Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Strategy to identify and quantify polysaccharide gums in gelled food concentrates
    Grün, C.H. ; Sanders, P. ; Burg, M. van der; Schuurbiers, E. ; Adrichem, L. van; Velzen, E.J.J. van; Roo, N. de; Brunt, K. ; Westphal, Y. ; Schols, H.A. - \ 2015
    Food Chemistry 166 (2015). - ISSN 0308-8146 - p. 42 - 49.
    locust bean gum - polymerase-chain-reaction - guar gum - capillary-electrophoresis - enzymatic determination - starch industry - raw-materials - xanthan gum - identification - additives
    A strategy for the unambiguous identification and selective quantification of xanthan gum and locust bean gum (LBG) in gelled food concentrates is presented. DNA detection by polymerase chain reaction (PCR) showed to be a fast, sensitive, and selective method that can be used as a first screening tool in intact gelled food concentrates. An efficient isolation procedure is described removing components that may interfere with subsequent analyses. NMR spectroscopy enabled the direct identification of xanthan gum and the discrimination between different galactomannans in the isolated polysaccharide fraction. An enzymatic fingerprinting method using endo-ß-mannanase, in addition to being used to differentiate between galactomannans, was developed into a selective, quantitative method for LBG, whereas monosaccharide analysis was used to quantify xanthan gum. Recoveries for xanthan gum and LBG were 87% and 70%, respectively, with in-between day relative standard deviations below 20% for xanthan gum and below 10% for LBG.
    Tropane alkaloids in food: poisoning incidents
    Adamse, P. ; Egmond, H.P. van; Noordam, M.Y. ; Mulder, P.P.J. ; Nijs, W.C.M. de - \ 2014
    Quality Assurance and Safety of Crops & Foods 6 (2014)1. - ISSN 1757-8361 - p. 15 - 24.
    datura-stramonium seeds - capillary-electrophoresis - analytical toxicology - mass-spectrometry - atropine - ingestion - leaves - enantioseparation - identification - chromatography
    A large number of wild and cultured plants produce secondary metabolites that can be toxic to humans and animals. The present study aims to provide insight into the routes of (un)intentional poisonings of humans by tropane alkaloids. Poisonings of humans by tropane alkaloids occur as unintended ingestions (contamination, mislabelling: thirteen reports; mistaken identity: eleven reports) or intended ingestions (overdoses: nine reports). Contamination of food occurs when toxic plant (parts) are accidentally mixed with edible plants during harvest or processing. Concentrations are usually highest in roots and seeds. Intended ingestions can be the result of consumption for recreational purposes (hallucinogenic effects) or for medical properties (e.g. treatment of arthritis, use as anaesthetic), or homicides and suicides. Carry-over of plant toxins in feed into food products of animal origin does not appear to be a relevant source of exposure. There are several analytical methods available for monitoring tropane alkaloids in food and feed but no regulatory limits have been set. The toxic doses are often not clear due to the lack of analytical data in the cases reported. Human foods that potentially contain tropane alkaloids are herbal teas, herbal preparations, blue-or black berries and edible flowers. Contamination has also been found in beans, buckwheat, soybean and linseed.
    Separation and identification of individual alginate oligosaccharides in the feces of alginate-fed pigs
    Jonathan, M.C. ; Bosch, G. ; Schols, H.A. ; Gruppen, H. - \ 2013
    Journal of Agricultural and Food Chemistry 61 (2013)3. - ISSN 0021-8561 - p. 553 - 560.
    mass-spectrometry - capillary-electrophoresis - molecular-weight - dietary fiber - growth - acid - cells - chromatography - fermentation - hydrolysis
    This research aimed to develop a method for analyzing specific alginate oligosaccharides (AOS) in a complex matrix such as pig feces. The data obtained were used to study alginate degradation by the microbiota in the large intestine during adaptation, including the individual variation between pigs. A method using an UHPLC system with an ethylene bridged hybrid (BEH) amide column coupled with MSn detection was able to distinguish saturated and unsaturated AOS with DP 2–10. Isomers of unsaturated trimer and tetramer could be separated and annotated. In the feces, saturated and unsaturated AOS were present. The presence of unsaturated AOS indicates that the microbiota produced alginate lyase. The microbiota utilized unsaturated AOS more than saturated AOS. The results also suggested that guluronic acid at the reducing end of AOS inhibits the utilization by microbiota during the first weeks of adaptation. After adaptation, the microbiota was able to utilize a broader range of AOS.
