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.

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Belo Molares presentation film English
Durksz, Durk - \ 2017
pretreatment - biomass - fermentation - gas production - machines - biobased economy
Systematic planning and cultivation of agricultural fields using a geo-spatial arable field optimization service: Opportunities and obstacles
Bruin, S. de; Lerink, P. ; Riviere, I.J. la; Vanmeulebrouk, B. - \ 2014
Biosystems Engineering 120 (2014). - ISSN 1537-5110 - p. 15 - 24.
margins - biodiversity - landscape - farmland - machines - guidance - coverage - habitat
This paper describes a geo-spatial arable field optimization service (GAOS) and an assessment of users' experiences after three years of experimental operation. The service was developed in close cooperation with farmers. It allows farmers to optimize the locations of tracks within their fields, explore different options and download these to commercial Global Navigation Satellite System-guided steering systems. GAOS runs as a web service using standards defined by the Open Geospatial Consortium and is being operated by a group of farmers who received a few hours of training. The objective of optimization is to maximize efficiency by avoiding both inefficient turns and discontinuous swaths. Where applicable, released space is converted into field margins that meet environmental objectives and potentially generate additional income. The system provides dedicated functionality for geometrical operations, such as uploading and splitting of fields, merging and splitting of field edges, and manual editing of reference lines in the headlands. Acknowledged beneficial features include reduced expenditures on time and wasted resources and support for planning spraying paths. Given its complexity, most farmers preferred specialists to operate the system rather than operating it themselves. Future development should aim for simpler operation and full support for interactive coverage planning as well as computational optimization.
Vergelijking van de bodembelasting bij agrarisch veldwerk in 1980 en 2010
Vermeulen, G.D. ; Verwijs, B.R. ; Akker, J.J.H. van den - \ 2013
Wageningen : Plant Research International, Business Unit Agrosysteemkunde (Rapport / Plant Research International 501) - 38
bodemfysica - gronddruk - bandenspanning - belasting (loads) - bodemstructuur - landbouwwerktuigen - machines - akkerbouw - vollegrondsteelt - soil physics - ground pressure - inflation pressure - loads - soil structure - farm machinery - arable farming - outdoor cropping
De doelstelling van de hier gerapporteerde studie was om te onderzoeken of de bodembelasting door verschillende typen landbouwmachines in de afgelopen 30 jaar inderdaad toegenomen is, zoals wordt verondersteld. Het begrip bomdembelasting wordt gebruikt voor zowel het drukpatroon op de bodem onder de wielen van machines (bodemdruk) als voor de daardoor veroorzaakte drukken op verschillende dieptes in de grond (grondspanningen). In het rapport wordt eerst de ontwikkeling van de bodemdruk van verschillende machines geïnventariseerd. Het bodemdrukpatroon wordt hoofdzakelijk bepaald door de wiellast, het type band, de bandenmaat en de banddruk (luchtdruk in de band). Om de belasting van de ondergrond te karakteriseren werd met de uit de machinegegevens afgeleide drukpatronen onder de wielen berekend wat de piekspanningen op 25, 40 en 50 cm diepte in de ondergrond waren, in 1980 en 2010.
Willy Wortels tegen het onkruid
Janmaat, L. ; Bleeker, P.O. - \ 2011
Ekoland 32 (2011)10. - ISSN 0926-9142 - p. 12 - 13.
onkruidbestrijding - mechanische bestrijding - akkerbouw - biologische landbouw - innovaties - innovatie adoptie - machines - landbouwtechniek - weed control - mechanical control - arable farming - organic farming - innovations - innovation adoption - agricultural engineering
Zodra de herbiciden in de kast blijven, is de akkerbouwer aangewezen op mechanische onkruidbestrijding en aanvullend handmatig wiedwerk. Ieder gewas vraagt weer om een om een specifieke aanpak. Inventieve telers ontwerpen hun eigen werktuigen, en soms nieuwe methoden.
