Papers by Ruud Van Der Sman
A method to produce monodisperse emulsions in a controlled and energy efficient way would be of g... more A method to produce monodisperse emulsions in a controlled and energy efficient way would be of great importance to various scientific and industrial fields. Several microfluidic droplet formation techniques can produce highly monodisperse emulsion on a small scale. Emulsification based on spontaneous droplet generation in microchannels is one of those techniques. Single microchannels are quite well understood, however, to achieve reasonable throughput, many microchannels have to be operated in parallel. Unfortunately, up-scaled systems do not perform as straightforward as expected. We have studied a single microchannel with several terrace lengths and found that longer terraces produce larger droplets and have a broader practical pressure range. Coupling effects between neighbouring channels have been studied as well. The droplet size is comparable to found for a single channel, but the pressure dependency is much more sensitive in a parallelized system. This is mainly caused by the formation droplets at each channel, which induces disturbing pressure gradients in the channels, leading to limited productivity. In the presentation of the conference, we will present design rules for microstructures, and present designs which do not suffer from these limitations.
Characterization of water diffusion in food products for MRI experiments
European project CAFE WP4: Model reduction, validation and simulation - Deliverable 4.2: Portable and documented simulation software for each demonstration process
Journal of Membrane Science
Hypotheses concerning the fouling of membranes during beer clarification via crossflow microfiltr... more Hypotheses concerning the fouling of membranes during beer clarification via crossflow microfiltration are reviewed. Beer has been classified into three groups of components, each having a different kind of fouling mechanisms -but also having interactions with other modes of fouling. The membrane fouling also strongly depends on the characteristics of the membrane. An optimal pore diameter and membrane morphology can be identified. The various hypotheses have been formulated in terms of mathematical models, which are tested using experimental data of dead-end filtration of beer. This comparison shows that our hypotheses are quite likely to be valid, and form a good basis for further model-based exploration of the optimization of the beer clarification process. Due to the similarity of beer with biotechnological broths, the presented fouling hypotheses extend beyond the original application of beer microfiltration.
Product-oriented intensive heating process design
Control of product quality and process yields in innovative food production processes can be larg... more Control of product quality and process yields in innovative food production processes can be largely improved through better understanding of the relations between process design and product quality.The effects of intensive heating processes such as frying, baking, roasting and microwave on product quality are still poorly understood. Currently, when designing new food processing lines, empirical knowledge of the effects of various process types on product quality is leading.With upcoming `new¿ heating methods, more fundamental insight is essential
ENVR 45-Fluids treatment without membrane fouling: Use of micro- and nanoengineered membranes and flow induced segregation
ACS National Meeting Book of Abstracts
Comparison of first principles model of beer microfiltration to experiments via systematic parameter identification
Journal of Membrane Science, 2015
ABSTRACT A first principles microfiltration model based on shear-induced diffusion is compared to... more ABSTRACT A first principles microfiltration model based on shear-induced diffusion is compared to experiments performed on the clarification of beer. After performing an identifiability and sensitivity analysis, the model parameters are estimated using global minimization of the sum of least squares. The model is compared to different series of experiments, where either crossflow or permeate flux is varied. This study is concluded with a parameter study on the scaling of the filtration time with various model parameters. We have found that the filtration time primarily depends on two dimensionless numbers, namely the normalized critical distance for cake layer formation, and the dimensionless time required to plug all pores in the selective layer. We have found that there is an optimal setting of these parameters, rendering a maximal amount of filtrated beer in one cycle.
Flow through deterministic ratchets for fractionation purposes
The Effect of Structure and Imbibition Mode on the Rehydration Kinetics of Freeze-dried Carrots
Special Publication, 2013
Complementary imaging techniques (µCT, SEM, MRI), NMR and quantitative image analysis methods wer... more Complementary imaging techniques (µCT, SEM, MRI), NMR and quantitative image analysis methods were used to obtain multi-length scale information of the porous structure of carrots in their freeze-dried, rehydrating and rehydrated form. This work established a predictive relation between freezing rate and freeze damage. Water imbibition rates could be explained from the porous structure induced during freeze-drying. In the rehydrated state, remaining structural integrity and anisotropy could be correlated with the textural quality.
