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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    Bolus matters: impact of food oral breakdown on dynamic texture perception
    Devezeaux de Lavergne, M.S.M. - \ 2015
    Wageningen University. Promotor(en): Tiny van Boekel, co-promotor(en): Markus Stieger; F. van de Velde. - Wageningen : Wageningen University - ISBN 9789462574496 - 227
    textuuranalyse - textuur - voedsel - structuur - eigenschappen - perceptie - spijsvertering - gels - elektromyografie - masticatie - kwalitatieve analyse - worstjes - texture analysis - texture - food - structure - properties - perception - digestion - gels - electromyography - mastication - qualitative analysis - sausages

    Background and aims:

    Texture is an important, yet complex, quality attribute of food. Food structure and properties can be linked to texture perception during the first bite. However, the perception of attributes during chew down is more difficult to explain, as food requires to be broken down to be swallowed safely. Food oral processing, which is a recent discipline connecting food science to the physiology of the eating process, is considered to be the key for understanding dynamic food texture perception. The aim of this thesis is to understand the link between food properties and texture perception by investigating oral food breakdown, in simple model foods.

    Methods:

    Gels were used as a model for soft solid foods. Several properties of the gels were controlled by modifying the composition of gels, including fracture stress and fracture strain, oil droplets binding to the gels matrix, melting, serum release and mechanical contrast. The texture perception of the gels was measured using several sensory methods. Qualitative descriptive analysis (QDA), progressive profiling and temporal dominance of sensations (TDS) were compared in the assessment of dynamic texture perception. In order to link gel properties to texture perception, the oral processing of gels was measured through analyses on the gel bolus and measurements of chewing behaviour. Gel boli were expectorated at various stages of oral processing and were analysed for gel fragments size and number, mechanical properties and saliva incorporation. These analyses were used to quantify the degree of breakdown of gels and to relate bolus properties to changes in texture perception. Chewing behaviour was measured using Electromyography (EMG) to understand the role of oral processing behaviour in bolus formation and dynamic texture perception.

    Results:

    Dynamic texture perception of gels could be measured by QDA, progressive profiling and TDS which were complementary methods. Fracture properties of gels could predict the perception of first bite texture attributes. Fracture stress and fracture strain were correlated to first bite firmness and brittleness respectively. During chew down, the link between gel properties and texture perception became less clear. Nonetheless, fracture properties and other gels properties, such as melting and serum release, related to chew down perception. Bolus properties depended on gel properties, but related better to chew down texture perception than gel properties. Mainly changes in mechanical properties and fragmentation of the bolus could explained the perception of complex texture attributes, such as creaminess and graininess respectively. Chewing behaviour depended on products properties. In addition, chewing behaviour impacted the formation of the bolus and could result in differences in dynamic texture perception between groups of individuals.

    Conclusions:

    The oral breakdown of food is a valuable input to understand the perception of complex chew down texture attributes. Such an input could be used to design foods with a desired texture sensory profile for reformulation of foods fitting in a healthier diet or foods for target consumer groups.

    Effecten bodem- en structuurverbeteraars; onderzoek op kleigrond 2010-2014
    Balen, D.J.M. van; Topper, C.G. ; Geel, W.C.A. van; Haan, J.J. de; Haas, M.J.G. de; Bussink, D.W. - \ 2015
    Lelystad : PPO AGV (Rapport / PPO-AGV 659) - 63
    akkerbouw - bodemstructuur - structuur - lichte-matig zware kleigronden - flevoland - poldergronden - bodemvruchtbaarheid - kalkmeststoffen - bodemverbeteraars - arable farming - soil structure - structure - clay loam soils - flevoland - polder soils - soil fertility - liming materials - soil conditioners
    In de praktijk lopen telers steeds vaker tegen problemen aan van een slechte bodemkwaliteit. Intensieve bouwplannen, steeds zwaardere mechanisatie, uitloging (Ca-uitspoeling), piekneerslagen en de schaalvergroting in de landbouw leiden tot vermindering van de fysische bodemvruchtbaarheid en de structuur van de bodem. Om de bodemstructuur te verbeteren, worden door industrie en handel zogeheten bodemverbeteraars en kalkmeststoffen aangeboden. Er is een grote variatie in type producten, de wijze waarop ze werken en de mate waarin ze een directe dan wel indirecte invloed op de bodemvruchtbaarheid hebben. Objectieve informatie over het effect van de aanbevolen producten op gewasopbrengsten en fysische, chemische en biologische bodemvruchtbaarheid ontbreekt. Uit eerdere proeven blijkt dat de effecten binnen 1 of 2 groeiseizoenen vaak afwezig zijn. Veel fabrikanten geven aan dat pas op langere termijn effecten te verwachten zijn.
    Protein mixtures: interactions and gelation
    Ersch, C. - \ 2015
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): A.H. Martin; Paul Venema. - Wageningen : Wageningen University - ISBN 9789462574212 - 199
    eiwit - wei-eiwit - sojaeiwit - gelering - gelatine - gels - reologie - structuur - moleculaire interacties - protein - whey protein - soya protein - gelation - gelatin - gels - rheology - structure - molecular interactions

    Gelation is a ubiquitous process in the preparation of foods. As most foods are multi constituent mixtures, understanding gelation in mixtures is an important goal in food science. Here we presented a systematic investigation on the influence of molecular interactions on the gelation in protein mixtures. Gelatin gels with added globular protein and globular protein gels with added gelatin were analyzed for their gel microstructure and rheological properties. Mixed gels with altered microstructure (compared to single gels) also differed in modulus from single gels. Mixed gels with microstructures similar to single gels were rheologically similar to single gels. Alterations in microstructure were attributed to segregative phase separation between proteins which occurred during gelation. Gelation was treated as a growth process from macromolecule to space spanning network. At conditions where electrostatic interactions were screened the occurrence of phase separation was attributed to the molecular size ratio between gelling and non-gelling proteins before gelation and changes of this size ratio during gelation. Here only mixtures that during gelation passed a region of high compatibility (similar molecular sizes) before entering a region of decreasing solubility phase separated. For applications this implies that whenever the gelling molecule is larger than the non-gelling molecule phase separation during gelation is unlikely while reversely, if the gelling molecules is smaller than the non-gelling molecule phase separation during gelation typically does occur

    Water holding of protein gels
    Urbonaite, V. - \ 2015
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Laurice Pouvreau; H.H.J. de Jongh. - Wageningen : Wageningen University - ISBN 9789462574229 - 206
    sojaeiwit - ovalbumine - wei-eiwit - waterbergend vermogen - gelering - structuur - morfologie - reologie - permeabiliteit - centrifugeren - soya protein - ovalbumin - whey protein - water holding capacity - gelation - structure - morphology - rheology - permeability - centrifugation

    Abstract

    Food products are typically multicomponent systems, where often the spatial volume is set by a protein continuous network. The ability of protein-based food products to entrap water and to prevent its exudation upon mechanical deformation is important for the texture and thus sensory perception of food products. Understanding of structural origins that determine gel water holding is therefore essential, and would allow designing foods with controlled sensory perception. Water removal from the gel (quantity, kinetics and mechanism) is related to the coarseness and deformation of the network. An understanding of the interplay between the effect of coarseness and stiffness on WH in fine and coarse gels allows one to take a better control and tune juiciness and the release of tastants from food products.

    Onkruiddruk blijft hoog bij niet-kerende grondbewerking
    Balen, D.J.M. van - \ 2014
    Boerderij 99 (2014)50. - ISSN 0006-5617 - p. 47 - 47.
    groenteteelt - koolsoorten - penen - daucus carota - cultuurmethoden zonder grondbewerking - gewasbescherming - onkruidbestrijding - teeltsystemen - opbrengst - houdbaarheid (kwaliteit) - structuur - bodemstructuur - bodemstructuur na grondbewerking - vegetable growing - cabbages - carrots - daucus carota - no-tillage - plant protection - weed control - cropping systems - outturn - keeping quality - structure - soil structure - tilth
    Hardere grond maar meer wortels bij proef niet-kerende grondbewerking PPO Lelystad. PPO-onderzoeker Derk van Balen licht e.e.a. toe.
    Structuring high-protein foods
    Purwanti, N. - \ 2012
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - S.l. : s.n. - ISBN 9789461731913 - 188
    eiwitten - structuur - gelering - reologische eigenschappen - wei-eiwit - proteins - structure - gelation - rheological properties - whey protein

    Increased protein consumption gives rise to various health benefits. High-protein intake can lead to muscle development, body weight control and suppression of sarcopenia progression. However, increasing the protein content in food products leads to textural changes over time. These changes result in product hardening over time and several negative sensorial attributes such as rubbery and dry mouth feel.

    This thesis describes the role of structuring to control the rheological and mechanical properties of high-protein model foods. By altering the internal structure of the model systems, textural properties of the model systems at initial stage (fresh products) can be improved.

    Content of this thesis can be distinguished into four parts. The first part reviews existing studies related to high-protein foods. The effects of ingredients and processing were evaluated with respect to food products having a high protein content. Some studies indicated typical problems occurring in products or model systems with an increased protein content such as product hardening over time. Ingredients that might be added to ameliorate product properties were plasticizers, peptides made from whey proteins, disulphide reducing agents, and components that block the free thiol groups in proteins. This part provides guidelines for structuring high-protein foods aimed at avoiding or reducing the unfavourable changes in properties over time. Concentrated proteins in their native (unmodified) form can be replaced by protein domains or structural elements with altered properties. These domains or elements mitigate the changes in product structure, resulting in a product that is softer than the one made from native proteins only.

    The second part focuses on the structural elements made from whey protein isolate (WPI), namely WPI aggregates and WPI microparticles. WPI aggregates were formed by different heating conditions at neutral pH. Generally, a higher concentration and a higher temperature resulted in bigger and less dense aggregates. A higher temperature also resulted in a higher reactivity (a larger number of available thiol groups). Heating an aggregate suspension led to a weaker gel than a gel made from native protein at similar. This result was hypothesized to originate from the lower number of contact points formed with larger aggregates. It was concluded that the most pronounced weakening effect could be obtained with aggregates that are large, dense, and non-reactive. That is why WPI microparticles were created. The particles were formed by gelling a concentrated WPI solution, and subsequent drying the gel and milling it into small particles. Partial replacement of native WPI with WPI microparticles resulted in a weaker gel than a gel made from native WPI only at the same total protein concentration. This result was attributed to the inability of the microparticles to form a gel. However, the weakening effect of these particles in the model system was limited due to water redistribution and the good bonding between the particles and the protein continuous phase.

    The third part describes how the properties of high-protein gels containing WPI microparticles change over time. A high-protein gel made from native WPI was used as a reference. The firmness and fracture stress of the gel made from WPI only increased during the first few days and then stabilized. The gel consisting of WPI microparticles in WPI or in a mixture of locust bean gum (LBG)–xanthan gum (XG) tended to harden for a longer period. Most likely, water redistribution is responsible for this observation.

    Structuring microspheres
    Wagdare, N.A. - \ 2011
    Wageningen University. Promotor(en): Cees van Rijn; Remko Boom, co-promotor(en): Ton Marcelis. - [S.l.] : S.n. - ISBN 9789085859239 - 111
    emulgering - membranen - inkapseling in microcapsules - structuur - emulsification - membranes - microencapsulation - structure

    Encapsulation and use of capsules for controlled release has several applications in pharmaceuticals, foods, cosmetics, detergents and many other products for consumers. It can contribute to sustainability, since it allows an efficient use of active materials, delivery at the required site and possibly a longer shelf life of the products. Many encapsulation systems are basically very thin shells (10 nm – 10 µm) around microscopic reservoirs (100 nm – 100 µm), in which active ingredients are trapped. The release properties are strongly dependent on the material properties of the shell, but also on their size and uniformity.

