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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Fundamenteel inzicht in calorie- en zoutverlaging. De kern van herformulering
Sman, R.G.M. van der; Renzetti, S. ; Noort, M.W.J. - \ 2019
Food Reformulation: Experts dagen voedingsindustrie uit
Renzetti, S. ; Noort, M.W.J. ; Janssen, A.M. ; Sman, R.G.M. van der - \ 2019
Understanding functionality of sucrose in biscuits for reformulation purposes
Sman, R.G.M. van der; Renzetti, S. - \ 2019
Critical Reviews in Food Science and Nutrition 59 (2019)14. - ISSN 1040-8398 - p. 2225 - 2239.
Biscuit baking - Food structure - Sugar functionality - Sugar replacement

We review the functionality of sucrose during the manufacture of biscuits from the perspective of sugar replacement. Besides to providing sweetness, sucrose has important functionalities concerning structure and texture formation. These functionalities also need to be mimicked in reformulated biscuits. First, we review the hypotheses concerning the development of structure and texture of biscuits during manufacturing, which are conveniently summarized in a qualitative way using the Complex Dispersed Systems methodology. Subsequently, we represent the changes of the state of the biscuit during manufacturing in the supplemented state diagram, which indicates the important phase transitions occurring during mixing and baking. We propose that when reformulated biscuits follow similar paths in the state diagram, similar structures and textures can be obtained. Physical theories exist for predicting these phase transitions for existing sucrose-rich biscuits and also reformulated biscuits containing extensive sweeteners as sugar replacers. More accurate predictions of structure and texture can be eventually obtained if they are combined with computational models, including heat and moisture transfer.

Moisture diffusivity in concentrated and dry protein-carbohydrate films
Siemons, I. ; Boom, R.M. ; Sman, R.G.M. van der; Schutyser, M.A.I. - \ 2019
Food Hydrocolloids 97 (2019). - ISSN 0268-005X
Casein - Free volume - Maltodextrin - Moisture diffusion coefficient - Thin film drying - Whey protein

Understanding moisture diffusivity behaviour over a wide range of moisture contents is pivotal for optimising drying operations. Generally, data on moisture diffusivity are scarce and the effect of matrix composition on moisture diffusivity at relevant temperature for drying processes is not yet well described. In this paper moisture diffusivity in protein-carbohydrate films is systematically investigated for a wide range of moisture contents at 80 °C. Diffusion data are obtained from controlled thin film drying experiments following the regular regime method and compared to theoretical models. Moisture diffusivity for binary maltodextrin-water and whey protein-water systems appeared similar and were reasonably well described with the Darken relation. Diffusivity was lower for casein-water systems at moisture contents above 0.15 kg water/kg, which may be explained by compartmentalization of water in the casein micelles. At low moisture contents all binary systems showed universal behaviour, which may be explained by random coil behaviour leading to similar water-molecule interactions. This behaviour could be well described by free-volume theory. In mixed systems of proteins and carbohydrates moisture diffusivity appeared strongly influenced by the presence of casein, probably due to their high voluminosity. Finally, it was surprisingly observed that diffusivity in multicomponent systems decreased sharply at lower water contents when compared to binary systems. This might be explained by a denser molecular packed system in the dry regime for multicomponent systems or water trapping by protein-carbohydrate complexes.

Scaling of Flory-Huggins interaction parameter for polyols with chain length and number of hydroxyl groups
Sman, R.G.M. van der - \ 2019
Food Hydrocolloids 96 (2019). - ISSN 0268-005X - p. 396 - 401.
Flory-huggins - Hydrophilicity - Sorption isotherm - Thermodynamics

The Flory-Huggins-Free-Volume (FHFV)theory, describing the moisture sorption of carbohydrates, is extended towards a wider range of compounds. Earlier application of the FHFV theory has been to carbohydrate/water mixtures, as can be found in foods. Now, we have extended the theory towards polyols (or polyalcohols)which are investigated in as proxies for secondary organic aerosols, whose behaviour is important for understanding climate behaviour. The investigated polyols are characterized by the ratio of the number hydroxyl groups NOH and the number of carbon atoms NC, which is often lower than ratios found in carbohydrates in food materials. We have found that the value of the Flory-Huggins interaction parameter is a function of the solute molecular properties, namely its chain length NC and the ratio NOH/NC of the solute. The deviation of this ratio from [Formula presented] can be viewed as a measure for its hydrophilicity. For food science, the extension of the theory has also significant implications, as the interaction parameter of newly investigated ingredients (rich in hydroxyl groups)can be estimated by means of the molecular properties. One must think of insoluble food fibers like xylan-glucans or arabinoxylans, or modified biopolymers based on starch or cellulose.