    Biorefinery of microalgae for food and fuel
    Vanthoor-Koopmans, M. ; Wijffels, R.H. ; Barbosa, M.J. ; Eppink, M.H.M. - \ 2013
    Bioresource Technology 135 (2013). - ISSN 0960-8524 - p. 142 - 149.
    pulsed electric-field - ionic liquids - capillary-electrophoresis - microfluidic devices - gas-chromatography - stationary phases - orange juice - extraction - separation - proteins
    Microalgae are a promising source for proteins, lipids and carbohydrates for the food/feed and biofuel industry. In comparison with soya and palm oil, microalgae can be grown in a more efficient and sustainable way. To make microalgae production economically feasible it is necessary to optimally use all produced compounds. To accomplish this focus needs to be put on biorefinery techniques which are mild and effective. Of the techniques described, Pulsed Electric Field (PEF) seems to be the most developed technique compared to other cell disruption applications. For separation technology ionic liquids seems most promising as they are able to both separate hydrophobic and hydrophilic compounds. But additional studies need to be evolved in the coming years to investigate their relevance as novel cell disruption and separation methods. We propose a complete downstream processing flow diagram that is promising in terms of low energy use and state of the art knowledge.
    Speciation analysis of aqueous nanoparticulate diclofenac complexes by solid-phase microextraction
    Zielinska, K. ; Leeuwen, H.P. van; Thibault, S. ; Town, R.M. - \ 2012
    Langmuir 28 (2012)41. - ISSN 0743-7463 - p. 14672 - 14680.
    bovine serum-albumin - walled carbon nanotubes - drug binding-sites - capillary-electrophoresis - aquatic environment - antiinflammatory drugs - mass-spectrometry - metal-complexes - water samples - nd-spme
    The dynamic sorption of an organic compound by nanoparticles (NPs) is analyzed by solid-phase microextraction (SPME) for the example case of the pharmaceutical diclofenac in dispersions of impermeable (silica, SiO(2)) and permeable (bovine serum albumin, BSA) NPs. It is shown that only the protonated neutral form of diclofenac is accumulated in the solid phase, and hence this species governs the eventual partition equilibrium. On the other hand, the rate of the solid/water partition equilibration is enhanced in the presence of the sorbing nanoparticles of SiO(2) and BSA. This feature demonstrates that the NPs themselves do not enter the solid phase to any appreciable extent. The enhanced rate of attainment of equilibrium is due to a shuttle-type of contribution from the NP-species to the diffusive supply of diclofenac to the water/solid interface. For both types of nanoparticulate complexes, the rate constant for desorption (k(des)) of bound diclofenac was derived from the measured thermodynamic affinity constant and a diffusion-limited rate of adsorption. The computed k(des) values were found to be sufficiently high to render the NP-bound species labile on the effective time scale of SPME. In agreement with theoretical prediction, the experimental results are quantitatively described by fully labile behavior of the diclofenac/nanoparticle system and an ensuing accumulation rate controlled by the coupled diffusion of neutral, deprotonated, and NP-bound diclofenac species.