    The overall objective of this research is to understand the formation process of microcapsules and microspheres by using phase separation in well-defined droplets of a polymeric solution. The primary droplets were produced with microsieve emulsification. The polymer used was Eudragit FS 30D (a commercial copolymer of poly(methyl acrylate-co-methyl methacrylate-co-methacrylic acid) 7:3:1), which contains charged carboxylate groups that make the polymer water-soluble at higher pH (>7), allowing for release by a change in pH.

    Chapter 2 presents results that give more insight into microsieve emulsification with high porosity micro-engineered membranes. The droplet formation was strongly influenced by the dynamics of surfactant adsorption. The presence of suitable surfactants in both phases prevents the coalescence of droplets and wetting of the microsieve membranes by the dispersed phase during oil droplet formation. This resulted in the formation of stable emulsions of droplets with a narrow size distribution. The flux of the dispersed phase could be increased an order of magnitude compared to previous methods, without loss of size-distribution of the droplets. Thus, use of a high-porosity membrane, in combination with suitable surfactants in both the dispersed and continuous phases resulted in a much more effective and efficient emulsification process.

    In Chapter 3 crossflow microsieve emulsification was used to prepare porous microcapsules with an average size of about 30 µm. A mixture of Eudragit and hexadecane in dichloromethane (DCM) was emulsified in water.Being a poor solvent for this polymer, demixing of the droplet into a polymeric shell and a hexadecane-rich core occurred upon extraction of the DCM into the water phase. At a low ratio of polymer to hexadecane, the resulting shells were found to be porous. Increasing this ratio resulted in a reduction of the porosity and pore size of the shell. The Eudragit has a pH-dependent solubility. It is insoluble at acidic conditions and rapidly dissolves at alkaline conditions. The capsules were found to be stable at a pH lower than 7.0, whereas the oil core was released within half an hour at pH 7.1 and within a minute at pH 8.0. The morphology of the microcapsules can be adapted with a careful choice of the concentrations of polymer, hexadecane and solvent. At higher concentrations of polymer, the tiny oil droplets that were captured in the forming Eudragit shell were unable to coalesce completely and small, isolated pores were formed within the shell matrix.

    The potential for new microcapsule morphologies was further explored in Chapter 4 where the formation of Eudragit capsules with other oils instead of hexadecane was studied, and in Chapter 5 where a blend of poly(methyl methacrylate) (PMMA) and Eudragit was used.

    In Chapter 4 the effects of chain lengths of vegetable oils on the formation of porous microcapsules with hollow and multi-compartment structures is discussed. The encapsulation of oil and the morphology of the resulting microcapsules depends on the interaction between the Eudragit polymer and the type of oil that was used. Microcapsule formation using long chain length oils such as sunflower oil, olive oil and coconut oil resulted in well-defined microcapsules with a single encapsulated oil droplet, covered with a Eudragit-rich shell. On the other hand, capsules prepared with relatively short chain length oils, such as medium chain triglyceride oil, resulted in capsules with many individual small oil droplets encapsulated in an Eudragit matrix. Extraction of the oil from the microcapsules with hexane results in the formation of hollow porous shells as was investigated with optical microscopy and SEM. These structures are formed during microcapsule formation due to the complex phase separation processes in the Eudragit-water-oil-DCM quaternary system.

    In Chapter 5 the formation of microcapsules is further explored by using a blend of PMMA and Eudragit. Microspheres formed with this blend were found to consist of a PMMA core inside an Eudragit-rich shell, which tends to be porous. As the amount of Eudragit is increased, a thicker and more porous outer shell is formed due to the enhanced interaction of water with Eudragit. After dissolution of the Eudragit at high pH, different core surface structures resulted, from irregular surfaces to microspheres with a fiber-like, swollen corona around it, and to a surface covered with small nodular structures, dependent on the concentrations of PMMA and Eudragit in the initial mixture. As already indicated above, these structures are formed as a result of complex phase separation processes between polymers and (non)solvents, and between the two polymers.

    In Chapter 6 the results described in this thesis were compared with existing literature, yielding an outlook on the field of microencapsulation through phase separation. A general concept is discussed on how to obtain various interesting complex structures with phase separation combined with microsieve emulsification. Finally, a conceptual process design is discussed for industrial scale production of microcapsules and microspheres with use of microsieve emulsification.

    This thesis has yielded insight in the formation of a range of microcapsule morphologies by investigating a range of new production methods (microsieves and demixing conditions) and formulations (different concentrations, oils and using one polymer or a blend), and through this provides better insight into the mechanisms of microcapsule formation. While some of the structures may be directly used for microcapsule formation, some other structures may well have potential for other applications.

    Figure. Examples of structured microcapsules and microspheres developed in this thesis.

