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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    The role of environmental shocks in shaping prosocial behavior
    Duchoslav, Jan - \ 2017
    Wageningen University. Promotor(en): E.H. Bulte, co-promotor(en): F. Cecchi. - Wageningen : Wageningen University - ISBN 9789463431477 - 190
    environment - behaviour - economic development - social behaviour - stress conditions - environmental temperature - physical properties - social environment - milieu - gedrag - economische ontwikkeling - sociaal gedrag - stress omstandigheden - omgevingstemperatuur - fysische eigenschappen - sociaal milieu

    All economic activity requires some degree of cooperation, and the process of economic development involves many social dilemmas. It is therefore crucial to understand how the preferences which guide our behavior vis-à-vis these situations are shaped. The ability and willingness to work for the benefit of the group rather than just one's own has evolved over many generations, and is – to some extent – innate to any healthy human being. At the same time, individual prosocial preferences are – also to a certain extent – endogenous to the physical and social environment within which we operate. This thesis identifies several ways in which environmental changes affect intrinsic prosocial preferences, and outlines a possible direction for fixing any such negative effects.

    In Chapter 1, I introduce the topic of prosocial preferences. I briefly describe how prosociality has been viewed over the course of scientific history, and summarize the current state of knowledge about the formation of social preferences. I further outline how extrinsic incentives can influence prosocial behavior without affecting the preferences which underpin it. Finally, the chapter contains an overview of the methodologies used throughout this thesis.

    In Chapter 2, I focus on an early formative factor of prosocial preferences—their fetal origins. I study how temperature shocks faced by pregnant women affect their children's later-life prosocial preferences. I find that exposure to higher than usual ambient temperatures during gestation reduces a child's probability of contribution to the public good, with the negative effect lasting into adulthood.

    Chapter 3 continues in the same vein as Chapter 2, looking at the fetal origins of prosocial preferences. In this chapter, I investigate how prenatal stress induced by random violence affects the preferences for cooperation among children born during an armed conflict. To do so, I exploit variations in the ratio of the lengths of the index and ring fingers—a marker of in utero hormone exposure negatively associated with high maternal distress during early fetal development. I show that prenatal stress reduces the probability that children contribute to the public good.

    In Chapter 4, I move away from the physical aspects of human environment, focusing instead on the social ones. I study the effects of a sudden introduction of a formal institution on individual cooperative behavior within informal arrangements. In particular, I look at how an NGO intervention which helped create a mutual health insurance affected cooperative behavior in a public goods game. I find that the introduction of formal insurance reduces contributions to the public good. This reduction in cooperation levels is, however, not due to the adopters of the formal insurance who may now have less need for informal reciprocal networks, and who therefore (partially) withdraw from them. It is instead the non-adopters who become less cooperative towards the adopters.

    To outline a possible direction for remedying the negative environmental effects on prosocial behavior described in the previous three chapters, I illustrate one of the ways in which prosocial behavior can be incentivized with a relatively simple and easily implementable policy. In Chapter 5, I evaluate the impact of introducing performance-based financial incentives on staff effort and, consequently, on allocative efficiency and output in healthcare provision. I show that in the case under investigation, financial incentives conditioned on output and worth roughly 5% of total expenditures increased staff effort to the extent that output rose by over 25%, without any detectable drop in the quality of the provided services. This not only shows the potential of incentive-compatible financing to improve the performance of underfunded healthcare systems in developing countries, but also that extrinsic motivation can be used to foster behavior which benefits the society rather than just the individual.

    Finally, I combine the main findings from the core chapters of the thesis in Chapter 6. I discuss their policy implications, and point out the some of the outstanding questions, outlining the directions for future research.

    Intracellular & extracellular lipolysis : regulation by the PPAR targets ANGPTL4 & HILPDA
    Dijk, Wieneke - \ 2016
    Wageningen University. Promotor(en): Sander Kersten. - Wageningen : Wageningen University - ISBN 9789462579460 - 248
    foams - foaming - milk products - processing - aggregates - casein - micelles - physical properties - schuim - schuimen - melkproducten - verwerking - bodemdeeltjes - caseïne - micellen - fysische eigenschappen

    The body efficiently stores energy in the form of triglyceride (fat) molecules. However, triglycerides cannot directly enter or exit our cells, but first need to be degraded to so-called fatty acids before moving in or out a cell. This degradation process, called lipolysis, is crucial for human physiology and is tightly regulated to prevent the accumulation of fats either within organs or within the bloodstream - hallmarks of diseases such as obesity and cardiovascular disease.

