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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Exergy analysis in industrial food processing
Zisopoulos, F.K. - \ 2016
University. Promotor(en): Remko Boom, co-promotor(en): Atze Jan van der Goot. - Wageningen : Wageningen University - ISBN 9789462578326 - 229
thermodynamics - energy - physical properties - food production - drying - food industry - efficiency - thermodynamica - energie - fysische eigenschappen - voedselproductie - drogen - voedselindustrie - efficiëntie

The sustainable provision of food on a global scale in the near future is a very serious challenge. This thesis focuses on the assessment and design of sustainable industrial food production chains and processes by using the concept of exergy which is an objective metric based on the first and second law of thermodynamics. Three case studies are presented, two on a chain level (industrial bread and mushroom production), and one on a process level (conceptual spray drying of a lactose solution). Furthermore, industrial food production chains are categorized as thermodynamic archetypes and general rules are derived for their sustainable design exergy-wise. Additional methodological aspects related to e.g. the impact of system boundaries, the allocation of exergy values to waste streams, and the influence of the selection of the environment of reference on the outcome of the analysis, are also discussed.

Drying and hydration of proteins at high concentration
Bouman, J. - \ 2015
University. Promotor(en): Erik van der Linden, co-promotor(en): Renko de Vries. - Wageningen : Wageningen University - ISBN 9789462575509 - 161
eiwit - wei-eiwit - zeïne - drogen - droogmethoden - geneesmiddeltoedieningssystemen - hydratatie - hydrofobiciteit - ph - vacuolen - protein - whey protein - zein - drying - drying methods - drug delivery systems - hydration - hydrophobicity - vacuoles

Proteins are the building blocks of life and serve a wide range of essential functions in organisms. Many metabolic reactions in organisms are catalysed by enzymes, DNA is replicated by proteins and in cells proteins often facilitate active transport of e.g. glucose or ions. Proteins also serve an essential functionality in foods, pharmaceutics, bioplastics and even clothing. Recently, the use of proteins towards higher concentrations is of interest for food, pharmaceutical and medical applications. Nevertheless, the preparation of products with desired product properties can be challenging, when approaching higher protein concentrations. Therefore, in this thesis we investigate proteins at higher concentrations, especially focussing on their drying and hydration behaviour.

In part one of the thesis, the focus is on the dynamics of drying of proteins towards higher concentrations. Dense proteins systems have been scarcely studied compared to proteins at lower concentrations. We address drying behaviour where we focus on the use of whey protein isolate as a model system. In part two of the thesis we focus on the hydration properties of the corn protein zein, where we apply it as a drug excipient. In this part we also investigate the influence of hydration on the release behaviour of drugs into the hydration media.

The drying part (part one) contains two studies. The first study is more fundamental in nature, focussing on the drying of a protein coating. In previous studies mainly the macroscopic properties of protein coatings after drying are investigated, leaving the drying dynamics virtually unexplored. Here we investigate the drying behaviour of the model protein β-lactoglobulin on multiple length scales with an unique combination of in-line techniques. On the microscopic length scale we use dynamic vapour sorption and magnetic resonance imaging while on a smaller length scales, we apply diffusing wave spectroscopy and IR-spectroscopy to monitor the drying process. For all used techniques, the changes in the measured physical properties of the coating as a function of water weight fraction Xw from Xw = 0.8 down to Xw = 0.2 are gradual. However, using dynamic vapour sorption and IR-spectroscopy we measure a sharp change below water weight fractions of Xw = 0.2. We hypothesise that changes in the molecular interactions caused by dehydration of the protein results in a change in the drying kinetics of the film.

In the second study of part one, protein drying is approached on a more applied level, where we study the drying of a spherical droplet. We use single droplet drying as a methods that can model the spray drying process in a simplified and well-controlled way. Sessile droplets are subjected to varying drying conditions such as temperature, initial protein concentration, presence of airflow and droplet rotation. During these experiments the morphological development is monitored by a camera. After drying, scanning electron microscopy and X-ray tomography are used to examine the particles that are formed after complete drying. Irrespective of the conditions used, we observe an initial droplet shrinkage, followed by the nucleation of a hole in the droplet skin, which is followed by the formation of a vacuole. The drying conditions used, strongly influenced the location of the hole and the locking point prior to hole formation. We hypothesise that the location of the hole is caused by local inhomogeneities in protein concentration causing a the nucleation of the hole where the local skin modulus is lowest. Also the locking point of the droplet is found to be due to a inhomogeneity over the whole droplet caused by rapid evaporation. These results can be of importance to understand powder structure and functionality as obtained in spray drying.

