Staff Publications

Staff Publications

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    '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.

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Effect of Glycation on the Flocculation Behavior of Protein-Stabilized Oil-in-Water Emulsions
Delahaije, R.J.B.M. ; Gruppen, H. ; Nieuwenhuijzen, N.H. van; Giuseppin, M.L.F. ; Wierenga, P.A. - \ 2013
Langmuir 29 (2013)49. - ISSN 0743-7463 - p. 15201 - 15208.
bovine serum-albumin - beta-lactoglobulin - physicochemical properties - adsorption dynamics - disjoining pressure - alpha-lactalbumin - interfaces - particles - thickness - size
Glycation of proteins by the Maillard reaction is often considered as a method to prevent flocculation of protein-stabilized oil-in-water emulsions. The effect has been suggested, but not proven, to be the result of steric stabilization, and to depend on the molecular mass of the carbohydrate moiety. To test this, the stabilities of emulsions of patatin glycated to the same extent with different mono- and oligosaccharides (xylose, glucose, maltotriose, and maltopentaose) were compared under different conditions (pH and electrolyte concentration). The emulsions with non-modified patatin flocculate under conditions in which the zeta potential is decreased (around the iso-electric point and at high ionic strength). The attachment of monosaccharides (i.e., glucose) did not affect the flocculation behavior. Attachment of maltotriose and maltopentaose (Mw > 500 Da), on the other hand, provided stability against flocculation at the iso-electric point. Since the zeta potential and the interfacial properties of the emulsion droplets are not affected by the attachment of the carbohydrate moieties, this is attributed to steric stabilization. Experimentally, a critical thickness of the adsorbed layer required for steric stabilization against flocculation was found to be 2.29–3.90 nm. The theoretical determination based on the DLVO interactions with an additional steric interaction coincides with the experimental data. Hence, it can be concluded that the differences in stability against pH-induced flocculation are caused by steric interactions.
Impact-based integrated real-time control for improvement of the Dommel River water quality
Langeveld, J. ; Benedetti, L. ; Klein, J.J.M. de; Nopens, I. ; Amerlinck, Y. ; Nieuwenhuijzen, A.F. van; Flameling, T. ; Zanten, O. van; Weijers, S. - \ 2013
Urban Water Journal 10 (2013)5. - ISSN 1573-062X - p. 312 - 329.
drainage systems - treatment-plant - models - calibration - pollution - design
The KALLISTO project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the river Dommel. Within the project, both acute and long term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with an integral monitoring campaign in the urban wastewater system (WWTP and sewers) and in the river. Based on this monitoring campaign, detailed models were calibrated. These models are partly simplified and integrated in a single model, which is validated using the detailed submodels. The integrated model was used to study the potential for impact-based real-time control (RTC). Impact based RTC proved to be able to improve the quality of the receiving waters significantly, although additional measures remain necessary to be able to meet the WFD requirements
Cost-effective solutions for water quality improvement in the Dommel river supported by sewer-WWTP-river integrated modelling
Benedetti, L. ; Langeveld, J. ; Nieuwenhuijzen, A.F. van; Jonge, J. de; Weijers, S. ; Klein, J.J.M. de; Nopens, I. ; Flameling, T. ; Zanten, O. van - \ 2013
Water Science and Technology 68 (2013)5. - ISSN 0273-1223 - p. 965 - 973.