    To allow for uptake by underlying organs, triglycerides in the circulation are efficiently broken down by an enzyme called lipoprotein lipase (LPL) that sits in the bloodstream of multiple organs (extracellular lipolysis). In this thesis, we characterized a protein named angiopoietin-like 4 (ANGPTL4) that potently inhibits LPL and, thereby, inhibits the breakdown of triglycerides in the bloodstream. Our data show that by adjusting the tissue expression levels of ANGPTL4, different organs collaborate to ensure that triglycerides are distributed to organs in need of energy. Moreover, we uncovered that, in the fat tissue, ANGPTL4 starts to inhibit LPL before LPL arrives in the bloodstream. By preventing the arrival of LPL in the bloodstream, ANGPTL4 is capable of rapidly adjusting the rates of triglyceride degradation and the concomitant uptake of fatty acids from the circulation to the energy requirements of the underlying organ.

    To exit our cells, stored triglycerides, such as present in our fat tissue, need to be broken down to fatty acids. Subsequently, the released fatty acids can fuel other organs in need of energy. To further clarify the mechanisms underlying this process of intracellular lipolysis, we investigated the role of a promising new protein called HILPDA. Our data show, however, that loss of HILPDA did not impact the release of fatty acids from the fat tissue, while a high abundance of HILPDA only had a mild attenuating effect on the release of fatty acids. This suggests that HILPDA is not a major physiological regulator of intracellular lipolysis in fat cells.

    In conclusion, in this thesis, we have clarified the regulation of intracellular and extracellular lipolysis by studying the respective roles of the proteins ANGPTL4 and HILPDA. Such efforts are clinically relevant, as regulators of lipolysis are potential therapeutic targets to lower cardiovascular disease risk.

    The role of casein micelles and their aggregates in foam stabilization
    Chen, Min - \ 2016
    Wageningen University. Promotor(en): Erik van der Linden; Toon van Hooijdonk, co-promotor(en): Marcel Meinders; Guido Sala. - Wageningen : Wageningen University - ISBN 9789462579842 - 124
    foams - foaming - milk - casein - micelles - physical properties - stabilization - schuim - schuimen - melk - caseïne - micellen - fysische eigenschappen - stabilisatie

    Many foam products derived from milk or specific dairy ingredients suffer from drainage, coalescence and/or disproportionation. Previous studies indicated that foam properties of milk are strongly influenced by the composition of the milk as well as by the processing conditions during foam production. The aim of this research was to get a better understanding of these two factors. Interestingly, the presence of aggregates of casein micelles was found to result in very stable foams. The interfacial properties (adsorption speed, adsorption energy, dynamical interfacial tension, interfacial dilatational moduli), thin film stability (rupture time) and foam properties (foamability, drainage, coalescence) of casein micelle dispersions were determined. Based on these data, the very stable foams were concluded to result from properties of the thin films in the foam, which were affected drastically by the presence of the large aggregates of casein micelles.

    Exergy analysis in industrial food processing
    Zisopoulos, F.K. - \ 2016
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - Wageningen : Wageningen University - ISBN 9789462578326 - 229
    thermodynamics - energy - physical properties - food production - drying - food industry - efficiency - thermodynamica - energie - fysische eigenschappen - voedselproductie - drogen - voedselindustrie - efficiëntie

    The sustainable provision of food on a global scale in the near future is a very serious challenge. This thesis focuses on the assessment and design of sustainable industrial food production chains and processes by using the concept of exergy which is an objective metric based on the first and second law of thermodynamics. Three case studies are presented, two on a chain level (industrial bread and mushroom production), and one on a process level (conceptual spray drying of a lactose solution). Furthermore, industrial food production chains are categorized as thermodynamic archetypes and general rules are derived for their sustainable design exergy-wise. Additional methodological aspects related to e.g. the impact of system boundaries, the allocation of exergy values to waste streams, and the influence of the selection of the environment of reference on the outcome of the analysis, are also discussed.

    Silky gels for cells : Self-assembling protein-based polymers for use in tissue engineering
    Wlodarczyk, M.K. - \ 2016
    Wageningen University. Promotor(en): Martien Cohen Stuart; Marleen Kamperman; S.C.G. Leeuwenburgh. - Wageningen : Wageningen University - ISBN 9789462576230 - 194
    polymers - proteins - biomedical engineering - biomaterials - recombinant dna - transplantation - compatibility - encapsulation - heparin - biodegradation - physical properties - polymeren - eiwitten - biomedische techniek - biomaterialen - recombinant dna - transplantatie - compatibiliteit - inkapselen - heparine - biodegradatie - fysische eigenschappen

    Tissue engineering is a relatively new, but actively developing field of biomedical science. It aims at organ or tissue regeneration by use of scaffolds, which are usually seeded with cells prior to implantation, and stimulated by bioactive cues or growth factors. It is a promising and valuable alternative to the use of transplants, for which the demand is greater than the supply, and for which application is connected with high risk of rejection and infection due to immunosuppressant medication. One of the main challenges of tissue engineering, that we tried to address in this thesis, is the design of biocompatible and functional biomaterials that could serve as cell scaffold. We investigated, if protein-based polymers, more specifically, if the de novo designed, C2SH48C2 copolymer, which self-assembles into fibers upon a pH-trigger, is a suitable material for cell scaffolds.

