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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Bodemsignalen grasland: praktijkgids voor bodemmanagement op melkveebedrijven
Eekeren, Nick van; Philipsen, Bert ; Bokhorst, Jan ; Berg, Coen ter - \ 2019
Zutphen : Roodbont Publishers - ISBN 9789087402433 - 112
Post-fire soil erosion mitigation at the scale of swales using forest logging residues at a reduced application rate
Prats, Sergio A. ; González-Pelayo, Óscar ; Silva, Flavio C. ; Bokhorst, Koen J. ; Baartman, Jantiene E.M. ; Keizer, Jan J. - \ 2019
Earth Surface Processes and Landforms 44 (2019)14. - ISSN 0197-9337 - p. 2837 - 2848.
effectiveness - erosion - mulch - organic matter - wildfire

Mulching with forest residues has proved to be highly effective in reducing post-fire soil losses at the plot scale. However, its effectiveness has not been quantified at the application rates that are typically used in operational post-fire land management (2–3 Mg ha-1 using straw), as well as at scales larger than 100 m2. The present study compared post-fire erosion rates for six convergent hillslopes or swales of 500 to 800 m2, three of which were left untreated while the other three were mulched immediately after the fire with shredded eucalypt bark at a rate of 2.4 Mg ha-1. Erosion rates were monitored at irregular intervals during the first three post-fire years, whilst ground cover was assessed yearly. Selected topsoil properties (0–2 cm) such as organic matter content and aggregate stability were determined at a single occasion – two years after the wildfire, for three micro-environments separately: bare soil, and under mulch/litter and vegetation. Soil losses on the untreated swales decreased with post-fire year from 2.2 to 0.4 and 0.11 Mg ha-1 yr-1 (respectively for the first, second and third post-fire years), while the mulched swales produced 84%, 77% and 38% less soil losses than the untreated swales. Soil losses also depended on slope aspect, with the north-facing swales producing less erosion than the west-facing ones. This could be linked to their significant differences in bare soil, vegetation and stone cover, or a combination thereof. The type of micro-environment also played a significant role in topsoil properties (stone content, bulk density, resistance to penetration/shear stress, porosity and organic matter content). The present results add to the increasing evidence that forest residues should be duly considered for operational post-fire land management. Forest residues were highly effective in reducing erosion from swales at application rates as low as the typical 2 Mg ha-1 of post-fire straw mulch.

Controlling Listeria
Verkleij, T.J. ; Bokhorst-van de Veen, H. van - \ 2019
Voedingsindustrie : vakblad 26 (2019)mei. - ISSN 2213-5758 - p. 14 - 17.
Beheersen van Listeria : Risicoproducten onder de loep
Verkleij, T.J. ; Bokhorst-van de Veen, H. van - \ 2019
Voedingsindustrie : vakblad 26 (2019)mei. - ISSN 2213-5758 - p. 14 - 17.
Inactivation of conidia from three Penicillium spp. isolated from fruit juices by conventional and alternative mild preservation technologies and disinfection treatments
Nierop Groot, Masja ; Abee, Tjakko ; Bokhorst-van de Veen, Hermien van - \ 2019
Food Microbiology 81 (2019). - ISSN 0740-0020 - p. 108 - 114.
Food spoilage - Minimal processing - Penicillium - Shelf life control - Spore resistance - Surface decontamination

Fungi are able to grow on diverse food products and contribute to food spoilage worldwide causing food loss. Consumers prefer freshly squeezed fruit juices, however, the shelf life of these juices is limited due to outgrowth of yeast and fungi. The shelf life of pulsed electric field (PEF) treated juice can be extended from 8 days up to a few weeks before spoilage by moulds becomes apparent. Conidia produced by three Penicillium ssp. (Penicillium expansum, Penicillium buchwaldii and Penicillium bialowiezense), previously isolated from spoiled PEF treated fruit juice and smoothie, were characterized for resistance towards selected mild physical processing techniques in orange juice and toward sanitizers on surfaces. The results show that Penicillium spp. conidia are susceptible to mild heat, high pressure pasteurization (HPP), PEF, cold atmospheric plasma (CAP), UV, and chemical sanitizers chlorine dioxide and hypochlorite albeit with different susceptibility. Treatment with mild heat, HPP, PEF, or chlorine dioxide reduced conidia by more than 5 log. For hypochlorite, UV, and CAP the reduction was between 1 and 3 log. Together, this study provides data for the development of intervention strategies to eliminate spoilage mould conidia in fruit juices.