    Oligosaccharides in feces of breast- and formula-fed babies
    Albrecht, S.A. ; Schols, H.A. ; Zoeren, D. van; Lingen, R.A. van; Groot Jebbink, L.J.M. ; Heuvel, E.G.H.M. van den; Voragen, A.G.J. ; Gruppen, H. - \ 2011
    Carbohydrate Research : an international journal 346 (2011)14. - ISSN 0008-6215 - p. 2173 - 2181.
    induced fluorescence detection - human-colon ecosystems - blood-group antigens - human-milk - capillary-electrophoresis - preterm infants - ce-lif - bacteria - glycoproteins - degradation
    So far, little is known on the fate of oligosaccharides in the colon of breast- and formula-fed babies. Using capillary electrophoresis with laser induced fluorescence detector coupled to a mass spectrometer (CE–LIF–MSn), we studied the fecal oligosaccharide profiles of 27 two-month-old breast-, formula- and mixed-fed preterm babies. The interpretation of the complex oligosaccharide profiles was facilitated by beforehand clustering the CE–LIF data points by agglomerative hierarchical clustering (AHC). In the feces of breast-fed babies, characteristic human milk oligosaccharide (HMO) profiles, showing genetic fingerprints known for human milk of secretors and non-secretors, were recognized. Alternatively, advanced degradation and bioconversion of HMOs, resulting in an accumulation of acidic HMOs or HMO bioconversion products was observed. Independent of the prebiotic supplementation of the formula with galactooligosaccharides (GOS) at the level used, similar oligosaccharide profiles of low peak abundance were obtained for formula-fed babies. Feeding influences the presence of diet-related oligosaccharides in baby feces and gastrointestinal adaptation plays an important role herein. Four fecal oligosaccharides, characterized as HexNAc-Hex-Hex, Hex-[Fuc]-HexNAc-Hex, HexNAc-[Fuc]-Hex-Hex and HexNAc-[Fuc]-Hex-HexNAc-Hex-Hex, highlighted an active gastrointestinal metabolization of the feeding-related oligosaccharides. Their presence was linked to the gastrointestinal mucus layer and the blood-group determinant oligosaccharides therein, which are characteristic for the host’s genotype.
    Occurrence of oligosaccharides in feces of breast-fed babies in their first six months of life and the corresponding breast milk
    Albrecht, S.A. ; Schols, H.A. ; Heuvel, E.G.H.M. van den; Voragen, A.G.J. - \ 2011
    Carbohydrate Research : an international journal 346 (2011)16. - ISSN 0008-6215 - p. 2540 - 2550.
    formula-fed infants - capillary-electrophoresis - mass-spectrometry - preterm infants - ce-lif - lewis - chromatography - lactation - urine
    The characterization of oligosaccharides in the feces of breast-fed babies is a valuable tool for monitoring the gastrointestinal fate of human milk oligosaccharides (HMOs). In the present study we monitored fecal oligosaccharide profiles together with the HMO-profiles of the respective breast milks up to six months postpartum, by means of capillary electrophoresis-laser induced fluorescence detection and mass spectrometry. Eleven mother/child pairs were included. Mother’s secretor- and Lewis-type included all combinations [Le(a-b+), Le(a+b-), Le(a-b-)]. The fecal HMO-profiles in the first few months of life are either predominantly composed of neutral or acidic HMOs and are possibly effected by the HMO-fingerprint in the respective breast milk. Independent of the initial presence of acidic or neutral fecal HMOs, a gradual change to blood-group specific oligosaccharides was observed. Their presence pointed to a gastrointestinal degradation of the feeding-related HMOs, followed by conjugation with blood group specific antigenic determinants present in the gastrointestinal mucus layer. Eleven of these ‘hybrid’-oligosaccharides were annotated in this study. When solid food was introduced, no HMOs and their degradation- and metabolization products were recovered in the fecal samples.
    N-glycoproteomics in plants: Perspectives and challenges
    Song, W. ; Henquet, M.G.L. ; Mentink, R. ; Dijk, A.D.J. van; Cordewener, J.H.G. ; Bosch, H.J. ; America, A.H.P. ; Krol, A.R. van der - \ 2011
    Journal of Proteomics 74 (2011)8. - ISSN 1874-3919 - p. 1463 - 1474.