    In Chapter 2 we described the design and production, by means of recombinant DNA technology, of C2SH48C2. The protein was efficiently secreted by Pichia pastoris at high yields of g/l levels and we proposed an effective purification method. We showed that fibers and gels form by self-assembly upon pH adjustment, and that rheological properties of the obtained hydrogels depend on the total protein concentration. In view of potential biomedical applications, erosion studies were performed, which indicated that the gels exhibited long term stability in conditions mimicking those in body fluid. The biocompatibility of the gel scaffolds was demonstrated in a 2D cell culture study. However, despite the cell viability, a low proliferation rate was observed.

    To improve cell performance in contact with C2SH48C2 hydrogels (Chapter 3) we incorporated active domains in the C2SH48C2 protein by recombinant functionalization. We described the synthesis of two protein variants: (1) BRGDC2SH48C2, N-terminally enriched in integrin-binding domains (RGD) and (2) BKRSRC2SH48C2, N-terminally enriched in heparin binding domains (KRSR). We showed precise control over the amount of active domains in the final gels, by simply mixing the variants of the proteins in the desired molar ratio before inducing gelation. A 23-day cell culture study, performed using MG-63 cells, revealed that the presence of RGD and KRSR domains positively influenced cell attachment, spreading and activity. A synergistic effect was observed, i.e. scaffolds containing both bioactive domains yielded fully confluent layers of cells at an earlier stage during cell culture than the other gels. We concluded that cell behavior can be controlled by tuning the content of functional domains.

    In Chapter 4, we tested the suitability of the C2SH48C2 protein, enriched in RGD domains, for cell encapsulation, as the conditions of 3D cell culturing are more similar to the environment of cells in the body. We independently varied gel stiffness (by means of protein concentration) and functional motif (RGD) density, and analyzed the influence of these parameters on the cellular response. The viability and proliferation of MG-63 cells, encapsulated in the gels at different protein concentrations and RGD densities, was investigated with a cell activity assay, and by quantitative analysis of confocal pictures of nuclei (DAPI stain) and F-actin (phalloidin). We showed that optimal cell behavior is obtained in the presence of RGD domains and at low protein concentrations. The results indicated that RGD functionality is not the sole requirement; the gel matrix needs to exhibit the right mechanical properties and architecture to allow for cell growth, cytoplasmic extension and migration.

    Finally, in Chapter 5, we showed that active domains (here KRSR) can serve multiple functions in the material. We demonstrated the cross-linking ability of KRSR domains in the presence of heparin, leading to structural and mechanical changes in the scaffolds. In dilute systems (0.1 % (w/v)), heparin increases the rate of fiber growth, and induces fiber bundling. At higher protein concentrations, leading to the hydrogel formation (2 % (w/v)), the gelation rate and final storage modulus can be tuned by the amount of heparin and KRSR domain density. We concluded that with this approach, the material properties of C2SH48C2 protein gels can be effectively and simply controlled in a straightforward and biocompatible way.

    In Chapter 6 we described the main requirements for biomaterials and discussed to what extent they are fulfilled by protein-based polymers, and in particular, by the presented C2SH48C2 protein. The main advantages over alternative materials, and the challenges that need to be addressed before application in tissue engineering becomes a reality, were discussed. We ended with suggestions to improve the properties of C2SH48C2 protein for use as a biomaterial, especially its biodegradability, and its structural and mechanical properties.

    Water retention in mushroom during sustainable processing
    Paudel, E. - \ 2015
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Ruud van der Sman. - Wageningen : Wageningen University - ISBN 9789462575967 - 148
    mushrooms - water holding capacity - physical properties - hydration - chemical composition - heat treatment - canning - process optimization - sustainability - paddestoelen - waterbergend vermogen - fysische eigenschappen - hydratatie - chemische samenstelling - warmtebehandeling - inblikken - procesoptimalisatie - duurzaamheid (sustainability)

    This thesis deals with the understanding of the water holding capacity of mushroom, in the context of a redesign of their industrial processing. For designing food process the retention of food quality is of the utmost importance. Water holding capacity is an important quality aspect of mushrooms. A convenient process design methodology which accounts also for product quality is Conceptual Process Design (CPD). An approach to follow CPD methodology is first to explore, the material properties of the products to find optimal processing conditions. In this stage the constraints of (existing) processing equipment are not considered. Later in the second stage, suboptimal processing conditions are determined considering the constrains of equipment.