Deterministic lateral displacement (DLD) ratchets are microfluidic devices, which are used for si... more Deterministic lateral displacement (DLD) ratchets are microfluidic devices, which are used for size-based sorting of cells or DNA. Based on their size, particles are showing different kinds of motion, leading to their fractionation. In earlier studies, so-called zigzag and displacement motions are observed, and in recent study by our group (Kulrattanarak et al., Meas Sci Technol, 2010a; J Colloid Interface Sci, 2010b), we have shown that also mixed motion occurs, which is an irregular alternation of zigzag and displacement motion. We have shown that the mixed motion is due to asymmetry of the flow lane distribution, induced by the symmetry breaking of the oblique primitive lattice cell . In this study, we investigate mixed motion in depth by numerical and experimental analysis. Via 3D simulations, we have computed explicit particle trajectories in DLD, and are able to show that there are two critical length scales determining the type of motion. The first length scale d f,1 is the first flow lane width, which determines the transition between zigzag motion and mixed motion. The other length scale, d f,c , determines the transition between mixed motion and displacement motion. Based on our experimental and numerical results we have been able to correlate the migration angle of particles showing mixed motion to the particle size, relative to the two critical length scales d f,1 and d f,c .
An adaptive optimal scheduling and controller design is presented that attempts to improve the pe... more An adaptive optimal scheduling and controller design is presented that attempts to improve the performance of beer membrane filtration over the ones currently obtained by operators. The research was performed as part of a large European research project called EU Cafe with the aim to investigate the potential of advanced modelling and control to improve the production and quality of food. Significant improvements are demonstrated in this paper through simulation experiments. Optimal scheduling and control comprises a mixed integer non-linear programming problem (MINLP). By making some suitable assumptions that are approximately satisfied in practice, we manage to significantly simplify the problem by turning it into an ordinary non-linear programming problem (NLP) for which solution methods are readily available. The adaptive part of our scheduler and controller performs model parameter adaptations. These are also obtained by solving associated NLP problems. During cleaning stages in between membrane filtrations enough time is available to solve the NLP problems. This allows for real-time implementation.
Impact of different drying trajectories on degradation of nutritional compounds in broccoli (Brassica oleracea var. italica)
ABSTRACT This work concerns the degradation of the nutritional compounds glucoraphanin (GR) and v... more ABSTRACT This work concerns the degradation of the nutritional compounds glucoraphanin (GR) and vitamin C (Vc), and the inactivation of the enzyme myrosinase (MYR) in broccoli (Brassica oleracea var. italica) during drying with air temperatures in the range of 30–60 °C. Dynamic optimization is applied to find the optimized temperature trajectories that minimize degradation and inactivation. Simulation and experimental results for optimized temperature trajectories are compared to constant inlet air temperature drying at 40 and 50 °C. The results show that with the optimized temperature trajectories the retention of GR, MYR and Vc improved significantly. Moreover, the experiments show that degradation and inactivation during drying is slower than expected from kinetic studies. The deviation is explained from the difference in the physical state of the samples used in the drying experiments, i.e. original plant tissue versus the grounded state of the plant tissue used in the experiments for the kinetic studies. The results indicate that besides temperature and moisture content the physical state is also an important aspect in the degradation of nutritional compounds and enzymes.
Procedia Food Science, 2011
The internal moisture distribution that arise in food products during drying, is a key factor for... more The internal moisture distribution that arise in food products during drying, is a key factor for the retention of quality attributes. To reveal the course of moisture content in a product, internal moisture profiles in broccoli florets are measured by MRI imaging during drying experiments with controlled air flow and temperature. The 3D images concern a matrix size of 64×64×64 elements. Signal intensity is converted to product moisture content with a linear relationship, while taking a minimum detectable moisture content of 0.3 kg water/ kg dry matter into account. Moisture content as a function of time is presented for a 2D cross sectional area in the middle of a broccoli sample. The average moisture contents for the cross sectional area obtained from the MRI imaging are compared with spatial model simulations for the moisture distribution. In that model the effective diffusion coefficient is based on the Free Volume Theory. This theory has the advantage that the changed mobility of water in the product during drying is taken into account and the theory also predicts the moisture transport in the porous broccoli floret. Key parameters for the Free Volume Theory are estimated by fitting to the experimental MRI results and the effective diffusion coefficient is given as a function of the product water content.
