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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    Lubrication and perception of foods : tribological, rheological and sensory properties of particle-filled food system
    Liu, K. - \ 2016
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Markus Stieger; Fred van de Velde. - Wageningen : Wageningen University - ISBN 9789462576803 - 236
    rheological properties - tribology - fat globules - particles - lubrication - sensory evaluation - simulation models - food - gels - rice - reologische eigenschappen - tribologie - vetbolletjes - deeltjes - smering - sensorische evaluatie - simulatiemodellen - voedsel - gels - rijst

    Background and aims

    Food structure is determined by its composition and the interaction between the compositional or structural elements. Both food structure and the texture perception of foods undergo dynamic changes during different phases of oral processing. During oral processing, both rheological and tribological properties of foods are relevant for sensory perception. The general aim of this thesis was to understand the relationship between the structural properties, rheological and tribological properties during food breakdown, and the sensory perception of foods. More specifically, this thesis aimed to link the properties of food particles in liquid and semi-solid matrices to the tribological and rheological properties, and in this way, understand the sensory perception of these systems.


    Fat droplets and micro-particle fat replacers based on protein and starch were investigated. These particles varied in size, morphology, deformability and stability, as well as their interaction with the surrounding matrix. These particles were dispersed in liquid or semi-solid gel phases, forming the food model systems under consideration. The friction and microstructural evolution of food model systems under shear was determined using a mouth-mimicking tribometer connected to a confocal laser scanning microscopy. The viscosities of liquid systems were analyzed using a rheometer, and the large deformation properties of semi-solid gel systems were determined during uniaxial compression tests. The sensory perception of the food model systems were measured using quantitative descriptive analysis. The release and deposition of fat droplets on the tongue were determined using in vivo fluorescence.


    Food structural elements could be manipulated to control the tribological properties of food model systems. Morphology, size, and deformability of food particles determine the lubrication behavior of the food systems. Spherical particles with micrometer size were able to reduce friction through a ball bearing mechanism, while irregularly shaped particles increased friction by increasing apparent surface asperity contacts. Deformable particles could flatten the surface by filling asperities, thus reduced friction. Coalescence of unstable droplets could plate-out on the surface and form film patches, thus reduced friction. Other structural elements, such as emulsifiers and sticky molecules, also influenced tribological properties of the systems. Interactions between the food structural elements could influence the rheological properties of liquid and semi-solid food systems. These properties as well as tribological properties were inter-related and all of them affect sensory perception. The inter-relations between physical and sensory properties of food systems were influenced by oral processing, such as oral processing duration and temperature. Furthermore, several fat reduction and replacement strategies were suggested, including increasing the availability of fat that is in contact with oral surfaces, improving the lubrication by ball bearing of particles, and reducing perception of negative attributes such as roughness.


    This thesis showed the importance of food particle properties in both the tribological properties and sensory perception of foods, and emphasized the different lubrication mechanisms of different structure elements and their relation to perception. The differences in behavior of food particles between liquid and semi-solid gel systems were highlighted. These findings would enable a better understanding of relationship between food structure and their physical and sensory properties, and this would allow designing or modifying food products with targeted texture and sensory perception.

    Oral coatings: a study on the formation, clearance and perception
    Camacho, S. - \ 2015
    Wageningen University. Promotor(en): Kees de Graaf, co-promotor(en): Markus Stieger; F. van de Velde. - Wageningen : Wageningen University - ISBN 9789462575653 - 223
    afdeklagen - eiwitten - orale toediening - tong - mond - smering - emulsies - in vivo experimenten - sensorische evaluatie - perceptie - dynamica - zoetheid - fluorescentie - coatings - proteins - oral administration - tongue - mouth - lubrication - emulsions - in vivo experimentation - sensory evaluation - perception - dynamics - sweetness - fluorescence

    Oral coatings are residues of food and beverages that coat the oral mucosa after consumption. Several studies have reported on the lubrication properties in mouth, and the after-feel and after-taste impact of oral coatings. Further, oral coatings have been suggested to influence subsequent taste perception. Although it is well known that oral coatings can influence sensory perception, there was little information available on the chemical composition and physical properties of oral coatings. As such, the aim of this thesis was to understand which factors influence the composition of oral coatings and their sensory perception.