    In mushroom canning, temperature induced loss of water holding capacity (WHC) of tissue manifests as a lower product yield. This loss of water is accompanied with the loss of nutrients, dissolved in the water. In addition to the loss of product quality like water holding capacity, mushroom canning (with alternating heating and cooling steps) also induces losses of useful resources as (potable) water. In terms of water use, water is added at several steps, and is discarded at other places. This shows that there is opportunity to improve the sustainability of the production system, but with the constraint that product quality is not impaired, or evenly improved.

    The WHC is an important property that determines several aspects of foods. For example, it determines the juiciness of fruits, vegetables and meat products; the freshness (firmness, or crispiness) of green-leafy vegetables; and the calorie intake per serving for high calorie containing foods such as cheese. Despite being a widely used term in food science, there is no clear definition of water holding capacity and its thermodynamic nature is not fully acknowledged. The understanding of the WHC is even poorer in structured cellular foods such as mushroom, where different water fractions are present in various compartments. In a cellular system water is present as 1) a solution in the vacuoles, 2) water osmotically bound to the cytoplasmic and the cell wall materials and 3) capillary water in pores, which might be filled during processing. Because they have a distinct capillary phase, the mushroom is a good system to study the contributions of various water fraction on the total water retention.

    The main aim of the current work is to provide insight for the development of canned mushroom processing where: 1) the resources of energy and water are efficiently used, and 2) the quality of mushroom is maintained. These two aims are related to the efficient use of raw materials and maintenance of full weight of mushroom during processing. The WHC is an important quality indicator of mushrooms. The analysis related to water retention of mushroom has been carried out at microscale where molecular and structural interactions in relation to water retention are studied. The micro scale analysis is discussed in chapter 2, chapter 3 and chapter 4. The sustainability analysis is carried out at mesoscale where analysis is carried out at the unit operation level which is described in chapter 5.

    In chapter 2, the heat-induced change in water holding capacity of particular the gel phase of the mushroom is interpreted with the Flory-Rehner theory, commonly applied to polymer gels. As done earlier for meat, we have first assumed that WHC loss in mushroom can also be attributed to the protein denaturation. This assumption is based on the experimental observation that, like meat, mushroom also follows a typical sigmoid relation with change in temperature. In the theory, we have regarded mushroom as a homogeneous biopolymer hydrogel, in which salt and sugar are dissolved. The water holding capacity is then understood as the swelling capacity of the biopolymer gel. The thermodynamic state of this simplified system is characterized by the so-called swelling pressure, which is decomposed into three independent contributions: 1) the mixing pressure induced by sugars and polymers, 2) the ionic pressure induced by the salt, and 3) the elastic pressure induced by the polymers. An assumption was made that the heat treatment denatures mushroom protein, which is reflected in the change of the Flory Huggins interaction for protein. It follows the same temperature dependency as the WHC loss by mushroom under zero mechanical load. The assumption of the temperature dependency of the interaction parameter is tested with an independent sorption measurement. With the assumption, the sorption curve for mushroom sample which were preheated previously at 30, 60 and 90 °C could accurately be predicted. Curve fitting of WHC under various mechanical loads has shown that model parameters that are associated with the elastic pressure, the crosslink density and fraction of the polymer in the relaxed state, are temperature dependant. The values of increased in contrast to the decrease of upon heating of mushroom tissue up to temperature of 70°C. The result indicates that heat treatment increases the polymer chain length between the cross links as original conformation of mushroom is lost. At the same time, more crosslinks are formed by a polymer because of aggregation of polymers. However, in our fitting procedure, we have excluded WHC data at low external pressure values, as water is present in both gel phase as in in the capillaries. This is done as the pores in this range are not fully collapsed and the Flory Rehner theory is valid only for the gel phase

    In chapter 2 mushroom is simplified in the sense that only compositional contribution is considered in WHC but not the structural contributions. In subsequent chapters we have acknowledged that mushroom has a cellular structure with a distinct pore phase. The pores are intentionally filled during processing via vacuum impregnation. The contribution of water present in the capillaries due to vacuum impregnation of mushroom has been discussed in chapter 3. Both the temperature of heat treatment and the initial porosity of mushroom contribute independently to water holding capacity of heat treated mushroom. The hydration of heat treated mushroom increases linearly with the initial porosity of mushroom for all the temperatures from 30 to 90 °C. The porosity of mushroom can also largely explain the increase in hydration of heat treated mushroom with storage as both porosity and the hydration increase simultaneously with the storage days. The fluid that filled in the capillaries acts against collapse of the hyphae which have inherent elastic force that works in the other direction. The initial porosity of mushroom is an important aspect that determines the hydration of the heat treated mushroom and therefore, cannot be ignored. In addition, the Flory-Rehner theory alone cannot capture the contribution of the capillary water. Hence an addition is needed in the theory to capture this effect.