    protein-quality control - capillary-electrophoresis - endoplasmic-reticulum - linked oligosaccharides - mass-spectrometry - oligosaccharyltransferase complex - transmembrane topology - glycosylated proteins - monoclonal-antibody - o-glycosylation
    In eukaryotes, proteins that are secreted into the ER are mostly modified by N-glycans on consensus NxS/T sites. The N-linked glycan subsequently undergoes varying degrees of processing by enzymes which are spatially distributed over the ER and the Golgi apparatus. The post-ER N-glycan processing to complex glycans differs between animals and plants, with consequences for N-glycan and glycopeptide isolation and characterization of plant glycoproteins. Here we describe some recent developments in plant glycoproteomics and illustrate how general and plant specific technologies may be used to address different important biological questions
    LC/CE–MS tools for the analysis of complex arabino-oligosaccharides
    Westphal, Y. ; Kuhnel, S. ; Schols, H.A. ; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Carbohydrate Research : an international journal 345 (2010)15. - ISSN 0008-6215 - p. 2239 - 2251.
    anion-exchange chromatography - capillary-electrophoresis - mass-spectrometry - cell-walls - lif
    Recently, various branched arabino-oligosaccharides as present in a sugar beet arabinan digest were characterized using NMR. Although HPAEC often has been the method of choice to monitor the enzymatic degradation reactions of polysaccharides, it was shown that HPAEC was incapable to separate all known linear and branched arabino-oligosaccharides present. As this lack of resolution might result in an incorrect interpretation of the results, other separation techniques were explored for the separation of linear and branched arabino-oligosaccharides. The use of porous-graphitized carbon liquid chromatography with evaporative light scattering and mass detection as well as capillary electrophoresis with laser-induced fluorescence and mass detection demonstrated the superiority of both the techniques toward HPAEC by enabling the separation and unambiguous identification of almost all the linear and branched arabino-oligosaccharides available. The elution behavior of all arabino-oligosaccharides for the three tested separation techniques was correlated with their chemical structures and conclusions were drawn for the retention mechanisms of the arabino-oligosaccharides on the different chromatographic and electrophoretic systems. The combination of the elution/migration behavior on LC/CE and the MS fragmentation patterns of the arabino-oligosaccharides led to the prediction of structures for new DP6 arabino-oligosaccharides in complex enzyme digests.
    MALDI-TOF MS and CE-LIF Fingerprinting of Plant Cell Wall Polysaccharide Digests as a Screening Tool for Arabidopsis Cell Wall Mutants
    Westphal, Y. ; Schols, H.A. ; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Journal of Agricultural and Food Chemistry 58 (2010)8. - ISSN 0021-8561 - p. 4644 - 4652.
    capillary-electrophoresis - aspergillus-aculeatus - black-currants - pectin - thaliana - identification - purification - oligosaccharides - biosynthesis - hydrolase
    Cell wall materials derived from leaves and hypocotyls of Arabidopsis mutant and wild type plants have been incubated with a mixture of pure and well-defined pectinases, hemicellulases, and cellulases. The resulting oligosaccharides have been subjected to MALDI-TOF MS and CE-LIF analysis. MALDI-TOF MS analysis provided a fast overview of all oligosaccharides released, whereas CE-LIF-measurements enabled separation and characterization of many oligosaccharides under investigation. Both methods have been validated with leaf material of known mutant Arabidopsis plants and were shown to be able to discriminate mutant from wild type plants. Downscaling of the MALDI-TOF MS and CE-LIF approaches toward the hypocotyl level was established, and the performance of MALDI-TOF MS and CE-LIF was shown in the successful recognition of the Arabidopsis mutant gaut13 as an interesting candidate for further analysis.