In the hydration part (part 2), we investigate the potential of zein as a sole excipient in macroscale caplets obtained by hot melt extrusion (HME) and injection moulding (IM). Zein is good candidate as a sustained release agent, because it is insoluble in two studies. In the first study zein matrices were loaded with the drug paracetamol. Physical mixtures of zein, water and crystalline paracetamol are extruded and injection moulded into caplets. Characterisation of these caplets is performed using differential scanning calorimetry, IR- spectroscopy, scanning electron microscopy and powder X-ray diffraction. The hydration and drug release kinetics from the caplet slices is measured. We find that the drug release kinetics is broadly independent of the dissolution medium and drug loading. The release kinetics is diffusion limited and could be well described by a 2D diffusion model. The results demonstrate that the drug release rate from zein caplet slices can be tuned by its dimensions.

In the second study, a wider range of drugs differing in hydrophobicity is studied. Next to paracetamol, we have used two other model drugs: the hydrophobic indomethacin and the more hydrophilic ranitidine. The zein matrix is capable to stabilize the different dugs in a non-crystalline state, which is promising especially for increasing the bioavailability of poorly water-soluble drugs. Overall crystallinity of the drugs in the caplets increases with its degree of hydrophobicity. For the poorly soluble indomethacin, dissolution rates at low pH were higher from caplet slices, compared to the dissolution rates of indomethacin crystals by themselves. In addition, we found that the electrostatic interactions between zein and drugs can also be used to influence the release kinetics.

Various aspects were found to be of importance both for drying and hydration of concentrated protein systems. The homogeneity during both processes deserves attention as its manipulation can strongly influence final properties if the system. Also the plasticising effect of water on dense proteins is often found essential, when understanding the dynamics of both drying and hydration processes. Finally protein hydrophobicity and its manipulation can provide a window of opportunities in many applications which are involve by drying or hydration.

De in vitro verteerbaarheid van gedroogde algen
Krimpen, M.M. van; Wikselaar, P.G. van; Bikker, P. - \ 2014
Wageningen : Wageningen UR Livestock Research (Report / Wageningen UR Livestock Research 812) - 13
voer - diervoeding - algen - drogen - voedingswaarde - in vitro verteerbaarheid - chemische samenstelling - bioraffinage - biobased economy - feeds - animal nutrition - algae - drying - nutritive value - in vitro digestibility - chemical composition - biorefinery
In deze studie is de chemische samenstelling en de in vitro organische stof- en stikstofverteerbaarheid van gedroogde algen bepaald. Het betrof een drietal algenproducten, namelijk algen gedroogd bij 700C, algen samen met een hulpstof gedroogd met een innovatieve techniek en algen samen met rijst gedroogd bij 700C. Als referentiegrondstoffen zijn in deze studie een eiwitrijke (sojaschroot) en een vezelrijke grondstof (kuilgras) meegenomen. Op basis van de in vitro resultaten is tevens nagegaan wat de voederwaardeprijs is van de algenproducten.
Ammoniakvorming in mestdroogsystemen op legpluimveebedrijven met mestbandbeluchting = Ammonia production in manure drying systems at layer farms with manure belt aeration
Winkel, A. ; Blanken, K. ; Ellen, H.H. ; Ogink, N.W.M. - \ 2014
Lelystad : Wageningen UR Livestock Research (Report / Wageningen UR Livestock Research 730) - 20
pluimveehouderij - hennen - pluimveehokken - ammoniakemissie - emissiereductie - droge stof - mestverwerking - drogen - luchtverontreiniging - poultry farming - hens - poultry housing - ammonia emission - emission reduction - dry matter - manure treatment - drying - air pollution
In this study, we investigated whether ammonia emissions from manure drying systems can be reduced by pre-drying the manure to ca. 55% of dry matter. This study shows that the ammonia emission of drying manure decreases with dry matter content. Pre-drying of manure to 55% of dry matter prevents the occurrence of high emissions in the first phase of the drying process and can reduce the emission from manure drying systems with 50–60%.
Emissies uit mestdroogsystemen op leghennenbedrijven bij dagontmesting en versneld drogen = Emissions from manure drying systems on layer farms using 24-h manure removal and rapid drying
Winkel, A. ; Huis in 'T Veld, J.W.H. ; Nijeboer, G.M. ; Schilder, H. ; Hattum, T.G. van; Ellen, H.H. ; Ogink, N.W.M. - \ 2014
Lelystad : Wageningen UR Livestock Research (Report / Wageningen UR Livestock Research 731) - 43
pluimveehouderij - hennen - ammoniakemissie - emissiereductie - pluimveehokken - mestverwerking - drogen - fijn stof - luchtverontreiniging - poultry farming - hens - ammonia emission - emission reduction - poultry housing - manure treatment - drying - particulate matter - air pollution
In dit onderzoek is de hypothese getoetst dat met het dagelijks afdraaien van alle stalmest naar een mestdroogsysteem (dagontmesting), gevolgd door snelle indroging, de extra ammoniakemissie uit deze droogsystemen aanzienlijk kan worden beperkt. Deze hypothese is bevestigd door het onderzoek. Daarnaast is gebleken dat de aangepaste manier van drogen nog steeds een aanzienlijke fijnstofreductie bewerkstelligt.
Drying of healthy foods : from mechanism to optimization
Jin, X. - \ 2013
University. Promotor(en): Gerrit van Straten; Remko Boom, co-promotor(en): Ton van Boxtel; Ruud van der Sman. - S.l. : s.n. - ISBN 9789461738141 - 168
broccoli - drogen - sorptie-isothermen - voedselkwaliteit - modelleren - simulatiemodellen - drying - sorption isotherms - food quality - modeling - simulation models

