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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    Data presented in the paper "Are all patterns created equal? Cooperation is more likely in spatially simple habitats"
    Bertolini, Camilla ; Hlebowicz, Kasper ; Schlichta, Flavia ; Capelle, Jacob J. ; Koppel, Johan van de; Bouma, Tjeerd J. - \ 2020
    NIOZ Royal Institute for Sea Research
    NCE - aggregation - behaviour - mussel beds - predation risk - self-organisation
    experiments to understand effects of predator cue on aggregation behaviour and reciprocal attachment of mussels
    How processing may affect milk protein digestion and overall physiological outcomes: A systematic review
    Lieshout, Glenn A.A. van; Lambers, Tim T. ; Bragt, Marjolijn C.E. ; Hettinga, Kasper A. - \ 2020
    Critical Reviews in Food Science and Nutrition 60 (2020)14. - ISSN 1040-8398 - p. 2422 - 2445.
    aggregation - bioavailability - Dairy - denaturation - glycation - protein quality

    Dairy is one of the main sources for high quality protein in the human diet. Processing may, however, cause denaturation, aggregation, and chemical modifications of its amino acids, which may impact protein quality. This systematic review covers the effect of milk protein modifications as a result of heating, on protein digestion and its physiological impact. A total of 5363 records were retrieved through the Scopus database of which a total of 102 were included. Although the degree of modification highly depends on the exact processing conditions, heating of milk proteins can modify several amino acids. In vitro and animal studies demonstrate that glycation decreases protein digestibility, and hinders amino acid availability, especially for lysine. Other chemical modifications, including oxidation, racemization, dephosphorylation and cross-linking, are less well studied, but may also impact protein digestion, which may result in decreased amino acid bioavailability and functionality. On the other hand, protein denaturation does not affect overall digestibility, but can facilitate gastric hydrolysis, especially of β-lactoglobulin. Protein denaturation can also alter gastric emptying of the protein, consequently affecting digestive kinetics that can eventually result in different post-prandial plasma amino acid appearance. Apart from processing, the kinetics of protein digestion depend on the matrix in which the protein is heated. Altogether, protein modifications may be considered indicative for processing severity. Controlling dairy processing conditions can thus be a powerful way to preserve protein quality or to steer gastrointestinal digestion kinetics and subsequent release of amino acids. Related physiological consequences mainly point towards amino acid bioavailability and immunological consequences.

    Are all patterns created equal? Cooperation is more likely in spatially simple habitats
    Bertolini, Camilla ; Hlebowicz, Kasper ; Schlichta, Flavia ; Capelle, Jacob J. ; Koppel, Johan van de; Bouma, Tjeerd J. - \ 2019
    Marine Ecology 40 (2019)6. - ISSN 0173-9565 - 10 p.
    aggregation - behaviour - musselbeds - NCE - predation risk - self-organisation
    Cooperative behaviours, such as aggregation with neighbouring conspecifics, canenhance resilience in habitats where risks (i.e. predation, physical disturbances) are high, exerting positive feedback loops to maintain a healthy population. At the same time, cooperation behaviours can involve some extra energy expenditures and in‐ creasing resource competition. For sessile reefs, like mussels, simulation models predict increased cooperation under increasing levels of environmental stress. Predation risk is viewed as a behaviour‐modifying stressor, but its role on cooperation mechanisms, such as likelihood of reciprocity, has not yet been empirically tested. This study harnesses this framework to understand how cooperation changes under different perceived levels of predation risk, using mussel beds as model of a complex“self‐organised” system. Hence, we assessed the context dependency of cooperation response in different “landscapes of fear,” created by changes in predator cues, sub‐ stratum availability and body size. Our experiments demonstrated that i) cooperation in a mussel bed system increases when predator cues are present, but that this relationship was found to be both, ii) strongly context‐dependent, particularly upon substratum availability and iii) size‐dependent. That is, while cooperation is in general greater for larger individuals, the response to risk results in greater cooperation when alternative attachment substratum is absent, meaning that simpler landscapes may be perceived as riskier. The context dependency of structural complexity is also an essential finding to consider in a changing world where habitats are losing complexity and cooperative strategies should be maximised.