Food and Bioprocess Technology, 2015
The change in water-holding capacity of mushroom with the temperature was interpreted using the F... more The change in water-holding capacity of mushroom with the temperature was interpreted using the Flory-Rehner theory for swelling of polymeric networks, extended with the Debye-Hückel theory for electrolytic interactions. The validity of these theories has been verified with independent sorption measurements. The change in water-holding capacity with temperature could be quantified as changes in three model parameters: the Flory-Huggins interaction parameter between the biopolymers and the aqueous solvent phase, the cross-link density of the network, and the biopolymer volume fraction at the relaxed state. The elastic pressure is analyzed using the Flory-Rehner theory, which is traditionally used to describe the swelling of polymers. From the explicit knowledge of the elastic pressure, we can determine how model parameters, such as the cross-link density, depend on temperature. We argue that the dependencies of model parameters can be understood as a consequence of protein denaturation. Having knowledge on how all contributions to the swelling pressure depend on temperature, and composition, we can compute the water-holding capacity of mushroom for a wide range of temperatures and mechanical loads.
Multiscale analysis of structure development in expanded starch snacks
Journal of Physics: Condensed Matter, 2014
In this paper we perform a multiscale analysis of the food structuring process of the expansion o... more In this paper we perform a multiscale analysis of the food structuring process of the expansion of starchy snack foods like keropok, which obtains a solid foam structure. In particular, we want to investigate the validity of the hypothesis of Kokini and coworkers, that expansion is optimal at the moisture content, where the glass transition and the boiling line intersect. In our analysis we make use of several tools, (1) time scale analysis from the field of physical transport phenomena, (2) the scale separation map (SSM) developed within a multiscale simulation framework of complex automata, (3) the supplemented state diagram (SSD), depicting phase transition and glass transition lines, and (4) a multiscale simulation model for the bubble expansion. Results of the time scale analysis are plotted in the SSD, and give insight into the dominant physical processes involved in expansion. Furthermore, the results of the time scale analysis are used to construct the SSM, which has aided us in the construction of the multiscale simulation model. Simulation results are plotted in the SSD. This clearly shows that the hypothesis of Kokini is qualitatively true, but has to be refined. Our results show that bubble expansion is optimal for moisture content, where the boiling line for gas pressure of 4 bars intersects the isoviscosity line of the critical viscosity 10(6) Pa.s, which runs parallel to the glass transition line.
Mesoscale models of dispersions stabilized by surfactants and colloids
Advances in Colloid and Interface Science, 2014
In this paper we discuss and give an outlook on numerical models describing dispersions, stabiliz... more In this paper we discuss and give an outlook on numerical models describing dispersions, stabilized by surfactants and colloidal particles. Examples of these dispersions are foams and emulsions. In particular, we focus on the potential of the diffuse interface models based on a free energy approach, which describe dispersions with the surface-active agent soluble in one of the bulk phases. The free energy approach renders thermodynamic consistent models with realistic sorption isotherms and adsorption kinetics. The free energy approach is attractive because of its ability to describe highly complex dispersions, such as emulsions stabilized by ionic surfactants, or surfactant mixtures and dispersions with surfactant micelles. We have classified existing numerical methods into classes, using either a Eulerian or a Lagrangian representation for fluid and for the surfactant/colloid. A Eulerian representation gives a more coarse-grained, mean field description of the surface-active agent, while a Lagrangian representation can deal with steric effects and larger complexity concerning geometry and (amphiphilic) wetting properties of colloids and surfactants. However, the similarity between the description of wetting properties of both Eulerian and Lagrangian models allows for the development of hybrid Eulerian/Lagrangian models having advantages of both representations.
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Papers by Ruud Van Der Sman