Characterization of four Paenibacillus species isolated from pasteurized, chilled ready-to-eat meals
Helmond, M.T.J. ; Nierop Groot, M.N. ; Bokhorst-van de Veen, H. van - \ 2017
Strategies to control Penicillium spp. spoilage in fruit juices by determining their susceptiblitiy to mild preservation techniques
Zhu, F. ; Abee, T. ; Nierop Groot, M.N. ; Bokhorst-van de Veen, H. van - \ 2017
The efficacy of chemical sanitizers on the reduction of Salmonella Typhimurium and Escherichia coli affected by bacterial cell history and water quality
Banach, J.L. ; Bokhorst-van de Veen, H. van; Overbeek, L.S. van; Zouwen, P.S. van der; Fels, Ine van der; Nierop Groot, M.N. - \ 2017
Food Control 81 (2017). - ISSN 0956-7135 - p. 137 - 146.
Bacterial attachment - Cross-contamination - Leafy greens - Pathogen inactivation - Starvation - Water disinfection

Washing fresh produce with potable water helps to remove microorganisms, providing about a 1- to 2-log reduction, but this process can also pose an opportunity for cross-contamination of bacteria in the washing tank. The objective of this study was to evaluate the efficacy of three chemical sanitizers, sodium hypochlorite, chlorine dioxide, and a silver-copper solution on the reduction of S. Typhimurium and extended-spectrum beta-lactamase (ESBL) E. coli as well as to evaluate the impact bacterial cell history and water quality had on sanitizer efficacy. This was investigated with three scenarios representing different contamination routes and history of cells: (i) on starved and non-starved cells in potable water, (ii) on starved and non-starved cells in lettuce wash water and on lettuce leaf punches, and (iii) on non-starved cells in organically loaded process wash water (PWW). Sodium hypochlorite (NaClO) and chlorine dioxide (ClO2) were more effective in preventing cross-contamination in the potable water than the silver-copper solution. Starved and non-starved bacterial cells displayed minor differences in their susceptibility to sanitizing agents in the (i) potable water and (ii) lettuce wash water demonstrating that other conditions greater influenced sanitizer efficacy. Particularly, the organic load of the water, wash water temperature, and pathogen attachment and release from the produce were shown to affect a sanitizer's efficacy during washing. Furthermore, results emphasize that chemical sanitizer use should focus more on wash water disinfection, rather than produce decontamination, to prevent pathogenic cross-contamination during processing. Future research should investigate the feasibility of ClO2 application during pilot-scale processing.

Characterization of four Paenibacillus species isolated from pasteurized, chilled ready-to-eat meals
Helmond, Mariette ; Nierop Groot, Masja N. ; Bokhorst-van de Veen, Hermien van - \ 2017
International Journal of Food Microbiology 252 (2017). - ISSN 0168-1605 - p. 35 - 41.
Growth limits - Paenibacilli - Shelf life control - Spore heat resistance

Food spoilage is often caused by microorganisms. The predominant spoilage microorganisms of pasteurized, chilled ready-to-eat (RTE) mixed rice-vegetable meals stored at 7 °C were isolated and determined as Paenibacillus species. These sporeforming psychrotrophic bacteria are well adapted to grow in the starch-rich environment of pasteurized and chilled meals. Growth of the Paenibacillus isolates appeared to be delayed by decreased (< 7 °C) temperature or chilled temperature (7 °C) combined with decreased pH (< 5), increased sodium chloride (> 5.5%, corresponding with an aw < 0.934), or decreased aw (< 0.931; using sucrose). To gain insight in the effect of the pasteurization processing of the meal on spore inactivation, heat-inactivation kinetics were determined and D-values were calculated. According to these kinetics, pasteurization up to 90 °C, necessary for inactivation of vegetative spoilage microorganisms and pathogens, does not significantly contribute to the inactivation of Paenibacillus spores in the meals. Furthermore, outgrowth of pasteurized spores was determined in the mixed rice-vegetable meal at several temperatures; P. terrae FBR-61 and P. pabuli FBR-75 isolates did not substantially increase in numbers during storage at 2 °C, but had a significant increase within a month of storage at 4 °C or within several days at 22 °C. Overall, this work shows the importance of Paenibacillus species as spoilage microorganisms of pasteurized, chilled RTE meals and that the meals' matrix, processing conditions, and storage temperature are important hurdles to control microbial meal spoilage.