    Differential Effects of Dry vs. Wet Heating of β-Lactoglobulin on Formation of sRAGE Binding Ligands and sIgE Epitope Recognition
    Zenker, Hannah E. ; Ewaz, Arifa ; Deng, Ying ; Savelkoul, Huub F.J. ; Neerven, R.J. van; Jong, Nicolette W. De; Wichers, Harry J. ; Hettinga, Kasper A. ; Teodorowicz, Malgorzata - \ 2019
    Nutrients 11 (2019)6. - ISSN 2072-6643
    aggregation - allergenicity - CML - glycation - IgE binding - sRAGE - β-lactoglobulin

    The effect of glycation and aggregation of thermally processed β-lactoglobulin (BLG) on binding to sRAGE and specific immunoglobulin E (sIgE) from cow milk allergic (CMA) patients were investigated. BLG was heated under dry conditions (water activity < 0.7) and wet conditions (in phosphate buffer at pH 7.4) at low temperature (<73 °C) and high temperatures (>90 °C) in the presence or absence of the milk sugar lactose. Nε-(carboxymethyl)-l-lysine (CML) western blot and glycation staining were used to directly identify glycation structures on the protein fractions on SDS-PAGE. Western blot was used to specify sRAGE and sIgE binding fractions. sRAGE binding was highest under wet-heated BLG independent of the presence of the milk sugar lactose. Under wet heating, high-molecular-weight aggregates were most potent and did not require the presence of CML to generate sRAGE binding ligands. In the dry system, sRAGE binding was observed only in the presence of lactose. sIgE binding affinity showed large individual differences and revealed four binding profiles. Dependent on the individual, sIgE binding decreased or increased by wet heating independent of the presence of lactose. Dry heating required the presence of lactose to show increased binding to aggregates in most individuals. This study highlights an important role of heating condition-dependent protein aggregation and glycation in changing the immunogenicity and antigenicity of cow's milk BLG.

    Creating a window of opportunity for establishing ecosystem engineers by adding substratum: a case study on mussels
    Capelle, Jacob J. ; Leuchter, Lennet ; Wit, Maurice ; Hartog, Eva ; Bouma, Tjeerd J. - \ 2019
    Ecosphere 10 (2019)4. - ISSN 2150-8925 - p. e02688 - e02688.
    aggregation - Density dependence - dislodgement - disturbance - flume - Mytilus edulis - positive feedback - stable state
    Ecosystem engineers typically exert positive feedback on their environment, which enhances their performance. Such positive feedback is lacking in the establishment phase, when densities are too low and/or patches are too small. There is a strong need to unravel the mechanisms for overcoming the resulting
    establishment thresholds, both for ecological restoration purposes and to be able to use their services. In the present study, we question whether providing a transient substratum can be used as tool to overcome establishment thresholds, by creating a window of opportunity for initial settlement, using mussels (Mytilus edulis) as a model system. Combining field and flume experiments, we study how biogenic substratum enrichment in the form of a shell layer on a soft mudflat affects the critical dislodgement thresholds and, thus, the chances of mussel establishment at different mussel densities and aggregation states. Flume results showed that the presence of a shell layer reduced dislodgement of mussel patches in low-energy environments but was conditional for establishment in high-energy environments. That is, in high-energy environments with shells, aggregation into clumps enhanced dislodgement, while dislodgement was reduced with increasing overall mussel biomass and overall mussel patch weight. Without shells, dislodgement was always 100%. These findings agreed with our field studies, which showed that coarse shell material reduced mussel losses (by a factor of 3), reduced aggregation (by a factor of 2.4), and increased attachment strength (by a factor of 2.4). Overall, our results show that the local presence of biogenic substratum increases the
    chance of mussel establishment by enhancing the critical hydrodynamic dislodgement threshold. Thus, the local addition of a biogenic substratum may create a window of opportunity to initiate settlement in more
    dynamic environments, to shift at a local scale from a bare mudflat state into an established biogenic reef state. Our findings have clear implications for how to approach restoration and management of ecosystem engineers dominated systems. For instance, when positive feedback of ecosystem engineers is lacking, (1) the transient offering of suitable settling substratum may be a necessary step to overcome establishment thresholds, and (2) this becomes increasingly important with increasing abiotic stress.