    Texture of food gels explained by combining structure and large deformation properties
    Berg, L. van den - \ 2008
    Wageningen University. Promotor(en): Tiny van Boekel; Erik van der Linden, co-promotor(en): F. van de Velde; Ton van Vliet. - S.l. : S.n. - ISBN 9789085049432 - 193
    gels - wei-eiwit - polysacchariden - textuur - structuur - mechanische eigenschappen - reologische eigenschappen - confocale microscopie - gels - whey protein - polysaccharides - texture - structure - mechanical properties - rheological properties - confocal microscopy
    Protein fibrillization: preparation, mechanism and application
    Akkermans, C. - \ 2008
    Wageningen University. Promotor(en): Remko Boom; Erik van der Linden, co-promotor(en): Atze Jan van der Goot; Paul Venema. - [S.l.] : S.n. - ISBN 9789085048794 - 162
    bèta-lactoglobuline - wei-eiwit - structuur - ingrediënten - voedingsmiddelen - vezels - fysische toestand - levensmiddelenfysica - beta-lactoglobulin - whey protein - structure - ingredients - foods - fibres - physical state - food physics
    The development of new functional ingredients is important for future food products. This PhD research aimed at the development of protein based structuring agents. Structuring agents are ingredrients that can be used to tailor the texture (and the mouth-feel) of products. Proteins were transferred into protein fibres (fibrils) that are long (1 micrometer) and very thin (few nanometers). Due to their special properties, protein fibrils offer unique possibilities to mimick meat structures and make products like yoghurt more creamy. This research shows that protein fibrils can be made from different protein sources (whey protein of milk, soy protein, potato protein) by heating an acidic protein solution. Furthermore, the mechanism of fibril formation was clarified. As a result, it was possible to optimize the fibril production and control the fibril properties. Finally, an important step was made towards the application of these fibrils in food products by studying the behaviour of fibrils in a model system for food products.
    Voedselaanbod voor gruttokuikens in de Hollandse veenweidegebieden
    Verhulst, J. ; Melman, T.C.P. ; Snoo, G.R. de - \ 2008
    Wageningen : Alterra (Alterra-rapport 1668) - 49
    limosa limosa - jonge dieren - graslandbeheer - graslanden - structuur - hoogte - hergroei - insecten - voedingsgedrag - voedsel - nederland - weidevogels - veenweiden - noord-holland - limosa limosa - young animals - grassland management - grasslands - structure - height - regrowth - insects - feeding behaviour - food - netherlands - grassland birds - peat grasslands - noord-holland
    Dit rapport verkent de voedselbeschikbaarheid van percelen die verschillen in beheer, grashoogte en structuur (uitgedrukt als variatie in grashoogte), voor gruttokuikens. In verschillende typen percelen met lang en kort gras zijn insecten bemonsterd met plakstrips. Het aantal grote insecten (> 4 mm) nam na begin mei sterk af, terwijl gruttokuikens meer afhankelijk worden van grote insecten door het seizoen. Percelen met kort gras (gemaaid of beweid) bevatten minder grote insecten dan ongemaaide percelen en vluchtstroken, maar percelen binnen reservaten verschilden hierin niet van boerenprecelen. Hergroeiende percelen lijken minder geschikt voor gruttokuikens dan ongemaaide percelen Structuurrijke percelen (over het algemeen die met met lang gras) bevatten vooral begin mei veel grote insecten
    Structuur en functie van habitattypen : nadere definiëring en monitoring in het kader van de Habitatrichtlijn. Dl. 1: Uitgangspunten
    Dobben, H.F. van; Janssen, J.A.M. ; Schmidt, A.M. - \ 2007
    Wageningen : Alterra (Alterra-rapport 1529) - 31
    monitoring - habitats - structuur - nederland - natura 2000 - abiotiek - habitatfragmentatie - monitoring - habitats - structure - netherlands - natura 2000 - abiotic conditions - habitat fragmentation
    De periodieke rapportage in het kader van de Europese Habitatrichtlijn dient naast informatie over de verspreiding en het oppervlak van de habitattypen ook informatie te bevatten over 'structuur & functie' en 'toekomstperspectief' van deze typen. Doel van de voorliggende studie is een nadere invulling te geven aan het begrip 'structuur & functie', zodanig dat duidelijk wordt welke informatie hierover in de rapportage moet worden opgenomen, en hoe de achterliggende gegevens kunnen worden ingewonnen. Aanbevolen wordt om 'structuur & functie' te beoordelen aan de hand van vegetatiestructuur, typische soorten, abiotische condities op de standplaats, en grootte van het habitat. Verder wordt aanbevolen wordt om regionale aspecten zoals depositie, hydrologie en versnippering niet onder structuur & functie mee te wegen, maar onder toekomstperspectief.
    Structure-rheology relations in sodium caseinate containing systems
    Ruis, H.G.M. - \ 2007
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Paul Venema. - [S.l.] : S.n. - ISBN 9789085046486 - 125
    natriumcaseïnaat - reologische eigenschappen - afschuifkracht - gelering - emulsies - structuur - verzuring - spectroscopie - licht - verstrooiing - sodium caseinate - rheological properties - shear - gelation - emulsions - structure - acidification - spectroscopy - light - scattering
    The general aim of the work described in this thesis was to investigate structure-rheologyrelations for dairy related products, focusing on model systems containing sodium caseinate. The acid inducedgelationof sodium caseinate, of sodium caseinate stabilized emulsions, and the effect of shear on the structure formation was characterized. Special attention was given to the sol-gel transition point, which was defined by a frequency independent loss tangent. It was shown that the sol-gel transition point is completely controlled by the pH and the temperature, independent of the concentration sodium caseinate or the applied shear rate. Considering sodium caseinate solutions, increase of the temperature of acidification caused a decrease of the critical pH forgelationand a more dense gel structure. The formed gels were not in thermodynamicequilibrium,however, due to the slow kinetics of the system they were stable on the time scale of the experiment. At the gel point we have strong indications that the structure can not be characterized by a single fractal dimension. During the acid inducedgelationof sodium caseinate stabilized emulsions a single sol-gel transition was observed. Addition of an excess of sodium caseinate to the emulsion resulted in two sol-gel transitions upon acidification. Application of shear during the acidification of the emulsions showed a decreasing radius of the aggregates formed at thegelpointwith increasing shear rate. The aggregates formed becamemore densedue to the application of shear while the network that was formed by the aggregates became less compact. No shear induced alignment was observed of emulsion droplets dispersed in water or ina sodiumcaseinatesolution, while emulsion droplets dispersed in axanthansolution did align in a shear field. Addition of sodium inhibited the string formation of the emulsion droplets
    Flow-induced structuring of dense protein dispersions
    Manski, J.M. - \ 2007
    Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - [S.l.] : S.n. - ISBN 9789085046103 - 222
    voedsel - structuur - textuur - eiwitproducten - caseïnaten - reologische eigenschappen - nieuwe voedingsmiddelen - voedselverwerking - apparatuur voor de voedselverwerking - kunstvlees - food - structure - texture - protein products - caseinates - rheological properties - novel foods - food processing - food processing equipment - meat analogues
    Both health and sustainability are drivers for the increased interest in the creation of novel foods comprising a high protein content. The key challenge is the formation of an attractive, stable and palatable food texture, which is mainly determined by the food structure. In this research, new processing routes based on flow are explored to create innovative protein-rich structures (exceeding 10%), and in parallel, insight is gained in the relevant mechanisms of structure formation. Dense dispersions of sodium caseinate and calcium caseinate, which are derived from milk, were mixed in a conventional mixer and sheared in an in house developed shear cell device. After mixing dense (sodium or calcium) caseinate dispersions, homogenous structures were obtained of which the properties were determined by the dispersed phase added, in this case palm fat. Shearing of dense calcium caseinate dispersions in combination with solidification using the enzyme transglutaminase resulted in completely different structures; highly fibrous structures were produced, which may serve as a basis for the creation of meat analogs. In contrast, after treating dense sodium caseinate dispersions using this novel structuring process, homogenous structures were obtained. It appeared that the intrinsic properties of protein dispersions are important for the formation of fibrous structures using well-defined flow. Based on the differences in performance between the two types of caseinates, tools and parameters can be derived to optimize and control the formation of fibrous products. In conclusion, the development of equipment that is dedicated to structure food ingredients is promising for the creation of novel foods on the one hand, and for gaining scientific understanding of structure formation on the other hand.
    Bacillus cereus spore formation, structure and germination
    Vries, Y.P. de - \ 2006
    Wageningen University. Promotor(en): Tjakko Abee; Willem de Vos; Marcel Zwietering. - [S.l. ] : S.n. - ISBN 9789085043690 - 127
    bacillus cereus - bacteriële sporen - sporenkieming - sporulatie - structuur - bacillus cereus - bacterial spores - spore germination - sporulation - structure
    Bacterial spores arespecializeddifferentiated celltypes fortypes,specificallydesigned for thesurvival of adverse conditions. Their structure is highly unique and very different from the structure of normal vegetative bacterial cells. Spores cause massive problems in the food industry, because their remarkable resistance allows them to survive food processing and conservation methods. The spore-forming Bacillus cereus is an important food-borne pathogen, is famousfor its ability to causefood poisoning, andisan importantspoilage organism inpasteurizeddairy products. The work presented in this thesis has focused on the formation, structure and germination of B. cereus spores. An easy and efficient way of producing synchronized and homogeneous B. cereus spore batches was developed, using a chemically defined medium in combination with an airlift fermenter system. This setup allowed precise monitoring and manipulation of key growth- and sporulation parameters. The conditions employed resulted in synchronous growth and sporulation, which facilitated gene-expression studies. The kinetics of expression of sigA , sigB , sigF and sigG followed the model developed for Bacillus subtilis , underscoring the conservation of sporulation mechanisms among bacilli. B. cereus was able to form spores on the chemically defined medium without glucose but with lactate as a main carbon source. Sporulation was not induced by nutrient limitation, because significant amounts of carbon and nitrogen sources were still present when the cells started to sporulate. The presence of glutamate delayed the final stages of sporulation, but not the moment of sporulation initiation. Clearly, the concentration of glutamate influenced key spore properties such as heat resistance and germination. The alternative sigma factor σ B , encoded by the sigB gene, is an important stress response regulator of B. cereus . An increase in sigB transcription was observed upon glucose depletion, coinciding with the transition from exponential growth to the stationary phase. This increase was specifically associated with the depletion of glucose. Deletion of sigB had a significant impact on spore heat resistance and spore germination properties. Spore heat resistance is caused by the physicochemical structure of the spore, which protects vital spore components such as membranes, proteins, and the DNA. A spin-probe-based Electron Spin Resonance (ESR) method for measuring the internal structure of intact bacterial spores was developed and applied, and provided the first direct data on the aqueous environment in the various compartments of B. subtilis and B. cereus spores. From the results obtained, it was concluded that the core cytoplasm is not in a glassy state. Instead, a three-dimensional molecular matrix incorporating free but highly viscous water exists in the core. Notably, neither heat activation nor partial germination (the excretion of DPA but not full rehydration and enzyme activity) altered the structural properties of the core matrix significantly. Complete germination resulted in the disappearance of the structure in the core, and a decrease of the micro viscosity in the core cytoplasm to levels encountered in normal vegetative cells. For a quantitative analysis of the behavior of individual spores in a large, germinating spore-population, a flow cytometry (FCM) method was developed and applied. By using several different fluorescent dyes, distinct germination parameters such as DNA accessibility and esterase activity were quantified. Finally, spore properties from a large number of B. cereus strains, including the B. cereus laboratory model strain ATCC14579 and a number of recent isolates from environmental and industrial settings were analyzed. The strains tested showed a large variation in heat resistance, and the majority had a higher heat resistance than the laboratory model strain. With respect to germination, many of the strains were less sensitive to the nutrients tested as compared to the laboratory model strain. Heat activation and ageing enhanced germination in response to several nutrients in various isolates. The knowledge that was gained and the methods that were developed in this study are expected to contribute to progress in the spore research field, and to enhanced spore control in the food industry.
    Development of dough under shear flow
    Peighambardoust, S.H. - \ 2006
    Wageningen University. Promotor(en): Remko Boom; Rob Hamer, co-promotor(en): Atze Jan van der Goot. - Wageningen : - ISBN 9789085043577 - 187
    deeg - vermenging - kneden - afschuifkracht - gluteninen - tarwegluten - structuur - doughs - mixing - kneading - shear - glutenins - wheat gluten - structure
    The overall objective of this thesis is to generate understanding of the relation between relevant process parameters in dough mixing and changes in product properties.
    Microstructure, rheology and demixing in emulsions flocculated by polysaccharides
    Blijdenstein, T.B.J. - \ 2004
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): G.A. van Aken; Ton van Vliet. - Wageningen : S.n. - ISBN 9789058089588 - 121
    emulsies - uitvlokking - polysacchariden - reologie - structuur - emulsions - flocculation - polysaccharides - rheology - structure
    keywords: Emulsion, b-lactoglobulin, polysaccharides, salt, sucrose, depletion, bridging, percolation, microstructure, micro-rheology, rheology, demixing, creaming, network compression. Abstract In this thesis, a study is presented on gravity-induced demixing behaviour of oil-in-water emulsions, stabilised by b-lactoglobulin and flocculated by various polysaccharides. Flocculation by polysaccharides mainly results in formation of emulsion droplet networks and can proceed via depletion and via bridging. Structural and rheological properties of these different networks were investigated and compared on a micro-and macroscopic level. These properties were related to the demixing behaviour of the emulsions. For emulsion droplet networks, gravity-induced compression of the network leads to separation of a serum layer. For depletion-induced networks, the initial rate of demixing by network compression is usually low and at high polysaccharide concentrations, usually a delay-time is observed before substantial demixing occurs. This delay-time scales with the permeability of the network, the viscosity and the density difference between oil and water. Once demixing has started, the network quickly collapses until the emulsion droplets are packed rather closely together. In bridging-flocculated emulsions, the initial demixing rate is higher, but more water was retained at longer times. The effects of protein, sugar and salts on demixing of depletion-flocculated networks were investigated as well. Protein affected the rate of flocculation and counteracted network formation. Sucrose affected the demixing rate via the viscosity and density of the aqueous phase, but it did not affect the droplet-droplet interactions. Salt affected the electrostatic droplet-droplet interactions. As a result, depletion-flocculation by dextran was inhibited at low salt concentrations. Addition of Ca2+ ions led to a decrease in repulsion between the protein layers, resulting in stronger droplet-droplet bonds, reinforcing a droplet network and retarding network compression.
    Structuur als basis voor gezonde koe. Minimale herkauwactiviteit voor 60 slagen per voerbolus noodzakelijk voor goede absorptie voedingsstoffen
    Hollander, C.J. ; Duinkerken, G. van - \ 2003
    Veeteelt 20 (2003)2. - ISSN 0168-7565 - p. 46 - 47.
    melkveehouderij - melkvee - rundveevoeding - voeropname - herkauwen - structuur - dairy farming - dairy cattle - cattle feeding - structure - feed intake - rumination
    In deel 4 van de serie Voeranalyse wordt de betekenis van de structuurwaarde van een voedermiddel aangegeven
    Bosdynamiek in bosreservaat Zeesserveld
    Clerkx, A.P.P.M. ; Goede, D.M. de; Sanders, M.E. - \ 2003
    Wageningen : Alterra (Alterra-rapport 668) - 46
    bossen - bosinventarisaties - vegetatie - structuur - beschermde bossen - bosecologie - nederland - overijssel - forests - forest inventories - vegetation - structure - reserved forests - forest ecology - netherlands - overijssel
    Bosreservaat Zeesserveld bij Ommen is in 2000 voor de tweede keer sinds aanwijzing geïnventariseerd. De boomlaag van grove den is niet veranderd. In de struiklaag heeft op de opgestoven gronden een sterke toename van sporkehout en Amerikaans krentenboompje plaatsgevonden. Hier begint ook blauwe bosbes in de bochtige-smelemat uit te breiden. Op de uitgestoven laagten verloopt deze ontwikkeling veel trager. Amerikaanse vogelkers breidde zich in beperkte mate uit. Zomereik en berk hebben moeite zich te vestigen en handhaven. De ontwikkeling naar een berken-eikenbos zal daarom een proces van lange adem zijn.
    Bosreservaat De Imboschberg : Bosstructuur en vegetatie bij aanwijzing tot bosreservaat
    Clerkx, A.P.P.M. ; Dort, K.W. van; Zuyderduyn, J.C. - \ 2002
    Wageningen : Alterra (Alterra-rapport 616) - 50
    bossen - beschermde bossen - structuur - vegetatie - nederland - gelderland - forests - reserved forests - structure - vegetation - netherlands - gelderland
    Bosreservaat De Imboschberg is in 1999 aangewezen. Het bestaat voor 50% uit heide. Het bos bestaat voornamelijk uit grove-dennenbos. Ruwe berk is algemeen als mengsoort, soms als hoofdboomsoort na spontane verstiging in stormvlakte uit 1972/1973. Er komen enkele stukken voormalig eikenhakhout voor. In de kruidlaag domineert blauwe bosbes. Beukenverjonging wijst op een ontwikkeling naar een wintereiken-beukenbos op termijn.
    A review of model designs
    Verdonschot, P.F.M. ; Nijboer, R.C. - \ 2002
    Wageningen : Alterra (Alterra-rapport 517) - 91
    aquatische gemeenschappen - ecologie - structuur - modellen - neurale netwerken - voorspelling - aquatische ecosystemen - aquatic communities - ecology - structure - models - neural networks - prediction - aquatic ecosystems
    The PAEQANN project aims to review current ecological theories which can help identify suited models that predict community structure in aquatic ecosystems, to select and discuss appropriate models, depending on the type of target community (i.e. empirical vs. simulation models) and to examine how results add to ecological water management objectives. To reach these goals a number of classical statistical models, artificial neural networks and dynamic models are presented. An even higher number of techniques within these groups will tested lateron in the project. This report introduces all of them. The techniques are shortly introduced, their algorithms explained, and the advantages and disadvantages discussed.
    Duurzame stedelijke ontwikkeling in en rond het IJmeer; benadering en advies
    Graaf, A.E. de - \ 2002
    Wageningen : Alterra (Alterra-rapport 587) - 71
    stadsontwikkeling - duurzaamheid (durability) - stedelijke planning - structuur - flevoland - ruimtelijke ordening - stedelijk gebied - Almere - IJmeer - urban development - durability - urban planning - structure - flevoland
    Duurzame stedelijke ontwikkeling wordt in dit onderzoek bekeken vanuit drie verschillende benaderingen. De eerste benadering is duurzame stedelijke ontwikkeling als strategie voor het omgaan met veranderingen. In ruimtelijke plannen is deze strategie herkenbaar door de toepassing van ruimtelijke flexibiliteit. De tweede benadering is duurzame stedelijke ontwikkeling als strategie voor de inrichting van de fysieke omgeving. Het resultaat van het toepassen van deze strategie heeft een positieve invloedop de fysieke omgeving. De derde benadering is duurzame stedelijke ontwikkeling als strategie voor de leefomgeving in brede zin. In deze strategie staat zowel de fysieke als de maatschappelijke omgeving centraal. Met behulp van de kennis die is opgedaan bij het bestuderen van de structuurplannen van Almere, Almere Poort en IJburg wordt een advies gegeven over het aanleggen van eilanden voor de kust van Almere vanuit de verschillende benaderingen van een duurzame stedelijke ontwikkeling.
    Haalbaarheidsstudie "over de bewoonde brug" oostflank Venlo; oplossingen voor de robuuste verweving van infrastructuur en ecologische structuren
    Groot, R. ; Mansfeld, M.J.M. van; Volkerts, A. ; Vreke, J. - \ 2002
    Wageningen : Alterra (Alterra-rapport 591) - 111
    ruimtelijke ordening - infrastructuur - ecologie - wegen - bruggen - integratie - structuur - wildpassages - noord-limburg - ecoduct - ecologische hoofdstructuur - landschapsarchitectuur - landschapsecologie - multifunctioneel ruimtegebruik - Limburg - Venlo - Duitsland - physical planning - infrastructure - ecology - roads - bridges - integration - structure - wildlife passages - noord-limburg
    Haalbaarheidsstudie ecoduct faunapassage. In de robuuste ecologische hoofdstructuur aan de oostflank van Venlo vormt de aanwezige en de toekomstige infrastructuur een knelpunt. Vanuit een offensieve benadering zijn deze ‘grijsgroene kruispunten’ echter geen knelpunt maar een kans. Met slimme meervoudige oplossingen kan meerwaarde bereikt worden voor zowel infrastructuur, natuur en andere belangrijke functies. Een ontwerpatelier heeft zes verschillende oplossingen opgeleverd, met als inzet: het realiseren van een robuuste ecologische verbinding, het verbeteren van de bereikbaarheid en het geven van een grensoverschrijdende impuls in de leefomgevingkwaliteit. In een tweede atelier is de haalbaarheid van de oplossingen getoetst, via het selecteren van criteria en doelstellingen die aansluiten bij beleid. Bestuurders toetsen de plannen en nemen het gedachtegoed verder mee.
    Bosreservaat Mattemburgh : bosstructuur en vegetatie bij aanwijzing tot bosreservaat
    Clerkx, A.P.P.M. ; Schelhaas, M.J. ; Sanders, M.E. - \ 2001
    Wageningen : Alterra (Alterra-rapport 223) - 49
    bossen - beschermde bossen - natuurreservaten - vegetatie - plantensuccessie - luchtfotografie - structuur - nederland - forests - reserved forests - nature reserves - vegetation - plant succession - aerial photography - structure - netherlands
    Bosreservaat Mattemburgh is als een voormalig landgoedbos aangelegd op de Zuidgeester Heide in de periode 1845-1860. Het bos bestaat uit een eerste boomlaag van grove den en een tweede boomlaag met zomereik. De bodemvegetatie wordt gedomineerd door bochtige smele, brede stekelvaren en pijpenstrootje. Na de bosaanleg is het bos nooit gedund. Al het dode hout is in het bos achtergebleven. Het bos is in ontwikkeling naar een zomereikenbos, waarin de rol van beuk voorlopig ondergeschikt is.
    Bosreservaat het Rot : Bosstructuur en vegetatie bij aanwijzing tot bosreservaat
    Clerkx, A.P.P.M. ; Sanders, M.E. ; Jans, W.W.P. ; Bijlsma, R.J. - \ 2001
    Wageningen : Alterra (Alterra-rapport 192) - 41
    fagus sylvatica - quercus petraea - bossen - beschermde bossen - vegetatie - plantengemeenschappen - structuur - bosecologie - bosinventarisaties - nederland - gelderland - fagus sylvatica - quercus petraea - forests - reserved forests - vegetation - plant communities - structure - forest ecology - forest inventories - netherlands - gelderland
    Bosreservaat Het Rot in de Achterhoek bestaat uit een wintereikenbos waarin plaatselijk beuk domineert. Waar wintereik domineert begint beuk vanuit een tweede boomlaag de wintereik te verdringen. Verjonging van wintereik komt niet voor. Plaatselijk is dit het gevolg van lichtconcurrentie door de beuk, maar ook vraat en adelaarsvaren belemmeren een succesvolle verjonging. In de nabije toekomst bestaat de vrees dat de wintereiken zullen verdwijnen, al zijn de beuken op deze natte bodems extra stormgevoelig, waardoor ze minder concurrentiekrachtig zijn
    Soy proteins : nomenclature, composition, structure and functionality
    Vereijken, J.M. - \ 2000
    Industrial Proteins 8 (2000)3. - ISSN 1381-0022 - p. 3 - 5.
    sojaeiwit - peulvruchteiwit - sojabonen - botanische samenstelling - structuur - structuuractiviteitsrelaties - emulgeren - eiwitten - globulinen - literatuuroverzichten - eiwittechnologie - soya protein - legume protein - soyabeans - botanical composition - structure - structure activity relationships - emulsifying - proteins - globulins - literature reviews - protein engineering
    De structuur van de belangrijkste soja-eiwitten is beschreven evenals hun verschil in functionaliteit
    The relationship between molecular structure and ion adsorption on variable charge minerals
    Rietra, R.P.J.J. ; Hiemstra, T. ; Riemsdijk, W.H. van - \ 1999
    Geochimica et Cosmochimica Acta 63 (1999)19-20. - ISSN 0016-7037 - p. 3009 - 3015.
    mineralen - structuur - adsorptie - minerals - structure - adsorption
    Ion adsorption modeling is influenced by the presumed binding structure of surface complexes. Ideally, surface complexes determined by modeling should correspond with those derived from spectroscopy, thereby assuring that the mechanistic description of ion binding scales from the nanoscopic molecular structure to the macroscopic adsorption behavior. Here we show that the structure of adsorbed species is a major factor controlling the pH dependency of adsorption. An important aspect of the pH dependency is the macroscopic proton-ion adsorption stoichiometry. A simple and accurate experimental method was developed to determine this stoichiometry. With this method, proton-ion stoichiometry ratios for vanadate, phosphate, arsenate, chromate, molybdate, tungstate, selenate and sulfate have been characterized at 1 or 2 pH values. Modeling of these data shows that the macroscopic proton-ion adsorption stoichiometry is almost solely determined by the interfacial charge distribution of adsorbed complexes. The bond valence concept of Pauling can be used to estimate this charge distribution from spectroscopic data. Conversely, the experimentally determined proton-ion adsorption stoichiometry allows us to successfully predict the spectroscopically identified structures of, for example, selenite and arsenate on goethite. Consequently, we have demonstrated a direct relationship between molecular surface structure and macroscopic adsorption phenomena.
    Effects of a pulsed treatment with the herbicide afalon (active ingredient linuron) on macrophyte-dominated mesocosms. II. Structural responses
    Geest, G. van; Zwaardemaker, N.G. ; Wijngaarden, W.R. van; Cuppen, J.G.M. - \ 1999
    Environmental Toxicology and Chemistry 18 (1999). - ISSN 0730-7268 - p. 2866 - 2874.
    pesticiden - milieueffect - ecosystemen - structuur - biocenose - sloten - nederland - aquatische ecosystemen - pesticides - environmental impact - ecosystems - structure - biocoenosis - ditches - netherlands - aquatic ecosystems
    Structure, stability and equilibrium (un)folding of flavodoxin
    Steensma, E. - \ 1998
    Agricultural University. Promotor(en): N.C.M. Laane; C.W. Hilbers; C.P.M. van Mierlo. - S.l. : Steensma - ISBN 9789054858300 - 142
    eiwitten - structuur - proteins - structure