Inzet van de beetle eater succesvol
Hamont, J. van; Broek, R.C.F.M. van den - \ 2011
Ekoland 32 (2011)10. - ISSN 0926-9142 - p. 8 - 8.
plagenbestrijding - plantenplagen - insectenplagen - mechanische bestrijding - coleoptera - asparagus - stengelgroenten - vollegrondsgroenten - landbouwtechniek - machines - pest control - plant pests - insect pests - mechanical control - stem vegetables - field vegetables - agricultural engineering
In de aspergeteelt is de asperge kever Crioceris asparagi een bekend insect, en dan niet in positieve zin. Een omgebouwde machine maakt korte metten met hem.
Tuinders investeren vooral in machines en werktuigen
Meer, R.W. van der - \ 2007
Agri-monitor 2007 / 13 (2007)3. - ISSN 1383-6455
tuinbouw - investering - werktuigen - landbouwwerktuigen - landbouwtechniek - glastuinbouw - machines - energiebesparing - horticulture - investment - implements - farm machinery - agricultural engineering - greenhouse horticulture - energy saving
De investeringen in de tuinbouw, zowel opengronds- als glastuinbouw, lagen in 2005 net boven de 1 miljard euro. Daarmee werd iets meer geïnvesteerd dan in het voorafgaande jaar. Er werd vooral geïnvesteerd in machines, werktuigen en installaties. De glastuinbouw richt zich daarbij met name op energiesparende technieken, zoals scherminstallaties en warmtekrachtinstallaties
Volop mogelijkheden voor nog minder middelgebruik (interview; thema Mechanisatie en spuittechniek; bijlage)
Jagers op Akkerhuis, F. ; Os, E.A. van - \ 2007
Groenten en Fruit. Algemeen 2007 (2007)28. - ISSN 0925-9694 - p. 2 - 3.
gewasbescherming - teeltsystemen - dosering - spuitapparaten - innovaties - technieken - oogsten - kassen - mechanisatie - automatisering - robots - stapelmachines - sorteren - sorteermachines - palletiseermachines - glastuinbouw - machines - plant protection - cropping systems - dosage - sprayers - innovations - techniques - harvesting - greenhouses - mechanization - automation - stackers - sorting - sorters - palleting machines - greenhouse horticulture
Themanummer over mechanisatie en spuittechniek, met daarin de volgende artikelen; -1. Volop mogelijkheden voor nog minder middelgebruik -2. 'Intelligent' oogsten biedt winst -3. Veelzijdige stapelrobot verlicht het werk enorm
Nieuwe machines voor mechanische onkruidbestrijding in de gewasrij van geplante zaaiuien
Bleeker, P.O. - \ 2006
Kennisakker.nl 2006 (2006)15 april.
uien - mechanisatie - onkruidbestrijding - landbouwtechniek - schoffelmachines - biologische landbouw - gewasbescherming - machines - akkerbouw - zaai-uien - onions - mechanization - weed control - agricultural engineering - steerage hoes - organic farming - plant protection - arable farming - spring-sown onions
Veronkruiding in de rij (ook wel aangeduid met de term ("intra-rij veronkruiding") is vooral bij de biologische teelt van uien een groot probleem. Maar ook bij veel andere gewassen in de biologische teelt is onkruidbestrijding in de rij bijzonder moeilijk. Bestaande mechanisatie is tot nog toe onvoldoende in staat gebleken om dit probleem op te lossen. Daardoor gaat de teelt van uien gepaard met een groot aantal handwieduren. De hiervoor benodigde menskracht is een beperkende factor. Daarnaast maakt dit veel teelten bijzonder duur. Oplossingen voor het intra-rij onkruidprobleem bij de teelt van uien zijn onontbeerlijk om de biologische teelt op termijn voldoende perspectief te bieden. Recentelijk zijn een aantal machines/prototypen ontwikkeld die waardevol voor de onkruidbestrijding in de biologische teelt kunnen zijn. Dit is een samenvatting van het rapport "Mechanische onkruidbestrijding geplante zaaiuien", er is een link naar dit rapport aanwezig.