    This study started with the development of an appropriate calibration method for an already described methodology to quantify oil oral coatings: in vivo fluorescence. Further, the samples studied were shifted from pure oil (used on previous studies) to a more realistic food beverage: o/w emulsions. Pig´s tongues are known to be a good model of human tongue. As such, Chapter 2 used pig´s tongues on the calibration of the method, to mimic the fluorescence in mouth of oil coatings. On chapter 2, Confocal Scanning Laser Microscopy images showed that stable o/w emulsions (1-20% (w/w)) stabilised by Na-caseinate created individual oil droplets on the surface of the pigs tongue, as such a new descriptor for oil coatings was developed. Oil fraction, i.e. mass of oil per surface area of the tongue, was shown to be higher on the back compared to the front anterior part of the tongue. This is thought to be due to the morphology of the tongue and abrasion of the oil coating owed to the rubbing with the palate. Further, in vivo measurements showed that oil fraction deposited on the tongue increased linearly with oil content of o/w emulsions. Coating clearance from the tongue was a fast process with around 60% of the oil being removed on the first 45s. After-feel perception (Fatty Film and Flavour Intensity) was shown to be semi-logarithmic related to oil fraction on the tongue.

    Chapter 3, further investigated different properties of 10% (w/w) o/w emulsions that influence the oil fraction deposited on the tongue, its clearance and after-feel perception. Three different properties were studied: protein type, protein content and viscosity of the o/w emulsions. To study the influence of protein type, two different proteins which behave differently in-mouth were studied: Na-caseinate - creates emulsions which do not flocculate under in mouth conditions, and lysozyme – creates emulsions which flocculate under in mouth conditions. To study the influence of protein content, three concentrations of Na-caseinate and lysozyme were used (0.2, 3, 5.8% (w/w) all in excess to stabilize the water/oil interface). To study the influence of viscosity of o/w emulsions, three o/w emulsions stabilized with 3% (w/w) Na-caseinate were thickened with varying concentrations of xanthan gum (0-0.5%) (w/w).

    Generally, the irreversible flocculation of lysozyme stabilized emulsions with saliva did not create a significant difference on oil deposition compared to emulsions stabilized with Na-caseinate, immediately after expectoration of the emulsions. Nevertheless, lysozyme stabilised emulsions caused slower oil clearance from the tongue surface compared to emulsions stabilized with Na-caseinate. Protein content had a negative relation with oil fraction on the tongue for lysozyme stabilized emulsions and no relation for Na-caseinate stabilized emulsions. The presence of thickener decreased deposition of oil on tongue, although viscosity differences (i.e., thickener content) did not affect oil fraction. After-feel perception of creaminess and fatty-film was strongly influenced by the presence of thickener likely due to lubrication in-mouth, i.e., the higher the concentration of thickener in the emulsions the stronger was the perception. Oral coatings perception was further influenced by the protein used in the emulsions, with Na-caseinate stabilised emulsions creating coatings with higher perception on creaminess and fatty-film.

    Chapter 2 and chapter 3 provided knowledge on the deposition and clearance of oil coatings, but little was known on the formation of oil coatings. Chapter 4 focused on the formation of oil coatings formed by Na-caseinate stabilised o/w emulsions (1-20% (w/w)). The formation of oil coatings was a rapid process, where the maximum oil deposition was achieved at normal drinking behaviour (~3s). Further, in Chapter 4 we investigated the hypothesis often referred on literature, in which oil coatings form a physical barrier which prevents tastants to reach the taste buds, and thus create a reduction on taste perception. It was concluded that oil coatings formed by emulsions within one sip did not affect subsequent sweetness perception of sucrose solutions. We suggested that the oil droplets deposited on the tongue (as seen on chapter 2) did not form a hydrophobic barrier that is sufficient to reduce the accessibility of sucrose to the taste buds and consequently does not suppress taste perception.

    Previous chapters focused on oral coatings formed by liquid o/w emulsions, however studies describing oral coatings formed by semi-solids and solids are scarce. As such, chapter 5 focused on the formation, clearance and sensory perception of fat coatings from emulsion-filled gels. Four emulsion-filled gelatin gels varying in fat content and type of emulsifier (whey protein isolate - created fat droplets bound to matrix; tween 20 - created fat droplets unbound to matrix) were studied. As in for oil coatings formed by liquid o/w emulsions, fat coatings formed by emulsion-filled gels reach their maximum deposition in the first seconds of mastication. This suggests that the first bites are the most relevant for the formation of fat coatings on the tongue. Further, fat fraction deposited on tongue increased when oral processing time of the gels increased. This trend was clearer for gels with higher fat content (15%) compared to gels with lower fat content (5%). Fatty perception increased with increasing mastication time, and decreased after expectoration with increasing clearance time. Fat fraction deposited on tongue and fatty perception are higher in gels with unbound droplets compared to bound droplets, as well as in gels with 15% fat compared to 5% fat.