stedelijk afvalwater - afvalwaterbehandeling - oppervlaktewaterkwaliteit - rivieren - aquatische ecologie - controle - infrastructuur - onzekerheidsanalyse - kaderrichtlijn water - noord-brabant - municipal wastewater - waste water treatment - surface water quality - rivers - aquatic ecology - control - infrastructure - uncertainty analysis - water framework directive - noord-brabant - urban drainage systems - real-time control - treatment-plant - simulation - management - pollution
This project aims at finding cost-efficient sets of measures to meet the Water Framework Directive (WFD) derived goals for the Dommel River (The Netherlands). Within the project, both acute and long-term impacts of the urban wastewater system on the chemical and ecological quality of the river are studied with a monitoring campaign in the urban wastewater system (wastewater treatment plant and sewers) and in the receiving surface water system. An integrated model, which proved to be a powerful tool to analyse the interactions within the integrated urban wastewater system, was first used to evaluate measures in the urban wastewater system using the existing infrastructure and new real-time control strategies. As the latter resulted to be beneficial but not sufficient, this paper investigated the use of additional infrastructural measures to improve the system cost-effectively and have it meet the Directive's goals. Finally, an uncertainty analysis was conducted to investigate the impact of uncertainty in the main model assumptions and model parameters on the performance robustness of the selected set of measures. Apart from some extreme worst-case scenarios, the proposed set of measures turned out to be sufficiently robust. Due to the substantial savings obtained with the results of this project, the pay-back time of the whole monitoring and modelling work proved to be less than 5 months. This illustrates the power of mathematical modelling for decision support in the context of complex urban water systems
Protein Concentration and Protein-Exposed Hydrophobicity as Dominant Parameters Determining the Flocculation of Protein-Stabilized Oil-in-Water Emulsions
Delahaije, R.J.B.M. ; Wierenga, P.A. ; Nieuwenhuijzen, N.H. van; Giuseppin, M.L.F. ; Gruppen, H. - \ 2013
Langmuir 29 (2013)37. - ISSN 0743-7463 - p. 11567 - 11574.
diffusing wave spectroscopy - beta-lactoglobulin - coalescence stability - disjoining pressure - drop size - adsorption - films - ph - interfaces - ovalbumin
DLVO theory is often considered to be applicable to the description of flocculation of protein-stabilized oil-in-water emulsions. To test this, emulsions made with different globular proteins (ß-lactoglobulin, ovalbumin, patatin, and two variants of ovalbumin) were compared under different conditions (pH and electrolyte concentration). As expected, flocculation was observed under conditions in which the zeta potential is decreased (around the isoelectric point and at high ionic strength). However, the extent of flocculation at higher ionic strength (>50 mM NaCl) decreased with increasing protein-exposed hydrophobicity. A higher exposed hydrophobicity resulted in a higher zeta potential of the emulsion droplets and consequently increased stability against flocculation. Furthermore, the addition of excess protein strongly increased the stability against salt-induced flocculation, which is not described by DLVO theory. In the protein-poor regime, emulsions showed flocculation at high ionic strength (>100 mM NaCl), whereas emulsions were stable against flocculation if excess protein was present. This research shows that the exposed hydrophobicity of the proteins and the presence of excess protein affect the flocculation behavior.
Mastspuit met sensoren geeft minder drift en spaart middel
Stallinga, H. ; Nieuwenhuijzen, A.F. van; Zande, J.C. van de; Lans, A.M. van der - \ 2013
De Boomkwekerij 2013 (2013)16. - ISSN 0923-2443 - p. 14 - 15.
straatbomen - boomteelt - spuiten - sensors - spuitapparatuur - proeven - drift - reductie - gebruiksefficiëntie - street trees - arboriculture - spraying - spraying equipment - trials - reduction - use efficiency
Praktijkproeven geven aan dat de mastspuit voorzien van sensoren minder drift geeft. Daarnaast geeft de mastspuit gemiddeld meer spuitvloeistof depositie in de bomen, een betere verdeling in de bomen en wordt tot eenderde aan middel bespaard.
Kallisto: successfully using an intagrated modelling approach for cost-effective Water Framework Directive compliance
Weijers, S. ; Jonge, J. de; Zanten, O. van; Flameling, T. ; Benedetti, L. ; Klein, J.J.M. de; Langeveld, J. ; Nieuwenhuijzen, A.F. van; Nopens, I. - \ 2012
Water 21 : magazine of the International Water Association 2012 (2012)Oktober. - ISSN 1561-9508 - p. 40 - 42.
Computer modelling provides a means of dealing with the complexity of devising and applying the integrated water resources management approaches required by the EU Water FrameWork Directive.