Convective drying is an effective post-harvest method to the extend shelf life of vegetables and to reduce the mass for transportation. The heat load during drying, however, affects the quality attributes negatively. Today, consumers in the industrialized world pay a raised attention on food quality, and especially to the nutritional value of food. This increased demand on quality has become a challenge for drying research, and to retain the nutritional value, mild drying conditions must be applied. However, at these conditions the energy efficiency to remove the water from the product by evaporation is low; often below 50%. Moreover, due to the growing global market for dried products, drying contributes more and more to the global energy consumption and CO2-emission. Hence, there is a need for high energy efficient drying methods with low CO2-emission. A straightforward solution to increase drying energy efficiency is high temperature drying, but these conditions are conflicting with the aim to retain nutritional components. To combine these two aims, i.e. energy efficient drying and retention of nutritional components, is a challenge for drying research.

In this thesis work, the conflict between quality retention and energy efficiency is investigated for the drying of broccoli. The approach in this work is based on mechanistic driven drying modeling and optimization. The approach includes three crucial elements: 1) mechanistic driven model development, 2) model validation, and 3) mechanistic model assisted optimization.

In the first parts of the thesis advanced mechanistic drying models are introduced. These are the Free Volume theory for moisture transport (Chapter 2), and the Flory-Huggins Free Volume theory to describe sorption isotherms (Chapter 3). The strength of these theories is that the mobility of water is based on the changes in physical state during drying (from rubbery to glassy state) and the mixing properties of water, biopolymers and solutes. These mechanistic models allow the extrapolation of the drying behavior to not experimentally validated conditions. Moreover, the model parameters have a physical basis and can directly be related to material properties. The drying behavior in broccoli is represented by 2D color maps to visualize the spatial distribution of moisture content, the progress of degradation of nutritional components in the product and shrinkage during drying. The influences of pre-treatments are also incorporated in the models.

The second part of the thesis concerns experimental validation of the models from Chapter 2 and Chapter 3. In Chapter 4 moisture transport during drying of broccoli is monitored with MRI (Magnetic Resonance Imaging) as a non-destructive technique. The results show the spatial distribution of moisture content, shrinkage and drying rate of differently pre-treated samples during drying. The images revealed non-Fickian diffusion behavior for fresh stalks. The non-Fickian diffusion is caused by the moisture transport resistance of the stalk skin which creates, together with shrinkage, center directed stress driven moisture transport. This phenomenon was absent in pre-treated broccoli samples for which the resistance for moisture transport in the skin was reduced.

The drying rates for broccoli florets and stalks are derived from MRI data in Chapter 5. The Free Volume theory for moisture transport is validated on the average moisture content from the MRI experiments. The fitting parameters are the mass transfer coefficient and the self-diffusion coefficient of solids. The results quantify the enhanced drying rates of fresh and pre-treated samples due to the removal of the transport resistance in the skin and the changed cell structure. The influence of pre-treatments on the drying rate is in line with the results of Chapter 4. Comparison of experiments in a pilot dryer showed a good agreement with the drying behavior in the MRI device.

Chapter 6concerns dynamic optimization to derive optimal drying trajectories that increase both energy efficiency and retention of nutritional components during drying of broccoli. For this step it was necessary to derive, from the spatial model, a drying model for the average moisture content and average value of the nutritional components. The kinetics for the degradation of glucosinolates and vitamin C (obtained from a parallel project) and the drying rate of broccoli are applied to calculate optimized drying trajectories for the control variables of temperature and air flow rate. The results have shown that with optimal trajectories the energy consumption can be halved, the vitamin C retention can be increased significantly, and the influence of drying on the degradation of glucosinolates is reduced to nearly zero. The optimized drying trajectories are plotted in an isokinetic temperature-moisture content state diagram which shows that the product areas with high degradation rates are circumvented.