    Exploring novel food proteins and processing technologies : a case study on quinoa protein and high pressure –high temperature processing
    Avila Ruiz, Geraldine - \ 2016
    Wageningen University. Promotor(en): Tiny van Boekel, co-promotor(en): Guido Sala; Markus Stieger. - Wageningen : Wageningen University - ISBN 9789462579095 - 152
    dietary protein - chenopodium quinoa - whey protein - food process engineering - heat treatment - in vitro digestibility - fractionation - maillard reaction products - ph - viscosity - gelation - aggregation - high pressure technology - sds-page - voedingseiwit - chenopodium quinoa - wei-eiwit - levensmiddelenproceskunde - warmtebehandeling - in vitro verteerbaarheid - fractionering - maillard-reactieproducten - ph - viscositeit - gelering - aggregatie - hogedruktechnologie - sds-page

    Foods rich in protein are nowadays high in demand worldwide. To ensure a sustainable supply and a high quality of protein foods, novel food proteins and processing technologies need to be explored to understand whether they can be used for the development of high-quality protein foods. Therefore, the aim of this thesis was to explore the properties of a novel food protein and a novel processing technology for the development of high-quality protein foods. For this, quinoa was chosen as an alternative protein source and high pressure – high temperature (HPHT) processing was chosen as a novel processing technology.

    Quinoa protein has been found to have a balanced amino acid profile and to be allergen-free. As this combination is not common among plant proteins, it is worth studying physicochemical and functional protein properties of quinoa further (Chapter 1). Extraction and processing conditions can influence protein properties and thus functionality. Therefore, quinoa protein properties were examined at different extraction and processing conditions (Chapter 2 and 3). For this, the protein was isolated from the seed using alkaline extraction and subsequent acid precipitation. The quinoa protein isolates (QPIs) obtained were examined in terms of protein purity, yield, solubility, denaturation, aggregation and gelation behaviour, and digestibility.

    It was found that when extraction pH increased, protein yield and denaturation increased, which was explained by a higher protein charge, leading to increased unfolding and solubilisation (Chapter 2). Protein purity decreased with increasing extraction pH, which was associated with a possible co-extraction of other seed components. QPIs obtained at extraction pH 8 (E8) and 9 (E9) had a higher solubility in the pH range of 3-4.5 (E9 solubility was highest at pH 7) compared to the isolates obtained at extraction pH 10 (E10) and 11 (E11). It was hypothesised that at a higher extraction pH, the larger extent of protein denaturation led to the exposure of hydrophobic groups, thus decreasing surface polarity and solubility. When suspensions of E8 and E9 were heated, protein aggregation increased and semi-solid gels with a dense microstructure were formed. In contrast, suspensions of E10 and E11 aggregated to a lower degree and did not form self-supporting gels upon heating. The gels obtained with E10 and E11 had furthermore a microstructure showing loose particles. Increased protein aggregation and improved gel formation at lower extraction pH were hypothesised to be due to a higher degree of hydration and swelling of protein particles during heating, leading to increased protein-protein interactions. These findings show that QPI obtained at an extraction pH below 9 might be used to prepare semi-solid gelled foods, while QPI obtained at pH values higher than 10 might be more suitable to be applied in liquid foods.

    Heat treatments of QPI suspensions lead to an increased protein denaturation and aggregation but to a decreased in vitro gastric protein digestibility, especially at a high temperature (120°C) and extraction pH (11) (Chapter 3). It was hypothesised that QPIs obtained at a higher extraction pH and treated at higher temperature were denatured to a greater extent and contained stronger protein crosslinks. Therefore, enzyme action was impaired to a higher degree compared to lower temperatures and extraction pH values. This means that by controlling extraction pH and treatment temperature the digestibility of quinoa protein can be optimised.

    The disadvantage of the conventional fractionation method used in Chapter 2 and 3 is that it requires high amounts of energy and water and the solvents used can denature the protein, possibly leading to a loss in functionality. Therefore, recently, a new method has been developed, hybrid dry and aqueous fractionation, which uses less energy and water and has proved successful for obtaining protein-rich fractions from pea. It was not known whether hybrid dry and aqueous fractionation can be used to obtain protein-rich fractions of quinoa (Chapter 4). Quinoa seeds were carefully milled to disentangle the protein-rich embryo from the starch-rich perisperm. Using subsequent air-classification, the embryo and perisperm were separated based on size into a protein-rich fraction and a starch-rich fraction, respectively (dry fractionation). The protein-rich fraction was further milled to a smaller particle size and suspended in water. This step was to solubilise the protein (aqueous fractionation), whereby a smaller particle size and adding NaCl optimised the solubilisation efficiency. The addition of salt helped to extract more salt-soluble proteins from quinoa, next to the water-soluble proteins. After centrifugation, the protein-enriched top aqueous phase was decanted and ultrafiltered for further protein concentration. The process generated a quinoa protein-rich fraction with a protein purity of 59.4 w/dw% and a protein yield of 62.0%. Having used 98% less water compared to conventional protein extraction, this new method is promising for industry to obtain quinoa protein concentrates in a more economic, sustainable and milder way.