Relations between sensorial crispness and molecular mobility of model bread crust and its main components as measured by PTA, DSC and NMR
Nieuwenhuijzen, N.H. van; Tromp, R.H. ; Mitchell, J.R. ; Primo-Martin, C. ; Hamer, R.J. ; Vliet, T. van - \ 2010
Food Research International 43 (2010)1. - ISSN 0963-9969 - p. 342 - 349.
glass-transition temperature - wheat-starch - fracture-behavior - pulsed h-1-nmr - water-content - gluten - foods - state
Consumer appreciation of brittle cellular foods, like bread crusts, depends on textural properties such as crispness. This crispy character is lost above a certain water activity. It is not known what exactly is happening in these crusts when water enters. So is it unclear whether it is the change in the starch or the gluten that initiates the loss of crispness with ageing time. In this paper the effect of water on the glass transition of model bread crusts was studied using two complementary techniques: phase transition analysis (PTA) and temperature modulated differential scanning calorimetry (TMDSC). The mobility of water was studied with nuclear magnetic resonance (NMR). The results were compared with sensory data. Bread crusts prepared with different types of flour were tested to evaluate the effect of flour composition on the crispness of model crusts equilibrated at different relative humidities. In addition the single flour components starch and gluten were studied. Sensory crispness scores decreased with increasing aw from 0.55 upwards. At aw 0.70 sensory crispness was completely lost. Both DSC and PTA showed a transition point at an aw of 0.70-0.75. NMR gave a transition point in the mobility of the protons of water at aw 0.58. This supports the hypothesis that loss of crispness starts as a result of processes at a molecular level, before the macroscopic glass transition. This also suggests that the presence of water that is not directly attached to the solid matrix causes the loss of crispness at low aw. At higher aw increased mobility of the macromolecules will start to play a role. NMR experiments with the separate flour components indicate that the T2 transition point in starch samples occurs at a lower RH than for gluten. This could imply that starch loses crispness at lower aw than gluten. Increased mobility of small components and side chains might induce increased energy dissipation upon deformation of the material resulting in less available energy for fracture propagation and with that in a less crispy product.
Water sorption and transport in dry crispy bread crust
Meinders, M.B.J. ; Nieuwenhuijzen, N.H. van; Tromp, R.H. ; Hamer, R.J. ; Vliet, T. van - \ 2010
Water sorption and dynamical properties of bread crust have been studied using gravimetric sorption experiments. Water uptake and loss were followed while relative humidity (RH) was stepwise in- or decreased (isotherm experiment) or varied between two adjusted values (oscillatory experiment). Experimental results were compared with the Fickian diffusion model and empirical models like the exponential and power-law model. Sorption curves of isotherm experiments could be best described by the Fickian diffusion model for low RH and by the exponential model for large RH. Isotherm equilibrium values could be best described by the GAB equation. Transport rates depend on moisture content and show a maximum around RH=70%. Adsorption and desorption curves from oscillatory sorption experiments could be described best by the exponential model. From comparison of experimental sorption curves and the power-law model for short times it followed for all bread crust that the diffusional coefficient n is close to one. Normally this is associated to so-called case II diffusion and water transport that is limited by relaxation of the solid material. However, additional observations suggest that this may not be a valid explanation and that a kinetic barrier for water transfer to the solid matrix may explain the observed exponential behavior
Water Content or Water Activity: What Rules Crispy Behavior in Bread Crust?
Nieuwenhuijzen, N.H. van; Primo-Martin, C. ; Meinders, M.B.J. ; Tromp, R.H. ; Hamer, R.J. ; Vliet, T. van - \ 2008
Journal of Agricultural and Food Chemistry 56 (2008)15. - ISSN 0021-8561 - p. 6432 - 6438.