Machines voor beheer van natte graslanden; een studie naar de kosten van beheer van natte en vochtige graslanden met aangepaste machines
Jong, J.J. de; Schaafsma, A.H. ; Aertsen, E.J.M. ; Hoksbergen, F.T.J. - \ 2003
Wageningen : Alterra (Alterra-rapport 747) - 45
bodems van waterrijke gebieden - veenmoerassen - overstroomde gronden - graslandbeheer - machines - wetland soils - bogs - flooded land - grassland management
In dit rapport is een studie beschreven naar aangepaste machines voor het maaien van natte graslanden. Er zijn onder verschillende omstandigheden tijdstudies verricht naar de machines. Op basis van informatie van de eigenaren van de machines zijn tarieven berekend. Daarnaast is informatie verzameld over het verwerken van maaisel. Onder beheerders van natte graslanden zijn de ervaringen met het gebruik van de verschillende machines geonventariseerd.
Extruder goed toepasbaar voor continue extractie en deegkneden
Stegeman, D. ; Luyten, H. - \ 2000
Voedingsmiddelentechnologie 33 (2000)7. - ISSN 0042-7934 - p. 30 - 32.
uitpersing - verwerking - broodbereiding - brood - vloeistofmechanica - prestatieniveau - kwaliteit - reologie - visco-elasticiteit - uitrusting - voedselindustrie - voedseltechnologie - productieprocessen - machines - extrusion - processing - breadmaking - bread - fluid mechanics - performance - quality - rheology - viscoelasticity - equipment - food industry - food technology - production processes
De voortdurende ontwikkeling van de apparatuur zorgt voor een continue uitbreiding van de toepassingsmogelijkheden van de extrusietechnologie. De werking van het extrusie-extractieproces is behandeld en schematisch weergegeven
Robots rukken langzaam maar zeker op
Hendrix, A.T.M. - \ 1999
Vakblad voor de Bloemisterij 54 (1999)35. - ISSN 0042-2223 - p. 48 - 49.
verwerking - productie - automatisering - robots - glastuinbouw - machines - processing - production - automation - greenhouse horticulture
Kenschetsing van ontwikkelingen in de automatisering en robotsisering in de glasgroenten en snijbloemen
Kverneland Packomat vergeleken met conventionele vorenpakkers
Kregmeier, B.J. ; Kouwenhoven, J.K. - \ 1999
Landbouwmechanisatie 50 (1999)4. - ISSN 0023-7795 - p. 30 - 31.
grondbewerking - ruggenploegen - voren - zaaibedbereiding - bodemverdichting - zandgronden - machines - tillage - ridgers - furrows - seedbed preparation - soil compaction - sandy soils
Resultaten van een onderzoek naar de verdichtende werking van verschillende vorenpakkers op zandgrond
Geen problemen met biologisch afbreekbare olie
Straelen, B.C.P.M. van - \ 1998
Tuin en Park Techniek 5 (1998)3. - ISSN 1380-3212 - p. 22 - 23.
green belts - public gardens - management - lubrication - lubricants - plant oils - plant fats - apparatus - cooling - cleaning - protection - cooling systems - sustainability - machines - groene zones - publieke tuinen - bedrijfsvoering - smering - smeermiddelen - plantaardige oliën - plantaardige vetten - apparatuur - koelen - schoonmaken - bescherming - koelsystemen - duurzaamheid (sustainability)
IMAG-DLO heeft de gebruiksmogelijkheden van biologisch afbreekbare smeermiddelen voor hydraulische en gecombineerde transmissie en hydraulische olie in 4 trekkers onderzocht
Rekenprogramma voor het voeren van bijproducten aan vleesvarkens
Wagenberg, C. van; Brakel, C. van; Scholten, R. - \ 1997
Praktijkonderzoek varkenshouderij 11 (1997)2. - ISSN 1382-0346 - p. 12 - 12.
samenstelling - computers - kostenanalyse - gegevensverwerking - microcomputers - minicomputers - varkens - machines - composition - cost analysis - data processing - pigs
Een vleesvarkenshouder wil vaak snel een indicatie hebben of een bepaald graan- of bijproductenrantsoen aantrekkelijk is voor zijn bedrijf. Het Praktijkonderzoek Varkenshouderij heeft hiervoor een rekenprogramma ontwikkeld dat snel en eenvoudig de totale kostprijs berekent van een willekeurig rantsoen voor een individueel vleesvarkensbedrijf.
