Evaluation of four isolation techniques for honey aroma compounds

The analysis of the volatile fraction of honey provides useful information for the determination of the botanical and geographical origin. However, the results obtained vary greatly upon the extraction procedure employed. Four different isolation techniques were compared, that is hydrodistillation (HD), micro‐simultaneous steam distillation–solvent extraction (MSDE), ultrasound‐assisted extraction (USE) and solid‐phase microextraction (SPME). From the data obtained, USE and SPME seem to be more suitable for the isolation of potent marker compounds. HD and MSDE have main drawbacks because of the drastic conditions used that lead to the formation of artefacts and the degradation of sensitive compounds. These drawbacks are avoided when employing USE and SPME. Copyright © 2004 Society of Chemical Industry     

Evaluation of mixed valent iron oxides as reactive adsorbents for arsenic removal

The objective of this research was to determine if Fe(II)-bearing iron oxides generate ferric hydroxides at sufficient rates for removing low levels of arsenic in packed-bed reactors, while at the same time avoiding excessive oxide production that contributes to bed clogging in oxygenated waters. Column experiments were performed to determine the effectiveness of three media for arsenic removal over a range in empty bed contact times, influent arsenic concentrations, dissolved oxygen (DO) levels, and solution pH values. Corrosion rates of the media as a function of the water composition were determined using batch and electrochemical methods. Rates of arsenic removal were first order in the As(V) concentration and were greater for media with higher corrosion rates. As(V) removal increased with increasing DO levels primarily due to faster oxidation of the Fe2+ released by media corrosion. To obtain measurable amounts of arsenic removal in 15 mM NaCl electrolyte solutions containing 50 microg/L As(V), the rate of Fe2+ released by the media needed to be at least 15 times greater than the As(V) feed rate into the column. In waters containing 30 mg/L of silica and 50 microg/L of As(V), measurable amounts of arsenic removal were obtained only for Fe2+ release rates that were at least 200 times greater than the As(V) feed rate. Although all columns showed losses in hydraulic conductivity overthe course of 90 days of operation, the conductivity values remained high, and the losses could be reversed by backwashing the media. The reaction products produced by the media in domestic tap water had average As-to-Fe ratios that were approximately 25% higher than those for a commercially available adsorbent.     

大豆蛋白的膜分离技术

本专题研究用膜分离技术从低温豆粕中提取分离大豆蛋白的工艺技术条件,膜对大豆蛋白提取液透过性的影响及相关技术参数,还研究膜的污染与清洗及通量恢复方法。     

洋葱中天然活性成分丙烯基半胱氨酸亚砜分离纯化方法的改进

丙烯基半胱氨酸亚砜(1-PeCSO)及其蒜酶催化产物具有很重要的生理活性.前人报道了它从洋葱中的提取分离方法,但在分离过程中因1-PeCSO在碱性条件下环化,导致产率较低(0.2%,w/w).本研究采用了改进的分离方法:洋葱粗提液先后经过四根阳离子或阴离子交换柱,通过缩短第四柱长度,流速提高至2.0mL/min,采用0.05mol/L的醋酸铵溶液进行pH从5.5到8.5的梯度洗脱,得到产量较高的丙烯基半胱氨酸亚砜(0.4%,w/w).     

Sewage sludge-derived materials as efficient adsorbents for removal of hydrogen sulfide

Sewage sludge-derived materials were used as adsorbents of hydrogen sulfide from moist air. The adsorbent obtained by carbonization at 950 degrees C has a capacity twice of that of coconut-shell-based activated carbon. The capacity of the sludge-derived materials increases with increasing carbonization temperature. It is likelythatduring carbonization at 950 degrees C a mineral-like phase is formed that consists of such catalytically active metals as iron, zinc, and copper. The results obtained demonstrate that the presence of iron oxide significantly increases the capacity of commercial carbon and activated alumina. The sludge-derived adsorbents are efficient for hydrogen sulfide removal until the pore entrances are blocked with sulfur as the product of oxidation reaction. For materials in which the catalytic effect is predominant, hydrogen sulfide is adsorbed until all pores are filled with sulfur. There is also indication that chemisorption plays a significant role in the removal of hydrogen sulfide from moist air.     

食品安全监督管理技术现状分析

现从法律体系、检测体系、标准体系、食品污染物监测网络、监控策略和技术、风险性信息交流6个方面分析食品安全监督管理技术的现状和问题,期望能对食品安全控制战略的制定有所帮助。     

Evaluation of techniques for enrichment and isolation of Escherichia coli O157:H7 from artificially contaminated sprouts.