    The cellular phase in mushroom tissue is even more complicated because water is present in this phase in two other forms, as gel water and the intracellular water. Chapter 4 takes into account the role of structure in the WHC. The role of cell membrane integrity and the cell-wall structural components is investigated for retention of the water fraction. The cell membrane integrity is calculated from the conductivity measurement of the fluid that leaches out from the vacuole that has salts in it. The loss of the cell membrane integrity largely explains the water loss from heat treated mushroom sample. The loss of cell membrane integrity is also related with the water loss from frozen mushroom, but additional losses occur during freezing due to novel crosslinks formed during the growth of ice crystals compressing the unfrozen cell wall material. The enzymatic hydrolysis of mushroom cellular components shows that chitin and mushroom protein both contribute to the water holding capacity either via osmotic binding or by their role to provide the mechanical strength to the mushroom hyphae. In addition, proteins have additional contributions to water retention by mushroom because of their electrostatic interaction as polyelectrolyte. This is evident as the hydration of the mushroom increases with pH of mushroom.

    In chapter 5, the efficiency of the use of the resources (raw materials, energy water) is investigated. The mass and exergy flow in the current production system is visualized with the Sankey diagrams. The sustainability of unit operations involved in the current production system of canned are analysed with the second law efficiency using exergy. Using ideas from Process Intensification three alternative routes are proposed for the production of canned mushrooms namely: 1). Slicing before vacuum hydration, and 2) Using hot water for vacuum hydration and 3) Using blanch water for vacuum hydration. Using hot water for vacuum hydration is not seen as a feasible option, since it consumed more resources. Slicing mushroom before their vacuum hydration and using blanch water for hydration of mushroom lowers the resources requirement for production. In addition, using blanch water for hydration also increases the final product yield.

    Finally, the main findings of this thesis are summarized in the general discussion in chapter 6. The findings from previous chapters are combined to an overall description of water loss from heat treated mushroom. The overall description of water holding capacity in mushrooms is given in terms of the thermodynamic conditions for equilibrium between the different compartments holding water. The two dimensions of the thesis, the higher water retention of processed mushroom and more sustainable operation are discussed in the light of conceptual process design, using a micro/mesoscale approach. At the microscale material properties of mushroom are discussed. The biggest effect comes from cell membrane integrity loss. The porosity of fresh mushroom and the ionic interactions of polymers are the other effects that influence the WHC. Mesoscale analysis shows that shifting the sequence of unit operations and reusing the blanch water that is discarded in the current production process can improve the sustainability. Finally based on outcome of current work, future perspective of current work is discussed briefly.

    Overall, this thesis demonstrated that there is substantial scope in improving the efficiency in the use of resources in producing preserved mushroom. Also scope in retention of water in the mushroom tissue is demonstrated. Thus this thesis shows that both aspects, product and process efficiency, can be improved at the same time.