    Next to exploring novel food proteins for the development of high-quality protein foods, novel processing technologies are also important to study. This is because traditional thermal processing can deteriorate the quality of protein-rich foods and beverages by causing undesired browning or too high viscosities. Therefore, for sterilisation purposes, HPHT processing was investigated for the treatment of protein foods (Chapter 5). Model systems, whey protein isolate – sugar solutions, were used to study the effect of pressure at high temperature on Maillard reactions, browning, pH, protein aggregation and viscosity at different pH. It was found that pressure retarded early and advanced Maillard reactions and browning at pH 6, 7 and 9, while it inhibited protein aggregation and, thereby, a high viscosity at pH 7. The mechanism behind this might be that pressure induces a pH drop, possibly via dissociation of ionisable compounds, and thus slows down Maillard reactions. Differences in protein conformation, protein-protein interactions and sensitivity of whey proteins, depending on pH, pressure and heat, might be at the base of the reduced protein aggregation and viscosity observed at pH 7. The results show that HPHT processing can potentially improve the quality of protein-sugar containing foods, for which browning and high viscosities are undesired, such as high-protein beverages.

    Finally, the properties of quinoa protein and HPHT processing were discussed in a broader context (Chapter 6). It was concluded that QPI obtained at pH 9 is a promising alternative to pea and soy protein isolate from a technical perspective and that QPI protein yields can be optimised. Also, quinoa protein-rich fractions obtained with the hybrid dry and aqueous fractionation method were predicted to have comparable properties to QPI, soy and pea protein isolates. However, from a marketing perspective, the protein-rich fraction was considered more advantageous to be up-scaled compared to QPI. High pressure at ambient or high temperature was found to have an added value compared to heat, which can be used for the development of high-quality protein food. Lastly, quinoa protein and HPHT processing might become more attractive for industry in the light of current trends, if present predictions can be confirmed and remaining issues can be resolved.

    Controlling the ratio between native-like, non-native-like, and aggregated β-lactoglobulin after heat treatment
    Delahaije, Roy J.B.M. ; Gruppen, Harry ; Eijk-Van Boxtel, Evelien L. Van; Cornacchia, Leonardo ; Wierenga, Peter A. - \ 2016
    Journal of Agricultural and Food Chemistry 64 (2016)21. - ISSN 0021-8561 - p. 4362 - 4370.
    aggregation - concentration - denaturation - ionic strength - pH - refolding - structure - temperature - unfolding

    The amount of heat-denatured whey protein is typically determined by pH 4.6 precipitation. Using this method, a significant amount of nondenatured protein was reported even after long heating times. Apparently, a fraction of the unfolded protein refolds into the "native" state rather than form aggregates. This fact is known and has been explained using kinetic models. How the conditions affect the refolding and aggregation is, however, not fully understood. Therefore, this study investigates the unfolding, refolding, and aggregation process of β-lactoglobulin using circular dichroism and size-exclusion chromatography to characterize different folding variants and to quantify their content. The proteins remaining in solution at pH 4.6 were confirmed to be native-like. The nonaggregated fraction contains proteins with a native-like and two types of non-native-like conformations. The nonaggregated fraction increased with decreasing temperature (60-90 °C) and concentration (1-50 g/L) and increasing electrostatic repulsion (pH 7-8; 0-50 mM). The native-like fraction in the nonaggregated fraction was independent of pH, ionic strength, and concentration but increased with decreasing temperature.

    Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution
    Koopmans, G.F. ; Hiemstra, T. ; Regelink, I.C. ; Molleman, B. ; Comans, R.N.J. - \ 2015
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1392 (2015). - ISSN 0021-9673 - p. 100 - 109.
    natural organic-matter - engineered nanoparticles - calcium-chloride - ionic-strength - humic acids - molar-mass - aggregation - retention - ph - speciation
    Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV–vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10–90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV–vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used.