    Flavodoxins function as low-potential one-electron carriers using a non-covalently bound FMN cofactor which can exist in three redox states. Flavodoxin structures are characterised by a five-stranded parallelbeta-sheet (orderbeta2-beta1-beta3-beta4-beta5) surrounded byalpha-helices at either side of the sheet. This topology is called the flavodoxin-like fold. In contrast to most folds, the flavodoxin-like fold is shared by many protein superfamilies which are sequentially and evolutionary unrelated.

    Studies on proteins with the flavodoxin-like fold can therefore be utilised to find answers to the so-called protein folding problem which can be captured by the following questions:

    • What is the physical basis of the stability of the folded protein conformation?
    • What processes or pathways determine which of the many possible conformations is the native folded conformation adopted by the protein?
    • What are the rules governing the relation between the amino acid sequence and three-dimensional structure of a protein?
    • Can the three-dimensional structure of a protein be predicted from its amino acid sequence?

    The research described in this thesis has been carried out to obtain a better understanding of the fundamental rules describing protein folding. This thesis focuses on the structure and stability of Azotobacter vinelandii (strain ATCC 478) flavodoxin II (henceforth designated flavodoxin) in its holo- and apoform (i.e. with and without cofactor FMN, respectively). The results obtained for this particular flavodoxin are compared with those for other flavodoxins, as well as with results obtained for sequentially unrelated proteins having a flavodoxin-like fold. The understanding of the equilibrium (un)folding of flavodoxin is a first step in the characterisation of the energy landscape determining the folding of this protein.

    A general introduction on protein folding, NMR spectroscopy and flavodoxins is presented in Chapter 1.

    To prevent dimerisation during structural and folding studies Cys69Ala and Cys69Ser mutants of wild-type flavodoxin were prepared. pH-Dependent semiquinone/hydroquinone redox potentials of wild-type, Cys69Ala and Cys69Ser flavodoxin were determined using cyclic voltammetry and confirmed by EPR-monitored redox titrations. No significant differences in redox properties of wild-type, Cys69Ala and Cys69Ser flavodoxin are observed. The pH dependence of the semiquinone/ hydroquinone redox potentials can be described using a model assuming two redox-linked protonation sites with a constant redox potential at high pH of -485 ± 4 mV. The electrochemical data which are presented in Chapter 2 show that replacement of Cys69 in the vicinity of the FMN by either an alanine or a serine residue do not alter the dielectric properties and structure of holoflavodoxin.