Finally, in Chapter 7 the contribution of the thesis work and the impact on drying research and the perspectives are discussed. The mechanistic driven drying modeling and optimization approach to produce healthy dried food is regarded as a fundamental approach which uses physical and chemical properties of the product. The advantage of the approach is the potential for application to a large range of processing conditions. The isokinetic temperature-moisture content state diagram, which gives a direct overview of possible pathways to retain heat sensitive components, is a powerful tool to support decision making in multi-objective problems in food process design. This thesis work is an important step in mechanistic modeling and optimization, but the end of this approach is not yet reached. Further adoption of the proposed methodology of monitoring and modeling transport phenomena and degradation of micronutrients in food matrices is believed to advance the quality of food products.

Energy-efficient low-temperature drying using adsorbents: a Process Systems Engineering approach
Atuonwu, J.C. - \ 2013
University. Promotor(en): Gerrit van Straten, co-promotor(en): Ton van Boxtel. - S.l. : s.n. - ISBN 9789461734617 - 183
drogen - energiebesparing - adsorberende middelen - procesbewaking - procesoptimalisatie - drying - energy saving - adsorbents - process control - process optimization

Diurnal evolution of organic aerosol over boreal and tropical forests

The first research question of this thesis is: how do local surface forcings and large-scale meteorological forcings shape the evolution of organic aerosol over the boreal and tropical forest? This question is dealt with in Chapters 3 and 4 in case studies for the boreal and tropical forest, respectively. To answer this question a modeling tool (MXLCH-SOA) is developed, which represents land surface conditions and dynamical and chemical processes that influence the evolution of organic aerosol (OA) in a balanced way. The novelty of our approach is that it combines the dynamics of a convective boundary layer (BL) with a reduced gas-phase chemistry mechanism and a module for gas/particle-partitioning of semi-volatile organic species. The principles and governing equations of this modeling tool are described in Chapter 2 and in the subsequent chapters the simplified chemical reaction schemes are presented to calculate secondary organic aerosol (SOA) formation from terpenes (Chapter 3 and 4) and from isoprene (Chapter 4).

Despite its simplicity, MXLCH-SOA is able to satisfactorily reproduce the main observed characteristics of dynamics, gas-phase chemistry and gas/particle partitioning for the two studied forest ecosystems and it enables us to explain the temporal variability of the concentrations of organic aerosol and its precursors as a function of the various processes. In short, the results show that the diurnal evolution of organic aerosol in a boreal and a tropical forest is the net result of land surface conditions, boundary layer dynamics, chemical transformations and gas/particle partitioning. In the case study for the boreal forest, the entrainment term of the background OA dominates the OA tendency, while in the tropical forest case it is the interplay of several local and large scale processes that shape the diurnal evolution of OA. A sensitivity analysis for the boreal forest case further shows that the OA concentration is sensitive to both volatile organic compound (VOC) emissions and the partitioning of the surface energy budget into a latent and a sensible heat flux. We have identified two regimes, based on which of the two studied land surface drivers dominates: one in which OA is mainly driven by SOA formation from the emitted VOCs and another in which dilution due to entrainment, as driven by the surface energy fluxes, determines the OA concentration. A background OA to fresh SOA ratio is introduced to facilitate the interpretation of this analysis and is used to quantify the contributions of both fresh and background components to the total OA concentration. One main difference between the two case studies is that in the boreal forest entrainment appears to dominate the diurnal cycle, which leads to a decreasing OA concentration during the day, while in the tropical forest the formation of SOA from both isoprene and terpenes leads to increasing OA concentrations during day time. The MXLCH-SOA framework therefore shows the need to represent all these biochemical and physical processes simultaneously in order to understand the diurnal evolution of OA.

As the boundary layer dynamics-chemistry system is not a closed system, it is necessary to further study the influence of external forcings on the diurnal evolution of OA, besides the surface forcings. Two types of large-scale meteorological forcings and their effects on OA evolution through their impact on BL dynamics have been studied: subsidence due to the presence of a high pressure system and advection of relatively cool air. In Chapter 3 a theoretical sensitivity analysis is given of OA evolution to subsidence, which is applied to the tropical forest case study in Chapter 4. Subsidence has a rather counter-intuitive effect on OA concentrations: even though it suppresses the growth of the BL and consequently decreases the mixing volume for chemical species, it leads to decreased OA concentrations. The reason for this is that entrainment is strongly enhanced in case of subsidence due to thermodynamic effects, which results in a stronger dilution of OA. This knowledge is applied in the case study for the tropical forest in Chapter 4, since results from a large-scale model show subsiding air motions over the measurement site and surroundings at Borneo.