Overview of Food Safety Hazards in the European Dairy Supply Chain : Food safety hazards in the dairy chain
Asselt, E.D. Van; Fels, Ine van der; Marvin, H.J.P. ; Bokhorst-van De Veen, H. Van; Nierop Groot, M. - \ 2017
Comprehensive Reviews in Food Science and Food Safety 16 (2017)1. - ISSN 1541-4337 - p. 59 - 75.
Monitoring of dairy products should preferably focus on the most relevant food safety hazards in the dairy supply chain. For this purpose, the possible presence of microbiological, chemical, and physical hazards as well as trends in the dairy supply chain that may affect their presence were assessed. A literature review was combined with available data from EFSA, RASFF, and the Dutch monitoring program on chemical hazards as well as expert information. This study revealed that microbiological hazards are encountered more frequently in dairy products than chemical and physical hazards. Listeria monocytogenes, Staphylococcus aureus, Salmonella, and human pathogenic Escherichia coli were identified as the most important microbiological hazards in dairy products. Soft and semisoft cheeses are most frequently associated with L. monocytogenes and S. aureus enterotoxins, whereas raw milk is most frequently associated with human pathogenic E. coli and Campylobacter spp., Cronobacter spp., and Salmonella spp. are the microbiological hazards of most concern in powdered infant formula. Based on literature, monitoring, and RASFF data, the most relevant chemical hazards in dairy products are aflatoxin M1, dioxins, and dioxin-like compounds and residues of veterinary drugs. Chemical hazards primarily occur at the dairy farm and may accumulate during further processing. The most relevant physical hazards are metal, glass, and plastic particles introduced during processing. Analysis of trends in the near future revealed that increased milk production is seen as most relevant in relation to food safety. Other trends affecting food safety are climate change and changes at the farm level, which aim to improve animal welfare and environmental sustainability.
Microbiologische gevaren in de pluimveevleesketen : Een literatuurstudie met additionele informatie van stakeholders
Bokhorst-van de Veen, Hermien van; Hazeleger, Wilma ; Nierop Groot, Masja ; Vollebregt, Martijntje ; Zwietering, Marcel - \ 2015
Wageningen : Wageningen UR Food & Biobased Research (Rapport / Wageningen UR Food &amp; Biobased Research 1567) - ISBN 9789462575165 - 76
Microbial hazards in the dairy chain : A literature study
Bokhorst-van de Veen, Hermien van; Minor, Marcel ; Zwietering, Marcel ; Nierop Groot, Masja - \ 2015
Wageningen : Wageningen UR Food & Biobased Research (Wageningen UR Food &amp; Biobased Research report 1553) - 93
How lovebirds maneuver rapidly using super-fast head saccades and image feature stabilization
Kress, Daniel ; Bokhorst, Evelien Van; Lentink, David - \ 2015
PLoS ONE 10 (2015)6. - ISSN 1932-6203 - 24 p.

Diurnal flying animals such as birds depend primarily on vision to coordinate their flight path during goal-directed flight tasks. To extract the spatial structure of the surrounding environment, birds are thought to use retinal image motion (optical flow) that is primarily induced by motion of their head. It is unclear what gaze behaviors birds perform to support visuomotor control during rapid maneuvering flight in which they continuously switch between flight modes. To analyze this, we measured the gaze behavior of rapidly turning lovebirds in a goal-directed task: take-off and fly away from a perch, turn on a dime, and fly back and land on the same perch. High-speed flight recordings revealed that rapidly turning lovebirds perform a remarkable stereotypical gaze behavior with peak saccadic head turns up to 2700 degrees per second, as fast as insects, enabled by fast neck muscles. In between saccades, gaze orientation is held constant. By comparing saccade and wingbeat phase, we find that these super-fast saccades are coordinated with the downstroke when the lateral visual field is occluded by the wings. Lovebirds thus maximize visual perception by overlying behaviors that impair vision, which helps coordinate maneuvers. Before the turn, lovebirds keep a high contrast edge in their visual midline. Similarly, before landing, the lovebirds stabilize the center of the perch in their visual midline. The perch on which the birds land swings, like a branch in the wind, and we find that retinal size of the perch is the most parsimonious visual cue to initiate landing. Our observations show that rapidly maneuvering birds use precisely timed stereotypic gaze behaviors consisting of rapid head turns and frontal feature stabilization, which facilitates optical flow based flight control. Similar gaze behaviors have been reported for visually navigating humans. This finding can inspire more effective vision-based autopilots for drones.