De Marke gebruikt hoofdreinigingsoplossing een maand laag!
Verstappen-Boerekamp, J.A.M. - \ 1997
Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 10 (1997)4. - ISSN 1386-8470 - p. 21 - 24.
watergebruik - schadepreventie - melkmachines - componenten - apparatuur - koelen - schoonmaken - bescherming - smering - koelsystemen - desinfectie - machines - water use - loss prevention - milking machines - components - apparatus - cooling - cleaning - protection - lubrication - cooling systems - disinfection
Sinds mei 1995 wordt op De Marke een systeem getest, waarbij de hoofdreinigingsoplossing meerdere keren wordt gebruikt voor reiniging en desinfectie van de melkleiding; voorraadreiniging genoemd. Het blijkt mogelijk de hoofdreinigingsoplossing een maandlang te gebruiken, zonder gevolgen voor melkkwaliteit. Door voorraadreiniging bespaart De M.e per jaar 65 m 3 water en 300 l reinigingsmiddel. De melkkwaliteit blijft uitstekend.
Let op bandenspanning bij berijden grasland!
Wouters, B. ; Everts, H. ; Dijkstra, B. - \ 1997
Praktijkonderzoek Rundvee, Schapen en Paarden. Praktijkonderzoek 10 (1997)1. - ISSN 1386-8470 - p. 10 - 11.
karren - deformatie - droge stof - graslanden - veengronden - bodem - bodemverdichting - bodemstructuur - trailers - banden - belastingskenmerken (grond) - machines - carts - deformation - dry matter - grasslands - peat soils - soil - soil compaction - soil structure - tyres - bearing characteristics
Het verlagen van de bandspanning vergroot de mogelijkheden voor het berijden zoals bleek uit onderzoek op veengrasland. Ook het berijden van grasland op zware klei bij sub-optimale omstandigheden blijkt nadelig voor de grasopbrengst.
Lagedrukbanden effectief tegen bodemverdichting
Akker, J.J.H. van den - \ 1997
Landbouwmechanisatie 48 (1997)2. - ISSN 0023-7795 - p. 14 - 15.
karren - deformatie - bodem - bodemverdichting - bodemdegradatie - bodemstructuur - trailers - banden - belastingskenmerken (grond) - machines - carts - deformation - soil - soil compaction - soil degradation - soil structure - tyres - bearing characteristics
Uit onderzoek naar bodemverdichting en structuurbederf blijkt dat het gebruik van lagedrukbanden aantrekkelijk is. Wel moet de gebruiker de bandenspanning laag houden
Simulatie van de communicatie op landbouwwerktuigen.
Hofstee, J.W. ; Goense, D. - \ 1997
Agro Informatica 10 (1997). - ISSN 0925-4455 - p. 11 - 16.
automatische regeling - automatisering - voertuigen zonder bestuurder - landbouwwerktuigen - landbouwbedrijven - mechanisatie - operatie - afstandsbediening - standaardisering - normen - bedrijfsinformatiesystemen - procesbewaking - machines - automatic control - automation - driverless vehicles - farm machinery - farms - mechanization - operation - remote control - standardization - standards - management information systems - process control
Door de landbouwwerktuigenindustrie is CAN gekozen als veldbus voor communicatie op landbouwwerktuigen. In het artikel zal eerst de structuur van de communicatie uiteengezet worden. Vervolgens wordt ingegaan op een simulatieprogramma dat geschreven is om verschillende netwerk configuraties en implementaties door te rekenen ten aanzien van de snelheid van data overdracht
Biopreservation in modified atmosphere packaged vegetables
Bennik, M.H.J. - \ 1997
Agricultural University. Promotor(en): F.M. Rombouts; L.G.M. Gorris. - S.l. : Bennik - ISBN 9789054858089 - 96
uitrusting - verpakking - verpakkingsmaterialen - verpakken - planten - dieren - behoud - machines - equipment - packaging - packaging materials - packing - plants - animals - preservation
<br/>Recent trends in food preservation are the use of mild preservation techniques, such as modified atmosphere (MA) packaging and refrigeration, to prolong the shelflife of foods without affecting the fresh character of the product. This has resulted in the development of a new generation of chill stored, minimally processed foods, such as vegetables that are packaged under reduced oxygen (0 <sub><font size="-1">2</font></sub> ) and elevated carbon dioxide (C0 <sub><font size="-1">2</font></sub> ) concentrations. These gas atmospheres in combination with refrigerated storage conditions reduce the respiration rates of these products, and can limit the growth of endogenous spoilage bacteria, thereby rendering prolonged shelflives as compared with storage under ambient conditions. Although MA packaged vegetables have a fair safety record, they may incidently harbor foodborne pathogens. Especially the outgrowth of psychrotrophic (cold tolerant) pathogens can be considered a safety concern, but quantitative data on their growth under MA conditions that are suitable for produce are essentially lacking. Detailed information on the outgrowth of both pathogens and vegetable-associated spoilage bacteria under these conditions may give better insight into possible antagonistic action of competing microflora on the growth of pathogens, and the development of adequate countermeasures toward their growth to hazardous levels.