    Spatially explicit fate modelling of nanomaterials in natural waters
    Quik, J.T.K. ; Klein, J.J.M. de; Koelmans, A.A. - \ 2015
    Water Research 80 (2015). - ISSN 0043-1354 - p. 200 - 208.
    engineered nanomaterials - aquatic environments - nanoparticles - aggregation - systems - exposure - sedimentation - calibration - matrices - silver
    Site specific exposure assessments for engineered nanoparticles (ENPs) require spatially explicit fate models, which however are not yet available. Here we present an ENP fate model (NanoDUFLOW) that links ENP specific process descriptions to a spatially explicit hydrological model. The link enables the realistic modelling of feedbacks between local flow conditions and ENP fate processes, such as homo- and heteroaggregation, resuspension and sedimentation. Spatially explicit simulations using five size classes of ENPs and five size classes of natural solids showed how ENP sediment contamination ‘hot spots’ and ENP speciation can be predicted as a function of place and time. For the catchment modelled, neglect of spatial heterogeneity caused relatively small differences in ENP retention. However, simplification of the number of size classes to one average class, resulted in up to 3.3 times lower values of retention compared to scenarios that used detailed size distributions. Local concentrations in sediment were underestimated up to 20 fold upon simplification of spatial heterogeneity or particle size distribution. We conclude that spatial heterogeneity should not be neglected when assessing the risks of ENPs.
    Partitioning of humic acids between aqueous solution and hydrogel. 2. Impact of physicochemical conditions
    Zielinska, K. ; Town, R.M. ; Yasadi, K. ; Leeuwen, H.P. van - \ 2015
    Langmuir 31 (2015)1. - ISSN 0743-7463 - p. 283 - 291.
    ionic-strength - alginate gel - heavy-metals - fluorescence - substances - ph - aggregation - media - soil - spectroscopy
    The effects of the physicochemical features of aqueous medium on the mode of partitioning of humic acids (HAs) into a model biomimetic gel (alginate) and a synthetic polyacrylamide gel (PAAm) were explored. Experiments were performed under conditions of different pH and ionic strength as well as in the presence or absence of complexing divalent metal ions. The amount of HA penetrating the gel phase was determined by measuring its natural fluorescence by confocal laser scanning microscopy. In both gel types, the accumulation of HA was spatially heterogeneous, with a much higher concentration located within a thin film at the gel surface. The thickness of the surface film (ca. 15 µm) was similar for both types of gel and practically independent of pH, ionic strength, and the presence of complexing divalent metal ions. The extent of HA accumulation was found to be dependent on the composition of the medium and on the type of gel. Significantly more HA was accumulated in PAAm gel as compared to that in alginate gel. In general, more HA was accumulated at lower background salt concentration levels. The distribution of different types of HA species in the gel body was linked to their behavior in the medium and the differences in physicochemical conditions inside the two phases.
    The effect of calcium on the composition and physical properties of whey protein particles prepared using emulsification
    Westerik, N. ; Scholten, E. ; Corredig, M. - \ 2015
    Food Chemistry 177 (2015). - ISSN 0308-8146 - p. 72 - 80.
    beta-lactoglobulin - aggregation - gelation - supplements - droplets - chloride - gels
    Protein microparticles were formed through emulsification of 25% (w/w) whey protein isolate (WPI) solutions containing various concentrations of calcium (0.0–400.0 mM) in an oil phase stabilized by polyglycerol polyricinoleate (PGPR). The emulsions were heated (at 80 °C) and the microparticles subsequently re-dispersed in an aqueous phase. Light microscopy and scanning electron microscopy (SEM) images revealed that control particles and those prepared with 7.4 mM calcium were spherical and smooth. Particles prepared with 15.0 mM calcium gained an irregular, cauliflower-like structure, and at concentrations larger than 30.0 mM, shells formed and the particles were no longer spherical. These results describe, for the first time, the potential of modulating the properties of dense whey protein particles by using calcium, and may be used as structuring agents for the design of functional food matrices with increased protein and calcium content.
    Lake retention of manufactured nanoparticles
    Koelmans, A.A. ; Quik, J.T.K. ; Velzeboer, I. - \ 2015
    Environmental Pollution 196 (2015). - ISSN 0269-7491 - p. 171 - 175.
    engineered nanomaterials - tio2 nanoparticles - fate models - aggregation - environment - sediment - exposure - heteroaggregation - impacts - release
    For twenty-five world lakes and three engineered nanoparticles (ENP), lake retention was calculated using a uniformly mixed lake mass balance model. This follows similar approaches traditionally used in water quality management. Lakes were selected such that lake residence times, depths and areal hydraulic loadings covered the widest possible range among existing lakes. Sedimentation accounted for natural colloid as well as suspended solid settling regimes. An ENP-specific mixed sedimentation regime is proposed. This regime combines ENP sedimentation through slow settling with natural colloids from the water column, with faster settling with suspended solids from a selected part of the water column. Although sedimentation data and hydrodynamic concepts as such were not new, their first time combination for application to ENPs shows in which cases lake retention is important for these particles. In combination with ENP emission data, lake retention translates directly into potential risks of ENPs for lake benthic communities.