    CE-LIF-MSn profiling of oligosaccharides in human milk and feces of breast-fed babies
    Albrecht, S.A. ; Schols, H.A. ; Heuvel, E.G.H.M. van den; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Electrophoresis 31 (2010)7. - ISSN 0173-0835 - p. 1264 - 1273.
    induced fluorescence detection - capillary-electrophoresis - mass-spectrometry - fed infants - sialylated oligosaccharides - liquid-chromatography - preterm - lactose - electrochromatography - combination
    Mixtures of the complex human milk oligosaccharides (HMOs) are difficult to analyze and gastrointestinal bioconversion products of HMOs may complicate analysis even more. Their analysis, therefore, requires the combination of a sensitive and high-resolution separation technique with a mass identification tool. This study introduces for the first time the hyphenation of CE with an electrospray mass spectrometer, capable to perform multiple MS analysis (ESI-MSn) for the separation and characterization of HMOs in breast milk and feces of breast-fed babies. LIF was used for on- and off-line detections. From the overall 47 peaks detected in off-line CE-LIF electropherograms, 21 peaks could be unambiguously and 11 peaks could be tentatively assigned. The detailed structural characterization of a novel lacto-N-neo-tetraose isomer and a novel lacto-N-fucopentaose isomer was established in baby feces and pointed to gastrointestinal hydrolysis of higher-Mw HMOs. CE-LIF-ESI-MSn presents, therefore, a useful tool which contributes to an advanced understanding on the fate of individual HMOs during their gastrointestinal passage.
    Introducing porous graphitized carbon liquid chromatography with evaporative light scattering and mass spectrometry detection into cell wall oligosaccharide analysis
    Westphal, Y. ; Schols, H.A. ; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1217 (2010)5. - ISSN 0021-9673 - p. 689 - 695.
    treated eucalyptus wood - hairy ramified regions - capillary-electrophoresis - black-currants - polysaccharides - pectin - xylogalacturonan - quantification - nomenclature - ionization
    Separation and characterization of complex mixtures of oligosaccharides is quite difficult and, depending on elution conditions, structural information is often lost. Therefore, the use of a porous-graphitized-carbon (PGC)-HPLC-ELSD-MSn-method as analytical tool for the analysis of oligosaccharides derived from plant cell wall polysaccharides has been investigated. It is demonstrated that PGC-HPLC can be widely used for neutral and acidic oligosaccharides derived from cell wall polysaccharides. Furthermore, it is a non-modifying technique that enables the characterization of cell wall oligosaccharides carrying, e.g. acetyl groups and methylesters. Neutral oligosaccharides are separated based on their size as well as on their type of linkage and resulting 3D-structure. Series of the planar ß-(1,4)-xylo- and ß-(1,4)-gluco-oligosaccharides are retained much more by the PGC material than the series of ß-(1,4)-galacto-, ß-(1,4)-manno- and a-(1,4)-gluco-oligosaccharides. Charged oligomers such as a-(1,4)-galacturonic acid oligosaccharides are strongly retained and are eluted only after addition of trifluoroacetic acid depending on their net charge. Online-MS-coupling using a 1:1 splitter enables quantitative detection of ELSD as well as simple identification of many oligosaccharides, even when separation of oligosaccharides within a complex mixture is not complete. Consequently, PGC-HPLC-separation in combination with MS-detection gives a powerful tool to identify a wide range of neutral and acidic oligosaccharides derived from various cell wall polysaccharides.
    Immunochromatographic Lateral-flow test strip for the rapid detection of added bovine rennet whey in milk and milk powder
    Martin-Hernandez, C. ; Munoz, M. ; Daury, C. ; Weymuth, H. ; Kemmers-Voncken, A. ; Corbation, V. ; Toribo, T. ; Bremer, M.G.E.G. - \ 2009
    International Dairy Journal 19 (2009)4. - ISSN 0958-6946 - p. 205 - 208.
    reversed-phase hplc - buttermilk powder - skim milk - uht milk - capillary-electrophoresis - solids - proteolysis
    An immunochromatographic lateral-flow test dipstick test was developed for the fast detection of bovine rennet whey in liquid milk and milk powder. The test is based on the binding of casein glycomacropeptide (cGMP) by two specific anti-bovine ¿-casein monoclonal antibodies and has a visual detection limit of around 15 ng mL¿1 for cGMP and 1% (v/v) for rennet whey in milk using standards and spiked samples. The dipstick performance was evaluated in a collaborative trial using skim milk powder and raw, pasteurized and UHT milk. The suitability of the dipstick was demonstrated in comparison with gel permeation-high performance liquid chromotography and a colorimetric method, by analysing 60 raw milk samples collected from farms in Brazil. The dipstick results correlated well with the HPLC results and were more reliable than those obtained with the colorimetric method. The dipstick test correctly identified all raw milk samples with a rennet whey content above 4%.