In addition to subsidence, the advection of cool air is needed to reproduce the observed boundary layer dynamics at Borneo: only if subsidence and advection of relatively cool air are accounted for, the observed low BL height can be reconciled with the large observed surface sensible and latent heat flux. This cool air suppresses BL growth and entrainment. Consequently, the aerosol is trapped in a shallower layer, which leads to an increased concentration compared to the case without advection of cooler air. In conclusion, the large-scale meteorological forcings subsidence and advection of cool air have opposing effects on the diurnal evolution of OA, even though both suppress BL growth. These findings show the utility of our method in identifying effects that should be accounted for in large-scale chemistry transport models.

The second research question is whether recently discovered pathways of isoprene chemistry are the key to closing the gap between measured and modeled organic aerosol concentrations in tropical forests and other high isoprene environments. To address this issue, several mechanisms which may affect SOA formation from isoprene are implemented in MXLCH-SOA and discussed in Chapter 4. The hydroxyl radical (OH), the main oxidant of isoprene, is thought to be regenerated in the oxidation of isoprene. We find that for the tropical forest case study, we cannot reconcile the modeled concentrations of VOCs, OH and OA with their observed concentrations and fluxes both for cases with and without OH recycling. Therefore, we conclude that the issue of recycling of the OH radical in the oxidation of isoprene has to be solved before its effect on SOA formation can be determined.

The formation of SOA from isoprene involves multiple generations of oxidation and due to this complex chemistry there is no single mechanism which can explain SOA formation from isoprene under all conditions. To gain understanding in this issue, we have implemented different pathways through which isoprene SOA is known to form, although we do not explicitly account for the detailed isoprene oxidation chain. A central aspect of this branching approach is whether the isoprene peroxy radical chemistry follows the low- or the high-NOx pathway. We find that the latter channel dominates in our case study. For SOA formed through the high-NOx channel, we further account for the effect of the NO2/NO ratio on SOA yields. In the presented case study this has little effect as this ratio is low, it but could be more important in regions with slower photochemistry or higher emissions of anthropogenic pollution. In the low-NOx regime, isoprene epoxides (IEPOX) are important intermediate gas-phase species in the formation of isoprene SOA. Even though the low-NOx pathway is only a minor one here, the amount of IEPOX SOA formed is likely substantial, although a better understanding of the exact mechanisms for its formation is needed to confirm this. However, as in previous studies we systematically underestimate the organic aerosol concentration in a tropical forest even though we incorporate the state-of-the-art knowledge on isoprene SOA formation in MXLCH-SOA. Nevertheless, we advocate accounting for NOx regime specific chemical pathways when modeling isoprene SOA formation. As this field is rapidly evolving in terms of the development of new measurement techniques and the discovery of chemical mechanisms, we strongly recommend the intensive use of our modeling system to gain further understanding of the diurnal variability of OA and for testing new hypotheses under atmospheric conditions.

Satellite observations of cloud droplet concentration over the boreal forest

The final objective of this thesis is to understand how aerosols and meteorological factors influence cloud droplet concentration over the boreal forest. This is a first step in translating the process understanding such as addressed in the previous chapters to larger spatio-temporal scales. Since this objective considers different temporal and spatial scales, a different method is applied in Chapter 5 than in the foregoing chapters. Observations of cloud properties by the MODIS instrument onboard the Terra satellite are combined with a model that contains the microphysics and thermodynamics of a single-layered water cloud to obtain a seasonal cycle of cloud droplet number concentrations, averaged over 9 years of data. This seasonal cycle in cloud droplet concentration is compared with aerosol concentrations at the surface and meteorological fields from ECMWF reanalysis. We find that the cloud droplet number concentration is related to the potential temperature gradient in the boundary layer, a measure for the strength of convection, while it shows no clear relationship with the cloud active aerosol concentration at the surface. From this we conclude that the convective transport of the aerosols from the surface to cloud base is the limiting factor for their activation as cloud droplets. However, convection will also influence the formation of clouds from a thermodynamic perspective. Therefore, it is likely that convection, as driven by land surface conditions, regulates both transport of aerosols to cloud base and the height of the cloud base, defined as the height at which water vapor reaches its saturation pressure. To ultimately understand the effect of the boreal forest on cloud properties, the effects of aerosols and thermodynamics should be studied simultaneously.

