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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    Characterisation of 3-aminoquinoline-derivatised isomeric oligogalacturonic acid by travelling-wave ion mobility mass spectrometry
    Huang, J.H. ; Bakx, E.J. ; Gruppen, H. ; Schols, H.A. - \ 2013
    Rapid Communications in Mass Spectrometry 27 (2013)20. - ISSN 0951-4198 - p. 2279 - 2285.
    cell walls - oligosaccharides - matrix - chromatography - separation - pectin - quantification - resolution
    RATIONALE Mass spectrometry has become a useful technique for elucidating the chemical structures of oligosaccharides. The combined use of chromatography and mass spectrometry for the separation and identification of oligosaccharides has shown much progress in recent years. However, no powerful method has yet been developed to quickly identify isomeric oligosaccharides in complex mixtures. METHODS A rapid travelling-wave ion mobility mass spectrometry (TWIMS-MS) method was developed for the identification of various isomeric oligogalacturonic acids in mixtures and determined their structures, using 3-aminoquinoline (3-AQ) as a labelling agent. RESULTS TWIMS successfully distinguished isomeric oligogalacturonic acids of various degrees of polymerisation (DPs) and levels of methyl-esterification. After derivatisation by 3-AQ, isomeric oligosaccharides of galacturonic acid, with the DP ranging from 2 to 9 and the number of methyl esters ranging from 1 to 5, were identified by 3-AQ-TWIMS-MS. The isomeric oligosaccharides with varying sites of methyl ester substitution were identified by the post-fragmentation mode of TWIMS using 3-AQ labelling to obtain simplified mass spectra. CONCLUSIONS Using the 3-AQ-TWIMS-MS method, the precise distribution of methyl esters within the pectin molecule and isomeric oligogalacturonic acids after enzyme degradation was determined. Simplified product ion mass spectra and precise analysis of the isomers were achieved by labelling 3-AQ at the reducing end of the oligosaccharides. Series of methyl-esterified galacturonic acid oligomers have predictable drift times, depending on the precise position of the methyl ester.
    PTR-MS monitoring of volatiles fingerprint evolution during grape must cooking
    Dimitri, G. ; Ruth, S.M. van; Sacchetti, G. ; Piva, G. ; Alewijn, M. ; Arfelli, G. - \ 2013
    Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 51 (2013)1. - ISSN 0023-6438 - p. 356 - 360.
    reaction-mass-spectrometry - maillard reaction - flavor retention - food - product - consumption - headspace - systems - storage - matrix
    The main aim of this study was to investigate the effect of processing temperature on the evolution of volatiles during grape must concentration upon cooking. The evolution of the volatiles fingerprint of grape must heated at 80, 90, and 100 °C was studied by Proton Transfer Reaction Mass Spectrometry (PTR-MS). The intensity of the heat treatment influenced the volatile molecules generated after the activation of the non enzymatic browning (NEB) reactions during the cooking process. These volatile compounds represent the most important molecules that characterise the aroma of highly cooked and concentrated must. Time and temperature of treatment influenced dramatically the evolution of must volatile compounds, so at the end of the treatment different volatile profiles were observed. Concentration being equal, high temperature-short time treatments limited the accumulation of volatiles associated to NEB while prolonged times of treatment favoured the formation of NEB flavours.
    Stiffening in gels containing whey protein isolate
    Purwanti, N. ; Veen, E. van der; Goot, A.J. van der; Boom, R.M. - \ 2013
    International Dairy Journal 28 (2013)2. - ISSN 0958-6946 - p. 62 - 69.
    physicochemical changes - body-composition - filled gels - aggregation - stability - matrix - bars - microstructure - storage - muscle
    Gels made only from whey protein isolate (WPI) stiffened over the first few days of storage, after which the textural properties remained nearly constant. However, protein gels containing WPI microparticles, at the same total protein content, stiffened over a longer period than those without microparticles. This stiffening was suggested to be the result of rearrangement of crosslinks in the gel. Addition of particles induces additional effects leading to water distribution between the protein particles and continuous phase. The stiffness change over time was different for gels made from a mixture of locust bean gum and xanthan gum containing microparticles. The stiffness of matrix gel and of gels containing 20% (w/w) microparticles was rather stable over time; microscopy analysis of these gels showed that particle size was constant after 72 h storage. Nevertheless, changes were observed in small deformation; this might be the consequence of slow rearrangements within the protein particles.