    Effects of rice straw on the speciation of cadmium (Cd) and copper (Cu) in soils
    Cui, Y.S. ; Du, X. ; Weng, L.P. ; Zhu, Y.G. - \ 2008
    Geoderma 146 (2008)1-2. - ISSN 0016-7061 - p. 370 - 377.
    cellulose degradation-products - donnan membrane technique - dissolved organic-matter - heavy-metals - capillary-electrophoresis - humic substances - model parameters - aqueous-solution - trace-metals - ion-binding
    Four soils were collected from different sites of China in Lechang (LC, Guangdong province), Changsha (CS, Hunan province), Jiaxing UX, Zhejiang province) and Hangzhou (HZ, Zhejiang province), and were spiked with Cu (50 mg kg(-1)) and Cd (5 mg kg(-1)). The effects of rice straw addition (6%) on the chemical distribution of both metal ions were studied by measuring the soluble metal ion concentrations and the free metal ion concentrations (using the Donnan membrane technique) after 1-, 3- and 6-month incubation. Results show that the addition of rice straw increased soil pH by about 0.4 pH unit on average, and increased DOC significantly in soil LC, CS and JX, but not in soil HZ. With the addition of rice straw, total soluble Cu concentration increased from 0.82 mu mol l(-1) (0.26-2.4 mu mol l(-1)) to 1.22 mu mol l(-1) (0.70-3.60 mu mol l(-1)), whereas total soluble Cd concentration decreased from 20 nmol l(-1) (2-70 nmol l(-1)) to 15 nmol l(-1) (2-56 nmol l(-1)). When rice straw was added, both free Cu 2 and Cd 21 concentrations decreased, for free Cu2+ concentration from 217 nmol l(-1) (31 to 369 nmol l(-1)) to 124 nmol l(-1) (22 to 263 nmol l(-1)) and for free Cd2+ concentration from 16 nmol l(-1) (1-55 nmol l(-1)) to 12 nmol l(-1) (1-43 nmol l(-1)). With the increase of incubation time, free Cu2+ concentration tended to increase but free Cd2+ concentration decreased. Speciation model calculations show that compared to the binding capacity of soil organic matter, the capacity of rice straw is much less important. The decrease of free metal ion concentration upon rice straw addition can be attributed mainly to the increased pH. The higher DOC content in the rice straw treatment could be the reason for higher soluble Cu concentration when rice straw was added. Adsorption to DOC is much less important for Cd than for Cu. Calculation also shows that adsorption to clay minerals plays a more important role for Cd than for Cu, which may explain the stronger ageing effects on Cd distribution. (c) 2008 Elsevier B.V. All rights reserved.
    An overview of analytical methods for determining the geographical origin of food products
    Luykx, D.M.A.M. ; Ruth, S.M. van - \ 2008
    Food Chemistry 107 (2008)2. - ISSN 0308-8146 - p. 897 - 911.
    virgin olive oils - ratio mass-spectrometry - principal component analysis - stable-isotope analysis - face fluorescence spectroscopy - nuclear-magnetic-resonance - french red wines - capillary-electrophoresis - gas-chromatography - multivariate-analysis
    There is an increasing interest by consumers for high quality food products with a clear geographical origin. These products are encouraged and suitable analytical techniques are needed for the quality control. This overview concerns an investigation of the current analytical techniques that are being used for the determination of the geographical origin of food products. The analytical approaches have been subdivided into four groups; mass spectrometry techniques, spectroscopic techniques, separation techniques, and other techniques. The principles of the techniques together with their advantages and drawbacks, and reported applications concerning geographical authenticity are discussed. A combination of methods analysing different types of food compounds seems to be the most promising approach to establish the geographical origin. Chemometric analysis of the data provided by the analytical instruments is needed for such a multifactorial approach.
