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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Derving in de supermarkt kan flink omlaag : Deel 2: onderzoek en maatregelen voedselverspilling in de biologische keten
Tromp, S.O. - \ 2018
Ekoland (2018)6. - ISSN 0926-9142 - p. 32 - 33.
Detection of titanium particles in human liver and spleen and possible health implications
Heringa, M.B. ; Peters, R.J.B. ; Bleys, R.L.A.W. ; Lee, M.K. van der; Tromp, P.C. ; Kesteren, P.C.E. van; Eijkeren, J.C.H. van; Undas, A.K. ; Oomen, A.G. ; Bouwmeester, H. - \ 2018
Particle and Fibre Toxicology 15 (2018)1. - ISSN 1743-8977
Human liver - Human spleen - Nanoparticle - Quantification - Risk assessment - Sp-ICP-HRMS - Tissue level - Titanium dioxide
Background: Titanium dioxide (TiO2) is produced at high volumes and applied in many consumer and food products. Recent toxicokinetic modelling indicated the potential of TiO2 to accumulate in human liver and spleen upon daily oral exposure, which is not routinely investigated in chronic animal studies. A health risk from nanosized TiO2 particle consumption could not be excluded then. Results: Here we show the first quantification of both total titanium (Ti) and TiO2 particles in 15 post-mortem human livers and spleens. These low-level analyses were enabled by the use of fully validated (single particle) inductively coupled plasma high resolution mass spectrometry ((sp)ICP-HRMS) detection methods for total Ti and TiO2 particles. The presence of TiO2 in the particles in tissues was confirmed by Scanning Electron Microscopy with energy dispersive X-ray spectrometry. Conclusions: These results prove that TiO2 particles are present in human liver and spleen, with ≥24% of nanosize (< 100 nm). The levels are below the doses regarded as safe in animals, but half are above the dose that is deemed safe for liver damage in humans when taking into account several commonly applied uncertainty factors. With these new and unique human data, we remain with the conclusion that health risks due to oral exposure to TiO2 cannot be excluded.
Efficiënte keten: preventie reststromen: rapportage 2015/2016
Staps, Sjef ; Tromp, Seth ; Gogh, Bart van; Burgh, Marianne van der - \ 2017
Driebergen : Louis Bolk Instituut - 59
reststromen - biologische landbouw - agro-industriële ketens - biologische voedingsmiddelen - voedselketens - verliezen - bederfelijke producten - houdbaarheid (kwaliteit) - voedselverspilling - bewaartijd - residual streams - organic farming - agro-industrial chains - organic foods - food chains - losses - perishable products - keeping quality - food wastage - storage life
Het onderhavige rapport is bedoeld als openbare verslaglegging van de eerste twee onderzoeksjaren van het publiek-private samenwerking (PPS) project ‘Efficiënte keten, preventie reststromen’ (2015-2018). De ambitie van dit PPS-project is om derving (verspilling) in de biologische agrifood-keten te voorkomen, en daar waar reststromen ontstaan de kansen voor het vermarkten van deze reststromen te vergroten. Het rapport kan gebruikt worden als referentie voor het vinden van mogelijkheden om derving (verspilling) te voorkomen en daar waar reststromen desondanks ontstaan de kansen voor het vermarkten van deze reststromen te vergroten.
Transfer Study of Silver Nanoparticles in Poultry Production
Gallocchio, Federica ; Biancotto, Giancarlo ; Cibin, Veronica ; Losasso, Carmen ; Belluco, Simone ; Peters, Ruud ; Bemmel, Greet van; Cascio, Claudia ; Weigel, Stefan ; Tromp, Peter C. ; Gobbo, Federica ; Catania, Salvatore ; Ricci, Antonia - \ 2017
Journal of Agricultural and Food Chemistry 65 (2017)18. - ISSN 0021-8561 - p. 3767 - 3774.
chicken - nanomaterials - silver - silver nanoparticles - spICP-MS - transfer