Because sprouted seed products are kept wet during and after production, have high levels of nutrients, and a neutral pH, they are subject to the outgrowth of pathogens such as Escherichia coli O157:H7. For these same reasons, these products also contain high levels of heterotrophic organisms and in particular coliform bacteria. Recent outbreaks have focused attention on the need to improve methodology for isolating this pathogen from sprouts. When 40 E. coli O157:H7 strains were grown in pure culture in enterohemorrhagic E. coli enrichment broth (EEB) as prescribed in the U.S. FDA-Bacteriological Analytical Manual (FDA-BAM) and in EEB modified by varying the cefixime concentration, outgrowth for all strains in EEB was inhibited at 0.05 mg/l but for only 2 of 40 strains when the cefixime level was adjusted to 0.0125 mg/l. These two enrichment formulae were compared to modified E. coli broth (mEC), modified Tryptic Soy Broth with 20 mg/l novobiocin (mTSB + N), modified Buffered Peptone Water (mBPW), and mBPW with added 10 mg/l acriflavin, 10 mg/l cefsulodin, and 8 mg/l vancomycin (mBPW + ACV) for isolation of E. coli O157:H7 from sprouts. These comparisons were performed using low-level (0.12 to 0.42 cfu/g) artificially contaminated alfalfa and mixed salad sprouts. After enrichment, two isolation methods were compared for recovery; direct plating to Tellurite-Cefixime Sorbitol MacConkey agar (TCSMAC) and immunomagnetic separation (IMS) (Dynabeads anti-E. coli O157, Dynal, Oslo, Norway) followed by plating to TCSMAC. In addition, an immunoprecipitin detection kit, VIP (BioControl, Bellevue, WA), was evaluated for detection after enrichment. We found that five of the six enrichments were equivalent for detection or recovery while one enrichment (mTSB + N without agitation) was less productive. Incubation for 24 h was more effective in recovering E. coli O157:H7 from sprouts than 6 h for all enrichment broths. Plating after IMS was more productive than direct plating at these low levels of contamination, yielding recovery in 70 of 90 trials compared to 37 of 90 trials without IMS for six enrichments. The sensitivity of VIP for detection of E. coli O157:H7 varied depending on the enrichment broth. Because of the rapid rate of growth of E. coli O157:H7 in mBPW, the high productivity of mBPW + ACV after 24-h enrichment and its compatibility with both IMS and detection with immunoprecipitin tests, mBPW + ACV at 42 degrees C with agitation was found to be the most promising enrichment protocol for testing sprouts.     

Wood sawdust and wood originate materials as adsorbents for heavy metal ions

The abilities of different types of wood sawdust and wood originate materials for removing some toxic heavy metal ions from water were investigated. Sawdust of poplar, willow, fir, oak and black locust wood, pulp and Kraft lignin were used as adsorbents. The effects of contact time, pH, metal concentration and sawdust particle size on the removal of Cu(II) ions by poplar sawdust have been studied. Leaching from these adsorbents into water during adsorption was also investigated.     

Wood sawdust and wood originate materials as adsorbents for heavy metal ions

The abilities of different types of wood sawdust and wood originate materials for removing some toxic heavy metal ions from water were investigated. Sawdust of poplar, willow, fir, oak and black locust wood, pulp and Kraft lignin were used as adsorbents. The effects of contact time, pH, metal concentration and sawdust particle size on the removal of Cu(II) ions by poplar sawdust have been studied. Leaching from these adsorbents into water during adsorption was also investigated.

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Sägemehl, Zellstoff und Lignin als Absorbentien für Schwermetallionen

Zusammenfassung Das Potenzial von Holzmehl aus verschiedenen Holzarten zum Entfernen von toxischen Schwermetallionen aus wässrigen Lösungen wurde untersucht. Neben Holzmehl von Pappel, Weide, Tanne, Eiche und Robinie wurden auch Zellstoff und Kraft-Lignin als Adsorbentien eingesetzt. Untersucht wurde der Einfluss der Behandlungszeit, des pH, der Metallkonzentration und der Partikelgröße auf das Entfernen von Cu(II)-Ionen durch Pappel-Sägemehl. Das teilweise Auflösen dieser Adsorbentien in Wasser während der Adsorption wurde ebenfalls untersucht.