    Interactive effects of landscape context constrain the effectiveness of local agri-environmental management
    Concepción, E.D. ; Díaz, M. ; Kleijn, D. ; Báldi, A. ; Batáry, P. ; Clough, Y. ; Gabriel, D. ; Herzog, F. ; Holzschuh, A. ; Knop, E. ; Marshall, J.P. ; Tscharntke, T. ; Verhulst, J. - \ 2012
    Journal of Applied Ecology 49 (2012)5. - ISSN 0021-8901 - p. 695 - 705.
    different spatial scales - farmland biodiversity - agricultural landscapes - species-diversity - field margins - schemes - corridors - europe - matrix - birds
    summary 1. Ecological theory predicts that the effectiveness of local agri-environmental management to enhance species richness at field scales will be the highest at intermediate levels of landscape complexity because of nonlinear effects of landscape context on field-scale diversity. 2. We examined how landscape complexity determined effectiveness of local agri-environmental management in terms of effects on species richness of birds, plants, spiders and bees in 232 extensive and intensive paired fields (112 arable fields and 120 grasslands) from 18 regions located in six European countries. 3. As predicted, landscape complexity enhanced field-scale species richness in a mostly nonlinear (sigmoidal) way, with earlier species richness increases in extensive than in intensive fields along landscape complexity gradients. Length of semi-natural boundaries (for arable fields) and proportion of unfarmed habitat (for grasslands) were the landscape features influencing species richness. 4. The relationships between effectiveness of local management and landscape complexity for all taxa were best described with hump-shaped curves, indicating the highest effectiveness at intermediate landscape complexities. 5. Synthesis and applications. We used models to investigate how and why effects of local management intensity on species richness vary along wide gradients of landscape complexity. We conclude that landscape-scale management options should take priority over local extensification measures within agri-environmental programmes. These programmes should follow a hierarchical multi-scale approach directed to address landscape-scale constraints on local diversity.
    Nanopatterned submicron pores as a shield for nonspecific binding in surface plasmon resonance-based sensing
    Rebe-Raz, S. ; Marchesini, G.R. ; Bremer, M.G.E.G. ; Colpo, P. ; Garcia, C.P. ; Guidetti, G. ; Norde, W. ; Rossi, F. - \ 2012
    The Analyst 137 (2012)22. - ISSN 0003-2654 - p. 5251 - 5259.
    biosensor immunoassays - protein adsorption - gold surfaces - blood-plasma - milk - immobilization - reduction - matrix - serum - size
    We present a novel approach to tackle the most common drawback of using surface plasmon resonance for analyte screening in complex biological matrices – the nonspecific binding to the sensor chip surface. By using a perforated membrane supported by a polymeric gel structure at the evanescent wave penetration depth, we have fabricated a non-fouling sieve above the sensing region. The sieve shields the evanescent wave from nonspecific interactions which interfere with SPR sensing by minimizing the fouled area of the polymeric gel and preventing the translocation of large particles, e.g. micelles or aggregates. The nanopatterned macropores were fabricated by means of colloidal lithography and plasma enhanced chemical vapor deposition of a polyethylene oxide-like film on top of a polymeric gel matrix commonly used in surface plasmon resonance analysis. The sieve was characterized using surface plasmon resonance imaging, contact angle, atomic force microscopy and scanning electron microscopy. The performance of the sieve was studied using an immunoassay for detection of antibiotic residues in full fat milk and porcine serum. The non-fouling membrane presented pores in the 92–138 nm range organized in a hexagonal crystal lattice with a clearance of about 5% of the total surface. Functionally, the membrane with the nanopatterned macropores showed significant improvements in immunoassay robustness and sensitivity in untreated complex samples. The utilization of the sensor built-in sieve for measurements in complex matrices offers reduction in pre-analytical sample preparation steps and thus shortens the total analysis time.