Silver nanoparticles (AgNPs) are of interest due to their antimicrobial activity and are seen as potential candidates to replace antibiotics in animal husbandry. A few studies have focused on this new application, but they lack any considerations about residual accumulation of AgNPs in edible animal tissues and animal products. In this research, a 22 day in vivo study was carried out by oral administration of 20 nm spherical PVP coated AgNPs to hens. Six doses of approximately 1 mg kg-1 of AgNPs-PVP each were administered to animals throughout the experimentation. Atomic absorption spectroscopy (AAS) was used for quantitative determination of residual total Ag in different organs and matrices. The analyses showed that Ag accumulates in livers (concentration ranging from 141 μg kg-1 to 269 μg kg-1) and yolks (concentration ranging from 20 μg kg-1 to 49 μg kg-1) but not in muscles, kidneys, and albumen belonging to hens of the treated group (tG2). Ag was not detected in animals of the control group (uG1) (i.e., total Ag < LOD = 10 μg kg-1). Single particle inductively coupled plasma mass spectrometry (spICP-MS) and scanning electron microscopy with energy dispersive X-ray detection (SEM-EDX) were employed to elucidate the presence of AgNPs in livers and yolks belonging to tG2 animals. spICP-MS highlighted that part of residual Ag found in livers (about 5-20%) is in NP form with an average dimension of approximately 20 nm. SEM-EDX technique confirmed the presence of AgNPs only in livers of treated animals. The results show that feeding AgNPs to hens may become a source of consumer exposure to AgNPs. As far as we know this is the first study showing transfer of AgNPs or reaction products thereof from animal feed to animal products.

Harnessing the advantages of hard and soft colloids by the use of core-shell particles as interfacial stabilizers
Buchcic, C. ; Tromp, R.H. ; Meinders, M.B.J. ; Cohen Stuart, M.A. - \ 2017
Soft Matter 13 (2017)7. - ISSN 1744-683X - p. 1326 - 1334.

The ability of colloidal particles to penetrate fluid interfaces is a crucial factor in the preparation of particle stabilized disperse systems such as foams and emulsions. For hard micron-sized particles the insertion into fluid interfaces requires substantial energy input, but soft particles are known to adsorb spontaneously. Particle hardness, however, may also affect foam and emulsion stability. The high compliance of soft particles may compromise their ability to withstand the lateral compression associated with disproportionation. Hence, particles which can spontaneously adsorb onto fluid interfaces, and yet depict low compliance may be ideal as interfacial stabilizers. In the present work, we prepared core-shell particles comprising a hard, polystyrene core and a soft poly(N-isopropylacrylamide) based shell. We found that such core-shell particles adsorb spontaneously onto various fluid interfaces. The absence of a pronounced energy barrier for interfacial adsorption allowed the facile preparation of particle-stabilized bubbles as well as emulsion droplets. For bubbles, the stability was better than that of bubbles stabilized by entirely soft particles, but disproportionation was not stopped completely. Emulsion droplets, in contrast, showed excellent stability against both coalescence and disproportionation. Lateral compression of core-shell particles due to disproportionation was clearly limited by the presence of the polystyrene core, leading to long-lasting stability. For emulsions, we even observed non-spherical droplets, indicating a negligible Laplace pressure. Our results indicate that core-shell particles comprising a hard core and a soft shell combine the advantageous properties of hard and soft particles, namely spontaneous adsorption and limited compliance, and can therefore be superior materials for the preparation of particle-stabilized dispersions.

On the validation of improved quality-decay models of potted plants
Tromp, Seth Oscar ; Harkema, Harmannus ; Hogeveen-van Echtelt, Esther ; Rijgersberg, Hajo ; Woltering, Ernst J. - \ 2017
Postharvest Biology and Technology 123 (2017). - ISSN 0925-5214 - p. 119 - 127.
Model - Potted plants - Quality decay - Storage - Transport - Validation

Storage experiments were carried out with potted plants: two Phalaenopsis cultivars and one Anthurium cultivar. The plants were stored in the dark for different storage times at different temperatures, to mimick a transport phase. Different quality aspects were scored immediately after the transport phase and after a subsequent display phase of 7 and 14 days at in-store conditions. Improved quality decay models compared to previous work were designed to quantify the effect of transport on the shelf life of potted plants. Of each cultivar, plants were obtained from two commercial growers in the Netherlands. Only the data from the first grower were used for improving the quality-decay models. The models were subsequently validated using the data from the second grower, as well as data from the first grower from year 2013 instead of 2015. So validation took place both in origin (a different grower) and in time (a different year). The validation showed that the behaviour of Anthurium ‘Arion’ was well predicted by the previously designed quality-decay models. For Phalaenopsis the performance of the quality-decay models differed per storage temperature. It was concluded that a quality-decay model first needs to be validated before it can be applied to predict the quality decay of a different production batch.