Improving the Digestive Tract Robustness of Probiotic Lactobacilli
Bokhorst-van de Veen, H. van; Bron, P.A. ; Kleerebezem, M. - \ 2015
In: Probiotics and Prebiotics: Current Research and Future Trends / Venema, K., Paula do Carmo, A., Norfolk, UK : Caister Academic Press - ISBN 9781910190098 - 560 p.
This chapter describes stress responses of probiotic lactobacilli, in relation to gastrointestinal (GI-)tract robustness. An overview is given of some newly developed tools to understand and improve stress responses of the model probiotic L. plantarum WCFS1 in relation to its GI persistence. These include a relative simple GI-tract assay and the development of transcriptome-trait matching that associates a trait of interest (e.g., GI-tract survival) with transcripts levels that enables the identification of genetic robustness markers, that can be modulated by pre-adaptation and/or genetic engineering to enhance robustness. Furthermore, specific additives to the in situ delivery matrix may enhance the relative tolerance of specific bacterial strains to detrimental conditions they may encounter in different regions of the GI-tract. Moreover, a methodology that allows the molecular quantification of single strains in a mixed bacterial population using engineered sequence-tags or naturally occurring discriminatory intergenic alleles in combination with next-generation sequencing offers another powerful tool for robustness evaluation. Finally, the stress responses of probiotic cultures in relation to improval of their GI persistence and some future directions for development and GI-tract research in the light of probiotic performance are discussed.
Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma and comparison to thermal and chemical based methods
Bokhorst-van de Veen, H. van; Xie, H. ; Esveld, D.C. ; Abee, T. ; Mastwijk, H.C. ; Nierop Groot, M.N. - \ 2015
Food Microbiology 45 (2015)part A. - ISSN 0740-0020 - p. 26 - 33.
low-temperature - gas plasma - subtilis spores - sterilization - salmonella - decontamination - microorganisms - hypochlorite - germination
Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity.
Microbïele risico's bij hergebruik van drankenkartons : rapportage naar aanleiding van een vergadering gehouden op 24 februari 2014 in aanwezigheid van experts op het gebied van microbiologie
Bokhorst-van de Veen, H. van; Brouwer, M.T. - \ 2014
Wageningen : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food &amp; Biobased Research nr. 1472) - ISBN 9789461739919 - 20
flessen - verpakkingsmaterialen - risicoschatting - microbiële besmetting - bordpapier - bottles - packaging materials - risk assessment - microbial contamination - cardboard
Regenwormen op het melkveebedrijf : handreiking voor herkennen, benutten en managen
Eekeren, N.J.M. van; Bokhorst, J. ; Deru, J. ; Wit, J. de - \ 2014
Driebergen : Louis Bolk Instituut (Rapport / Louis Bolk Instituut 2014-004 LbD) - 37 p.
aardwormen - bodemkwaliteit - bodemvruchtbaarheid - bodemvruchtbaarheidsbeheer - melkveehouderij - bodembiologie - graslanden - bouwland - graslandbeheer - earthworms - soil quality - soil fertility - soil fertility management - dairy farming - soil biology - grasslands - arable land - grassland management
In deze brochure worden handreikingen gegeven voor de praktijk, waarbij zowel strooiselbewonende, bodembewonende en pendelende regenwormen aan bod komen.
PPS Milde conservering WP7 Hurdle technology. Karaktisering van Paenibacilli: invloed van pasteurisatie en zoutreductie op ontkieming en uitgroei van sporen in koelverse maaltijden
Helmond, M.T.J. ; Bokhorst-van de Veen, H. van; Matser, A.M. - \ 2014
Wageningen : Wageningen UR - Food & Biobased Research
Genotypic adaptations associated with prolonged persistence of Lactobacillus plantarum in the murine digestive tract
Bokhorst-van de Veen, H. van; Smelt, M.J. ; Wels, M. ; Hijum, S.A.F.T. van; Vos, P. de; Kleerebezem, M. ; Bron, P.A. - \ 2013
Biotechnology Journal 8 (2013)8. - ISSN 1860-6768 - p. 895 - 904.
gastrointestinal-tract - rhamnosus gg - human flora - mice - host - strains - protein - genome - genes - identification
Probiotic bacteria harbor effector molecules that confer health benefits, but also adaptation factors that enable them to persist in the gastrointestinal tract of the consumer. To study these adaptation factors, an antibiotic-resistant derivative of the probiotic model organism Lactobacillus plantarum WCFS1 was repeatedly exposed to the mouse digestive tract by three consecutive rounds of (re)feeding of the longest persisting colonies. This exposure to the murine intestine allowed the isolation of intestine-adapted derivatives of the original strain that displayed prolonged digestive tract residence time. Re-sequencing of the genomes of these adapted derivatives revealed single nucleotide polymorphisms as well as a single nucleotide insertion in comparison with the genome of the original WCFS1 strain. Detailed in silico analysis of the identified genomic modifications pinpointed that alterations in the coding regions of genes encoding cell envelope associated functions and energy metabolism appeared to be beneficial for the gastrointestinal tract survival of L. plantarum WCFS1. This work demonstrates the feasibility of experimental evolution for the enhancement of the gastrointestinal residence time of probiotic strains, while full-genome re-sequencing of the adapted isolates provided clues towards the bacterial functions involved. Enhanced gastrointestinal residence is industrially relevant because it enhances the efficacy of the delivery of viable probiotics in situ.
Recent advances in non-thermal nitrogen plasma as food processing technology
Nierop Groot, M.N. ; Bokhorst-van de Veen, H. Van; Esveld, D.C. ; Mols, M. ; Abee, T. ; Mastwijk, H. - \ 2013
In: Microbials Spoilers in Food 2013, 01 - 03 July, 2013, Quimper, France. - Quimper : - p. 132 - 132.
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