    Meer mogelijkheden om in te spelen op lage zoutopname
    Voogt, W. ; Kierkels, T. ; Heuvelink, E. - \ 2013
    Onder Glas 10 (2013)10. - p. 42 - 43.
    glastuinbouw - groenten - snijbloemen - teeltsystemen - hergebruik van water - zouttolerantie - irrigatiewater - natriumchloride - fysische eigenschappen - gewasteelt - greenhouse horticulture - vegetables - cut flowers - cropping systems - water reuse - salt tolerance - irrigation water - sodium chloride - physical properties - crop management
    De komende jaren worden de spuinormen steeds strenger en moeten tuinbouwbedrijven het water steeds meer gaan hergebruiken. Dan zijn planteigenschappen als zoutgevoeligheid of een lage zoutopname nog belangrijker dan nu. Het is dus zaak om daar meer zicht op te krijgen om goed te kunnen sturen.
    Baseline survey B11-5 on the German Continental Shelf
    Glorius, S.T. ; Weide, B.E. van der; Kaag, N.H.B.M. - \ 2013
    Den Helder : IMARES (Rapport / IMARES Wageningen UR C098/13) - 45
    waterbodems - noordzee - chemische eigenschappen - fysische eigenschappen - biologische eigenschappen - sediment - textuur - inventarisaties - water bottoms - north sea - chemical properties - physical properties - biological properties - sediment - texture - inventories
    A consortium, consisting of Wintershall Holding GmbH, GdF Suez, RWE Dea and EWE AG, is planning an exploration well in block B11-5, located within the Doggerbank (N2000 area). In order to assess any effect from this activity on the biological, physical and chemical properties of the seafloor Wintershall Noordzee BV asked IMARES to perform a baseline study prior to the drilling activities. In this baseline study the following environmental elements are included; seafloor texture and presence of any structures (including stones and boulders), the physical (grain size and organic content), chemical (oil and metal content) and biological (abundance and structure of benthic species) properties of the sediment. At 29 stations located at different angles and distances of the drill site, sediment samples were taken and video recordings of the seafloor made. In an area of 2000 x 2000 m around the centre, side scan sonar footage were made as well.
    Influence of pectin characteristics on complexation with ß-lactoglobulin
    Sperber, B.L.H.M. - \ 2010
    Wageningen University. Promotor(en): Fons Voragen; Willem Norde, co-promotor(en): Henk Schols. - [S.l. : S.n. - ISBN 9789085858355 - 174
    pectinen - bèta-lactoglobuline - ladingskenmerken - fysische eigenschappen - chemische eigenschappen - binding (scheikundig) - pectins - beta-lactoglobulin - charge characteristics - physical properties - chemical properties - bonding
    Pectin and proteins are both common food constituents. The type of pectin that forms complexes with protein is known to be of great influence on the structure and stability of liquid foods. Therefore, the aim of this thesis is to investigate the influence of the overall charge and local charge density of pectin on the formation of soluble complexes with β-lactoglobulin (β-lg).
    Combination of state diagrams and binding isotherms shows that a high local charge density of pectin is a prerequisite to form soluble complexes with β-lg at higher ionic strength. A high overall charge of pectin results in the close proximity of the GalA blocks. Therefore, β-Lg neighbours bind close together on pectin with a high overall charge, which leads to lateral repulsion and hence, maxima in the binding constant and the pH where insoluble complexes form with increasing ionic strength.
    The formation of soluble complexes has an enthalpic driving force from electrostatic attraction and an entropic driving force from the release of small counterions from the electric double layer and water molecules from hydrophobic surroundings. A high local charge density, at low ionic strength results in complex formation dominated by an enthalpic driving force. A low local charge density gives a more even distribution between enthalpic and entropic contributions. An increase in ionic strength decreases the enthalpic contribution, with a relative increase in the entropic contribution, supporting the idea of water release from hydrophobic surroundings.
    Adsorption from β-lg–pectin mixtures to a hydrophobic surface leads to low adsorption rates due to a low concentration of free protein. Sequential adsorption of β-lg and pectin shows that low overall charge pectin protrudes more into the solution than high overall charge pectin, resulting in a more negative ζ-potential for low overall charge pectin. After sequential adsorption, β-lg is most stable against wash-out with a terminal pectin layer.
    Polyelectrolyte complex micelles as wrapping for enzymes
    Lindhoud, S. - \ 2009
    Wageningen University. Promotor(en): Martien Cohen Stuart; Willem Norde, co-promotor(en): Renko de Vries. - [S.l.] : S.n. - ISBN 9789085854388 - 206
    elektrolyten - micellen - inkapselen - enzymen - fysische eigenschappen - electrolytes - micelles - encapsulation - enzymes - physical properties
    Kinetic modeling of reactions in Foods
    Boekel, M.A.J.S. van - \ 2008
    Boca Raton : CRC Press - ISBN 9781574446142 - 400
    wiskundige modellen - kinetica - chemische reacties - voedselkwaliteit - voedingsmiddelen - houdbaarheid (kwaliteit) - opslagkwaliteit - fysische eigenschappen - fysicochemische eigenschappen - modelleren - mathematical models - kinetics - chemical reactions - food quality - foods - keeping quality - storage quality - physical properties - physicochemical properties - modeling
    The level of quality that food maintains as it travels down the production-to-consumption path is largely determined by the chemical, biochemical, physical, and microbiological changes that take place during its processing and storage. Kinetic Modeling of Reactions in Foods demonstrates how to effectively capture these changes in an integrative fashion using mathematical models. Thus, kinetic modeling of food changes creates the possibility to control and predict food quality from a technological point of view.
    Zuurstof verbruikssnelheid gemeten met de OUR Methode : Venige substraten en toeslagstoffen voor de potgrondindustrie.
    Blok, C. ; Weerheijm, F. - \ 2008
    Wageningen : Wageningen UR Glastuinbouw - 24
    groeimedia - substraten - meetapparatuur - testen - gebruikswaarde - fysische eigenschappen - growing media - substrates - meters - testing - use value - physical properties
    In dit verslag wordt een nieuwe methode getest die voor meer substraatmaterialen is te gebruiken en die mogelijk meer klassen kan onderscheiden. Het is een van de BOD metingen (Biological Oxygen Demand) afgeleide methode, bekend als OUR meting (Oxygen Uptake Rate)
    Cloud physical properties retrieval for climate studies using SEVIRI and AVHRR data = Afleiden van fysische eigenschappen van wolken voor klimaatstudies met behulp van SEVIRI en AVHRR gegevens
    Roebeling, R.A. - \ 2008
    Wageningen University. Promotor(en): Bert Holtslag, co-promotor(en): A.J. Feijt; P. Stammes. - [S.l.] : S.n. - ISBN 9789085048923 - 158
    wolken - fysische eigenschappen - optische eigenschappen - meteorologie - meteorologische waarnemingen - satellieten - klimatologie - clouds - physical properties - optical properties - meteorology - meteorological observations - satellites - climatology
    Accurate and long term information on the physical properties of clouds is required to increase our understanding on the role of clouds in the current climate system, and to better predict the behavior of clouds in a changing climate. This thesis investigates if retrievals of cloud physical properties from satellite imagers can be used to prepare time series of these properties for monitoring climate change, and to evaluate parameterizations of cloud processes in weather and climate prediction models.

