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1.
Fatty acids in presence of water film alter calcite surface to oil-wet. The wettability alteration is dependent on the structure of the fatty acids, water composition and pH. Long chain fatty acid (stearic acid), strongly adsorbs onto the calcite surface from “oil phase” (n-C10) in oil/water/calcite system as indicated by contact angle measurements. On the other hand, short chain fatty acid (heptanoic acid) adsorbs on the calcite surface to a lesser extent, which agrees with “Traube's rule”.Adsorption of carboxylate anion is influenced by the ionic composition of the water, ionic strength and pH. The presence of Mg2+ and SO42− ions is shown to increase the water-wetness of the calcite. The degree of wetting is dependent on the pH. At pH < 7 in stearic acid/n-decane/water/calcite system, both ions reduce the contact angle. Higher reduction is obtained in presence of SO42− compared to Mg2+. The measured advancing contact angles are 95°, 108° at pH 5 and 88°, 82° at pH 7 in presence of SO42− and Mg2+, respectively. Further increase of the pH in the presence of Mg2+ causes more reduction of contact angle (68° at pH 10); while in the presence of SO42− ions an inflection point occurred where the advancing contact angle increased to 100°. In other words, the calcite surface became slightly more oil-wet.  相似文献   

2.
NaCl solution (0.5 M) of pH 2 was electrolyzed at 1000 Am?2 at room temperature. Addition of Pt4+ and Fe3+ to the prepared MnMo-oxide anode deposited on IrO2/Ti substrate, significantly improves the performance of anode for the oxygen evolution reaction (OER) during NaCl electrolysis. After 2000 h of electrolysis, the oxygen evolution efficiency (OEE) is in the order of MnMoPt-oxide > MnMoFe-oxide > MnMo-oxide anodes with 100%, 99%, and 93.2% OEE, respectively. The loss in weight of MnMo-oxide is reduced from about 13% to 3.2% and 0.0% by addition of iron and platinum cations, to the deposition electrolyte. The mean average grain size of MnO2, MnMo-, MnMoFe- and MnMoPt-oxide deposits prepared in electrolytes of pH 0.0 are in the range of 25.5, 16.22, 13.5  16.5 and 13  17.5 nm, respectively. The physicochemical properties of the deposits were characterized using X-ray diffraction spectroscopy (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and electrochemical techniques. EDX analysis illustrates that IrO2/Ti is stable during the deposition process and behaves only as conductive substrate. SEM illustrates that, all elements constituting MnMoPt- and MnMoFe-oxide deposits are homogeneously distributed in the oxide surface.  相似文献   

3.
《Food Control》2007,18(4):375-378
In the present study, 36 samples of pasteurised, ultra-high-temperature (UHT) treated and goat milk powder traded in the city of Campinas, Brazil, were analysed for aflatoxin M1 (AFM1), from October to December 2004 and March to May 2005. Results showed 25 (69.4%) positive samples for AFM1 at levels of 0.011–0.161 μg L−1 of milk, which were below the tolerance limit of 0.500 μg L−1 as adopted for AFM1 in milk by Brazilian regulations. Mean levels of AFM1 in pasteurised, UHT and goat milk powder were 0.072 ± 0.048, 0.058 ± 0.044 and 0.056 ± 0.031 μg L−1, respectively. It is concluded that the incidence of AFM1 in goat milk traded in Campinas is high, but at levels that probably leads to a non-significant human exposure to AFM1 by consumption of goat milks.  相似文献   

4.
A method for aflatoxin B1 (AFB1) and ochratoxin A (OTA) determination in breakfast cereals is described using a simultaneous methanolic-aqueous extraction followed by immunoaffinity columns clean-up step and High Pressure Liquid Chromatography (HPLC) with Fluorescence Detector (FD). Recoveries were found to be 78% and 83% for AFB1 and OTA, respectively, while the detection limit (DL) was 0.02 ng g?1 for both mycotoxins. Both determinations were applied in fifty five samples of breakfast cereals purchased from Athens market. Results revealed the presence of AFB1 in 56.3% of the samples examined (mean 1.42 ng AFB1 g?1). Seven samples (median 3.5 ng AFB1 g?1) were found to be contaminated at levels higher than the EU limit (2 g g?1). OTA was detected in 60% of the samples (mean 0.18 ng g?1). Nineteen samples were found to be contaminated by both mycotoxins. In addition in the present study the daily exposure to AFB1 and OTA is discussed.  相似文献   