    Errors and uncertainties in microwave link rainfall estimation explored using drop size measurements and high-resolution radar data
    Leijnse, H. ; Uijlenhoet, R. ; Berne, A.D. - \ 2010
    Journal of Hydrometeorology 11 (2010). - ISSN 1525-755X - p. 1330 - 1344.
    path-averaged rainfall - x-band radar - dual-frequency - communication-networks - video disdrometer - weather radar - axis ratios - attenuation - matrix - distributions
    Microwave links can be used for the estimation of path-averaged rainfall by using either the path-integrated attenuation or the difference in attenuation of two signals with different frequencies and/or polarizations. Link signals have been simulated using measured time series of raindrop size distributions (DSDs) over a period of nearly 2 yr, in combination with wind velocity data and Taylor’s hypothesis. For this purpose, Taylor’s hypothesis has been tested using more than 1.5 yr of high-resolution radar data. In terms of correlation between spatial and temporal profiles of rainfall intensities, the validity of Taylor’s hypothesis quickly decreases with distance. However, in terms of error statistics, the hypothesis is seen to hold up to distances of at least 10 km. Errors and uncertainties (mean bias error and root-mean-square error, respectively) in microwave link rainfall estimates due to spatial DSD variation are at a minimum at frequencies (and frequency combinations) where the power-law relation for the conversion to rainfall intensity is close to linear. Errors generally increase with link length, whereas uncertainties decrease because of the decrease of scatter about the retrieval relations because of averaging of spatially variable DSDs for longer links. The exponent of power-law rainfall retrieval relations can explain a large part of the variation in both bias and uncertainty, which means that the order of magnitude of these error statistics can be predicted from the value of this exponent, regardless of the link length.
    Grab a Golgi: Laser trapping of golgi bodies reveals in vivo Interactions with the endoplasmic reticulum
    Sparkes, I.A. ; Ketelaar, T. ; Ruijter, N.C.A. de; Hawes, C. - \ 2009
    Traffic 10 (2009)5. - ISSN 1398-9219 - p. 567 - 571.
    export sites - plant-cells - protein - arabidopsis - membrane - transport - apparatus - stacks - matrix - trafficking
    In many vacuolate plant cells individual Golgi bodies appear to be attached to tubules of the pleiomorphic cortical endoplasmic reticulum (ER) network. Such observations culminated in the controversial mobile secretory unit hypothesis to explain transport of cargo from the ER to Golgi via Golgi attached export sites. This proposes that individual Golgi bodies and an attached ER exit machinery move over or with the surface of the ER whilst collecting cargo for secretion. By the application of infrared laser optical traps to individual Golgi bodies within living leaf cells, we show that individual Golgi bodies can be micromanipulated to reveal their association with the ER. Golgi bodies are physically attached to ER tubules and lateral displacement of individual Golgi bodies results in the rapid growth of the attached ER tubule. Remarkably, the ER network can be remodelled in living cells simply by movement of laser trapped Golgi dragging new ER tubules through the cytoplasm and new ER anchor sites can be established. Finally we show that trapped Golgi ripped off the ER are "sticky" and can be docked on to and attached to ER tubules, which will again show rapid growth whilst pulled by moving Golgi
    Non-specific interactions are sufficient to explain the position of heterochromatic chromocenters and nucleoli in interphase nuclei
    Nooijer, S. de; Wellink, J. ; Mulder, B. ; Bisseling, T. - \ 2009
    Nucleic acids research 37 (2009)11. - ISSN 0305-1048 - p. 3558 - 3568.
    chromosome territories - arabidopsis-thaliana - genome organization - confined polymers - chromatin - architecture - cells - matrix - compartmentalization - transcription
    The organization of the eukaryote nucleus into functional compartments arises by self-organization both through specific protein–protein and protein–DNA interactions and non-specific interactions that lead to entropic effects, such as e.g. depletion attraction. While many specific interactions have so far been demonstrated, the contributions of non-specific interactions are still unclear. We used coarse-grained molecular dynamics simulations of previously published models for Arabidopsis thaliana chromatin organization to show that non-specific interactions can explain the in vivo localization of nucleoli and chromocenters. Also, we quantitatively demonstrate that chromatin looping contributes to the formation of chromosome territories. Our results are consistent with the previously published Rosette model for Arabidopsis chromatin organization and suggest that chromocenter-associated loops play a role in suppressing chromocenter clustering.