    In Chapter 3, a new doubly sensitivity-enhanced 3D 1H- 15N TOCSY-HSQC experiment is described and analysed using the product operator formalism . The overall gain in signal-to-noise ratio obtained using this doubly sensitivity-enhanced TOCSY-HSQC pulse sequence is, compared to the standard (non-enhanced) sequence, 2.49 or 1.89 for spectra obtained for 15N-labelled or 15N-/ 13C-labelled holoflavodoxin samples, respectively. The main factors leading to the signal-to-noise enhancement are the introduction of two enhanced coherence transfer sequences, the elimination of water presaturation and the inclusion of a water flip-back pulse. Incorporation of gradients for coherence pathway selection, however, leads to a reduction in signal intensity.

    The determination of the solution secondary structure of holoflavodoxin is described in Chapter 4. A five-stranded parallelbeta-sheet (beta2-beta1-beta3-beta4-beta5) is surrounded by fivealpha-helices. The loops extending from the carboxy termini of strandsbeta1,beta3 andbeta4 are involved in FMN binding. Hydrogen/deuterium exchange experiments suggest that (i) amide proton exchange within the core of holoflavodoxin occurs via the apoform of the molecule and that (ii) exchange of the N(3)H proton of FMN only occurs when the cofactor is free in solution. The solvent inaccessibility of the non-polar environment around N(3) could, at least in part, establish the low semiquinone /hydroquinone redox potential. The amide proton exchange rates do not suggest that holoflavodoxin is divided in two subdomains as has been found for the structurally, but not sequentially, homologous protein Che Y. The amide backbone protons of 65 residues and three indole side-chain protons exchange sufficiently slowly (k ex < 10 -5s -1) to be able to perform hydrogen exchange pulse labelling experiments and to study the kinetics of flavodoxin folding in great structural detail.

    The structural characteristics of apoflavodoxin as determined by NMR spectroscopy are presented in Chapter 5. Apoflavodoxin has a stable, well-ordered core consisting of a five-stranded parallelbeta-sheet surrounded by fivealpha-helices. Large parts of holo- and apoflavodoxin have identical conformations and similar internal dynamics. However, the flavin binding region in apoflavodoxin exhibits considerable conformational dynamics. Flexibility is a likely prerequisite to enable the flavin to enter the interior of the apoprotein. Hydrogen/deuterium exchange measurements suggest that the stable nucleus in apoflavodoxin at least comprises residues in strandsbeta1,beta3,beta4 andbeta5a and in helicesalpha4 andalpha5 in the C-terminal part of the protein. We propose that this is a general feature of flavodoxins. In contrast, the stable nucleus of the sequentially unrelated proteins cutinase and Che Y which share the flavodoxin-like fold is not found in their respective C-terminal parts. The amide proton exchange results show that the stable nucleus may be found in different parts of the flavodoxin-like topology. If folding of flavodoxin is initiated with the collapse of the stable nucleus, as has been found for several other proteins, the folding pathways of structurally homologous proteins seem to be unrelated as well.

    Chapter 6 reflects on the research described in this thesis and combines the NMR studies, as described in Chapters 4 and 5, with equilibrium (un)folding studies on apo- and holoflavodoxin using fluorescence and circular dischroism spectroscopy which have been performed by van Mierlo et al. The following picture for equilibrium (un)folding of flavodoxin arises: (i) holoflavodoxin has a compact stable fold consisting of a five-stranded parallelbeta-sheet surrounded by fivealpha-helices; (ii) upon release of the FMN cofactor, apoflavodoxin is formed which has a stable core but a flexible FMN binding region; (iii) in the (un)folding pathway a relatively stable apoflavodoxin folding intermediate is found which is characterised by the loss of tertiary interactions without the complete loss of secondary structure; (iv) the unfolded state of flavodoxin presumably contains some residual structure of an aromatic cluster as a remnant of helixalpha4. The results obtained on the equilibrium (un)folding of flavodoxin are discussed with respect to the implications for the kinetics of flavodoxin folding.

    Predictability of weather regime transitions
    Oortwijn, J. - \ 1998
    Agricultural University. Promotor(en): J. Grasman; J. Barkmeijer. - S.l. : Oortwijn - ISBN 9789054858683 - 116
    klimatologie - structuur - mechanica - atmosfeer - thermodynamica - climatology - structure - mechanics - atmosphere - thermodynamics

    The atmospheric circulation is not completely random. Certain circulation patterns will occur more often than others. The preferred patterns of the atmosphere on time scales of one week to one or more months are called weather regimes. The weather in Europe is for a large part determined by the occurrence of two weather regimes, a blocking regime (a high) and a strong zonal flow regime (a westerly wind). The atmospheric circulation will alternate between these regimes, with transitional intervals in between.

    The transition of one regime to the other can occur very fast, within a couple of days, and is very difficult to predict. In this thesis, the sensitivity in the initial conditions for changes in the regimes a few days later are studied. It appears that the sensitivity fluctuates each day. Flows with a high sensitivity, and a low predictability, are characterized by a strong jetstream to the west of a diffluent flow.

    Formation and stability of foam made from aqueous protein solutions.
    Prins, A. - \ 1997
    Industrial Proteins 4 (1997)2. - ISSN 1381-0022 - p. 3 - 5.
    eiwitten - peptiden - structuur - schuim - schuimen - reologie - fysica - vloeistofmechanica - reologische eigenschappen - moleculaire fysica - proteins - peptides - structure - foams - foaming - rheology - physics - fluid mechanics - rheological properties - molecular physics
    Onderzoek naar de relatie tussen moleculaire structuur van eiwitten en het schuimgedrag van de oplossing
    Wheat bran glucuronoarabinoxylans : biochemical and physical aspects
    Schooneveld - Bergmans, M.E.F. - \ 1997
    Agricultural University. Promotor(en): A.G.J. Voragen; G. Beldman. - S.l. : Schooneveld-Bergmans - ISBN 9789054857167 - 125
    graansoorten - maling - Triticum aestivum - tarwe - hexaploïdie - voedsel - voedingsmiddelen - koolhydraten - zetmeel - vezel - polysacchariden - structuur - chemische reacties - cereals - milling - Triticum aestivum - wheat - hexaploidy - food - foods - carbohydrates - starch - fibre - polysaccharides - structure - chemical reactions

    Arabinoxylans are present in cereal cell walls and in vitro they have interesting physicochemical properties, such as viscosity and gelation. Although many studies on these properties were reported for wheat flour arabinoxylan, not much research has been directed towards exploitation of these polysaccharides as food gum. For that purpose glucuronoarabinoxylans of wheat bran, a cheap by-product of the cereal industry, were studied with regard to their extractability, their structural and physicochemical properties.

    Approximately 50% of the glucuronoarabinoxylans of wheat bran cell wall material were recovered in high purity by barium hydroxide extraction at 70 to 95°C. Delignification or other treatments to open up the cell wall structure were not effective in increasing the yield. The extracted glucuronoarabinoxylans were very diverse in chemical structure and physicochemical properties. About 30% of them had a low degree of substitution, were easily degradable by xylanolytic enzymes and hardly influenced the viscosity of the solvent as a result of extensive aggregation. Over 50% of them had a high degree of substitution, were supposed to contain dimeric branches of arabinose and xylose, were scarcely degradable by xylanolytic enzymes, gave moderate viscosity to solutions and were very effective in stabilizing emulsions. The structure of these glucuronoarabinoxylans could only be speculated upon and it could not be enzymatically modified as a consequence of its complexity and the lack of appropriate enzymes. The remaining glucuronoarabinoxylans either had an intermediate or very high degree of substitution, of which the latter was presumed to be connected to lignin-fragments.

    Gel-forming glucuronoarabinoxylans were recovered only in low yield by dilute alkali extraction and subsequent purification was necessary. These feruloylated glucuronoarabinoxylans gelled upon addition of oxidative agents, of which peroxide - peroxidase, glucose - glucoseoxidase - peroxidase and ammonium persulphate were investigated. In comparison with wheat flour arabinoxylans, those of wheat bran appeared to give less flexible networks at high concentration, which was ascribed to their high degree of substitution and high ferulic acid content. Of the dimers formed upon cross-linking, the generally known diferulic acid, being a 5-5 coupled dimer, was only present in relatively low amounts. Dimers, in which the 8-position of the ferulic acid residue is involved were preponderant. The distribution of the dimers was not affected by the type of cross- linking agent or the type of arabinoxylan. However, the presence of lignin fragments in the bran extract was presumed to cause a low ferulic acid recovery upon cross-linking.

    Glucuronoarabinoxylans from sorghum grain
    Verbruggen, M.A. - \ 1996
    Agricultural University. Promotor(en): A.G.J. Voragen; G. Beldman. - S.l. : Verbruggen - ISBN 9789054855026 - 131
    sorghum bicolor - polysacchariden - structuur - chemische reacties - sorghum - sorghum bicolor - polysaccharides - structure - chemical reactions - sorghum

    Water-unextractable cell wall materials (WUS) were prepared from raw, polished, and malted sorghum ( Sorghum vulgare cv. Fara Fara). Except for the amounts, hardly any difference could be observed between the WUS of these three raw materials. This means that cell wall materials of the endosperm cell walls are basically the same as those of the outer endosperm and pericarp layers, and that the cell walls largely persist, during malting. These preparations were further fractionated by a sequential extraction procedure using aqueous solutions of saturated Ba(OH) 2 , 1M KOH and 4M KOH. The WUS preparations were composed of glucuronoarabinoxylans (GAX), (1→3),(1→4)-β-D-glucans, cellulose, and some protein. GAX was primarily extracted by Ba(OH) 2 solutions. All GAX fractions were composed of a highly substituted (1→4)-β-D-xylan backbone, substituted by arabinose and uronic acid. It was concluded that sorghum GAX populations were characterized by a reasonable homogeneity, since they could not be separated further by several chromatographic and precipitation techniques.

    Degradation studies using purified xylanases, arabinofuranosidases and a glucuronidase alone or in combination, showed that the GAX populations were hardly broken down. Some oligomers were formed by digesting Ba(OH) 2 extracted GAX with a combination of endoxylanase I and (1→4)-β-D-arabinoxylan arabinofuranohydrolase, both purified from Aspergillus awamori . These oligomers were found to have a main chain of three or four xylose units, and to contain α-glucuronic acid linked to O -2 of the non-reducing terminal xylose unit. Two oligomers were found to have a dimeric (1→2)-linked arabinose side, chain linked at O -3 of an internal xylose unit. Also single arabinose substitution occured at O -3 of an internal xylose unit. There are strong indications that these side groups can also be linked at O -2 of an internal xylose residue. The reducing xylose units were unsubstituted. A model for the GAX populations from sorghum was proposed combining the results of the degradation studies, the identification of the oligomers, and knowledge about the mode of action of the enzymes used.

    Finally, the developed techniques to investigate GAX in particular, were used to study the behaviour of GAX in the brewing process. Worts and spent grains of mashes, supplemented with commercial enzyme preparations containing xylanases among others were studied. Except for the amount of solubilized GAX, the GAX hardly changed with respect to the sugar composition and molecular weight distribution. A direct relationship between GAX, xylanases, and filtration behaviour of worts prepared from malted sorghum, could therefore not be established.