     

Caged multiwalled carbon nanotubes as the adsorbents for affinity-based elimination of ionic dyes

Multiwalled carbon nanotubes (MWCNTs) were used as the active elements for the first time for affinity-based elimination of ionic dyes. MWCNTs were encapsulated in cross-linked alginate (ALG) microvesicles using Ba2+ as the bridging ion. The Ba2+-alginate matrix constitutes a cage which holds the physically trapped MWCNTs. The cage carries negative charges on its surface. The cage restricts the access of anions of large molecular weight, such as humic acids, because of electrostatic repulsion. The cage also restricts the access of colloids of large size, because of size exclusion. Ionic dyes partition into the cage and then are captured by MWCNTs probably on the basis of van der Waals interactions occurring between the hexagonally arrayed carbon atoms in the graphite sheet of MWCNTs and the aromatic backbones of the dyes. As a result of these interactions the target species, namely, the ionic dyes, are eliminated efficiently by the MWCNTs of Ba2+-ALG/MWCNT composite adsorbents. The adsorptive capacities for elimination of acridine orange, ethidium bromide, eosin bluish, and orange G (the model species used for this study) were found as high as 0.44, 0.43, 0.33, and 0.31 micromol, respectively, for 1.0 mg of the caged MWCNTs. Adsorptive experiments with carbon nanofibers and activated carbons as the adsorbents were also performed. The MWCNT-based adsorbents provided the best capability for the affinity-based elimination of these targeted species. Biocompatibility experiments performed in vitro and in vivo provided promising results, suggesting potential applications of the caged MWCNTs in in situ environmental remediation.     

Selective adsorption of limonin and naringin from orange juice to natural and synthetic adsorbents

In the majority of citrus juices, bitterness is mainly ascribed to the presence of limonoids (triterpenes) and flavanone glycosides (flavonoids), namely limonin and naringin. In this study, the selective removal of limonin and naringin from citrus juice by batch adsorption to different materials was investigated. Since the removal of reducing sugars, pigments and vitamin C may also occur, the eventual adsorption of these compounds was also investigated. The following adsorbents were tested: activated diatomaceous earths, granulated activated carbon and synthetic neutral resins (Amberlite XAD-4, XAD-7 and XAD-16). Both Freundlich and Langmuir isotherm models showed a good fit to the adsorption of limonin to the resins used. Concerning naringin adsorption, a good fit of these models was only observed when the XAD-7 resin was used. Sigmoidal profiles were obtained for the adsorption of limonin to granular activated carbon. Unfavourable isotherms were also observed for limonin and naringin adsorption to activated earths. These isotherm adsorption profiles can be explained by a multilayer adsorption phenomenon. The highest adsorption efficiency for the bitter compounds was observed when synthetic neutral resin, Amberlite XAD-7 was used. The separation factor limonin/naringin varied from 16 (with earths) to 57 (with XAD-7 resin). The adsorption of sugars and pigments to the resins was low. No adsorption of vitamin C was detected for any of the adsorbents tested. The estimated affinity and separation factors show that the neutral resins tested are adequate for the selective removal of limonin from orange juices. The estimated values of free energy of adsorption, lower than -13.3 kJ mol^-1 K^-1, indicate that a physiosorption process occurred.     

Proteins and protein-rich biomass as environmentally friendly adsorbents selective for precious metal ions

Proteins exhibit specific interactions with various metal ions, which play important roles in a living cell. Here, we found that various proteins selectively adsorbed precious metal ions at a wide range of pH values. Studies on protein sequences and on synthesized peptides revealed that a histidine-containing sequence had specific interactions with precious metal ions (Au3+ and Pd2+). We then investigated a few types of protein-rich biomass as adsorbents for precious metal ions. In the presence of various transition metal ions, Au3+ and Pd2+ were also selectively adsorbed onto the biomass tested. The bound precious metal ions were recovered by aqua regia after charring the metal-bound biomass. Finally, we demonstrated the successful recovery of Au3+ and Pd2+ from a metal refining solution and a metal plating waste using the biomass. We propose an environmentally friendly recycling system for precious metal ions using protein-rich biomass.     

新型纺纱技术的研究分析

对转杯纺、喷气纺等新型纺纱设备及其纱线产品的现状与发展趋势进行了评述,提出应不断完善和提高技术装备水平,加强纱线产品开发,才能真正使新型纺纱技术推广应用,促进纺织行业的发展.文中介绍了转杯纺纱现状、国产转杯纺纱机设备水平、各种转杯纱所采用的不同工艺路线以及不同纺杯转速下的适纺和经济细度,提出了产品开发的方向,对转杯纺纯棉产品和非棉产品的开发进行了讨论.     