    Identification of plant proteins in adulterated skimmed milk powder by high-performance liquid chromatography-mass spectrometry
    Luykx, D.M.A.M. ; Cordewener, J.H.G. ; Ferranti, P. ; Frankhuizen, R. ; Bremer, M.G.E.G. ; Hooijerink, H. ; America, A.H.P. - \ 2007
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1164 (2007)1-2. - ISSN 0021-9673 - p. 189 - 197.
    fast atom bombardment - electrospray-ionization - reversed-phase - capillary-electrophoresis - perfusion chromatography - soybean proteins - dairy-products - pea - biomolecules - cheese
    The EU subsidises the use of skimmed-milk powder (SMP) in compound feeding stuffs. There are indications of falsified SMP content due to the addition of plant proteins. These proteins are not allowed in SMP and cannot be identified by the official reference method. Since soy and pea proteins are most likely to be added to SMP, manufactured SMP containing 1 and 5% of these plant proteins was used to develop a sensitive protein identification method based on mass spectrometry (MS). The method included a pre-fractionation step to enrich for plant proteins by using a borate buffer. A very fast perfusion liquid chromatography method including sensitive and selective intrinsic fluorescence detection was developed for monitoring and quantifying the efficiency of the pre-fractionation and screening for plant proteins. After tryptic digestion of the enriched fraction from manufactured adulterated SMP, numerous peptides originating from the major seed proteins of soy (glycinin, ß-conglycin) and pea (legumin, vicilin) could be identified by MS/MS analysis on a quadrupole time-of-flight MS instrument.
    Electroporation of cells in microfluidic devices: a review
    Fox, M.B. ; Esveld, D.C. ; Valero, A. ; Luttge, R. ; Mastwijk, H.C. ; Bartels, P.V. ; Berg, A.B.A. van den; Boom, R.M. - \ 2006
    Analytical and Bioanalytical Chemistry 385 (2006)3. - ISSN 1618-2642 - p. 474 - 485.
    pulsed-electric-field - dielectrophoretic impedance measurement - capillary-electrophoresis - high-intensity - biological cells - single cells - microfabricated devices - analysis systems - mass-transfer - patch-clamp
    In recent years, several publications on microfluidic devices have focused on the process of electroporation, which results in the poration of the biological cell membrane. The devices involved are designed for cell analysis, transfection or pasteurization. The high electric field strengths needed are induced by placing the electrodes in close proximity or by creating a constriction between the electrodes, which focuses the electric field. Detection is usually achieved through fluorescent labeling or by measuring impedance. So far, most of these devices have only concerned themselves solely with the electroporation process, but integration with separation and detection processes is expected in the near future. In particular, single-cell content analysis is expected to add further value to the concept of the microfluidic chip. Furthermore, if advanced pulse schemes are employed, such microdevices can also enhance research into intracellular electroporation.
    Determination of sunset yellow in multi-vitamin tablets by photoacoustic spectroscopy and a comparison with alternative methods
    Doka, O. ; Bicanic, D.D. ; Ajtony, Z. ; Koehorst, R.B.M. - \ 2005
    Food Additives and Contaminants 22 (2005)6. - ISSN 0265-203X - p. 503 - 507.
    spectrophotometric determination - capillary-electrophoresis - food colorants - least-squares - allura-red - identification - chromatography - tartrazine - mixtures - powders
    Photoacoustic (PA) spectroscopy in the visible wavelength region was shown to be suitable for a direct (no preparatory steps involved) quantification of sunset yellow (E110) colour in effervescent multi-vitamin tablets. Measurements on powdered tablets containing E110 were performed at 480?nm at which wavelength this synthetic colour shows appreciable absorbance. The PA data obtained were compared to the results acquired by diffuse reflectance spectroscopy and conventional spectrophotometry. Intrinsic simplicity, ease of sampling and rapid response were the most important advantages of the PA technique. In terms of sensitivity the performance of the three methods were comparable
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