    Economische groei, duurzaamheid en emancipatie
    Haagsma, R. - \ 1996
    Den Haag : Emancipatieraad - 70
    luchtverontreiniging - samenstelling - economische groei - werkgelegenheid - milieuwetgeving - milieubeleid - gezinnen - overheidsbeleid - huishoudens - arbeidsmarkt - natuurlijke hulpbronnen - Nederland - bescherming - herstel - hulpbronnengebruik - bodemverontreiniging - structuur - duurzaamheid (sustainability) - waterverontreiniging - vrouwen - vrouwenemancipatie - gelijke behandeling van de vrouw - feminisme - air pollution - composition - economic growth - employment - environmental legislation - environmental policy - families - government policy - households - labour market - natural resources - Netherlands - protection - rehabilitation - resource utilization - soil pollution - structure - sustainability - water pollution - women - emancipation of women - female equality - feminism
    Structural characterization of pectic hairy regions isolated from apple cell walls = Structuurkenmerken van vertakte pectine fragmenten afkomstig van de celwanden van appel
    Schols, H. - \ 1995
    Agricultural University. Promotor(en): A.G.J. Voragen. - S.l. : Schols - ISBN 9789054854050 - 155
    appelsap - pectinen - organische verbindingen - structuur - apple juice - pectins - organic compounds - structure

    Cell wall pectic substances have a great influence on the production and quality aspects of apple juice. Apple juices were characterized by their polysaccharide content and composition. A pectic fraction, retained by ultrafiltration of a liquefaction juice, was isolated and termed MHR (modified hairy regions). MHR, resistant to further enzymic degradation by the liquefaction enzymes, was characterized using chemical and enzymic methods. Next to a high arabinose content, this fraction was characterized by a high rhamnose to galacturonic acid ratio and a high acetyl content. Rhamnogalacturonase (RGase), an enzyme able to hydrolyze galacturonic acid-(1->2)-rhamnosyl linkages within the rhamnogalacturonan backbone, was purified and characterized.

    Next to high molecular weight degradation products, rhamnogalacturonase released characteristic oligosaccharides from MHR. Various 2D-NMR techniques were used to identify these RGase oligomers, which consisted of a tetrameric or hexameric backbone of alternating rhamnose and galacturonic acid residues with a galactose residue substituted at C-4 of part of the rhamnose moieties.

    Analogous MHR fractions were isolated from potato fibre, pear, carrot, leek, and onion tissue, although variations occurred with respect to the arabinose and xylose content. All MHR fractions were degraded by RGase in a comparable fashion resulting in the same type of oligomers in an almost equal ratio.

    Comparison of the MHR with non-modified pectic hairy regions of apple cell wall, isolated in a mild and defined way, revealed great resemblance indicating that the modifications of the MHR during enzymic liquefaction were only minor. The oligomers liberated by RGase from the various pectic hairy regions differed in absolute as well as in relative amount.

    After degradation by RGase of the highest molecular weight population of apple MHR, three subunits were characterized representing a xylogalacturonan segment, residual stabs of the backbone rich in arabinose and regions of alternating rhamnose-galacturonic acid residues of unknown length. The substitution of xylose residues and methylestergroups over the galacturonan backbone was studied by NMR and was found to be random.

    De marginalisering van het gezin aan het einde van de 20ste eeuw: een poging tot opheldering van een hardnekkig misverstand.
    Hoog, K. de - \ 1995
    Wageningen : LU - 22
    samenstelling - gezinnen - huishoudens - verwantschap - colleges (hoorcolleges) - nederland - sociologie - structuur - composition - families - households - kinship - lectures - netherlands - sociology - structure
    Oligosacchariden als bifidogene factoren.
    Hartemink, R. ; Nout, M.J.R. ; Rombouts, F.M. - \ 1994
    Voedingsmiddelentechnologie 27 (1994)20. - ISSN 0042-7934 - p. 27 - 29.
    bifidobacterium - koolhydraten - chemische reacties - microbiële afbraak - polysacchariden - structuur - bifidobacterium - carbohydrates - chemical reactions - microbial degradation - polysaccharides - structure
    Levende bacterien die een gunstige invloed hebben op de darmflora. Ze worden probiotica genoemd en ze worden toegepast in zowel de humane voeding als de veevoeding
    Duurzame verzorging als technologische uitdaging.
    Terpstra, M.J. - \ 1994
    Wageningen : Landbouwuniversiteit Wageningen - 29
    samenstelling - economische ontwikkeling - milieu - milieubeheer - milieubescherming - gezinnen - huishoudkunde - huishoudens - colleges (hoorcolleges) - bedrijfsvoering - natuurlijke hulpbronnen - bescherming - kwaliteit - herstel - hulpbronnengebruik - plattelandsontwikkeling - sociale ontwikkeling - sociale voorzieningen - sociaal welzijn - structuur - duurzaamheid (sustainability) - technische vooruitgang - technologie - theorie - welzijnsvoorzieningen - milieuwetenschappen - natuurwetenschappen - organisatie - wetenschap - sociaal werk - composition - economic development - environment - environmental management - environmental protection - families - home economics - households - lectures - management - natural resources - protection - quality - rehabilitation - resource utilization - rural development - social development - social services - social welfare - structure - sustainability - technical progress - technology - theory - welfare services - environmental sciences - natural sciences - organization - science - social work
    Tailor-made produktie van oligosacchariden.
    Laere, K.M.J. van; Schols, H.A. ; Voragen, A.G.J. - \ 1994
    Voedingsmiddelentechnologie 27 (1994)20. - ISSN 0042-7934 - p. 33 - 35.
    koolhydraten - chemische reacties - chemische structuur - chemicaliën - voedselindustrie - voedseltechnologie - polysacchariden - eigenschappen - structuur - invloeden - carbohydrates - chemical reactions - chemical structure - chemicals - food industry - food technology - polysaccharides - properties - structure - influences
    De gewenste oligosacchariden kunnen met behulp van specifieke enzymen en chromatografische technieken 'op maat' worden gemaakt
    Vrouwen, huishouden en krediet in West Java.
    Niehof, A. - \ 1994
    Huishoudstudies 4 (1994)2. - p. 3 - 12.
    samenstelling - krediet - kredietbeleid - economie - werkende vrouwen - werkgelegenheid - gezinnen - vrouwelijke arbeidskrachten - gezinsinkomen - huishoudens - individuen - Java - hypotheken - hulpbronnen - besparingen - structuur - vrouwen - vrouwelijke werknemers - werk - composition - credit - credit policy - economics - employed women - employment - families - female labour - household income - households - individuals - Java - mortgages - resources - savings - structure - women - women workers - work
    Aan de hand van resultaten van een project in West Java dat de ondersteuning van inkomensgenererende activiteiten van vrouwen tot doel had, komt aan de orde wat economische activiteit en inkomen voor vrouwen en hun huishoudens betekenen en welke strategische rol krediet vervult
    De prijsgevoeligheid van huishoudelijk watergebruik.
    Kooreman, P. - \ 1993
    ESB Economisch Statistische Berichten 78 (1993). - ISSN 0013-0583 - p. 181 - 183.
    luchtverontreiniging - samenstelling - consumentengedrag - consumptie - drinkwater - dumping - milieuwetgeving - milieubeleid - gezinnen - overheidsbeleid - huishoudkunde - huishoudelijke consumptie - huishoudens - marktconcurrentie - Nederland - prijszetting - prijzen - kwaliteit - bodemverontreiniging - structuur - aanbod - kraanwater - waterverontreiniging - watervoorziening - prijsbepalende factoren - sanitaire voorzieningen - air pollution - composition - consumer behaviour - consumption - drinking water - dumping - environmental legislation - environmental policy - families - government policy - home economics - household consumption - households - market competition - Netherlands - price fixing - prices - quality - soil pollution - structure - supply - tap water - water pollution - water supply - price determining factors - sanitary facilities
    Het kabinet wil het mogelijk maken dat huishoudens een rekening krijgen voor waterverbruik, rioolrechten en zuiveringsheffing. De hoogte van die rekening moet geheel afhankelijk zijn van de hoeveelheid water die het huishouden verbruikt. De achterliggende gedachte hierbij is dat dit mensen ertoe zal aanzetten zuiniger met water om te springen. Hoe prijsgevoelig is het huishoudelijk waterverbruik?
    The bending elasticity of surfactant monolayers and bilayers and its effect on the swelling of free liquid films
    Barneveld, P.A. - \ 1991
    Agricultural University. Promotor(en): J. Lyklema; J.M.H.M. Scheutjens. - S.l. : Barneveld - 150
    grensvlak - film - structuur - samenstelling - interface - film - structure - composition

    The present study was carried out to obtain more insight into the unusual swelling behaviour of surfactant layers. Here, swelling means that the thickness of the water layer between two surfactant layers increases. It was shown recently that high salt concentrations can bring about swelling in aqueous multilayer vesicles and free liquid films of nonionic surfactants (polyoxyethylenated n-dodecyl alcohols). By this so-called salt-induced swelling the water layer becomes thicker up to relatively high salt concentrations (1-2 kmole/m 3), reaches a maximum and, beyond these concentrations, shrinks again. In multilayer vesicles, the maximum swelling can be substantial (extreme swelling): the water layer thickness can easily be 10 times the surfactant layer thickness.

    Until now, an explanation for salt-induced swelling in terms of interaction forces between the surfactant layers was not available. The Van der Waals force is relatively unaffected by the ionic strength of the water layer. On the basis of steric repulsion, shrinking is expected due to salting-out of the ethylene oxide head groups of the nonionic surfactant. This could explain the decreasing part of the swelling curve. A problem with this explanation is that the bilayers in the vesicles are too far apart for the head groups to interact. When pushed to extremes, electrostatic repulsion could lead to some swelling if salt ions adsorb specifically onto the surfactants. In that case, as a function of salt concentration two regimes can be distinguished: in low concentrations the electrostatic double layer is built up by an increasing surface charge, leading to swelling, whereas in high salt concentrations the double layer is compressed, leading to shrinking. In chapter 3 this mechanism is shown to be quantitatively insufficient to account for the thickness variation of free liquid films, let alone for the extreme swelling in multilayer vesicles.

    Helfrich has suggested that thermal undulations of nearby surfactant layers provide an additional steric repulsion between the layers. Since this is a long range force, it could be responsible for the extreme swelling in multilayer vesicles. Quantitative analyses are required to test this suggestion. A parameter that dominates the magnitude of the Helfrich force is the mean bending elasticity modulus of the surfactant layer involved: a small modulus implies strong undulations and hence, large repulsions. The presence of a surface tension restricts the undulations. The surface tension of vesicles is negligible, but that of a film is significant. However, monolayers are thinner than bilayers and hence may be less rigid so that undulations can still be large enough to affect the film thickness.

    A major part of the present study is the modelling of surfactant monolayers and bilayers, with the aim to calculate bending moduli from the solution properties of the surfactants (see chapters four and five). Based on these calculations, it was predicted that the thickness of free liquid films containing n-alcohol instead of salt would show qualitatively the same trends if Helfrich repulsion is responsible for the salt-induced swelling. The experimental verification of this prediction is described in chapter six. The results agree very well with the proposed influence of undulations.