5.
《Food Control》2005,16(2):117-120
In the present study, 60 samples of corn meal and flour traded in São Paulo were analysed for determination of aflatoxins and fumonisins B1 (FB1) and B2 (FB2). No aflatoxin was found in samples of both products. In corn meal, the concentrations of FB1 and FB2 ranged from 1.1 to 15.3 mg kg−1 (mean: 5.2 mg kg−1) and 0.2 to 3.9 mg kg−1 (mean: 1.0 mg kg−1), respectively. Corn flour presented lower levels of FB1 (0.5–7.2 mg kg−1; mean: 2.1 mg kg−1) and FB2 (0.1–1.8 mg kg−1; mean: 0.7 mg kg−1). Considering the average values of FB1 found in corn meal samples, as well as food consumption estimates in Brazil, the worst case of FB1 consumption would be 2.9 μg kg body weight−1 per day. Results indicate the need for the adoption of practices to control the occurrence of fumonisins by manufacturers of corn products, mainly in corn meal.  相似文献   

6.
《Food Control》2006,17(5):378-382
The objective of this research was to establish the reduction in the incidence of carcass faecal contamination and microbial counts that could be achieved in a beef slaughter plant using a novel information technology based online monitoring system. On 18 separate visits over the course of 6 months, every carcass (approximately 500 per day) was examined at the final inspection stand for visible faecal contamination. Each incidence was attributed to dehiding or evisceration operations. On each visit, 10 carcasses were swabbed at the trimming stand, at the hock, rump, anus, brisket and flank to determine total viable counts (TVC), Escherichia coli counts (ECC), total enteric counts (TEC) and total coliform counts (TCC). Over the course of this study, faecal contamination rates for dehiding and evisceration were reduced from 54.2% to 28.2% and from 32.5% to 13.7%, respectively. TVC remained constant at approximately 3.0 log10 cfu cm−2 while ECC, TEC and TCC decreased by 0.56 log10 cfu cm−2, 0.83 log10 cfu cm−2 and 0.9 log10 cfu cm−2, respectively. Online monitoring is therefore an effective means of reducing the incidence of bovine carcass faecal and enteric counts.  相似文献   

7.
《Food Control》2010,21(9):1245-1249
Farmed European sea bass and Gilthead sea bream were obtained from four different fish farms in Turkey during 2008–2009, for determination of 17 2,3,7,8-Cl-substituted PCDDs and PCDFs, and coplanar and indicator PCBs.Concentrations of ∑PCDD/Fs and DL-PCBs, as TEQ, in fish samples, ranged from 0.14 to 0.70 pg TEQ(1998) g−1 wet weight and from 0.46 to 4.51 pg TEQ(1998) g−1 wet weight, respectively. The concentrations of total indicator PCBs in fish samples ranged from 3.1 ng g−1 to 22.1 ng g−1 wet weight. Concentrations of PCDD/Fs and DL-PCBs were below the EU regulation (EC No. 1881/2006) limits.  相似文献   

8.
《Food Control》2010,21(7):988-991
Eighty-one rice samples were purchased from different markets in Vienna and were analysed for their aflatoxin content. The samples were extracted using methanol in water (80/20 v/v) followed by immunoaffinity clean up. The determination was carried out by HPLC–FLD coupled to a Kobracell. Different samples including basmati rice, whole grain rice, long grain rice, short grain rice as well as puffed rice were investigated. Moreover, conventionally and organically produced rice were compared. The results revealed that 24 out of 81 samples contained detectable amounts of aflatoxins. Aflatoxin B1 could be quantified in 15 samples and aflatoxin B2 in one sample. The contamination range was noted to be between 0.45 μg kg−1 and 9.86 μg kg−1 for aflatoxin B1 and 1.5 μg kg−1 for aflatoxin B2. Aflatoxins G1 and G2 were not detected in any sample. Three samples exceeded the maximum levels set in the European Union; having AFB1 concentrations of 2.16, 2.85 and 9.86 μg kg−1. In the three organic produced rice samples only traces of aflatoxins were found.  相似文献   