    To elucidate the role of protein on oral coatings, Chapter 6 focused on the development of a method to quantify protein in the oral coatings. Further, Chapter 6 studied the influence of protein content, in-mouth protein behaviour (lysozyme - protein which creates flocs with saliva vs. Na-Caseinate - protein which does not create flocs with saliva) and presence of thickener on the formation of protein oral coatings and sensory perception of protein coatings. Protein coatings were collected from the front and middle part of the anterior tongue using cotton swabs after subjects orally processed protein solutions for different time periods. Protein concentration of the coating (mass protein/mass coating) was quantified with the Lowry method. Similarly to oil/fat coatings, results show protein coatings are formed rapidly, reaching maximum deposition on the first seconds of the samples´ oral processing. Further, different protein in mouth-behaviour (Na-caseinate vs. lysozyme) did not create differences on protein deposition on the tongue. Presence of xanthan-gum in the processed samples decreased protein deposition on the tongue, compared to when samples without xanthan-gum were processed. The perception of protein coatings was strongly influenced by the viscosity and protein used in the samples. Higher viscosity of the samples lead to higher intensity on creaminess and thickness. Lysozyme samples created coatings with high sweetness and astringent intensity, which is related to the molecular structure of the protein.

    Changes in the viscosity of beverages can cause changes in thickness perception. The changes in thickness perception can be accompanied by differences in other sensory properties, such as sweetness and creaminess which might be undesirable when reformulating beverages or developing new products. Knowledge on the differences by which viscosity of beverages can be modified to create a difference in sensory perception is currently lacking. Chapter 7 focus on the determination of the Just Noticeable Difference (the minimal difference that can be detected between two stimuli) for thickness perception of beverages. Oral thickness sensitivity (K=0.26) was found to be comparable to literature values for kinesthetic food firmness and spreadability, creaminess, sourness and bitterness perception.

    The aim of this thesis was to determine and characterize factors influencing oral coatings and their sensory perception. For this purpose, reliable methods to quantify oil and protein deposited on the tongue had to be developed to later study the macronutrients deposition. Further, the influence of stimulus properties on the formation and clearance dynamics of oral coatings and their impact on sensory perception were investigated.