Comparison of analytical techniques for dynamic trace metal speciation in natural freshwaters

Several techniques for speciation analysis of Cu, Zn, Cd, Pb, and Ni are used in freshwater systems and compared with respect to their performance and to the metal species detected. The analytical techniques comprise the following: (i) diffusion gradients in thin-film gels (DGT); (ii) gel integrated microelectrodes combined to voltammetric in situ profiling system (GIME-VIP); (iii) stripping chronopotentiometry (SCP); (iv) flow-through and hollow fiber permeation liquid membranes (FTPLM and HFPLM); (v) Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE-SV). All methods could be used both under hardwater and under softwater conditions, although in some cases problems with detection limits were encountered at the low total concentrations. The detected Cu, Cd, and Pb concentrations decreased in the order DGT > or = GIME-VIP > or = FTPLM > or = HFPLM approximately = DMT (>CLE-SV for Cd), detected Zn decreased as DGT > or = GIME-VIP and Ni as DGT > DMT, in agreement with the known dynamic features of these techniques. Techniques involving in situ measurements (GIME-VIP) or in situ exposure (DGT, DMT, and HFPLM) appear to be appropriate in avoiding artifacts which may occur during sampling and sample handling.     

Evaluation of enzyme efficiency for soy oleosome isolation and ultrastructural aspects

Two procedures and four commercial enzymes were compared to isolate intact oleosomes from dry soybean flour. Results showed that Multifect^® Pectinase FE efficiently liberated intact oleosomes in both procedures. The increase in oleosome extraction yield and reducing sugar production indicates that there was a synergistic effect on degrading the cell wall when theses enzymes were used together. In the control with no enzymes, 34.06% and 67.66% of the total soybean oil were obtained from oleosomes, respectively, with the initial and the simplified procedures which mimics the initial procedure, but using less buffer. Transmission electron micrographs of extracts from the simplified procedure showed intact oleosomes, indicating that the extraction conditions did not affect oleosome integrity. Native soybean proteins were recovered from the aqueous supernatant in addition to the oleosome fraction. Using Multifect^® Pectinase FE resulted in the disappearance of the α′ and α subunits of the β-conglycinin.     

天然黄酮类化合物分离纯化研究进展

为了进一步分离纯化天然黄酮类化合物,综述了黄酮类化合物的分离纯化常用的方法有柱层析法、重结晶法、铅盐沉淀法及高效液相色谱法等方法,旨在为黄酮类化合物的研究、开发和应用提供借鉴.     

Evaluation of Petrifilm for the isolation of Staphylococcus aureus from milk samples

Four experiments were conducted to evaluate the Petrifilm Staph Express Count plate (3M, Minneapolis, MN) for diagnosis of mastitis caused by Staphylococcus aureus. The objective of experiment 1 was to determine the sensitivity of Petrifilm compared with results of standard and augmented microbiological techniques, and the objective of experiment 2 was to compare microbiological results of composite and quarter milk samples processed using Petrifilm. Experiment 3 was conducted to determine the specificity of the Petrifilm method based on different interpretation parameters, and the objective of experiment 4 was to determine the repeatability of reading Petrifilm Staph Express plates. Results of standard microbiological techniques used for experiments 1 and 2 were compared with results of samples preprocessed using centrifugation or preincubation. The prevalence of recovery of Staph. aureus from milk samples processed using Petrifilm was significantly greater than the prevalence of milk samples processed using standard microbiological techniques. The sensitivity of isolation of Staph. aureus was 65.6, 75.0, 84.4, and 87.5% for standard, centrifugation, incubation, and Petrifilm methods, respectively. The occurrence of a distinct pink zone surrounding a colony was highly specific for Staph. aureus, and the specificity was 98.5 and 96.0% for experiments 3 and 4, respectively. The use of a weak pink zone to diagnose Staph. aureus resulted in a high rate of false-positive results. The interpretation of results of Petrifilm Staph Express was associated with the person that read the plates. Results from all 4 experiments indicate potential for the Petrifilm products as a diagnostic tool in some herd situations when Staph. aureus is the pathogen of interest. Results also indicate the need for standardization of interpretive criteria for personnel working with the products.