Alternatieven water geven phalaenopsis in de wacht
Kromwijk, J.A.M. - \ 2012
Vakblad voor de Bloemisterij 67 (2012)36. - ISSN 0042-2223 - p. 34 - 35.
phalaenopsis - sierplanten - irrigatie - dompelen - drogen - alternatieve methoden - landbouwkundig onderzoek - besluitvorming - teeltsystemen - ornamental plants - irrigation - dipping - drying - alternative methods - agricultural research - decision making - cropping systems
Wageningen UR en Fytofocus onderzochten twee alternatieve manieren om phalaenopsis water te geven. Droogblazen na water geven en dompelen. Dompelen biedt perspectief, maar vervolgonderzoek komt er niet.
Droogblazen na watergeven biedt minder perspectief: Dompelen goed alternatief voor droogstoken phalaenopsis (interview met Arca Kromwijk)
Arkesteijn, M. ; Kromwijk, J.A.M. - \ 2011
Onder Glas 8 (2011)11. - p. 43 - 43.
phalaenopsis - cultuurmethoden - watervoorziening - dompelen - energiebesparing - drogen - proeven - glastuinbouw - groenten - potplanten - cultural methods - water supply - dipping - energy saving - drying - trials - greenhouse horticulture - vegetables - pot plants
Phalaeonopsisplanten krijgen in de teelt bovendoor water. Daarna worden de planten en de kas drooggestookt om ziekten te voorkomen. Hier valt energie te besparen. Onderzoeker Arca Kromwijk bekeek twee alternatieven: het dompelen van de planten zodat het gewas droog blijft en het droogblazen van het gewas na het bovendoor water geven.
Verbetering kuubskist : Energie-efficiënt drogen in een half(1/2)-laagssysteem
Wildschut, J. ; Sapounas, A. ; Wit, P. de; Bisschops, B. - \ 2010
Lisse : PPO Bloembollen en Bomen - 44
bloembollen - kratten - drogen - luchtstroming - optimalisatiemethoden - operationeel onderzoek - energiebesparing - ornamental bulbs - crates - drying - air flow - optimization methods - operations research - energy saving
Op basis van eerdere testen is het ontwerp van een alternatieve kuubskist naar een idee van Peter de Wit (bloembollenbedrijf N.N.J. de Wit/Nord Lommerse) d.m.v. CFD(modellering verbeterd. De 2 dwars op het palletkanaal ongeveer halverwege de kisthoogte geplaatste buizen van hetzelfde geperforeerde materiaal als de kistbodem zijn hierbij 10 cm hoger en 2,5 cm meer naar binnengeplaatst. Om ook tussen de buizen de luchtstroom te verbeteren zijn de perforaties in het bovenste en onderste kwadrant van de buizen gesloten. De resultaten samengevat in 6 punten op een poster ' Alternatieve kuubskist' zijn: Gelijkmatiger luchtverdeling over de kisten, kortere opstartfase van het droogproces, lagere weerstand en daardoor hoger debiet, 30% eerder sneldroog, kans op ziektes kleiner, 17 % op gas en 34% op elektra bespaard.
Korte inventarisatie naar het perspectief van het drogen van digestaat bij biogasinstallaties
Timmerman, M. ; Rulkens, W.H. - \ 2010
Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 289) - 27
mest - biogas - dierlijke meststoffen - veehouderij - drogen - digestaat - drijfmest - fermentatie - bemesting - biobased economy - manures - animal manures - livestock farming - drying - digestate - slurries - fermentation - fertilizer application
A short survey has been done into the prospect of drying of digestate at biogas plants. This survey gave a global overview of the (im)possibilities of drying of digestate at different scale sizes of (co)digestion.
Bedrijfseconomische vergelijking tussen gaasbak en kuubskist op handels- en exportbedrijven
Roelofs, P.F.M.M. ; Wildschut, J. - \ 2009
bloembollen - drogen - kratten - modellen - bedrijfseconomie - bedrijfskosten - arbeid (werk) - ornamental bulbs - drying - crates - models - business economics - operating costs - labour
Tegenwoordig wordt er in de teelt vrijwel alleen gewerkt met kuubskisten en worden ze ook in de handel gebruikt. Met een model zijn verschillende bedrijfssituaties (scenario’s) doorgerekend. Hiebij de resultaten van een zevental scenarioberekeningen. Bij dit onderzoek wordt gekeken naar alle bloembollen in gaasbakken of alle bloembollen in kuubskisten.
NIZO food research komt met optimalisatie
Schutyser, M.A.I. ; Straatsma, H. ; Hadiyanto, M. ; Akkerman, C. ; Jong, P. de - \ 2008
Bulk 2008 (2008)3. - ISSN 1380-569X - p. 12 - 17.
drogen - voedseltechnologie - droogmethoden - technieken - voedselkwaliteit - productieprocessen - drying - food technology - drying methods - techniques - food quality - production processes
Droogprocessen opereren vaak suboptimaal. Dit heeft te maken met de complexe afweging van energiekosten, productkwaliteit, drogerontwerp en veiligheid. NIZO food research kan bij het vinden van oplossingen assisteren middels een stapsgewijze optimalisatieaanpak. Bij deze aanpak worden naast proces- en productscans ook simulatietechnieken gebruikt. Het blijkt dat al snel besparingen van 10-20% in de operationele kosten kunnen worden gerealiseerd. Naast sproeidrogen vinden ook droogtechnologieën zoals walsdrogen, zeolietdrogen en vriesdrogen een steeds breder toepassingsgebied.
Development of appropriate processing technology for fruit export by smallholder farmers : technical assistance in the processing of products of Equator Products Ltd. in Kenya : report of research activities in 2008
Bartels, P.V. - \ 2008
Wageningen : Agrotechnology and Food Sciences Group (A&F report / Agrotechnology and Food Sciences Group 990) - ISBN 9789085853428 - 49
voedselbewaring - drogen - droogmethoden - drogers - zonne-energie - zonne-energieverwarming - decontaminatie - spaanse pepers - kenya - food preservation - drying - drying methods - driers - solar energy - solar heating - decontamination - chillies
Energy efficient multistage zeolite drying for heat sensitive products
Djaeni, M. - \ 2008
University. Promotor(en): Gerrit van Straten; Johan Sanders, co-promotor(en): Ton van Boxtel; Paul Bartels. - [S.l.] : S.n. - ISBN 9789085852094 - 162
drogers - drogen - droogmethoden - absorptie - adsorptie - adsorberende middelen - energiegebruik - ontvochtiging - drogende lucht - energiebesparing - computationele vloeistofdynamica - driers - drying - drying methods - absorption - adsorption - adsorbents - energy consumption - dehumidification - drying air - energy saving - computational fluid dynamics
Although drying takes a significant part of the total energy usage in industry, currently available drying technology is often not efficient in terms of energy consumption. Generally, the energy efficiency for drying processes ranges between 20-60% depending on the dryer type and product to be dried. This research focuses on the development of single and multistage zeolite drying combined with heat recovery unit to enhance the energy efficiency. The evaluation using steady state and two dimensional model showed that for single stage system the energy efficiency can reach 70-75% and it increases corresponding to the stage number. For 2-3 stages, the energy efficiency 80-90% can be achieved. The experimental work using single stage zeolite dryer also showed that the energy efficiency is close to conceptual approach. Based on the impressive results, a number of potential options have been formulated to construct the zeolite dryer in continuous operating systems for industrial application.
Extrusion processing : effects on dry canine diets
Tran, Q.D. - \ 2008
University. Promotor(en): Martin Verstegen; Wouter Hendriks, co-promotor(en): Thomas van der Poel. - [S.l.] : S.n. - ISBN 9789085049036 - 108
honden - hondenvoeding - droogvoer - diëten - uitpersing - drogen - eiwit - lysine - zetmeelkorrels - smakelijkheid - voedermiddelbewerking - dogs - dog feeding - dry feeds - diets - extrusion - drying - protein - starch granules - palatability - feed processing
Keywords: Extrusion, Canine diet, Protein, Lysine, Starch gelatinization, Palatability, Drying.