<p>One of the objectives of the studies that are described in this thesis was to obtain information on the impact of refrigerated MA storage conditions on the growth of microorganisms on minimally processed, MA packaged produce. Since our initial studies substantiated the possible hazard which can be posed by psychrotrophic pathogens, the use of biopreservation for adequate control of these microorganisms was investigated. In this respect, we have focused on lactic acid bacteria (LAB) because they occur naturally on fresh and minimally processed vegetables, and are able to produce a variety of antimicrobial substances, amongst which bacteriocins.<p><strong>Chapter 1</strong> gives a short introduction on the technology of MA packaging of minimally processed vegetables and their current microbiological safety and quality status. Furthermore, the possible role of LAB as biopreservation agents in foods is addressed with special emphasis on those strains that are able to produce bacteriocins. The characteristics and mode of action of different bacteriocins that are produced by LAB are described, as well as aspects which are relevant to the application of these antimicrobial compounds or their producing organisms as food preservatives.<p>Detailed information on the impact of refrigerated MA storage on the population dynamics of the endogenous microflora on vegetables is limited. Therefore, the prevailing epiphytic microorganisms on model produce ( <em>i.e</em> . chicory endive, and mungbean sprouts) were identified before and after MA storage. Subsequently, the growth characteristics of the predominant spoilage bacteria were determined under MA conditions ( <strong>Chapter 2</strong> ). It was found that the major strains on both products were <em>Enterobacteriaceae</em> and <em>Pseudomonas</em> species. There were changes in the prevalent species on chicory endive before and after MA storage, but this was not observed for mungbean sprouts. To quantify the influence of C0 <sub><font size="-1">2</font></sub> and 0 <sub><font size="-1">2</font></sub> on the growth of the individual spoilage bacteria, a model agar system was developed that mimicked the <em>in situ</em> growth of bacteria on the surface of vegetables. The analysis of the growth of the predominant strains under controlled 0 <sub><font size="-1">2</font></sub> and C0 <sub><font size="-1">2</font></sub> concentrations at 8°C indicated that, in general, lag times were not present under the various conditions tested, and that the maximum population sizes were not affected. However, the maximum specific growth rates generally decreased with increasing C0 <sub><font size="-1">2</font></sub> concentrations, which was independent of the 0 <sub><font size="-1">2</font></sub> concentrations applied. This effect was more pronounced for <em>Pseudomonas</em> species than for <em>Enterobacteriaceae.</em> Representatives of the former subpopulation already showed significantly reduced maximum specific growth rates at C0 <sub><font size="-1">2</font></sub> concentrations that are suitable for MA packaged vegetables.<p>In <strong>Chapter 3</strong> , the effects of different 0 <sub><font size="-1">2</font></sub> and C0 <sub><font size="-1">2</font></sub> concentrations on the growth of <em>Aeromonas hydrophila, Yersinia enterocolitica, L. monocytogenes,</em> and a cold tolerant strain of <em>Bacillus cereus</em> were quantified in the above mentioned model agar system at 8°C. Again, the maximum specific growth rates of the various microorganisms decreased significantly with increasing C0 <sub><font size="-1">2</font></sub> concentration, while the maximum population densities were not affected and lag times were not observed. Extrapolation of the results from the model system to MA packaged vegetables suggested that growth of the above pathogens may occur at 8°C to the same maximum population densities as compared to ambient conditions, but at 10 to 20% lower maximum specific growth rates. Because we have shown that MA packaging can only moderately retard the growth of psychrotrophic pathogens, these bacteria can be considered a safety hazard to which countermeasures need to be developed.