    The fate of fat: tribology, adhesion and fat perception of food emulsions
    Dresselhuis, D.M. - \ 2008
    Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): E.H.A. de Hoog; G.A. van Aken. - [S.l.] : S.n. - ISBN 9789085048657 - 152
    voedingsvet - vetten - emulsies - perceptie - tribologie - frictie - smering - adhesie - sensorische evaluatie - mond - orale biologie - dietary fat - fats - emulsions - perception - tribology - friction - lubrication - adhesion - sensory evaluation - mouth - oral biology
    Met de toename van het aantal mensen met overgewicht neemt ook de vraag naar producten die minder vet bevatten, maar nog steeds wel een lekker smaak hebben toe. Om zulke producten te maken is het heel belangrijk te weten wat er tijdens consumptie met het product gebeurt en hoe mensen eigenlijk vet waarnemen. We hebben ons in ons onderzoek vooral gericht op de bijdrage van vet op wat we noemen het mondgevoel en hoe fysische chemische processen in de mond dit kunnen beïnvloeden. Allereerst hebben we vastgesteld dat mensen als ze tijdens en na het consumeren van een vloeibaar product een lage frictie waarnemen tussen tong en verhemelte, ze dit associëren met vet en romigheid. In het tweede deel van het onderzoek hebben we aanwijzingen gevonden hoe de capaciteit van levensmiddelen-emulsies om een smerende laag op de tong te vormen (en dus de frictie in de mond te verlagen), afhangt van de kans dat de emulsiedruppels plakken (adhesie) en kunnen spreiden op de tong. Met deze kennis over plakken en spreiden van emulsies op de tong kunnen we nu emulsies proberen te maken waarbij we meer efficiënt gebruik maken van de hoeveelheid vet in het product en dus mogelijkheden scheppen om het vetgehalte te verlagen zonder aan smaak in te boeten.
    Toxiciteitonderzoek van regenwormen 2003 : toxiciteit van biologische en chemische producten op de regenworm Aporrectodea caliginosa in vitro
    Rozen, K. van; Ester, A. - \ 2003
    Wageningen : Praktijkonderzoek Plant & Omgeving B.V. - 15
    aardappelen - oogsten - neerslag - oogstschade - gewasverliezen - aardwormen - schuifweerstand - smering - bodemkwaliteit - potatoes - harvesting - precipitation - crop damage - crop losses - earthworms - sliding friction - lubrication - soil quality
    In Oostelijk en Zuidelijk Flevoland komen sinds de jaren ’90 problemen voor met de oogst van aardappelen. Na veel neerslag kan in het najaar plaatselijk veel regenwormen in de vochtige aardappelruggen voorkomen. De activiteit van regenwormen resulteert in versmering van de klei, dit resulteert onder drogende weersomstandigheden in een harde, betonachtige structuur. Ondanks een luchtig wormengangenstelsel onder het oppervlak kit het oppervlak van de klei dermate, dat het rooien van deze aardappelruggen bij zowel natte als droge omstandigheden leidt tot grote hoeveelheden tarra in het geoogste product. Vanuit het HPA en SPF (bijeenkomst 7 januari 2003) is verzocht om biologische en chemische producten te testen op de toxiciteit op regenwormen. In dit rapport is het onderzoek in vitro beschreven
    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
    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 - machines
    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.
    Smeerolie en Milieu
    Straelen, B.C.P.M. van - \ 1996
    Landbouwmechanisatie 47 (1996)4. - ISSN 0023-7795 - p. 50 - 51.
    apparatuur - schoonmaken - koelen - koelsystemen - boerderij uitrusting - landbouwwerktuigen - smeermiddelen - smering - plantaardige vetten - plantaardige oliën - bescherming - machines - apparatus - cleaning - cooling - cooling systems - farm equipment - farm machinery - lubricants - lubrication - plant fats - plant oils - protection
    In de Nederlandse landbouw gaat een flinke hoeveelheid aan smeermiddelen om. Uit een recent Duits onderzoek blijkt dat de helft van de olie die in de mobiele sector, waartoe de landbouw behoort, gebruikt wordt ongecontroleerd in het milieu terecht komt. Het is onwaarschijnlijk dat de situatie in Nederland een geheel ander beeld te zien geeft
    Kortere wachttijd na voorspoelen vermindert temperatuurverlies tijdens de reiniging
    Soede, H.J. - \ 1995
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 8 (1995)2. - ISSN 0921-8874 - p. 22 - 25.
    apparatuur - schoonmaken - componenten - koelen - koelsystemen - desinfectie - warmte - warmteoverdracht - smering - melkmachines - bescherming - thermische geleiding - thermodynamica - transmissie - arbeidskunde - machines - apparatus - cleaning - components - cooling - cooling systems - disinfection - heat - heat transfer - lubrication - milking machines - protection - thermal conductivity - thermodynamics - transmission - work study - machines
    De belangrijkste factoren die invloed hebben op de afkoeling zijn; tijd, uitvoering van de reiniging en omgevingstemperatuur.
    Optimalisatie spoeleffect
    Soede, H.J. ; Laan, R.P. - \ 1993
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 6 (1993)5. - ISSN 0921-8874 - p. 61 - 65.