    The synergistic effect of combining woodlands and green veining for biodiversity
    Grashof-Bokdam, C.J. ; Chardon, J.P. ; Vos, C.C. ; Foppen, R. ; Wallis de Vries, M.F. ; Veen, M. van der; Meeuwsen, H.A.M. - \ 2009
    Landscape Ecology 24 (2009)8. - ISSN 0921-2973 - p. 1105 - 1121.
    agri-environment schemes - agricultural landscapes - fragmented landscapes - habitat fragmentation - interpatch movements - red squirrel - matrix - connectivity - populations - dispersal
    Combining nature reserves with small semi-natural elements (green veining) may improve the persistence of plant and animal species in fragmented landscapes. A better understanding of this synergy is essential to improve species diversity in the European Natura 2000 sites and in green veining elements. To test this hypothesis, we investigated the relationship between the occurrence of 40 forest plant and animal species in 1,000 km grid cells in the Netherlands and the spatial cohesion of the surrounding large woodlands and small woody elements. Two types of synergy were found. First, nine species were more often present if there was more cohesion of large elements; small elements enhanced this effect. Second, 11 other species were more often present when there was more cohesion of small elements; large elements enhanced this effect. Eight species showed both effects, indicating two-way synergy. The remaining 12 species preferred landscapes dominated by either large or small elements, or displayed no positive relationship whatsoever to woody elements. Species showing synergy often had a low dispersal capacity; the type of synergy seemed to be related to their habitat preference. These results imply that species diversity could be improved by integrating different policy instruments used for nature reserves and green veining. Using a zoning principle where green veins surround and connect nature reserves, the different spatial and habitat preferences of species can be secured. In this way a coherent network could become reality
    Geostatistical simulation of two-dimensional fields of raindrop size distributions at the meso-¿ scale
    Schleiss, M.A. ; Berne, A. ; Uijlenhoet, R. - \ 2009
    Water Resources Research 45 (2009). - ISSN 0043-1397 - 10 p.
    prediction model - rainfall fields - time - precipitation - variability - space - resolution - variables - spectra - matrix
    The large variability of the raindrop size distribution (DSD) in space and time must be taken into account to improve remote sensing of precipitation. The ability to simulate a large number of 2-D fields of DSDs sharing the same statistical properties provides a very useful simulation framework that nicely complements experimental approaches based on DSD ground measurements. These simulations can be used to investigate radar beam propagation through rain and to evaluate different radar retrieval techniques. The proposed approach uses geostatistical methods to provide structural analysis and stochastic simulation of DSD fields. First, the DSD is assumed to follow a Gamma distribution with three parameters. As a consequence, 2-D fields of DSDs can be described as a multivariate random function. The parameters are normalized using a Gaussian anamorphosis and simulated by taking advantage of fast Gaussian simulation algorithms. Variograms are used to characterize the spatial structure of the DSD fields. The generated fields have identical spatial structure and are consistent with the observations. Because intermittency cannot be simulated using this technique, the size of the simulation domain is limited to the meso-¿ scale (2-20 km). To assess the proposed approach, the method is applied to data collected during intense Mediterranean rainfall. Taylor's hypothesis is invoked to convert time series into 1-D range profiles. The anisotropy of the fields is derived from radar measurements. Simulated and measured reflectivity fields are in good agreement with respect to the mean, the standard deviation, and the spatial structure, demonstrating the promising potential of the proposed stochastic model of DSD fields
    Jute fiber reinforced polypropylene produced by continuous extrusion compounding. Part 1. Processing and ageing properties
    Oever, M.J.A. van den; Snijder, M.H.B. - \ 2008
    Journal of Applied Polymer Science 110 (2008)2. - ISSN 0021-8995 - p. 1009 - 1018.