<p><em>L. monocytogenes is</em> a relevant psychrotrophic pathogen on minimally processed vegetables that requires adequate control measures. This Gram-positive bacterium can be inhibited by a number of bacteriocins that are produced by LAB. Thus, biopreservation using bacteriocin producing LAB strains may effectively prevent the growth of this bacterium, and possibly other psychrotrophic pathogens. With respect to practical application, an effort was made to obtain bacteriocinogenic LAB from minimally processed vegetables since these strains might be best adapted to the specific conditions under which their antimicrobial activity is required. Out of a total of 890 LAB isolates from mungbean sprouts and chicory endive, only nine strains were found to produce bacteriocins ( <strong>Chapter 4</strong> ). Three of these strains exhibited antimicrobial activity towards a wide variety of Gram- positive bacteria, including the foodborne pathogens <em>L.</em><em>monocytogenes,</em> and <em></em> nonproteolytic Clostridium botulinum. Two of these bacteriocinogenic isolates were identified as Pediococcus parvulus on the basis of fermentation patterns and ribotyping. Recombinant DNA experiments revealed the presence of the pediocin PA-1 gene in both LAB strains, and further biochemical analysis confirmed the production of pediocin PA-1 in absence of other bacteriocins.<p>The third broad spectrum bacteriocin-producing strain was identified as <em>Enterococcus mundtii</em> ( <strong>Chapter 5</strong> ). Its bacteriocin was purified to homogeneity and characterized. Elucidation of the complete primary amino acid sequence revealed a novel bacteriocin of 43 amino acids (M <sub><font size="-2">r</font></sub> 4287.2), designated as mundticin, that belongs to the class <strong>IIa</strong> bacteriocins of LAB. Other LAB that produce this class of antimicrobial peptides have previously been isolated from a wide variety of meat and dairy products, and their apparent wide-spread occurrence in foods may allow for the selection of strains that are ecologically adapted to specific food environments.<p>As further described in <strong>Chapter 5</strong> , mundticin exhibited bactericidal activity towards <em>L.</em><em>monocytogenes,</em> and was shown to dissipate the membrane potential of whole cells, and to deplete their intracellular ATP pools. Mundticin was selected as a prototype of class <strong>IIa</strong> bacteriocins to investigate the biophysical properties of this peptide by molecular computer analysis. It was found that mundticin and related bacteriocins, contain a central α-helical region that was predicted to insert at an angle of 30 to 50° in a simulated hydrophobic/hydrophilic interface. This oblique insertion is proposed to cause a destabilisation of the phospholipid bilayer and facilitate the insertion and/or aggregation of monomers into functional pores in the cytoplasmic membrane. This concept is of interest for the rational design of bacteriocins with, for example, better biopreservation properties.<p>For the effective application of bacteriocins as biopreservation agents, it is essential to gain more insight into the variation in the susceptibility of Gram-positive bacteriocins towards bacteriocins. The comprehensive study that is described in <strong>Chapter 6</strong> addresses several factors which are associated with the natural variability in the bacteriocin-sensitivity of closely related non- bacteriocinogenic LAB. Two sets of strains for which the minimal inhibitory concentrations for nisin and pediocin PA-1 differed 100 to 1000-fold were compared. Our data provide evidence that the association of bacteriocins with the cell membrane and their subsequent insertion into the membrane take place in a similar way for cells that have a high or a low natural bacteriocin tolerance. For insensitive strains, the overall constitution of the membrane, rather than the mere membrane fluidity, may preclude the formation of pores with sufficient diameters and lifetimes to ultimately cause cell death. Further analysis of this phenomena may require more attention for the structural role of proteins in biological membranes.