    An algorithm for retrieval of Cloud Physical Properties (CPP) from visible and near-infrared reflectances of the AVHRR instrument onboard NOAA and the SEVIRI instrument onboard METEOSAT is presented. This algorithm retrieves cloud optical thickness, effective radius, and liquid water path, whereas a cloud model is used to simulate cloud geometrical thickness and droplet number concentration. Due to the large differences found between the reflectances from the different instruments (up to 25%), a recalibration procedure is developed that successfully reduces the retrieval differences to less than 5%. The uniqueness of the SEVIRI cloud property retrievals is in its unprecedented sampling frequency (15 minutes) that ensures the statistical significance of the dataset. One year of cloud liquid water path retrievals is validated against simultaneous Cloudnet microwave radiometer observations over Europe. The results show that during summer the agreement is very good while during winter an overestimation of about 20% is observed. Possible reason for this overestimation is the plane-parallel assumption in the CPP algorithm used to simulate real clouds. For single-layer stratocumulus days, a sub-adiabatic cloud model is used to obtain cloud geometrical thickness and cloud droplet number concentration. During these days good agreement is found between geometrical thickness simulations and Cloudnet lidar and radar observations, and cloud liquid water path retrievals and Cloudnet microwave radiometer observations. The simulated droplet concentration is found to vary independently from liquid water path and the geometrical thickness, which suggests possible interactions between aerosols and clouds. This shows potential in our dataset for studies of the indirect aerosol effect.

    The SEVIRI dataset of cloud property retrievals is used to evaluate the Regional Climate Model (RACMO) over Europe during a six-month period. The results show that RACMO represents the spatial variations of cloud amount and cloud liquid water path realistically, but underpredicts cloud amount by 20% and overpredicts liquid water path by 30%. Examination of the diurnal cycle shows that the RACMO maximum liquid water path occurs two hours earlier than that observed by SEVIRI, while the RACMO maximum cloud amount agrees reasonably well with SEVIRI’s amount. The largest differences in the diurnal cycle between RACMO and SEVIRI are found in regions of alternating stratiform and convective regimes where RACMO has difficulty representing the transition between these regimes. The SEVIRI dataset of cloud physical properties proves to be a powerful tool for evaluating parameterizations of cloud and precipitation processes in weather and climate prediction models, and thus helps increase the confidence in these models.