Effects of dietary seaweed supplementation on hypoxia tolerance and oxidative stress response in gilthead sea bream (Sparus aurata)
Magnoni, Leonardo ; Querioz, Augusto ; Martos-Sitcha, Juan Antonio ; Tromp, Kevin ; Schrama, J.W. ; Gonçalves, José ; Calduch-Giner, Josep Alvar ; Pérez-Sánchez, Jaume - \ 2016
Intensive aquaculture practices involve rearing fish at high densities in enclosed spaces, circumstances in which they may experience hypoxic events. Seaweeds (SW) and their derived compounds when included into fish diets may increase antioxidant defenses, improving welfare. The gilthead sea bream (Sparus aurata) has a growing importance in the European aquaculture sector. Thus, our aim was to evaluate the effect that dietary SW supplementation has on the metabolic profile and antioxidant capacity of sea bream juveniles subjected to an acute hypoxic event and ulterior recovery to normoxia. For this purpose, fish (105±2 g) were distributed into 24 tanks (60 L, 7 fish/tank) and fed for 34 days a commercial diet supplemented with Gracilaria sp. (+GR, 5%) or Ulva sp. (+UL, 5%), or without SW supplementation (Control). Fish were subjected to acute hypoxia (4 tanks/diet, 24h, DO 1.3mg/L) in a controlled system and sampled 24h after returning to normoxia (Hypoxia/Recovery). Another group remained in normoxia during the whole trial (4 tanks/diet, DO 8.6mg/L). Hypoxia produces an increase in the O2 carrying capacity in the fish, displayed by an increase in HCT values in all dietary groups, although the increase was most noticeable in the MC[Hb] of +GR and +UL treatments. At transcriptional level, a PCR-array of 29 selected genes in liver and heart showed differentially expressed markers related to oxidative stress, which improve oxidative capacity during normoxic and/or hypoxia/recovery conditions preferentially in those fish fed +GR diet. Such results are in accordance with the higher survival rates of fish fed +GR diet than of those fed a control diet (61±4% and 29±6%, respectively, P=0.017). Our results suggest that compounds with antioxidant properties in +GR diet may have a protective role during hypoxia. The nature of these compounds and possible mechanisms implied in the response are currently being investigated.
On preventing chilled-food waste at the retail outlet
Haijema, R. ; Tromp, S. - \ 2016
A systematic approach to preventing chilled-food waste at the retail outlet
Tromp, Seth Oscar ; Haijema, René ; Rijgersberg, Hajo ; Vorst, Jack G.A.J. van der - \ 2016
International Journal of Production Economics 182 (2016). - ISSN 0925-5273 - p. 508 - 518.
Food waste - Quality decay - Retail outlet - Shelf life - Simulation - Use-by date

The objective of this paper is to develop a systematic overview of interventions for preventing chilled-food waste at retail outlets, and to assess the impact of these interventions for a particular case of fresh-cut iceberg lettuce at a Dutch retail outlet. The structure of the simulation model as presented in this paper is generic, hence suitable for other retailers and other chilled-food products as well. The generated systematic overview focusses on interventions that do not require a system change. A distinction is made into technical, logistical and marketing interventions. Model simulations show the effectiveness of these interventions. It is concluded that a number of ‘waste drivers’ exists, such as a low and varying consumer demand, high selection behaviour, the order lead time, a fixed order unit, and a short use-by date. The retailer can fine-tune the replenishment level of his order policy and the way of rounding to the given order unit, but by doing so he is at best able to exchange waste for out-of-stock or the other way around. The systematic overview of interventions is valuable input to future research on defining and estimating the effectiveness of combining interventions, and interventions that do require a system change.