    mechanical-properties - coupling agent - pla composites - sisal fiber - flax fibers - glass - wood - compatibilizer - interfaces - matrix
    This article addresses the processing and ageing properties of jute fiber reinforced polypropylene (PP) composites. The composite has been manufactured by a continuous extrusion process and results in free flowing composite granules, comprising up to 50 weight percent (wt %) jute fiber in PP. These granules have similar shape and diameter as commercially available PP granules. Rheological analysis shows that viscosity of the compounds follows the same shear rate dependency as PP and is on the same level as glass-PP compounds. The mechanical properties show very little variation and exhibit strength and stiffness values at the upper range of competing natural fiber reinforced compounds for injection molding. The mechanical performance reduces gradually upon prolonged thermal loading and immersion in water. The low water diffusion coefficient of the 50 wt % jute-PP composites indicates that the fibers are not forming a continuous network throughout the polymer. The jute fibers exhibit a stabilizing effect against ultra violet irradiation (UV) on PP polymer and, as a consequence, the mechanical properties of jute-PP composites hardly decrease during an accelerated UV ageing test. Bacteria, fungi, and garden mold grow easily on the compound material, but only have a limited effect on mechanical properties. The resistance to growth of bacteria on the materials surface can be increased using a biostabilizer.
    Influence of process parameters on formation of fibrous materials from dense calcium caseinate dispersions
    Manski, J.M. ; Zalm, E.E.J. van der; Goot, A.J. van der; Boom, R.M. - \ 2008
    Food Hydrocolloids 22 (2008)4. - ISSN 0268-005X - p. 587 - 600.
    extrusion-cooking - mozzarella cheese - simple shear - moisture - microstructure - deformation - particles - proteins - blends - matrix
    Concentrated calcium caseinate (Ca-caseinate) in the presence of palm fat forms hierarchical fibrous materials after enzymatic crosslinking under well-defined deformation. The presence of fat induces the protein fibers to be arranged in bundles of 200 fibers, separated by layers that are concentrated in fat. We investigated the effect of shear rate; shear time and protein concentration on the formation of fibrous materials in the two-phase protein¿fat system. The ratio between crosslinking rate and shear rate determined whether a fibrous structure was formed or not, indicating a subtle interplay between material properties and process conditions. Prolonged shear time influenced the transition from fibrous materials into damaged structures accompanied by syneresis. The experimental results are concluded in a generalized diagram, which provides an initial explanation of the structural transitions induced by solidification and shear.
    Comprehensive two-dimensional liquid chromatography with ultraviolet, evaporative light scattering and mass spectrometric detection of triacylglycerols in corn oil
    Klift, E.J.C. van der; Vivó-Truyols, G. ; Claassen, F.W. ; Holthoon, F.L. van; Beek, T.A. van - \ 2008
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1178 (2008)1-2. - ISSN 0021-9673 - p. 43 - 55.
    plant oils - argentation chromatography - gas-chromatography - reversed-phase - performance - separation - column - lipids - matrix - fats
    An improved comprehensive two-dimensional (LC × LC) HPLC system for the analysis of triacylglycerols was developed. In the first-dimension, a Ag(I)-coated cation exchanger (250 mm × 2.1 mm, 5 ¿m) was employed with a gradient from 100% MeOH to 6% MeCN in MeOH at 20 ¿L/min. Using a 10-way valve with two switching loops, 1 min sections of the first-dimension were introduced in the second-dimension consisting of a 30 mm × 4.6 mm C18 (1.8 ¿m) column with an isocratic mobile phase of methanol¿methyl tert-butyl ether (70:30) at 3.0 mL/min. As the second-dimension solvent was stronger than the first-dimension solvent, focusing in the second-dimension took place, leading to better separations than in previously reported analyses in which hexane was the main constituent of the first-dimension eluent. Compounds differing by 2 in their partition number were baseline separated in the second-dimension. Detection took place by UV at 210 nm, evaporative light scattering and (+)-atmospheric pressure chemical ionisation-MS with the latter giving the best results. Corn oil was investigated and 44 compounds could be detected: 34 triacylglycerols (TAGs), 8 oxygenated TAGs, and 2 TAGs containing a trans double bond. Data manipulation allowed the construction of contour plots and the automated calculation of the first- and second-dimension retention times and peak areas. Quantitative results are compared with a fatty acid methyl ester analysis, and with literature data.