    Modification of Ovalbumin with Fructooligosaccharides: Consequences for Network Morphology and Mechanical Deformation Responses
    Munialo, C.D. ; Ortega, R.G. ; Linden, E. van der; Jongh, H.H.J. de - \ 2014
    Langmuir 30 (2014)46. - ISSN 0743-7463 - p. 14062 - 14072.
    protein gels - rheological properties - beta-lactoglobulin - maillard reaction - pea protein - neutral ph - mixed gels - gelation - aggregation - perception
    The Maillardation of proteins has been used as a natural alternative to improve its functionality by covalent coupling of proteins with saccharides. However, the impact of Maillard reaction on the structural aspects of protein networks and, as a consequence, the mechanical breakdown properties of the gel networks has not been reported. The objective of this study was to evaluate how the attachment of linear oligo-sugar moieties onto ovalbumin affects its aggregation, network morphology, and consequently the mechanical deformation properties including the ability of the networks to elastically store energy in this material. To potentially alter the morphology of the network structure, ovalbumin was modified by conjugating some of its amino groups with fructooligosaccharide (FOS) moieties via the Maillard reaction. It was demonstrated that the attachment of FOS to ovalbumin does not affect the integrity of the secondary and tertiary structure as characterized using circular dichroism and tryptophan fluorescence. Differences in the network morphology were observed by scanning electron microscopy for FOS-modified ovalbumin variants. Upon increased modification, the microstructure of the gels had more and larger pores and had thinner strands than nonmodified variants. Evaluation of the large deformation properties of the gels demonstrated that FOS-modified gels were less strong and less brittle and showed lower stiffness than nonmodified variants. The recoverable energy (elastically stored energy) of gels reduced with an increase in the degree of modification. The results show that the attachment of FOS to ovalbumin alters the structural and mechanical (large) breakdown properties of the protein gels. The consequences of the alteration of the network structure and large deformation properties of FOS-modified ovalbumin offer opportunities to efficiently design food materials with desirable techno-functional applications
    Multimedia Modeling of engineered Nanoparticles with SimpleBox4Nano: Model Definition and Evaluation
    Meesters, J. ; Koelmans, A.A. ; Quik, J.T.K. ; Hendriks, A.J. ; Meent, D. van de - \ 2014
    Environmental Science and Technology 48 (2014)10. - ISSN 0013-936X - p. 5726 - 5736.
    saturated porous-media - environmental exposure - manufactured nanoparticles - aquatic environments - particle deposition - double-layer - nanomaterials - aggregation - transport - fate
    Screening level models for environmental assessment of engineered nanoparticles (ENP) are not generally available. Here we present SimpleBox for Nano (SB4N) as the first model of this type, motivate its validity and evaluate it by comparisons with a known material flow model. SB4N expresses ENP transport and concentrations in and across air, rain, surface waters, soil, and sediment, accounting for nano-specific processes such as aggregation, attachment and dissolution. The model solves simultaneous mass balance equations (MBE) using simple matrix algebra. The MBEs link all concentrations and transfer processes using first-order rate constants for all processes known to be relevant for ENPs. The first-order rate constants are obtained from the literature. The output of SB4N is mass concentrations of ENPs as free dispersive species, hetero-aggregates with natural colloids and larger natural particles in each compartment in time and at steady state. Known scenario studies for Switzerland were used to demonstrate the impact of the transport processes included in SB4N on the prediction of environmental concentrations. We argue that SB4N predicted environmental concentrations are useful as background concentrations in environmental risk assessment.
    Rapid settling of nanoparticles due to heteroaggregration with suspended sediment
    Velzeboer, I. ; Quik, J.T.K. ; Meent, D. van de; Koelmans, A.A. - \ 2014
    Environmental Toxicology and Chemistry 33 (2014)8. - ISSN 0730-7268 - p. 1766 - 1773.