Core-shell particles at fluid interfaces : performance as interfacial stabilizers
Buchcic, C. - \ 2016
University. Promotor(en): Martien Cohen Stuart, co-promotor(en): R.H. Tromp; Marcel Meinders. - Wageningen : Wageningen University - ISBN 9789462578968 - 140 p.
stabilization - stabilizers - particles - colloidal properties - adsorption - interface - fluids - stabilisatie - stabiliseermiddelen - deeltjes - colloïdale eigenschappen - adsorptie - grensvlak - vloeistoffen (fluids)

There is a growing interest in the use of particles as stabilizers for foams and emulsions. Applying hard particles for stabilization of fluid interface is referred to as Pickering stabilization. By using hard particles instead of surfactants and polymers, fluid interfaces can be effectively stabilized against Ostwald ripening and coalescence. A drawback of the use of hard particles as interfacial stabilizers is that they often experience a pronounced energy barrier for interfacial adsorption and that hard particles are very specific with regard to the type of fluid interface they can adsorb to. Soft particles, on the other hand, are known as good stabilizers against coalescence and they spontaneously adsorb to a variety of different fluid interfaces.

The aim of this thesis was to investigate core-shell particles comprising a hard core and soft shell with regard to their interfacial behaviour and their ability to act as sole stabilizers for foams and emulsions. We hypothesised that the presence of the soft shell allows for easier interfacial adsorption of core-shell particles compared to the hard core particles only. To test this hypothesis, we prepared core-shell particles comprising a solid polystyrene (PS) core and a soft poly-N-isopropylacrylamide (PNIPAM) shell. To ascertain the effect of shell thickness, we prepared a range of core-shell particles with different shell thicknesses, containing identical core particles. We found that core-shell particles are intrinsically surface active and can generate high surface pressures at the air-water interface and oil-water interfaces, whereas core particles seemed to experience a large energy barrier for interfacial adsorption and did not lower the surface tension. We also confirmed by microscopy that core-shell particles are actually adsorbing to the fluid interface and form densely packed interfacial layers. Further, we found that a certain critical thickness of the soft shell is necessary in order to ensure facile interfacial adsorption. If the PNIPAM shell on top of the core particles is well above 100nm thick, particle adsorption at the air-water interface was found to be diffusion limited.

By gentle hand-shaking we were able to produce dispersion of air bubbles and emulsion droplets solely stabilized by core-shell particles. The resulting bubbles still underwent Ostwald ripening, albeit slowly. For oil-in-water emulsions of hexane and toluene, both of which have a relatively high solubility in the continuous phase, we found that core-shell particles can stop Ostwald ripening. The resulting emulsion droplets adopted pronounced non-spherical shapes, indicating a high elasticity of the interface. The high stability and the remarkable non-spherical shape of the emulsion droplets stabilized by core-shell particles were features we also observed for fluid dispersion stabilized by hard particles. This shows that in terms of emulsion stability core-shell particles behave similar to hard particles as interfacial stabilizer.

As to why the differences between the stability of bubble and oil dispersions arise could not be finally answered. Yet, microscopic analysis of the interfacial configuration of core-shell particles at the air-water interface reveals some peculiar insights which may suggest that core-shell particles adsorb in a polymer-like fashion with the soft PNIPAM shells adsorbing to the air-water interface only, while the hard PS cores reside in the continuous phase.

In summary, we showed that core-shell particles with a hard core and a soft shell can indeed combine the advantageous properties of hard and soft particles. The soft shell enables spontaneous adsorption to a variety of fluid interfaces. Despite their spontaneous adsorption, core-shell particles strongly anchor and do not spontaneously desorb from the fluid interface again. Further, the hard core provides enough rigidity to the core-shell particles to allow the establishment of a stress bearing interfacial particle network. This network eventually stops Ostwald ripening in oil-in-water emulsions. Our results therefore show that in the case of oil-water interfaces, core-shell particles can perform better than solely hard particles as interfacial stabilizers.

Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry
Helsper, Hans ; Peters, Ruud J.B. ; Bemmel, Greet van; Herrera Rivera, Zahira ; Wagner, Stephan ; Kammer, Frank von der; Tromp, Peter C. ; Hofmann, Thilo ; Weigel, Stefan - \ 2016
Analytical and Bioanalytical Chemistry 408 (2016)24. - ISSN 1618-2642 - p. 6679 - 6691.
Asymmetric flow field flow fractionation - Inductively coupled plasma mass spectrometry - Nanomaterials - Size distribution - Titanium dioxide - Zirconium

Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based “diameters of gyration” (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

Waste reduction of fresh food at retail outlets
Snels, J.C.M.A. ; Haijema, R. ; Tromp, S.O. ; Rijgersberg, H. ; Vorst, J.G.A.J. van der - \ 2015
In: Bijdragen Vervoerslogistieke werkdagen 2015. - Arnhem : - ISBN 9789087070397
Measures for reducing chilled-food losses at retail outlets
Tromp, S.O. ; Haijema, R. ; Rijgersberg, H. ; Vorst, J.G.A.J. van der - \ 2015
Modelling the quality of potted plants after dark storage
Tromp, S.O. ; Harkema, H. ; Rijgersberg, H. ; Westra, E.H. ; Woltering, E.J. - \ 2015
Postharvest Biology and Technology 103 (2015). - ISSN 0925-5214 - p. 9 - 16.
Prolonged dark storage affects the quality of potted plants. A model was designed to quantify the effect of storage time and temperature on the display life of potted plants, such that logistics can be optimized, resulting in increased remaining quality and less rejected plants. Experiments were carried out with two Phalaenopsis cultivars, two Anthurium cultivars and two Cyclamen cultivars, the latter with two colour variants per cultivar. Plants were stored for different storage times at different temperatures. The aim of the chosen times and temperatures was to determine the quality effect of transport at optimal and suboptimal temperatures. After storage, plants were stored at 20 °C for 14 days, for simulating a display period. Different quality aspects were scored immediately after storage and after 7 and 14 days of display.