Extrusion cooking is a useful and economical tool for processing animal feed. This high temperature, short time processing technology causes chemical and physical changes that alter the nutritional and physical quality of the product. Effects of extrusion on the feed quality for other animals than pets have been well recognized. Our studies investigated to what extent extrusion and/or drying of a complete canine diet affects lysine reactivity, amino acids, fatty acids, starch gelatinization and physical parameters.
In order to create a general view of dog food quality in practice, the physical and nutritional quality of commercial canine diets available in the Netherlands were examined. This study showed unveiled variation in lysine reactivity and starch gelatinization of commercial dry canine diets. A study was then carried out on the effects of extrusion on the physical and nutritional values of canine diets in a FIDO model. The extrusion conditions (temperatures in the range of 110 to 150ºC, 300 g/kg moisture) increased lysine reactivity, starch gelatinization and in-vitro starch digestibility. Protein digestibility and dispersibility were not affected by the extrusion conditions used. The increase in the extrusion temperature used (110 to 150ºC) decreased kibble durability but did not affect hardness. This study also concluded that optimisation of extrusion conditions during production of commercial canine diets should include the measurement of the reactive to total lysine ratio. Single ingredients of a complete canine diet did not respond in a similar way during extrusion: extrusion had no effects on animal ingredients (higher lysine contents) while extrusion could decrease (in barley) or increase (in rice) the reactive lysine content in vegetable ingredients (lower lysine content). Both reactive lysine content and ratios of reactive to total lysine of the mixture of all vegetable ingredients were hugely increased during extrusion. Finally, an additional study was carried out on the effects of drying on extruded canine diets. The results of this study showed that drying temperature (in the range of 120-160ºC) and drying time did not affect the quality of extruded canine diets in terms of amino acids and fatty acids levels while these drying temperatures reduced drying time from hours to minutes. Drying temperature only affected the reactive lysine content and, therefore, the ratio of reactive to total lysine of kibbles dried at a temperature of 200ºC. Drying temperature also affected a minority of fatty acids with fatty acid C18:3 n-3 being the most affected at a drying temperature of 200ºC.
In conclusion, extrusion at temperatures in the range of 130-150ºC and at a moisture of 300 g/kg is a mild heat treatment with respect to protein quality for pet food production. Measurement of the ratio of reactive to total lysine should be included in optimisation of extrusion conditions during pet food production. Drying temperature in the range of 120-160ºC and drying time do not affect the amino acids and fatty acids level of extruded canine diets.