food-products - wheat-starch - gluten - temperature - mobility - h-1-nmr
A dry crust loses its crispness when water migrates into the crust. It is not clear if it is the amount of water absorbed or the water activity (aw) that leads to a loss of crispness. The hysteresis effect observed when recording a water sorption isotherm allowed us to study the effects of aw and moisture content separately. All experiments were carried out on model bread crusts made from Soissons bread flour. The effect of water content and water activity on the glass transition of model bread crusts was studied in detail using two complimentary techniques: phase transition analysis (PTA) and nuclear magnetic resonance (NMR). The results were compared with sensory data and results from a puncture test, which provided data on acoustic emission and fracture mechanics during breaking of the crusts. The water content of the crust was found to be decisive for the transition point as measured by PTA and NMR. However, both water content and water activity had an effect on perceived crispness and number of force and sound peaks. From this may be concluded that the distribution of the water in the samples with a history of high water content is more inhomogeneous, which results in crispy and less crispy regions, thus making them overall more crispy than samples with the same water content but higher aw.
Water Uptake Mechanism in Crispy Bread Crust
Nieuwenhuijzen, N.H. van; Meinders, M.B.J. ; Tromp, R.H. ; Hamer, R.J. ; Vliet, T. van - \ 2008
Journal of Agricultural and Food Chemistry 56 (2008)15. - ISSN 0021-8561 - p. 6439 - 6446.
sorption - moisture - diffusion - foods
Crispness is an important quality characteristic of dry solid food products such as crispy rolls. Its retention is directly related to the kinetics of water uptake by the crust. In this study, a method for the evaluation of the water sorption kinetics in bread crust is proposed. Two different sorption experiments were used: an oscillatory sorption test and a sorption test in which the air relative humidity (RH) was increased stepwise. These two experiments had different time scales, which made it possible to get a better understanding of the mechanisms involved. Results show that the adsorption and desorption dynamics of the oscillatory sorption test could be described by a single exponential in time. The water uptake rate (k) was one of the fitting parameters. A maximum in the water uptake rate was found for a RH value between 50 and 70%. The rate parameters of the experiment where RH was increased stepwise were around a factor 10 lower than those derived from oscillatory sorption experiments. This is an important factor when designing experiments for the determination of water uptake rates. In addition, also a parameter describing the time dependence of the rate parameters of the oscillatory sorption experiment was calculated (C), again by fitting a single exponential to the rate parameters. C was in the same range as the rate parameter of the isotherm experiment. This indicates that different (relaxation) processes are acting at the same time in the bread crust during water uptake.
Molecular mobility in crispy bread crust
Nieuwenhuijzen, N.H. van - \ 2008
Wageningen University. Promotor(en): Rob Hamer, co-promotor(en): Ton van Vliet; R.H. Tromp. - [S.l.] : S.n. - ISBN 9789085048565 - 133
brood - broosheid - aw-waarde - wateropname (planten) - sensorische evaluatie - moleculaire fysica - levensmiddelenfysica - bread - brittleness - water activity - water uptake - sensory evaluation - molecular physics - food physics
The aim of the PhD study on molecular mobility was to analyse the molecular grounds for the deterioration of crispy/crunchy characteristics of cellular solid foods. A fresh baguette for example has a crispy crust and a moist and soft interior. Moisture migrates from crumb to crust. Already at a water content of 9% (crumb contains around 45% water) the crispness of the crust decreases. During the study methods were developed to measure the speed of water uptake to test different ingredients on their potential to prolong crispness. Also the glass transition (which means an increase in mobility of the protein and starch molecules in the crust) and its relation with sensorial loss of crispness was investigated. The history of the crust in terms of water content and water activity as well as the morphology of the crust was found to be important for crispness and crispness retention.