    Studies on the intra- and intermolecular distributions of substituents in commercial pectins
    Guillotin, S.E. - \ 2005
    Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Henk Schols. - [S.l.] : S.n. - ISBN 9789085042655 - 155
    pectinen - chemische eigenschappen - fysische eigenschappen - voedseladditieven - pectins - chemical properties - physical properties - food additives
    Commercial pectins are mainly used for the gelling, thickening and stabilizing properties in food products. The different physical properties of pectins strongly depend on the galacturonic acid level and the level of methyl-esterification as well as on the molecular weight distribution. However, the conventional chemical analysis of the pectins does not always show differences between pectins while they behave differently. Two highly methyl-esterified pectins with similar chemical characteristics but different reactivity towards calcium were analysed. They were found to be a mixture of pectic populations differing in the degree of methyl-esterification as well as in the distribution of these methyl-esters. Amidated pectins with similar chemical features but different calcium sensitivity were also found to be a mixture of different pectic populations. Even for pectins having a similar degree of substitution, the ratio of amide groups versus methyl-esters varied significantly. In addition, the distribution of these substituents was found to differ.
    Interactions of phenolic compounds with globular proteins and their effects on food-related functional properties
    Prigent, S.V.E. - \ 2005
    Wageningen University. Promotor(en): Fons Voragen; Harry Gruppen, co-promotor(en): G.A. van Koningsveld. - Wageningen : - ISBN 9789085042679 - 132
    globulinen - eiwitten - fenolverbindingen - chlorogeenzuur - interacties - fysicochemische eigenschappen - fysische eigenschappen - voedsel - globulins - proteins - phenolic compounds - chlorogenic acid - interactions - physicochemical properties - physical properties - food
    In order to modulate the functional properties of food proteins, the interactions between globular proteins and the monomeric phenolic, caffeoylquinic acid (CQA, chlorogenic acid), and the oligomeric phenolics, procyanidins, were characterized and investigated for their effect on protein functional properties. Non-covalent interactions between proteins and CQA involved a low affinity and did not affect protein solubility. Proteins show a medium affinity for procyanidins of an average degree of polymerization (DP) of 5.5, but weakly interacted with smaller procyanidins. Procyanidins of DP 5.5 strongly decreased protein solubility. Covalent interactions between proteins and CQA oxidised by polyphenol oxidase (PPO) or oxidised at alkaline pH resulted in protein modification mainly via dimeric CQA quinones. The covalent modifications of proteins with CQA strongly reduced protein solubility. Lysine, tyrosine, histidine and tryptophan were able to interact with CQA quinones. It can be concluded that for food non-covalent interactions are restricted to oligomeric phenolic.
    Effect of frying conditions on the fat content of French fries : final report
    Schuten, H.J. ; Gijssel, J. van; Slotboom, E. - \ 2004
    onbekend : Agrotechnology & Food Sciences Group (Report / Agrotechnology and Food Innovations 023) - 16
    patates frites - frituren - bakoliën - bakvetten - fysische eigenschappen - temperatuur - vochtgehalte - vetgehalte - chips (French fries) - deep fat frying - cooking oils - cooking fats - physical properties - temperature - moisture content - fat content
    Detailed characterization of adsorption-induced protein unfolding
    Engel, M.F.M. - \ 2004
    Wageningen University. Promotor(en): Ton Visser; Sacco de Vries, co-promotor(en): Carlo van Mierlo. - [S.l.] : S.n. - ISBN 9789085040019 - 125
    runderserumalbumine - alfa-lactalbumine - moleculaire structuur - grensvlak - fysische eigenschappen - adsorptie - spectroscopie - bovine serum albumin - alpha-lactalbumin - molecular conformation - interface - physical properties - adsorption - spectroscopy
    Licht onder water : pilot-onderzoek naar het doorzicht voor duikers in recreatieplas De Berendonck
    Zaal, L.Z. - \ 2003
    Wageningen : Wetenschapswinkel Wageningen UR (Rapport / Wetenschapswinkel Wageningen UR nr. 184) - 50 p.
    lichtpenetratie - duiken - nederland - oppervlaktewater - meren - fysische eigenschappen - waterrecreatie - gelderland - surface water - lakes - physical properties - light penetration - water recreation - diving - netherlands - gelderland
    The goal of this pilot-project is to gain insight into the causes of the poor sight. The secondary goal is to draft initial improvement proposals. The research questions are: - to which degree is there a case of bad sight and in which water layers is it present ? - what are the possible causes of this lesser sight, in view of determining matter in the water and determining events in the history of the lake ? - which proposals can be made to improve the sight ?
    Physical chemistry of foods
    Walstra, P. - \ 2003
    New York [etc.] : Marcel Dekker (Food science and technology 121) - ISBN 9780824793555 - 807
    fysische chemie - fysische eigenschappen - voedsel - fysica - voedselchemie - voedselwetenschappen - studieboeken - physical chemistry - physical properties - food - physics - food chemistry - food sciences - textbooks
    Exploring the structure and physical and chemical properties of solutions, dispersions, soft solids, fats, and cellular systems, this text describes the physicochemical principles essential to the comprehension and prediction of reactions and conversions that occur during the manufacture, handling, and storage of foods. The book contains practical examples of starch gelatinization and retrogradation, protein denaturation, lipid crystallization, foam and emulsion formation, colloidal interactions, glass transitions, and food freezing and structure, etc.
    Visionsystemen in de agro- en voedingsmiddelenindustrie
    Timmermans, T. - \ 2000
    Voedingsmiddelentechnologie 33 (2000)21. - ISSN 0042-7934 - p. 57 - 58.
    voedselindustrie - kwaliteitscontroles - voedselinspectie - kwaliteitsnormen - sensors - detectors - fysische eigenschappen - fysicochemische eigenschappen - food industry - quality controls - food inspection - quality standards - sensors - detectors - physical properties - physicochemical properties
    De toegevoegde waarde van visionsystemen ligt vooral in het detecteren van afwijkende producten in het kader van voedselveiligheid, certificering van producten en productiesystemen
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