    apparatuur - schoonmaken - koelen - koelsystemen - smering - melkkwaliteit - melkopbrengst - optimalisatie - bescherming - rioolwater - volume - afvalwater - machines - apparatus - cleaning - cooling - cooling systems - lubrication - milk quality - milk yield - optimization - protection - sewage - volume - waste water - machines
    In dit onderzoek is gekeken of het verhogen van het vacuüm en het toepassen van luchtinlaten (injecties) een optimalisatie van de uitspoeling geeft.
    Milieusparend reinigen melkwinningsapparatuur
    Wolters, G.M.V.H. - \ 1993
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 6 (1993)5. - ISSN 0921-8874 - p. 21 - 26.
    apparatuur - schoonmaken - koelen - koelsystemen - drinkwater - afvoerwater - energiebehoud - milieu - milieubeheer - milieubescherming - smering - melkmachines - bescherming - kwaliteit - rioolwater - rioolafvalwater - kraanwater - afvalhergebruik - afvalwater - hergebruik van water - machines - apparatus - cleaning - cooling - cooling systems - drinking water - effluents - energy conservation - environment - environmental management - environmental protection - lubrication - milking machines - protection - quality - sewage - sewage effluent - tap water - waste utilization - waste water - water reuse - machines
    In dit artikel worden diverse mogelijkheden van brongerichte besparingen bij vooral de reiniging van de melkleidinginstallatie belicht.
    Olieverbruik en milieubelasting vacuümpompen
    Holtkuile, A.H.M. ; Schuiling, H.J. - \ 1993
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 6 (1993)3. - ISSN 0921-8874 - p. 18 - 20.
    lucht - luchtverontreiniging - apparatuur - schoonmaken - componenten - koelen - koelsystemen - efficiëntie - energie - energiegebruik - brandstofverbruik - hygiëne - smering - melkmachines - bescherming - pompen - onderzoek - transport - machines - air - air pollution - apparatus - cleaning - components - cooling - cooling systems - efficiency - energy - energy consumption - fuel consumption - hygiene - lubrication - milking machines - protection - pumps - research - transport - machines
    Om enig inzicht te krijgen in het olieverbruik van de vacuümpompen en de werking van de olieafscheider heeft het PR een onderzoek uitgevoerd op enkele proefbedrijven.
    Blikseminslag en inductie in de agrarische sector : schade en preventie
    Anonymous, - \ 1984
    Wageningen : I.M.A.G. (Publikatie / Instituut voor Mechanisatie, Arbeid en Gebouwen no. 204) - 54
    computers - minicomputers - microcomputers - gegevensverwerking - mechanisatie - automatisering - weer - schade - landbouw - bliksem - atmosfeer - elektriciteit - apparatuur - koelen - schoonmaken - bescherming - smering - koelsystemen - oogstverliezen - opslag - machines - data processing - mechanization - automation - weather - damage - agriculture - lightning - atmosphere - electricity - apparatus - cooling - cleaning - protection - lubrication - cooling systems - yield losses - storage
    In deze publikatie wordt verslag gedaan van de inventarisatie, analysering en beoordeling van de risiko's met betrekking tot blikseminslag en/of induktie in de agrarische sektor. Er worden beveiligingspakketten en proefvoorstellen voor de bepaling van de effektiviteit hiervan geformuleerd
    Een geautomatiseerd schoonmaaksysteem in een koeler voor voorgebakken frites
    Laarhoven, G.J.M. van; Klundert, C.J.A. van de; Schild, J.H.W. van der - \ 1981
    Wageningen : IBVL (Publikatie / Instituut voor Bewaring en Verwerking van Landbouwprodukten 343) - 4
    apparatuur - patates frites - schoonmaken - koelen - koelsystemen - voedselbewaring - voedingsmiddelen - smering - onderhoud - aardappelproducten - bescherming - machines - apparatus - chips (French fries) - cleaning - cooling - cooling systems - food preservation - foods - lubrication - maintenance - potato products - protection
    Beproeving Life - Saver steigerbegrenzer
    Anonymous, - \ 1962
    Wageningen : [s.n.] (Bulletin / Instituut voor landbouwtechniek en rationalisatie no. 198) - 4
    trucks - trekkers - apparatuur - koelen - schoonmaken - bescherming - smering - koelsystemen - machines - trucks - tractors - apparatus - cooling - cleaning - protection - lubrication - cooling systems - machines
    Beproeving Rumptstad steigerbegrenzer
    Anonymous, - \ 1960
    Wageningen : [s.n.] (Bulletin / Instituut voor landbouwtechniek en rationalisatie no. 131) - 3
    trucks - trekkers - apparatuur - koelen - schoonmaken - bescherming - smering - koelsystemen - machines - trucks - tractors - apparatus - cooling - cleaning - protection - lubrication - cooling systems - machines
    Beproeving Sirocco trekkerhoes
    Anonymous, - \ 1959
    Wageningen : [s.n.] (Bulletin / Instituut voor landbouwtechniek en rationalisatie no. 111) - 4
    trucks - trekkers - apparatuur - koelen - schoonmaken - bescherming - smering - koelsystemen - machines - trucks - tractors - apparatus - cooling - cleaning - protection - lubrication - cooling systems - machines
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