    De inkomensvorming en de inkomensverdeling in de Nederlandse landbouw verklaard vanuit de huishoudproduktietheorie
    Elhorst, J.P. - \ 1990
    Den Haag : LEI - ISBN 9789052420950 - 179
    landbouw - landbouwbeleid - inkomen - inkomsten uit het landbouwbedrijf - inkomensverdeling - huishoudens - gezinnen - structuur - samenstelling - familiebedrijven, landbouw - nederland - economische sectoren - agrarische bedrijfsvoering - econometrie - inkomensbeleid - vermogensverdeling - landbouw als bedrijfstak - agriculture - agricultural policy - income - farm income - income distribution - households - families - structure - composition - family farms - netherlands - economic sectors - farm management - econometrics - income policy - wealth distribution - agriculture as branch of economy
    In dit verslag wordt een model ontwikkeld om de inkomensvorming en de inkomensverdeling in de Nederlandse landbouw te verklaren. Factoren die daarbij de aandacht krijgen zijn: de prijzen van produkten en vlottende produktiefactoren, produktiequota, de inzet van kapitaalgoederen en gezinsarbeid, de ondernemerskwaliteit, afschrijvingen op kapitaalgoederen, de wijze van bedrijfsfinanciering, inkomsten van buiten het bedrijf, belastingen en premies. Het ontwikkelde model is toegepast op de akkerbouw, de melkveehouderij en de varkenshouderij
    Werkloze hoofdkostwinners in Friesland en hun omgang met geld.
    Ophem, J.A.C. van - \ 1990
    Tijdschrift voor huishoudkunde 11 (1990)3. - ISSN 0169-1295 - p. 65 - 72.
    budgetten - samenstelling - uitgaven voor consumptie - consumptie - gezinnen - huishoudelijke consumptie - huishouduitgaven - huishoudens - inkomen - armoede - sociale structuur - sociaal welzijn - sociologie - structuur - werkloosheid - financieel beheer - friesland - nationaal vermogen - personen - vermogensverdeling - budgets - composition - consumer expenditure - consumption - families - household consumption - household expenditure - households - income - poverty - social structure - social welfare - sociology - structure - unemployment - financial management - friesland - national wealth - persons - wealth distribution
    Bespreking van een onderzoek naar de economische omstandigheden en het arbeidsmarktgedrag van langdurig werklozen in Friesland
    Financieel management en het conventionele huishouden.
    Ophem, J.A.C. van; Knippers, E.W. - \ 1990
    Tijdschrift voor huishoudkunde 11 (1990)1. - ISSN 0169-1295 - p. 15 - 19.
    samenstelling - consumptie - gezinnen - financiële planning - huishoudens - nederland - armoede - structuur - financieel beheer - nationaal vermogen - vermogensverdeling - composition - consumption - families - financial planning - households - netherlands - poverty - structure - financial management - national wealth - wealth distribution
    Daar moet ik alles mee doen : portretten van mensen met een minimum-uitkering
    Kullberg, J. ; Goossens, R. ; Vos, E. de - \ 1990
    Nederhorst den Berg : Variant - ISBN 9789064485244 - 126
    samenstelling - consumptie - gezinnen - huishoudens - inkomensverdeling - laag inkomen - nederland - structuur - financieel beheer - personen - vermogensverdeling - composition - consumption - families - households - income distribution - low income - netherlands - structure - financial management - persons - wealth distribution
    De huishouding van minima, een onderzoek naar de huishoudvoering van ontvangers van RWW, ABW, AOW.
    Goossens, R.C. ; Vos, E.L. de; Hoog, C. de; Ophem, J.A.C. van - \ 1990
    Wageningen : Landbouwuniversiteit - ISBN 9789067541749 - 269
    samenstelling - gezinnen - huishoudens - inkomensverdeling - laag inkomen - nederland - structuur - financiële ondersteuning - materiële hulp - personen - vermogensverdeling - composition - families - households - income distribution - low income - netherlands - structure - financial support - material assistance - persons - wealth distribution
    Agrarische huishoudens : een onderzoek naar de veranderende relatie tussen gezin en bedrijf in Oost - Gelderland
    Zwart, S.I. - \ 1990
    Agricultural University. Promotor(en): G.A. Kooy. - S.l. : Zwart - ISBN 9789067541756 - 240
    huishoudens - gezinnen - statistiek - familiebedrijven, landbouw - structuur - samenstelling - agrarische bedrijfsvoering - sociologie - verwantschap - boeren - nederland - gelderland - achterhoek - households - families - statistics - family farms - structure - composition - farm management - sociology - kinship - farmers - netherlands - gelderland - achterhoek
    This study of farm family households in the east of The Netherlands is based on a field survey carried out in spring 1984. Rapid changes in the structure and processes of agriculture in the Netherlands since the 1950's and radical change in the family, notably with relation to sex roles, have caused increasing political and academic concern for the future and the viability of family farming. This has also led to women's position in agriculture being subjected to much discussion and increasing scholarly interest. These, the most important motives for initiating this study, are outlined in the first chapter, together with the most important post-war changes in Dutch agriculture. This chapter also includes a review of the literature on the changing forms and functions of family and marriage and of women's position in family and society and it ends by discussing the implications of these changes for farm families and farm women.

    The second chapter presents a detailed description of the study. It includes a definition of the research problem, a description of its theoretical basis, concepts and hypotheses, an explanation of the design of the study and finally a description of the construction of the questionnaires and the sampling and data collection methods.

    Farm family households are social institutions composed of complex networks of interwoven and mutually dependent roles. The family and the farm enterprise are thus seen as interdependent social subsystems. This view of the farm family household yields the first main theme of this study: how family and farm are intertwined. The way in which this interconnectedness is shaped, its specific form, is subject to change because it is linked to the particular historical, social and cultural environment in which it is situated.

    This view of the farm family household leads on to an elaboration of the second main theme of this study: the sexual division of labour and decisions. The way in which husband and wife divide or share labour and decisions in various domains is not an isolated phenomenon. In this study it is interpreted as an aspect of family structure. Until recently the way in which families divided work and decisions was subject to traditional sex role ideology. Husband and wife, father and mother, farmer and farmer's wife were roles with relatively well defined rights and obligations. But during the last 30 years this normative structure has been weakening and other factors are becoming more important in determining how marital roles take shape.

    By placing the two main themes of this study (the way in which family and farm are intertwined and the sexual division of labour and decisions) within the context of societal change, the differences found in farm couples in these two respects can be interpreted as ultimately resulting from general processes of change as they relate to agriculture and marriage and the family. For theoretical as well as for common sense reasons four complexes of factors were selected for this study: factors related to farm characteristics and agricultural change; sex role ideologies; the household cycle; and socio-demographic characteristics. Consequently an eclectic research model emerged, and the following basic research questions were formulated.

    1) Are there differences between farm family households in the way family and farm are intertwined? And, if so, which variables cause these differences?
    2) Are there differences between farm family households in the way husband and wife divide labour and decisions in various domains? And, if so, which variables cause these differences?
    3) What is the relationship between the way family and farm are intertwined and the way in which husband and wife divide labour and decisions?

    The fieldwork for this study was carried out in Winterswijk local government area, situated in the east of the province of Gelderland. This particular local government area was chosen because several studies were done in the fifties, describing its agriculture and its farm family households, and these provided valuable baseline data. A stratified sample of 92 farm couples younger than 65 years on farms larger than 5 ha was drawn, evenly divided over various ages. Husband and wife were interviewed at the same time but independently from each other, using two partly overlapping, partly different standardized questionnaires.

    In chapter three a brief history of the community of Winterswijk is given. Various characteristic features of the region are outlined and the correspondence between Winterswijk and other regions in the Netherlands in terms of agriculture, farms, families and households is discussed. The farms and farming do not differ greatly from those elsewhere in the country. Until recently, traditional multigeneration family households were relatively numerous in this region, whereas in most other regions in The Netherlands the nuclear family household was the dominant pattern. In the fifties about half of Winterswijk's farm households consisted of members of three or four generations living communally in the same house.

    In chapter four a descriptive analysis of the farm family households and their farms is presented. The first section deals with socio- demographic characteristics and household features such as age, education, religious affiliation, household composition, life cycle, neighbourhood bonds, and participation in professional and social organizations. Since the fifties, nuclear families have gradually loosened the close ties with their relatives, the church and the neighbourhood in a process which is generally described as family nuclearization and individualization. Nuclear families of successive generations nowadays have their separate living arrangements, even though they remain working together on the same farm. Families have closed, in the sense that they tolerate less interference in family matters from relatives, neighbours and church. Farmers and farmers' wives are more strongly oriented toward the world beyond their own community than their counterparts 30 years ago. For instance the strong preference for a marriage partner from the same neighbourhood, the same church and the same socio-economic background that was typical in the older generation seems to be gradually diminishing with the younger.

    The sex role ideologies of the farm couple are also discussed. Opinions on women's place in family and society were measured on an attitudinal scale. It seems that women hold more modern sex role orientations than men. Moreover, younger women and those with a better education have more modern sex role orientations; to a lesser degree so do women who have more contact with agricultural extension officers. For the farmers, age and education were the most important determinants of their sex role orientations, and their religious affiliation was slightly less important.

    Next, the farms and the changes that have occurred in the 1950's are discussed. On average the farms have a cultivated area of 17 ha. The larger holdings generally specialize in dairy farming, the smaller ones often specialize in pigs or combine the two. Since the fifties considerable specialization, intensification, mechanization, and economies of scale have taken place and the influence of agro- industry and banking has increased. Consequently, rational economic considerations have assumed increasing importance in farming. Nevertheless the family is still central to the continuity of the farm enterprise.

    The farmers and their wives were asked how these changes of the last 40 years affected their satisfaction with their lives and their work. Men and women agreed on the most important aspects. Although farmwork is less physically demanding nowadays, the psychlogical pressure under which they have to work is greater. Both women and men experience more personal freedom and less control from the social environment. On the other hand, life moves at a faster pace and there is little time and very little opportunity for relaxed social contacts. The men in particular relatively frequently expressed feelings of social isolation. In contrast, women seemed to have gained more freedom for social participation and for orientation on the outside world, e.g. for further education and training and for joining clubs and organizations. The evaluations of the men and the women also differ. Women in particular experienced living with the older generation as an intrusion on their privacy and consequently as a heavy burden. Separating the households of the younger and the older generations and converting the farmhouse into separate dwellings for each family contributed greatly to their feeling of personal freedom. For the men the traditional living arrangements (generally with their own parents) carried less weight. Furthermore, it is noteworthy that the farmers more often referred to the higher standard of living but also to financial problems. Although some women did mention economic pressures such as rising costs and taxes, in general the financial problems of the farm signified less of a burden to them than for their husbands. All in all the data suggest that according to their own evaluations, the women benefited more than did the men from the changes that have taken place since the fifties.

    Chapter four goes on to deal with the way family and farm are interwoven, by examining which aspects form a coherent and consistent pattern. These were: the spatial arrangements (i.e. the layout of the house and farm buildings) on-farm sale of products (retail), the use of a fixed household budget, separate bank accounts for household and farm enterprise, marriage settlements, and the legal form of the farm enterprise. Based on the aspects as mentioned, a mean interweave score was computed, which was used in the further analyses.

    The last section of this chapter describes farm couples' division of labour and decisions in a number of domains and also deals with the number of hours both spouses spend on household chores and farm work. The women do by far the larger share of the housework. On average farmers' wives spend 43 hours weekly on household chores including childcare; they get little help from others. The farmers spend an average of 1.7 hours per week on housework. On average, farmers spend 60 hours weekly on farm work, doing by far the largest share. All the women interviewed work on the farm for a number of hours per week, for an average of 20 hours per week. So, husband and wife have more or less equally long working days. Sons who will eventually succeed their fathers on the farm, also contribute considerably to the farm work. Daughters rarely do farm work, and the contributions of other family members are also negligible. Most of the farmers' wives have one or more fixed chores; typically these are feeding the calves and pigs, cleaning the sheds, milking parlour and milking equipment and, less frequently, milking. Other fixed chores women frequently perform and assume responsibility for are "cord keeping, financial administration, receiving telephone calls and running errands. Seen from the angle of the woman's life cycle, the following work pattern emerges. During the first years of marriage (or from the moment the couple starts cohabitating) before children are born, the young woman remains working in her original job. (Most of the women worked in the service sector and had not had any training in agriculture.) In many cases the woman's father-in-law, and sometimes also her mother in law, is still working along with the woman's husband . During the stage when children are born, the woman quits her off-farm job and gradually takes on a few farm chores. Sometimes she tries to catch up on her technical agricultural knowlegde of agriculture by following training courses. When the children reach primary school age her share in the farm work increases considerably as her father-in-law gradually withdraws. Her share in the farm work is reduced again when one of her children who will eventually take over the farm starts working with the father.