9.
Control of Fusarium moulds and fumonisin B1 in seeds by gamma-irradiation   总被引:1,自引:0,他引:1  
《Food Control》2007,18(11):1337-1342
The distribution of naturally occurring Fusarium moulds producing fumonisin B1 in seeds was determined. Fusarium infection of seed samples ranged from 10% to 60%, Fusarium moniliforme was the predominant species. Fusarium counts in wheat seeds were 8.1 × 104 CFU/g, 6.3 × 106 CFU/g in maize and 4.8 × 103 CFU/g in barley. Wheat, maize and barley seeds naturally contaminated with varying levels of fumonisin B1 1.4–5.8, 8.0–13.8 and 0.1–0.5 μg/g, respectively. F. moniliforme and Fusarium proliferatum were major Fusarium contaminants producing fumonisin B1. The effect of gamma irradiation on Fusarium moulds and levels of fumonisin B1 was also determined. The viable counts of Fusarium in seeds decreased by increasing the radiation dose levels and the growth of Fusarium spp. was inhibited at 4.0 kGy for barley and 6.0 kGy for wheat and maize. Application of radiation dose at 5 kGy inactivated fumonisin B1 by 96.6%, 87.1% and 100% for wheat, maize and barley, respectively, and a dose of 7 kGy was sufficient for complete destruction of fumonisin B1 in wheat and maize.  相似文献   

10.
Rice husk silica (RHS) was extracted from local rice husk by acid digestion and burning at 650 °C. RHS-Ni catalyst was prepared by dissolving RHS in 1 N NaOH and titrating with 3 N HNO3 containing 10 wt.% Ni2+. The organic modifiers, either p-amino benzoic acid (A) or p-phenylenediamine (PDA) were incorporated in 5 wt.% and reduced in H2 flow. Investigation of the three catalysts, (RHS-Ni)R350, (RHS-Ni–A)R350 and (RHS-Ni–PDA)R350, confirmed good dispersion of Ni nanoparticles; all catalysts were amorphous. The BET surface areas increased in the order: (RHS-Ni)R350 < (RHS-Ni–A)R350 < (RHS-Ni–PDA)R350 with controlled pore sizes. The as-prepared catalysts were applied for both hydroconversion of cyclohexene with molecular H2 and ethanol dehydrogenation, using a flow-type reactor, at different temperatures. The activity in cyclohexene hydroconversion and selectivity to cyclohexane depended upon the reaction temperature; at t < 150 °C, the increased hydrogenation activity was referred to the formed SiO2–Ni–amine complex, pore regulation as a prime requirement for H2 storage and homogeneous distribution of incorporated Ni nanoparticles. At t > 150 °C, the backward dehydrogenation pathway was more favored, due to unavailability of H2; the process became structure-sensitive. In ethanol conversion, the prevailing dehydrogenation activity of organically modified catalyst samples was encouraged by improved homogeneous distribution of Ni nanoparticles and created micropre system.  相似文献   

11.
The objective of this work is to enhance the adsorbing performance of the natural Egyptian phyllosilicate mineral, glauconite (greensand), through surface modification to obtain a particular combination of physical and chemical properties. It was found that Zn removal increased from 84% to 94%, while Pb removal varied from 96.67% to 99% by using 10–25 g/l modified glauconite in a solution having 50 mg/l Zn2+ and 30 mg/l pb2+ ions. Adsorption data were investigated using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Linear regression methods are used to determine adsorption capacities and optimum adsorption isotherms. R2 value of Langmuir isotherm model for pb2+ is higher than other models. The maximum monolayer coverage (Qo) from Langmuir isotherm model was calculated to be 15.363 and 21.654 mg/g and the separation factor indicating a favorable sorption experiment is 0.0324 and 0.13207 for Zn2+ and Pb2+ respectively. Also from Freundlich isotherm model, the intensities of adsorption (n) that indicated favorable sorption are 1.3036 and 1.364 for Zn2+ and Pb2+ respectively. The heat of sorption process was calculated from Temkin isotherm model to be 6.44101 and 4.1353 J/mol for Zn2+ and Pb2+ respectively, that indicated to the physisorption process which B < 20 kJ/mol so, Temkin isotherm is not fitted with experimental adsorption but the mean free energy was calculated from DRK isotherm which are 24.693 and 47.093 kJ/mol, where ED < 8 proved that the adsorption experiment followed a chemisorption process. So the relative adsorption capacity for metals was in the order Pb < Zn.  相似文献   