Oscillatory water sorption test for determining water uptake
Nieuwenhuijzen, N.H. van; Tromp, R.H. ; Hamer, R.J. ; Vliet, T. van - \ 2007
Crust crispiness is an important driver of consumer appreciation for baked goods. Loss of crispiness is a relevant problem, poorly understood on a molecular level. This requires detailed knowledge of the behaviour of water. Unfortunately, interpretation in kinetic terms of results obtained by current sorption tests requires knowledge of the shape and surface area of the sample. We present a new sorption method where water uptake and the amount of exchanging water are followed while the relative air humidity (RH) oscillates between two set values. The obtained curves are analysed using a Langmuir-type adsorption model. Factors studied were the rate limiting step for water uptake, the effect of crust particle size on the Langmuir sorption parameters and the use of the Langmuir equation for the calculation of the number of sorption sites (deltam(max)). Different crust components were considered. Both the Langmuir sorption parameters and deltam(max) were found to depend on the crust particle size. Results showed no significant difference between oscillation times of 28 and 48 minutes. Based on these results we conclude that the water uptake kinetics over these times is dominated by one process. Likely this is water diffusion into the particles. Surface adsorption (wetting) will proceed faster while effects due to structural reorganisation of the solid crust matrix will take hours to days. The maximum RH level at which the test can be used is around 60%. At higher RH, large structural changes of the material occur. With this constraint, our test allows a quantitative and physically sound analysis of water uptake behaviour, without prior knowledge of shape and surface area of the sample.
Oscillatory Water Sorption Test for Determining Water Uptake Behavior in Bread Crust
Nieuwenhuijzen, N.H. van; Tromp, R.H. ; Hamer, R.J. ; Vliet, T. van - \ 2007
Journal of Agricultural and Food Chemistry 55 (2007)7. - ISSN 0021-8561 - p. 2611 - 2618.
fracture-behavior - vapor adsorption - flour components - glassy state - diffusion - gluten - foods
In this work, water sorption kinetics of bread crust are described using an oscillatory sorption test in combination with a Langmuir type equation. Both kinetic and thermodynamic information could be obtained at the same time. An advantage of applying a Langmuir type equation for a quantitative description of the water uptake kinetics is that no prior knowledge is necessary with respect to shape and surface area of the sample. It was shown that adsorption and desorption of water to the bread crust particle surface is much faster than the experimental time used (15 min at minimum). From this, we may conclude that diffusion of water into the solid matrix is the rate-limiting step in the water sorption process. The method also allows one to calculate a Gibbs free energy. The method is suitable for use up to relative humidities of 60%.
Crystallinity changes in wheat starch during the bread-making process: starch crystallinity in the bread crust
Primo-Martin, C. ; Nieuwenhuijzen, N.H. van; Hamer, R.J. ; Vliet, T. van - \ 2007
Journal of Cereal Science 45 (2007)2. - ISSN 0733-5210 - p. 219 - 226.
heat-moisture treatment - mas nmr-spectroscopy - c-13 cp/mas nmr - phase-transitions - water-system - amylose - gelatinization - amylopectin - polymorphs - potato
The crystallinity of starch in crispy bread crust was quantified using several different techniques. Confocal scanning laser microscopy (CSLM) demonstrated the presence of granular starch in the crust and remnants of granules when moving towards the crumb. Differential scanning calorimetry (DSC) showed an endothermic transition at 70 degrees C associated with the melting of crystalline amylopectin. The relative starch crystallinity, as determined by X-ray and DSC, from different types of breads was found to lie between 36% and 41 % (X-ray) and between 32% and 43 % (DSC) for fresh bread crust. Storage of breads in a closed box (22 degrees C) for up to 20 days showed an increase in crust crystallinity due to amylopectin retrogradation both by X-ray and DSC. However, DSC thermograms of 1-day old bread crust showed no amylopectin retrogradation and after 2 days storage, antylopectin retrogradation in the crust was hardly detectable. C-13 CP MAS NMR was used to characterize the physical state of starch in flour and bread crumb and crust. The intensity of the peaks showed a dependence on the degree of starch gelatinization. Comparison of the results for two different types of bread showed that the baking process influenced the extent of starch crystallinity in the bread crust. Antylopectin retrogradation, which is the main process responsible for the staling of bread crumb, cannot be responsible for crispness deterioration of the crust as amylopectin retrogradation upon storage of breads could only be measured in the crust after 2 days storage. Under the same conditions loss of bread crust crispness proceeds over shorter times.
Visie Vis(serij)sector Scheveningen Haven
Nieuwenhuijzen, J. ; Taal, C. - \ 2005
Den Haag : United Fish Auctions - 49 p.