For each cultivar, a model was fitted consisting of a logistic function for representing the storage-time dependency of quality. In order to cope with both senescence symptoms at higher temperatures and chilling injury at lower temperatures, two non-interfering Arrhenius equations were incorporated. Because the effects of chilling exposure are commonly manifest only when the chilled plants are returned to ambient temperatures, the quality of Phalaenopsis and Anthurium plants measured immediately after storage at low temperatures was not taken into account. The behaviour of the Phalaenopsis and the Anthurium cultivars was well described by their models. The coefficients of determination based on the unexplained variation due to lack of fit were in the range of 0.89–0.99.
Assembly of jammed colloidal shells onto micron-sized bubbles by ultrasound
Buchcic, C. ; Tromp, R.H. ; Meinders, M.B.J. ; Cohen Stuart, M.A. - \ 2015
Soft Matter 11 (2015)7. - ISSN 1744-683X - p. 1326 - 1334.
interfacial rheological properties - aqueous foams - stabilized emulsions - contact-angle - particles - water - surfactants - polymerization - nanoparticles - adsorption
Stabilization of gas bubbles in water by applying solid particles is a promising technique to ensure long-term stability of the dispersion against coarsening. However, the production of large quantities of particle stabilized bubbles is challenging. The delivery of particles to the interface must occur rapidly compared to the typical time scale of coarsening during production. Furthermore, the production route must be able to overcome the energy barriers for interfacial adsorption of particles. Here we demonstrate that ultrasound can be applied to agitate a colloidal dispersion and supply sufficient energy to ensure particle adsorption onto the air–water interface. With this technique we are able to produce micron-sized bubbles, solely stabilized by particles. The interface of these bubbles is characterized by a colloidal shell, a monolayer of particles which adopt a hexagonal packing. The particles are anchored to the interface owing to partial wetting and experience lateral compression due to bubble shrinkage. The combination of both effects stops coarsening once the interface is jammed with particles. As a result, stable bubbles are formed. Individual particles can desorb from the interface upon surfactant addition, though. The latter fact confirms that the particle shell is not covalently linked due to thermal sintering, but is solely held together by capillary interaction. In summary, we show that our ultrasound approach allows for the straightforward creation of micron-sized particle stabilized bubbles with high stability towards coarsening.
Translocation of positively and negatively charged polystyrene nanoparticles in an in vitro placental model
Kloet, S.K. ; Walczak, A.P. ; Louisse, J. ; Berg, H.J. van den; Bouwmeester, H. ; Tromp, P. ; Fokkink, R.G. ; Rietjens, I.M.C.M. - \ 2015
Toxicology in Vitro 29 (2015)7. - ISSN 0887-2333 - p. 1701 - 1710.
To obtain insight in translocation of nanoparticles across the placental barrier, translocation was studied for one positively and two negatively charged polystyrene nanoparticles (PS-NPs) of similar size in an in vitro model. The model consisted of BeWo b30 cells, derived from a human choriocarcinoma grown on a transwell insert forming a cell layer that separates an apical from a basolateral compartment. PS-NPs were characterized with respect to size, surface charge, morphology and protein corona. Translocation of PS-NPs was not related to PS-NP charge. Two PS-NPs were translocated across the BeWo transwell model to a lower extent than amoxicillin, a model compound known to be translocated over the placental barrier to only a limited extent, whereas one PS-NP showed a slightly higher translocation. Studies on the effect of transporter inhibitors on the translocation of the PS-NPs indicated that their translocation was not mediated by known transporters and mainly dependent on passive diffusion. It is concluded that the BeWo b30 model can be used as an efficient method to get an initial qualitative impression about the capacity of NPs to translocate across the placental barrier and set priorities in further in vivo studies on translocation of NPs to the fetus.
Translocation of differently sized and charged polystyrene nanoparticles in in vitro intestinal cell models of increasing complexity
Walczak, A.P. ; Kramer, E.H.M. ; Hendriksen, P.J.M. ; Tromp, P. ; Helsper, J.P.F.G. ; Zande, M. van der; Rietjens, I.M.C.M. ; Bouwmeester, H. - \ 2015
Nanotoxicology 9 (2015)4. - ISSN 1743-5390 - p. 453 - 461.
Intestinal translocation is a key factor for determining bioavailability of nanoparticles (NPs) after oral uptake. Therefore, we evaluated three in vitro intestinal cell models of increasing complexity which might affect the translocation of NPs: a mono-culture (Caco-2 cells), a co-culture with mucus secreting HT29-MTX cells and a tri-culture with M-cells. Cell models were exposed to well characterized differently sized (50 and 100¿nm) and charged (neutral, positively and negatively) polystyrene NPs. In addition, two types of negatively charged NPs with different surface chemistries were used. Size strongly affected the translocation of NPs, ranging up to 7.8% for the 50¿nm NPs and 0.8% for the 100¿nm NPs. Surface charge of NPs affected the translocation, however, surface chemistry seems more important, as the two types of negatively charged 50¿nm NPs had an over 30-fold difference in translocation. Compared with the Caco-2 mono-culture, presence of mucus significantly reduced the translocation of neutral 50¿nm NPs, but significantly increased the translocation of one type of negatively charged NPs. Incorporation of M-cells shifted the translocation rates for both NPs closer to those in the mono-culture model. The relative pattern of NP translocation in all three models was similar, but the absolute amounts of translocated NPs differed per model. We conclude that for comparing the relative translocation of different NPs, using one intestinal model is sufficient. To choose the most representative model for risk assessment, in vivo experiments are now needed to determine the in vivo translocation rates of the used NPs