    Effects of landscape structure on movement patterns of the flightless bush cricket Pholidoptera griseoaptera
    Diekötter, T. ; Speelmans, M. ; Dusoulier, F. ; Wingerden, W.K.R.E. van; Malfait, J.P. ; Crist, T.O. ; Edwards, P.J. ; Dietz, H. - \ 2007
    Environmental Entomology 36 (2007)1. - ISSN 0046-225X - p. 90 - 98.
    metrioptera-roeseli - orthoptera-tettigoniidae - metapopulation dynamics - decticus-verrucivorus - range expansion - dispersal - habitat - ecology - corridors - matrix
    Because the viability of a population may depend on whether individuals can disperse, it is important for conservation planning to understand how landscape structure affects movement behavior. Some species occur in a wide range of landscapes differing greatly in structure, and the question arises of whether these species are particularly versatile in their dispersal or whether they are composed of genetically distinct populations adapted to contrasting landscapes. We performed a capture-mark-resight experiment to study movement patterns of the flightless bush cricket Pholidoptera griseoaptera (De Geer 1773) in two contrasting agricultural landscapes in France and Switzerland. The mean daily movement of P. griseoaptera was significantly higher in the landscape with patchily distributed habitat (Switzerland) than in the landscape with greater habitat connectivity (France). Net displacement rate did not differ between the two landscapes, which we attributed to the presence of more linear elements in the connected landscape, resulting in a more directed pattern of movement by P. griseoaptera. Significant differences in the movement patterns between landscapes with contrasting structure suggest important effects of landscape structure on movement and dispersal success. The possibility of varying dispersal ability within the same species needs to be studied in more detail because this may provide important information for sustainable landscape planning aimed at maintaining viable metapopulations, especially in formerly well-connected landscapes.
    Review of relationships between grey-tone co-occurrence, semivariance, and autocorrelation based image texture analysis approaches
    Sanden, J.J. van der; Hoekman, D.H. - \ 2005
    Canadian Journal of Remote Sensing 31 (2005)3. - ISSN 1712-7971 - p. 207 - 213.
    land-cover - classification - matrix
    In the present paper we review relationships between commonly used statistical approaches to analysis of image texture. The approaches considered characterize image texture by means of the statistics of grey- tone co- occurrence contrast, grey- tone co- occurrence correlation, semivariance, and autocorrelation. In the literature, the relationships between these textural measures are rarely discussed and sometimes overlooked. Grey-tone co- occurrence contrast and semivariance are shown to represent identical statistics. The expectations for the statistic of grey-tone co- occurrence correlation and the coefficient of autocorrelation are demonstrated to agree. Grey-tone variance is shown to link the statistics of grey-tone co-occurrence contrast and grey-tone co-occurrence correlation.
    Fluorescence analysis of the Hansenula polymorpha peroxisomal targeting signal-1 receptor, Pex5p
    Boteva, R. ; Koek, A. ; Visser, N.V. ; Visser, A.J.W.G. ; Krieger, E. ; Zlateva, T. ; Veenhuis, M. ; Klei, I. van der - \ 2003
    European Journal of Biochemistry 270 (2003). - ISSN 0014-2956 - p. 4332 - 4338.