State-of-the-Art bewaarsysteem tulpenbollen
Wildschut, J. ; Kok, M. ; Kreuk, F. - \ 2007
Lisse : PPO Bloembollen en Bomen - 30 p.
bloembollen - tulpen - energiebesparing - opslag met klimaatbeheersing - operationeel onderzoek - drogen - opslagkwaliteit - ornamental bulbs - tulips - energy saving - controlled atmosphere stores - operations research - drying - storage quality
Het State-of-the-Art systeem voor het bewaren van tulpenbollen bestaat uit 4 componenten waarvan in eerder onderzoek is aangetoond dat deze ieder afzonderlijk veel energie kunnen besparen: 1) De moderne systeemwand met afgeronde uitblaasopeningen en een interne schuine wand en 2) de aangepaste kuubskist met afgeschuinde hoekbalken en smallere bodemlatten reduceren de luchtweerstand en verhogen daardoor het debiet, 3) verminderde circulatie met frequentieregelaars vermindert het kWh-verbruik van de ventilatoren en 4) ethyleengestuurde ventilatie vermindert het gasverbruik en verbetert daarnaast de kwaliteit van de bollen. Doelstelling van het State-of-the-Art project is om te onderzoeken hoe op praktijkbedrijven de combinatie van deze componenten plus sturing door de klimaatcomputer, uitpakt in termen van energie- en kostenbesparing en om het ‘State-of-the-Art’-systeem te demonstreren aan de doelgroep: telers en broeiers van tulpenbollen.
Energiestroom tulp en hyacint
Wildschut, J. ; Kok, M. ; Bisschop, B. - \ 2006
Lisse : PPO Bloembollen en Bomen - 25
bloembollen - forceren van planten - drogen - opslag met klimaatbeheersing - optimalisatiemethoden - energiegebruik - ornamental bulbs - forcing - drying - controlled atmosphere stores - optimization methods - energy consumption
De projectdoelstellingen zijn: 1) Het actualiseren en beter in kaart brengen van de energiestromen voor teelt (gas en elektra) en broei (elektra) van tulpen. 2) Het actualiseren en beter in kaart brengen van de energiestromen (gas en elektra) voor teelt en broei van hyacint. 3) Het afleiden van de meest optimale droog- en bewaarmethode (en/of omstandigheden en/of strategie en/of apparatuur), uit een analyse van de spreiding in gasverbruik/ha bij de teelt van tulpen.
Modelling and dynamic optimisation of quality indicator profiles during drying
Quirijns, E.J. - \ 2006
University. Promotor(en): Gerrit van Straten, co-promotor(en): Wilko van Loon. - [S.l.] : S.n. - ISBN 9085044286 - 254
drogen - droogkwaliteit - kwaliteitsnormen - kwaliteitscontroles - indicatoren - optimalisatie - optimalisatiemethoden - dynamische modellen - drying - drying quality - quality standards - quality controls - indicators - optimization - optimization methods - dynamic models
Teelthandleiding graszaad - drogen
Borm, G.E.L. - \ 2005
Kennisakker.nl 2005 (2005)15 juni.
grassen - zaadbehandeling - drogen - ventilatie - akkerbouw - graszaden - teelthandleidingen - grasses - seed treatment - drying - ventilation - arable farming - grass seeds - cultivation manuals
In deze teelthandleiding wordt ingegaan op het ventileren en drogen van zaad, de techniek van het drogen en de droogsystemen.
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