Particle related fractionation and characterisation of municipal wastewater
Nieuwenhuijzen, A.F. van; Graaf, J.H.J.M. van der; Kampschreur, M.J. ; Mels, A.R. - \ 2004
Water Science and Technology 50 (2004)12. - ISSN 0273-1223 - p. 125 - 132.
afvalwaterbehandeling - deeltjesgrootte - besmetters - deeltjesgrootteverdeling - filtratie - membranen - fractionering - waste water treatment - particle size - contaminants - particle size distribution - filtration - membranes - fractionation
Several studies show that a more detailed characterisation of the particulate matter in municipal wastewater gives a better understanding and prediction of removal efficiencies of physical-chemical treatment techniques and the application of optimal chemical dosages. Such a characterisation should include the distribution of contaminants over various particle sizes. This article describes a method and results of experimental and full-scale investigations, conducted to determine how contaminants in wastewater are distributed over different particle sizes. For this purpose, particle size fractionations of wastewater influents originating from more than thirteen WWTP were carried out. One of these fractionations (WWTP Venray) is shown and interpreted in this article. First, the wastewaters were fractionated into 5 to 6 particle fractions (45, 5.0, 1.0/1.2, 0.45 and 0.1 m) after which the fractions were analyzed for various water quality parameters like organic components, nutrients, salts, solids and turbidity. Based on the results the effects of removal of the different size fractions on design of the biological treatment and energy balance of a wastewater treatment plant can be assessed. The method also indicates whether a certain wastewater is efficiently treatable with physical-chemical pre-treatment methods. It is concluded wastewater fractionation on particle size is very useful, but that wastewater characteristics and particle size distributions should not be generalised, but have to be interpreted as indications for a certain average wastewater composition. To give more insight into the distribution of contaminants over particle size and the particle removal potential, a specific wastewater fractionation has to be carried out per WWTP
Characterisation of particulate matter in municipal wastewater treatment plants
Nieuwenhuijzen, A.F. van; Mels, A.R. - \ 2002
In: Chemical Water and Wasteater Treatment VII / Hahn, H.H., Hoffmann, E., Odegaard, H., London, UK : IWA Publishing - ISBN 9781843390091 - p. 203 - 211.
Turbidity-related dosing of organic polymers to control the denitrification of flocculated municipal wastewater
Mels, A.R. ; Nieuwenhuijzen, A.F. van; Klapwijk, A. - \ 2002
In: Chemical Water and Wastewater Treatment VII / Hahn, H.H., Hoffmann, E., Odegaard, H., London, UK : IWA Publishing - ISBN 9781843390091 - p. 71 - 79.
Sturing van de deeltjesverwijdering bij de fysisch-chemische voorzuivering van afvalwater
Mels, A.R. ; Nieuwenhuijzen, A.F. van - \ 2002
Afvalwaterwetenschap 1 (2002)2. - ISSN 1568-3788 - p. 33 - 42.
afvalwaterbehandeling - waterzuivering - filtratie - polymeren - voorbehandeling - geactiveerd slib - afvalwater - stedelijke gebieden - verwijdering - troebelheid - stikstof - chemisch zuurstofverbruik - waste water treatment - water treatment - filtration - polymers - pretreatment - activated sludge - waste water - urban areas - removal - turbidity - nitrogen - chemical oxygen demand
Dit artikel beschrijft experimenten met een voorzuiveringssysteem op laboratoriumschaal bestaande uit een polymeerdoseer- en mengsysteem en een bezinker. In het systeem werd afvalwater uit het dorp Bennekom (voor)behandeld
Scenario Studies into Advanced Particle Removal in the Physical-Chemical Pre-treatment of Wastewater
Nieuwenhuijzen, A.F. van - \ 2002
Delft : DUP Science - ISBN 9789040722493 - 256
afvalwaterbehandeling - voorbehandeling - fysische chemie - duurzaamheid (sustainability) - deeltjes - waste water treatment - pretreatment - physical chemistry - sustainability - particles
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