    engineered nanomaterials - silver nanoparticles - aquatic environments - aggregation - exposure - water - particles - matrices - carbon - quantification
    Sedimentation of engineered nanoparticles (ENPs) has been studied mainly in artificial media and stagnant systems mimicking natural waters. This neglects the role of turbulence and heteroaggregation with sediment. We studied the apparent sedimentation rates of selected ENPs (CeO2, PVP-Ag and SiO2-Ag) in agitated sediment-water systems resembling fresh, estuarine and marine waters. Experiments were designed to mimic low energy and periodically resuspended sediment water systems (14 days), followed by a long term aging, resuspension and settling phase (6 months), as would occur in receiving shallow lakes. ENPs in systems with periodical resuspension of sediment were removed with sedimentation rates between 0.14 and 0.50¿m/d. The sedimentation rates did not vary much among ENP type, salinity and aging time, which is attributed to the capture of ENPs in sediment flocks. The sedimentation rates were one to two orders of magnitude higher than those reported for aggregation-sedimentation in stagnant systems without suspended sediment. Heteroaggregation rates were estimated and ranged between 0.151 and 0.547 L/mg/d, which is up to 29 times higher than those reported for natural colloids under quiescent settling conditions. We conclude that rapid scavenging and sedimentation drives removal of ENPs from the water column
    Recirculatie potorchidee 5. Zink
    Blok, C. ; Kromwijk, J.A.M. - \ 2014
    potplanten - orchidales - recirculatiesystemen - hergebruik van water - zink - aggregatie - reductie - effecten - pot plants - orchidales - recirculating systems - water reuse - zinc - aggregation - reduction - effects
    Als het zinkgehalte in het aanvoerwater hoger is dan de plantopname, loopt de concentratie in de wortelomgeving op. Recirculatie van drainwater leidt dan tot het langzaam maar gestadig oplopen van het zinkgehalte. Schadegrenzen voor potorchidee zijn niet bekend. Deze flyer geeft inzicht in effecten van zinkophoping bij andere gewassen en methoden om zinkophoping te verminderen.
    Heteroaggregation and sedimentation rates for nanomaterials in natural waters
    Quik, J.T.K. ; Velzeboer, I. ; Wouterse, M. ; Koelmans, A.A. ; Meent, D. van de - \ 2014
    Water Research 48 (2014)1. - ISSN 0043-1354 - p. 269 - 279.
    sedimentatie - zwevende deeltjes - aggregatie - nanotechnologie - emissie - schatting - colloïden - waterstroming - zeewater - oppervlaktewaterkwaliteit - sedimentation - suspended solids - aggregation - nanotechnology - emission - estimation - colloids - water flow - sea water - surface water quality - engineered nanomaterials - silver nanoparticles - carbon nanotubes - manufactured nanoparticles - aggregation kinetics - aquatic environments - ceo2 nanoparticles - organic-matter - fate - exposure
    Exposure modeling of engineered nanomaterials requires input parameters such as sedimentation rates and heteroaggregation rates. Here, we estimate these rates using quiescent settling experiments under environmentally relevant conditions. We investigated 4 different nanomaterials (C60, CeO2, SiO2-Ag and PVP-Ag) in 6 different water types ranging from a small stream to seawater. In the presence of natural colloids, sedimentation rates ranged from 0.0001md-1 for SiO2-Ag to 0.14md-1 for C60. The apparent rates of heteroaggregation between nanomaterials and natural colloids were estimated using a novel method that separates heteroaggregation from homoaggregation using a simplified Smoluchowski-based aggregation-settling equation applied to data from unfiltered and filtered waters. The heteroaggregation rates ranged between 0.007 and 0.6Lmg-1 day-1, with the highest values observed in seawater. We argue that such system specific parameters are key to the development of dedicated water quality models for ENMs.
    A multiple criteria decision making approach to manure management systems in the Netherlands
    Gebrezgabher, S.A. ; Meuwissen, M.P.M. ; Oude Lansink, A.G.J.M. - \ 2014
    European Journal of Operational Research 232 (2014)3. - ISSN 0377-2217 - p. 643 - 653.
    goal-programming approach - greenhouse-gas emissions - livestock manure - cattle slurry - nitrous-oxide - energy - optimization - technologies - aggregation - preferences
    The intensification of livestock operations in the last few decades has resulted in an increased social concern over the environmental impacts of livestock operations and thus making appropriate manure management decisions increasingly important. A socially acceptable manure management system that simultaneously achieves the pressing environmental objectives while balancing the socio-economic welfare of farmers and society at large is needed. Manure management decisions involve a number of decision makers with different and conflicting views of what is acceptable in the context of sustainable development. This paper developed a decision-making tool based on a multiple criteria decision making (MCDM) approach to address the manure management problems in the Netherlands. This paper has demonstrated the application of compromise programming and goal programming to evaluate key trade-offs between socio-economic benefits and environmental sustainability of manure management systems while taking decision makers’ conflicting views of the different criteria into account. The proposed methodology is a useful tool in assisting decision makers and policy makers in designing policies that enhance the introduction of economically, socially and environmentally sustainable manure management systems.