12.
This study was carried out to determine the efficacy of phenolic antioxidant butylated hydroxyanisole (BHA) under different interacting water activity (aW) and temperature regimes on the lag phase and growth rate by Aspergillus section Nigri strains. In this experiment four A. section Nigri strains were used. Peanut meal extract agar (PMEA) was prepared at 2%. The aW of the medium was adjusted to 0.995, 0.980 and 0.930, BHA at 1, 5, 10 and 20 mmol l?1 was added to the basic medium. The plates were inoculated and incubated for 30 days at 18 and 25 °C. Radial growth rates (mm d?1) and lag phase (h) were calculated. In control treatments, the growth rate decreased as water activity reduced in all strains assayed. At all aW levels tested, BHA at 20 mmol l?1 completely inhibited growth. In general, at 10 mmol l?1 and 0.995 and 0.980aW level, a significant reduction respect to control was observed. This antioxidant completely inhibited OTA production, at concentrations of 20 mmol l?1, regardless of aW used by all the strains evaluated.  相似文献   

13.
《Food Control》2006,17(8):609-616
This study was conducted to evaluate the efficacy of gaseous ozone exposure on Listeria innocua 2030c growth during cold-smoke processing of Oncorhynchus mykiss (salmon-trout). Three sets of experiments were performed: inoculation with L. innocua 2030c followed by a 20 min ozone exposure were applied to (a) fresh salmon-trout after filleting, (b) to fresh whole fish, and (c) to fresh whole fish after removal of the fish slime. In sets (a) and (b) fillets were subsequently cold-smoked but not in set (c). The ozone concentration inside the exposure chamber after 20 min reached 0.1 × 10−3 g/l.Counts of L. innocua 2030c were performed after treatment for sets (a), (b) and (c), after smoking and weekly during 21 days in vacuum packs at 5 °C, for sets (a) and (b). Sampling for total Aerobic Plate Counts (APC) of non-inoculated samples was also performed in set (a). The percentage of salt in the water phase, peroxide values and the effect of treatment on sensory properties of cold-smoked salmon-trout fillets were also determined in the first and second set. In the first set, a decrease of less than 1 log10 in L. innocua numbers occurred on ozone treated samples in all sampling occasions. APC was slightly lower on fresh fillets after treatment and on smoked fillets at 3 weeks of storage at 5 °C (less than 1 log10 CFU/g). In the second set, a reduction greater than 1 log10 L. innocua/g occurred on smoked fillets at the end of the storage period. In the third set, the slime removal resulted in a 1 log10 L. innocua/g reduction on fresh treated samples.Ozone treatment had no significant (p > 0.05) effect on L. innocua counts on samples compared to those on untreated fish. In both sets, no significant differences among ozone treated/untreated samples were noticeable by sensory evaluation (p > 0.05).  相似文献   

14.
《Food Control》2006,17(7):551-556
A sensitive and selective spectrophotometric method has been developed for determination of trace cadmium in tableware leach solution, the method based on the reaction of cadmium(II) with new reagent 2,6-dimethylphenyldiazoaminobenzene (DMPDAAB). In 0.2 mol l−1 ammonia medium, DMPDAAB reacts with cadmium(II) to form 1:3 red complex with a maximum absorption peak at 523 nm. The apparent molar absorption coefficient of the complex and Sandell’s sensitivity were 2.27 × 105 l mol−1 cm−1 and 0.495 ng cm−2, respectively. The detection limit for cadmium and relative standard deviation were found to be 0.18 ng/g and 1.06%, respectively. Under optimal conditions, the reaction can complete instantly and absorbance of the complex remain stable for 12 h at least. Absorbance of the complex at 523 nm obey Beer’s law in the cadmium(II) range of 0–0.48 μg/ml. Moreover, we also studied the effect of foreign ions on the determination of cadmium in detail, the results showed the method has excellent selectivity, it has been applied to determine cadmium in tableware leach solution satisfactorily.  相似文献   

15.
《Food Control》2010,21(4):554-558
This survey evaluated the presence of AFM1 in human urine samples from a specific Brazilian population, as well as corn, peanut, and milk consumption measured by two types of food inquiry. Urine samples from donors who live in the city of Piracicaba, State of São Paulo, Brazil were analyzed to detect the presence of aflatoxin M1 (AFM1), an aflatoxin B1 metabolite, which may be used as aflatoxin B1 exposure biomarker. The AFM1 analysis was performed using immunoaffinity clean-up and detection by high-performance-liquid chromatography with fluorescence detector. A total of 69 samples were analyzed and 45 of them (65%) presented contaminations ⩾1.8 pg ml−1, which was the limit of quantification (LOQ). Seventy eight percent (n = 54) of the samples presented detectable concentrations of AFM1 (>0.6 pg ml−1). The AFM1 concentration among samples above LOQ ranged from 1.8 to 39.9 pg ml−1. There were differences in food consumption profile among donors, although no association was found between food consumption and AFM1 concentration in urine. The high frequency of positive samples suggests exposure of the populations studied to aflatoxins.  相似文献   