    protein-protein interactions - import - matrix - repeats - pex14
    Correct sorting of newly synthesized peroxisomal matrix proteins is dependent on a peroxisomal targeting signal (PTS). So far two PTSs are known. PTS1 consists of a tripeptide that is located at the extreme C terminus of matrix proteins and is specifically recognized by the PTS1-receptor Pex5p. We studied Hansenula polymorpha Pex5p (HpPex5p) using fluorescence spectroscopy. The intensity of Trp fluorescence of purified HpPex5p increased by 25% upon shifting the pH from pH 6.0 to pH 7.2. Together with the results of fluorescence quenching by acrylamide, these data suggest that the conformation of HpPex5p differs at these two pH values. Fluorescence anisotropy decay measurements revealed that the pH affected the oligomeric state of HpPex5p, possibly from monomers/dimers at pH 6.0 to larger oligomeric forms at pH 7.2. Addition of dansylated peptides containing a PTS1, caused some shortening of the average fluorescence lifetime of the Trp residues, which was most pronounced at pH 7.2. Our data are discussed in relation to a molecular model of HpPex5p based on the three-dimensional structure of human Pex5p.
    Modelling the effect of oil/fat content in food systems on flavour absorption by LLDPE.
    Dekker, M. ; Willige, R.W.G. van; Linssen, J.P.H. ; Voragen, A.G.J. - \ 2003
    Food Additives and Contaminants 20 (2003)2. - ISSN 0265-203X - p. 180 - 185.
    low-density polyethylene - packaging interactions - aroma compounds - aluminum foil - sorption - adhesion - matrix - films - acids - oil
    One of the phenomena in food packaging interactions is flavour absorption. Absorption of flavour compounds from food products into food-packaging materials can result in loss of flavour compounds or an unbalance in the flavour profile changing a product's quality. The food matrix influences the amounts of absorbed flavour compounds; the presence of oil or fat especially determines the ability to absorb flavour compounds from the food to the package. On the other hand, the polarity of the flavour compound itself is a characteristic that also influences the level of absorption into synthetic polymers. A model based on the effect of the polarity (log P) of flavour compounds and on their partitioning coefficients between the food (matrix) and the packaging material is described. The model can be used for predicting absorption of flavour compounds from foods into LLDPE. However, an attempt to apply the proposed model on real foods shows serious limitations of the model for (very) low fat products. Predictive values deviate from the measured values, probably due to other interaction phenomena, e.g. with proteins. Predictive and measured values from a product with a substantial amount of fat match much better, suggesting that the model is valid for products having a substantial amount of (free) fat.
    Influence of flavour absorption on oxygen permentation through LDPE, PP, PC and PET plastics food packaging
    Willige, R.W.G. van; Linssen, J.P.H. ; Meinders, M.B.J. ; Stege, H.J. van der; Voragen, A.G.J. - \ 2002
    Food Additives and Contaminants 19 (2002)3. - ISSN 0265-203X - p. 303 - 313.
    low-density polyethylene - limonene absorption - aroma compounds - aluminum foil - sorption - adhesion - matrix - films - acids - oil
    The effect of flavour absorption on the oxygen permeability of low-density polyethylene (LDPE), polypropylene (PP), polycarbonate (PC) and polyethylene terephthalate (PET) was studied using an isostatic continuous flow system. Polymer samples were exposed to a model solution containing limonene, hexyl acetate, nonanone and decanal at 40°C. After exposure, one part of each sample was analysed for absorbed flavour compounds using a Large Volume Injection GC Ultrasonic 'in vial' extraction method, and from the other part, oxygen permeability was measured in a permeation cell at 25°C. After 8h of exposure, LDPE and PP samples showed a significant linear (R2 = 0.82 and 0.99) increase in oxygen permeability of 21 and 130%, respectively. Owing to swelling of the polymer samples resulting from flavour absorption, the structure of the polymeric network changed (i.e. opened) and consequently increased oxygen permeability. The oxygen permeability of exposed PC showed a significant linear (R2 = 0.78) decrease of 11% after 21 days. PC obviously did not swell like LDPE or PP. Therefore, it was suggested that absorbed flavour compounds occupied or blocked 'microcavities' through which normally oxygen is transported. Absorption of flavour compounds by PET did not affect the oxygen permeability of PET significantly
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