    Hydrodynamic Interactions between Two Equally Sized Spheres in Viscoelastic Fluids in Shear Flow
    Snijkers, F. ; Pasquino, R. ; Vermant, J. - \ 2013
    Langmuir 29 (2013)19. - ISSN 0743-7463 - p. 5701 - 5713.
    spherical-particles - boger fluids - suspensions - rheology - alignment - microstructure - aggregation - evolution - liquid
    The effect of using a viscoelastic suspending medium, on the;in-plane hydrodynamic interaction between two equally sized spheres in shear flow is studied experimentally to understand flow-induced assembly behavior (i.e., string formation). A counterrotating device equipped with a Couette geometry is used together with quantitative videomicroscopy. To evaluate the effects of differences in rheological properties of the suspending media, fluids have been selected that highlight specific constitutive feature's. These include a reference Newtonian fluid (N), a,constant-viscosity, high-elasticity Boger fluid (BF), a wormlike micellar surfactant solution with a, single dominant relaxation time (WMS), and a broad spectrum shear-thinning elastic polymer solution (ST). As expected, the trajectories are symmetric in the Newtonian fluid. In the BF, the midpoints. of the spheres are observed to remain in the same plane before and after,the interaction, as in the Newtonian fluid, although the path lines are in this case no longer symmetric. Interactions in the, ST and WMS are highly asymmetric. Two, fundamentally different kinds of path lines are Observed in the WMS and ST: reversing and Open trajectories: The type of trajectory depends on the initial Configuration of the spheres with respect to:each,other and on the shear rate. On the basis of the obtained results, shear-thinning of the viscosity seems to be the key rheological parameter that determines the overall nature of, the interactions rather than the relative magnitude of the normal stress differences.
    Asymmetric flow field-flow fractionation as a new approach to analyse iron-(hydr)oxide nanoparticles in soil extracts
    Regelink, I.C. ; Weng, L.P. ; Koopmans, G.F. ; Riemsdijk, W.H. van - \ 2013
    Geoderma 202-203 (2013). - ISSN 0016-7061 - p. 134 - 141.
    organo-mineral associations - natural colloids - trace-metals - iron-oxides - matter - ferrihydrite - mossbauer - stability - aggregation - dissolution
    Iron-(hydr)oxide nanoparticles are important for the sequestration of organic carbon because of their small size and consequently large specific surface area. Therefore, there is an increasing interest in analytical techniques such as asymmetric flow field-flow fractionation (AF4) that allow for a direct measurement of the size distribution of nanoparticles (1–150 nm). We used AF4 coupled to high-resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) to analyse the size distribution and elemental composition of nanoparticles dispersed from three horizons of a podzol. We tested three extractants for the amount of dispersed Fe-(hydr)oxide nanoparticles. No Fe-(hydr)oxide nanoparticles were dispersed in 5 mM NaCl. In a 1 mM NaOH extraction (pH 9.0), the amount of Fe dispersed in the form of Fe-(hydr)oxide nanoparticles amounted to 0.2–0.8 g kg- 1, which corresponded to 2–13% of the Fe content as extracted with ammonium oxalate (Fe-ox). Pyrophosphate was found to be the most effective extractant for Fe-(hydr)oxide nanoparticles and extracted 1.0–4.7 g kg- 1 Fe as Fe-(hydr)oxide nanoparticles, corresponding to 16–47% of the Fe-ox content. These Fe-(hydr)oxide nanoparticles were 2–20 nm in size and maximum concentrations were found at a particle diameter of 5 nm. The dispersion of Fe-(hydr)oxide nanoparticles in pyrophosphate coincided with the extraction of a large fraction of the soil organic carbon content (55–69%) which shows that dispersion of organo-mineral aggregates results in the release of Fe-(hydr)oxide nanoparticles from the soil. The amount of Fe-(hydr)oxide nanoparticles extracted from the soil did not increase after ultrasonic treatment of the pyrophosphate suspension. Since not all Fe-(hydr)oxides can be dispersed from the soil as primary particles, AF4 cannot be used as a tool to analyse the specific surface area of the Fe-(hydr)oxides in the soil. Instead, AF4 should be considered as a complementary technique providing a direct measurement for the size of the Fe-(hydr)oxide nanoparticles in soil extracts.
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