Analysis of light scattered by turbid media in cylindrical geometry
Tromp, R.H. ; Liemert, A. ; Meinders, M.B.J. - \ 2014
Langmuir 30 (2014)28. - ISSN 0743-7463 - p. 8276 - 8282.
diffusing-wave-spectroscopy - photon transport - casein micelles - milk - suspensions - dynamics - probes - fluids - foam
The angle dependence of the transmitted light through a cylindrical turbid sample (latex suspension, developing milk gel, draining/coarsening milk, and protein foams) in a standard light scattering setup was analyzed in terms of the transport mean free path length or scattering length l* (a measure for the turbidity) and the absorption length labs. By variation of the concentration of an absorbing dye, the independence of l* and labs was demonstrated. The resulting value of the specific extinction coefficient of the dye was found to be in fair agreement with direct spectroscopic determination and practically identical in milk and latex suspensions. The validity of this technique for obtaining l* was demonstrated by monitoring the acid-induced gelation of milk. The possibility to simultaneously determine l* and labs was used to follow the time development of a draining and coarsening protein foam which contained an absorbing dye. It was shown that labs can be used as a measure for the volume fraction of air in the foam. This method of monitoring the transmission of multiple light scattering provides an easy way to determine l* and, specifically for foams, quantitative data dominated by the bulk of the foam.
Verwaarding van reststromen in de biologische retail (deel 2) : een casestudie bij Udea/EkoPlaza
Tromp, S. ; Staps, S. ; Gogh, J.B. van; Steverink, M. ; Broek, E.M.F. van den; Burgh, M. van der - \ 2014
Wageningen : Wageningen UR - Food & Biobased Research (Rapport / Wageningen UR Food &amp; Biobased Research nr. 1527) - 61
biologische voedingsmiddelen - reststromen - voedselverspilling - duurzaamheid (sustainability) - voedselafval - afvalhergebruik - houding van consumenten - veevoeder - compostering - organic foods - residual streams - food wastage - sustainability - food wastes - waste utilization - consumer attitudes - fodder - composting
Het terugdringen van voedselverliezen vormt een belangrijk thema in de verduurzaming van de voedselketen. Ook de biologische supermarkt Udea/EkoPlaza is continu op zoek naar nieuwe oplossingen voor de reststromen die ontstaan in zowel de EkoPlaza-winkels als in het distributiecentrum van Udea. De productgroep aardappelen, groente en fruit (AGF) kent bij Udea/EkoPlaza de grootste reststroom. In dit onderzoek zijn diverse mogelijkheden tot verwaarding van deze reststroom aan bod gekomen. Zo is de aankoopintentie onderzocht van consumenten ten aanzien van zogenaamde geüpcyclede producten. Dit zijn voedingsproducten die geproduceerd zijn op basis van reststromen. Er is onderzocht in hoeverre aansluiting kan worden gevonden bij lopende initiatieven omtrent de herbenutting van reststromen in diervoeder. Ook is de mogelijkheid onderzocht van de vergisting en/of compostering van reststromen.
Characterization of Titanium Dioxide Nanoparticles in Food Products: Analytical Methods To Define Nanoparticles
Peters, R.J.B. ; Bemmel, M.E.M. van; Herrera-Rivera, Z. ; Helsper, J.P.F.G. ; Marvin, H.J.P. ; Weigel, S. ; Tromp, P.C. ; Oomen, A.G. ; Rietveld, A.G. ; Bouwmeester, H. - \ 2014
Journal of Agricultural and Food Chemistry 62 (2014)27. - ISSN 0021-8561 - p. 6285 - 6293.
field-flow fractionation - plasma-mass spectrometry - efficiency - exposure - tio2
Titanium dioxide (TiO2) is a common food additive used to enhance the white color, brightness, and sometimes flavor of a variety of food products. In this study 7 food grade TiO2 materials (E171), 24 food products, and 3 personal care products were investigated for their TiO2 content and the number-based size distribution of TiO2 particles present in these products. Three principally different methods have been used to determine the number-based size distribution of TiO2 particles: electron microscopy, asymmetric flow field-flow fractionation combined with inductively coupled mass spectrometry, and single-particle inductively coupled mass spectrometry. The results show that all E171 materials have similar size distributions with primary particle sizes in the range of 60–300 nm. Depending on the analytical method used, 10–15% of the particles in these materials had sizes below 100 nm. In 24 of the 27 foods and personal care products detectable amounts of titanium were found ranging from 0.02 to 9.0 mg TiO2/g product. The number-based size distributions for TiO2 particles in the food and personal care products showed that 5–10% of the particles in these products had sizes below 100 nm, comparable to that found in the E171 materials. Comparable size distributions were found using the three principally different analytical methods. Although the applied methods are considered state of the art, they showed practical size limits for TiO2 particles in the range of 20–50 nm, which may introduce a significant bias in the size distribution because particles
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