    In this study the farm couples' division of labour and decisions is envisaged as role enactment in various domains, i.e. the household, the social and recreational domain, emotional and expressive domain and the farm. The tasks and decisions relating to childcare were not treated as a separate domain but were divided between the other domains. Three dimensions of the division of labour and decisions were distinguished. As well as studying the relative participation of husband and wife in the tasks of the domains mentioned above, the role specialization versus role flexibility and the stereotypy of the role performance were dealt with. Starting from these domains and dimensions, the division of tasks and decisions among farm couples can be outlined as follows. The overall picture has a certain symmetry. Both the farmer and his wife operate in a more or less autonomous fashion in one domain, the women performing most of the household chores and the farmers most of the farm work, more or less along the lines of the traditional indoor/outdoor pattern. In contrast, the other domains are characterized much more by working together, sharing, flexibility and exchange, although traces of a traditional pattern remain here too, notably so in the emotional expressive domain. Decision making is shared to a larger extent. In the household domain the woman usually makes the decisions on daily matters that do not have major financial consequences, and the farmer makes the decisions on daily affairs concerning the farm. Typically major decisions within both domains are made jointly. At first sight this pattern corresponds with the traditional division of labour among urban middle-class married couples in the fifties. The highly specialized indoor/outdoor, housewife/breadwinner division of labour and joint decision making was typical of this pattern. In the farm households studied, I found a similar balance, although women seem to wield more control in farm matters than the farmers exercise over the household. Some of the women were visibly active in farm matters, doing fixed chores on a daily basis. In contrast, the farmers tend to help their wives with household chores, without assuming responsibilities of their own. On the other hand the data suggest that a certain degree of mutual adjustment between family and farm does indeed occur, but that it is the women who do most of the adjusting, adapting themselves to the demands of the farm.

    In the fifth chapter the hypotheses that were formulated at the outset of the study are explored and tested. In accordance with the design of the study, it explores the way sex role attitudes, farm characteristics, household cycle and social-demographic and participation variables explain the variation in how the spheres of family and farm are intertwined and how labour and decisions are divided between the farm couples. Finally the relationships between the two dependent variables are examined. It turned out that the way in which family and farm are intertwined is especially is connected with the economic inportance (Dutch farm size unit) of the farm enterprise. In the larger farms the delimitations in all aspects of both spheres were much sharper. Also, the intergenerational transfer of the farm and the ways the generations overlap, i.e. the ways in which they organize their living and housing arrangements and cooperate at the various stages of the life cycle, are very important to the concept of intertwinement of family and farm. However this concept cannot be understood in terms of economic and socio- structural factors only, but is also connected with cultural values. The nature of the interconnection between family sphere and farm aspects is shaped, is also connected to the couple's sex role ideologies. Couples with more egalitarian attitudes delineated sharper boundaries between family and farm.

    As regards the division of labour and decisions it first appeared that every dimension considered in this study has a specific pattern of relationships with the explanatory variables. The same holds true for the different domains. Each of the domains identified in the design of the study has its own dynamics and rules. So, even though there is in a sense, a certain spatial fusion of farm and household tasks in farm family households, especially as as far as women's work is concerned, these tasks cannot be regarded as a homogeneous continuum divided between farmer and wife according to the same logic. In the household domain as well as in the social and recreational and emotional-expressive domains, sex role ideologies are important determinants for the way tasks and decisions are divided.

    Concomitantly, the results of the survey indicate that a change toward a more symmetrical, flexible and non-stereotyped pattern is gradually taking place, with the younger and better educated couples showing a more modern pattern in all three dimensions. Relationships are not as clear cut for the farm tasks and decisions. Sex role attitudes play an important part here too, as becomes clear from the fact that women's work is largely restricted to chores in and around the farm buildings. However, no clearcut trend is discernable. The division of farm labour and decisions is strongly connected with the stage that has been reached in the intergenerational transfer of the farm, and on how the generations work and live together and on the corresponding characteristics of the farm. On farms where men of two generations (father and son) work together, the women play less active roles in farm affairs. In addition, the greater efficiency of the farm production process also fits in with a pattern of division of farm labour and decisions in which women tend to participate less.

    When the tasks and decisions of all the domains are considered, it appears that the woman's level of education and the efficiency of the organization of the production process both for milk and pigs, best predict an egalitarian, flexible and non-stereotyped way of dividing tasks and decisions. In other words, role enactment in farm family households can be understood from the way the farm production process is organized as well as from the age of the farm couple, which is an important indicator of peoples' sex role attitudes.

    As regards the relationship between the way family and farm are intertwined and the role enactment of farm couples, it is suggested that the processes of change taking place in both phenomena are part of a more comprehensive process of change and modernization in which attitudes towards farm organization and farm management probably also play a part.

    In chapter six the most important conclusions are summarized and reviewed in the light of the future of farm family households and women's position on the farm and in agriculture in the Netherlands. A number of theoretical aspects are questioned and some recommendations for agricultural and social policy are made.

    The problems and opportunities facing farm households in the Netherlands in the future, and the viability of the family farm are discussed within the context of how family and farm are intertwined. It is pointed out that farm family households should be viewed as dynamically adapting themselves to changing agriculture and society at large. Many failed to keep their place in agriculture in the post- war period. Those that succeeded transformed the traditional family patterns, modernized their farms and farm management and were able to adjust the two spheres in such a fashion that vital, contemporary units emerged, able to cope with the current situation and its problems. This vitality augurs well for the survival of the family farm. In the long term farm family households may be confronted with an increasing number of difficulties, and as a consequence they may find it increasingly difficult to redefine the relationships and the intertwinement of farm and family spheres. The future of family farming not only depends on current problems in agriculture and on its political, economic and technological conditions, but also on processes of change affecting marriage and the family, which can form a potential threat to the family farm. Phenomena like individualization, the loosening of family ties and increasing instability in marital relations may put the family farm under serious pressure in the future.

    To date, policymakers and extension officers have neglected the family context of agricultural enterprises, focusing instead on the model of a rational economic enterprise. Family matters are treated as separate, private aspects that are only indirectly related to the business enterprise. Family issues are not generally an object of agricultural policy, and policy makers tend to see marriage and the family in terms of traditional stereotypes. A better understanding of the interconnectedness of family and farm, as described in this study, promotes a realistic vision of family farming and benefits scholars, agricultural extension agencies and policy makers.

    The changes that have taken place in farm family households in the Nether~ lands since the fifties largely conform with the process of family nuclearization or individualization as outlined in mainstream family sociology. However, farm family households differ from the general picture in two respects. In the first place, in about half the families surveyed strong bonds exist between the generations, both spatially as well as in terms of intergenerational cooperation. Secondly, the farm family household can be conceived of as a multifunctional institution, which is a unit of consumption as well as a unit of production. In the context of mainstream family sociology these phenomena should be conceived of as a cultural lag, as somewhat archaic traits that will disappear in due course. However, this study suggests that family relationships in farm family households are in essence not traditional phenomena at all but should rather be viewed as idiosyncratic relations and functions. The way in which the intertwinement between family and farm is shaped in the farm family household, can be viewed as a dynamic answer to societal change. Consequently, the standard sociological view of farm families as essentially traditional is too narrow and needs to be revised.

    The position of the majority of women in Dutch agriculture is to a considerable degree defined by their marriage. As long as the family farm remains the dominant social context for agricultural production and as long as farms continue to be passed on from father to son, women's place in agriculture will remain primarily a derived one, embedded as it is in the family context. Farm women do not have an occupational status of their own. As well as pointing at this fundamental constant, this study highlights some of the marked changes that have taken place in the lives of farmers' wives. Some of these changes are connected with agricultural change, but others are related to women's position in family and society. These changes have had farreaching consequences on the type and the amount of farm work done by the women and on their household work, as well as on the general context of their everyday life.

    No major discontent with this situation was observed in this study. But future developments may bring some change to this situation. An increasing number of farmers' wives may continue their own career, but those who opt for a place on their husband's farm will increasingly claim better defined positions, with mutual rights and obligations delimited and accounted for formally. Also, an increasing number of women will want to farm in their own right, that is independent of their family and/or husband. Although in each of these three situations the woman's relationship to the farm is different, her position can be expected to become more problematic in the future. Therefore it is important for farm couples to face up to the formal material, economic and legal aspects of their relationship. Future farm couples would be well advised to agree formally on their mutual rights and obligations, not only regarding the farm but also regarding income-earning activities, and the household and childrearing. Although this advice conflicts with romantic values like unity and harmony, this study has made clear that both the couple's relationship and the farm business will benefit from this modern 'marriage de raison'.

    Zuinigheid met vlijt bouwt huizen als kastelen.
    Hoog, C. de - \ 1989
    Tijdschrift voor huishoudkunde 10 (1989)4. - ISSN 0169-1295 - p. 101 - 104.
    samenstelling - consumptie - gezinnen - huishoudens - laag inkomen - armoede - structuur - financieel beheer - nationaal vermogen - personen - vermogensverdeling - composition - consumption - families - households - low income - poverty - structure - financial management - national wealth - persons - wealth distribution
    Beschouwing over armoede in relatie tot huishoudelijk handelen
    Huishoudens en inkomensdaling, enkele facetten uit een studie.
    Ophem, J.A.C. van - \ 1989
    Tijdschrift voor huishoudkunde 10 (1989). - ISSN 0169-1295 - p. 79 - 86.
    budgetten - samenstelling - uitgaven voor consumptie - consumptie - gezinnen - huishoudelijke consumptie - huishouduitgaven - huishoudens - bevolking - inkomen - laag inkomen - nationale bestedingen - structuur - financieel beheer - personen - budgets - composition - consumer expenditure - consumption - families - household consumption - household expenditure - households - human population - income - low income - national expenditure - structure - financial management - persons
    Bespreking van : enige resultaten van een onderzoek naar reacties van huishoudens op inkomensachteruitgang in het begin van de jaren tachtig in Nederland; het belang van de huishoudeconomische rationaliteit en de confrontatie met onverwachte gebeurtenissen; de tracering van potentieel kwetsbare huishoudens
    'Sociale aspecten van voeding onderschat'
    [Unknown], - \ 1988
    Voedingsinformatie : bestemd voor mensen die voorlichting geven over voeding 11 (1988)1. - ISSN 0165-7496 - p. 1 - 3.
    samenstelling - consumptiepatronen - voorlichting - gezinnen - voedsel - voedselsamenstelling - voedselhygiëne - voedingsmiddelen - huishoudens - informatiediensten - voedingseducatie - voedingsinformatie - voedingstoestand - voedingswaarde - eigenschappen - kwaliteit - structuur - composition - consumption patterns - extension - families - food - food composition - food hygiene - foods - households - information services - nutrition education - nutrition information - nutritional state - nutritive value - properties - quality - structure
    Een gesprek met mevrouw Edema over voedingsvoorlichting en het belang van sociologische aspecten rond voeding
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