16.
《Food Control》2007,18(1):59-62
A total of 102 helva samples consisting of 34 plain helva, 34 helva containing cacao, and 34 helva containing pistachio nuts purchased from helva-factories and supermarkets in Adana of Turkey were analysed for aflatoxin B1 (AFB1) by thin-layer chromatography. The detection limit of AFB1 was 1 μg kg−1. Recovery experiments were carried out with spiked samples in the range 2–10 μg kg−1 of AFB1. No AFB1 was found in any plain helva and helva containing cacao samples. On the other hand, of 34 helva containing pistachio nuts AFB1 was determined in eight samples. AFB1 was found in excess of Turkish legal limit of 5 μg kg−1 in 4 of 102 helva samples. This paper reports the data of the first survey for the presence of AFB1 in helva in Turkey.  相似文献   

17.
The feasibility of measuring Aflatoxin B1 (AFB1) in red chili powder was investigated by using Fourier transform near-infrared (FT-NIR) spectroscopy in diffuse reflectance mode combined with appropriate chemometric techniques. Aflatoxin free chili powder samples were spiked with known amount of AFB1 ranging from 15 to 500 μg/kg and used for calibration model building based on partial least squares (PLS) regression algorithm. Different spectral preprocessing methods were investigated and optimized based on the lowest values of root mean square error of cross validation (RMSECV). Spectral wavenumber range of 6900.3–4998.8 and 4902.3–3999.8 cm?1 and straight line subtraction preprocessing technique predicted AFB1 content with best accuracy with lowest RMSECV = 0.654% and maximum correlation coefficient for validation plots (R2 = 96.7). The overall results demonstrate that FT-NIR spectroscopy can be used for rapid, non destructive quantification of Aflatoxin B1 in red chili powder.  相似文献   

18.
《Food Control》2005,16(7):623-628
This study was undertaken to assess the microbiological quality of fresh-cut organic vegetables produced in Zambia. Fresh-cut organic mixed vegetables and green beans produced in Zambia were analysed for aerobic plate counts, coliforms, Enterobacteriaceae, Escherichia coli, Bacillus cereus, Clostridium perfringens, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and yeast and mould counts. The study included 160 samples for most of the parameters. The vegetables were grown on farms meant primarily for the export market. The vegetables were treated/washed with 150 μg ml−1 chlorine solution at the processing plant prior to sampling. The aerobic plate count ranged between 3 log10 and 9.7 log10 CFU/g, with the highest count recorded for green beans. The largest grouping (26.1%) of vegetable samples fell between 3 and 4 log10 CFU/g. Coliform counts were between 1.0 log10 and 7.7 log10 CFU/g. The highest incidence level was 31.4% for total coliform counts between 3 log10 and 4 log10 CFU/g. E. coli was only detected on mixed vegetables in the range of 0.6 log10 to 3 log10 CFU/g, while Enterobacteriaceae counts ranged between 1.6 log10 and 9.8 log10 CFU/g with the highest counts being found on green beans. The highest incidence level was of 25.8% for counts within the same range as the aerobic plate counts. Yeast and mould counts showed the highest incidence level between 5 log10 and 6 log10 CFU/g with an overall range between 1.5 log10 and 5.6 log10 CFU/g. L. monocytogenes, Salmonella spp. and S. aureus were detected in 20%, 23.1% and 83.9% of samples, respectively . C. perfringens and B. cereus were not detected in any of the samples analysed.  相似文献   

19.
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.  相似文献   

20.
The removal of pollutants from effluents by electrocoagulation has become an attractive method in recent years. The study deals with the enhancement of removal of Methylene Blue dye by using an electromagnetic field during the electrocoagulation process. Effects of electrolyte concentration, dye concentration, intensity and the direction of the electromagnet on the decolorization efficiency have been investigated. The formed ferric hydroxide flocs trap colloidal particles and make solid–liquid separation easier during the next stage. The electrocoagulation stages must be optimized in order to design an economically feasible process. The results showed that the optimum electrolysis was 10–20 min at a current density of 8 mA/cm2, while the optimum concentration of the electrolyte (NaOH) was found to be 2 wt.% when the dye concentration was 50 mg/L. The utilization of an electromagnetic field enhanced the dye removal due to the induced motion of paramagnetic ions inside the solution. The power consumption required to remove the dye was reduced by 45% in the case of applying an electromagnetic field.  相似文献   

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