收率不会受夹层、隔层的影响;④对无气顶底水的陆相沉积油层,选择与油层相交的长度略长的水平井是稳妥的。图３参６（陈志宏摘）     

CT系列催化剂在大型天然气净化厂的应用效果分析及活性预测技术研究

硫磺回收装置是含硫天然气开发生产的配套处理装置,对酸气中H 2S进行催化转化,能起到资源回收、降低SO2排放的重要作用,而装置所用催化剂的性能很大程度上决定其硫回收率的高低,对装置整体运行效率有重要影响。分析评价了CT系列催化剂在某大型天然气净化厂硫磺回收装置的应用效果情况,并以催化剂反应热力学平衡为基础,结合催化剂性能变化研究,对在运催化剂的活性进行预测。结果表明,通过活性预测技术的应用,可为装置的平稳、安全、高效运行提供科学客观的性能参数,也能为CT系列催化剂的持续改进与优化提供参考。