<p>The last part of this dissertation comprises a study on the potential of the vegetable- associated bacteriocin-producing bacteria and mundticin to act as biopreservation agents on refrigerated, MA-stored vegetables ( <strong>Chapter 7</strong> ). Both <em>P. parvulus</em> strains were found to be unsuitable for this purpose, due to the lack of bacteriocin production at 4 and 8°C. By contrast, <em>E. mundtii</em> displayed a number of characteristics that favor an application as a biopreservative agent, such as limited acid production, production of a bacteriocin with anti-listeria activity at low temperatures, and high growth rates under MA conditions. Despite these properties, this strain failed to effectively inhibit the growth of <em>L. monocytogenes</em> on fresh mungbean sprouts. This is probably not due to a lack of <em>in situ</em> bacteriocin production, but rather the result of proteolytic degradation of mundticin or the growth of <em>L. monocytogenes</em> cells that are resistant to mundticin. Experiments with mundticin in a washing step and as a component of a coating were successful and warrant further research on the potential of this compound as a natural preservative agent for minimally processed vegetables.<p>In conclusion, this dissertation has contributed to a better understanding of the microbiological characteristics of minimally processed vegetables that are stored under MA conditions. A general concern for the possible outgrowth of psychrotrophic pathogens on MA stored vegetables was substantiated by our investigations, which stresses that hygienic cultivation and processing conditions of this type of products remain indispensable. Although bacteriocins cannot be used as the sole preservatives to enhance the safety of refrigerated MA-stored minimally processed vegetables, they can contribute to tackle safety problems that may arise from certain cold tolerant, Grampositive pathogens.
Use-oriented courseware development for agricultural education : an ecological approach
Blom, J.J.C. - \ 1997
Agricultural University. Promotor(en): J. van Bergeijk; J.C.M.M. Moonen. - S.l. : Blom - ISBN 9789054857051 - 296
computers - onderwijs - lesmaterialen - minicomputers - microcomputers - gegevensverwerking - onderwijzen - opleiding - vrije tijd - landbouw - agrarisch onderwijs - nederland - machines - education - teaching materials - data processing - teaching - training - leisure - agriculture - agricultural education - netherlands
<p>This thesis investigates the disappointing use of computers and courseware in Dutch agricultural education. The central question is: How to develop courseware that will be used by teachers in agricultural education practice? On the basis of a theoretical frame of reference and by means of two case studies, the use of courseware in the context of Dutch agricultural education is described, understood and explained; and use influencing factors are established. Prescriptions are formulated that reckon with these factors and presumably increase the likelihood of use in practice. In two additional case studies, both the process and the organisation of courseware development for Dutch agricultural education are described, understood and explained. On the basis of this understanding, the prescriptions, phrased in the two preceding case studies, are adjusted and extended. The resulting prescriptions fit into five categories:<br/>a) courseware should address needs<p>b) courseware should lead to lower costs of use<br/>c) courseware development should match teacher learning<br/>d) courseware development should reckon with contexts of use<br/>e) courseware development should be organised in manner that facilitates use<br/>increasing development<p>Essentially, the formulation of these use-increasing prescriptions as described above amounts to tailoring the courseware-development process to the context in which the courseware will be used. For this process of tailoring, insight is needed in the contingencies between courseware- development characteristics and the attributes of a context of use. These contingencies are described in the last chapter of this thesis. Risk prevention is the most important argument in selecting a specific courseware-development characteristic for a given context.<p>In this research, this tailoring process is applied to Dutch agricultural education. The resulting alternative and supposedly use-increasing approach of courseware development can be characterised as situation specific, teacher-driven, and processoriented. Important domains of expertise are those of subject matter, of teachers as users, of project and educational innovation management and of instructional design. This approach combines a small scale with a high level of ambition. This approach is termed ecological since insights from ecology offer instructive analogies that for courseware development can be phrased as follows. Courseware may offer a wide range of educational improvements, the contexts of use determine the quality characteristics of viable courseware applications. Consequently, characterising, a viable courseware application implies describing its context of use.
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