Starch gelatinization temperature in sugar and polyol solutions explained by hydrogen bond density
Sman, R.G.M. van der; Mauer, Lisa J. - \ 2019
Food Hydrocolloids 94 (2019). - ISSN 0268-005X - p. 371 - 380.
Glass transition - Plasticizers - Starch gelatinization - Viscosity

In this paper we show that the shift of the gelatinization temperature of starch in sugar and polyol solutions is explained by nOH,eff , the volumetric density of hydrogen bonds in the solutions. nOH,eff is computed using the dry glass transition temperatures of the low molecular weight carbohydrates. This correlation of starch gelatinization temperature to nOH,eff is shown for 19 different sugar and polyol compounds in solutions at different concentrations, as measured in an earlier study by Allan et al. (2018). The earlier study found that the measured viscosity of the solutions best correlated to starch gelatinization temperature, but it was assumed that there is a more fundamental property of the sweetener that alters both the viscosity and the starch gelatnization behaviour. Here, it is shown that nOH,eff is this fundamental property responsible for controlling both the viscosity and starch gelatinization temperature differences in the used sugar and polyol solutions. Because nOH,eff is also related to Tg, the glass transition temperature of the carbohydrate solutions, the viscosity of a wide variety of carbohydrate solutions can be mapped to a single master curve if plotted against Tg/T, the ratio of glass transition and the actual temperature. Older hypotheses concerning the shift of the starch gelatinization temperature in carbohydrate solutions have explained it in terms of water activity. However, we show that nOH,eff relates to water activity only for carbohydrates with similar molecular weights. We conclude that sugar and polyol solutions can be viewed effectively as a single solvent, which is characterized by nOH,eff . This measure for volumetric density of hydrogen bonds in these solutions can be used to predict the starch gelatinization temperature in different formulations.

Manipulation of Recrystallization and Network Formation of Oil-Dispersed Micronized Fat Crystals
Nikolaeva, Tatiana ; Adel, Ruud den; Sman, Ruud van der; Martens, Koen J.A. ; As, Henk Van; Voda, Adrian ; Duynhoven, John van - \ 2019
Langmuir 35 (2019)6. - ISSN 0743-7463 - p. 2221 - 2229.

A detailed investigation was carried out on the modulation of the coupling between network formation and the recrystallization of oil-dispersed micronized fat crystal (MFC) nanoplatelets by varying oil composition, shear, and temperature. Sunflower (SF) and bean (BO) oils were used as dispersing media for MFC nanoplatelets. During MFC dispersion production at high shear, a significant increase in the average crystal thickness (ACT) could be observed, pointing to recrystallization of the MFC nanoplatelets. More rapid recrystallization of MFC occurred in the SF dispersion than in the BO dispersion, which is attributed to higher solubility of MFC in the SF oil. When the dispersions were maintained under low shear in narrow gap Couette geometry, we witnessed two stages of recrystallization (measured via rheo-SAXD) and the development of a local yield stress (measured via rheo-MRI). In the first stage, shear-enabled mass transfer induces rapid recrystallization of randomly distributed MFC nanoplatelets, which is reflected in a rapid increase in ACT (rheo-SAXD). The formation of a space-filling weak-link MFC network explains the increase in yield stress (assessed in real time by rheo-MRI). In this second stage, recrystallization slows down and yield stress decreases as a result of the formation of MFC aggregates in the weak link network, as observed by confocal Raman imaging. The high fractal dimension of the weak-link network indicates that aggregation takes place via a particle-cluster mechanism. The effects of oil type and shear on the recrystallization rate and network strength could be reproduced in a stirred bowl with a heterogeneous shear stress field, which opens perspectives for the rational manipulation of MFC thickness and network strength under industrial processing conditions.

Phase separation, antiplasticization and moisture sorption in ternary systems containing polysaccharides and polyols
Sman, R.G.M. van der - \ 2019
Food Hydrocolloids 87 (2019). - ISSN 0268-005X - p. 360 - 370.
Antiplasticization - phase separation - Sorption isotherm - Starch - Thermodynamics

In this paper, we investigate whether the Flory-Huggins-Free-Volume (FHFV) theory can describe the rich thermodynamics of the ternary mixtures of starch, polyol, and water. These systems exhibit 1) non-monotonic moisture sorption with increasing plasticizer concentration, 2) phase separation, and 3) antiplasticization. After extending the FHFV theory with 1) the proper formulation of the chemical potential of water and polyol, and 2) the proper composition dependency of the interaction parameter between starch and water, the theory is well able to describe the above described complex thermodynamic behavior, showing good agreement with experimental data. Furthermore, our analysis shows that phase separation can already occur when the ternary mixture is still in the glassy state. Overall, the phase separation happens after the antiplasticization/plasticization transition, which can be linked to the minimum in moisture sorption, when increasing the polyol concentration at equal water activity. We think that the extended theory will become an important tool for analysis and design of complex food materials, pharmaceutical systems, and biopolymeric films having carbohydrates as plasticizers.

Effects of filler ingredients on the structure and texture of starchy, extruded snacks
Sman, R.G.M. van der; Vollebregt, H.M. ; Meinders, M.B.J. ; Beri, A. - \ 2018
Food Structure 18 (2018). - ISSN 2213-3291 - 13 p.
Crispiness - Expanded snacks - Filler ingredients

Several starchy snacks differing in filler ingredients have been analysed regarding (1) the fate of filler ingredients during processing, and (2) the role of filler ingredients with respect to texture and structure. The structure has been characterized with X-ray tomography, and the texture has been evaluated via acoustic emissions from snack compression using a texture analyzer, which is assumed to be representative for crispiness. Our study shows that one has to distinguish hard and soft fillers. The absence of any filler or the presence of many hard fillers lead to a snack with a hard, coarse and non-crispy texture. However, if a significant amount of soft fillers is used then one attains a fine, and crispy texture.

Analysis of particle formation during drying of very small droplets
Siemons, Isabel ; Boom, R.M. ; Schutyser, M.A.I. ; Sman, R.G.M. van der - \ 2018
Clumping of frozen par-fried foods : Lessons from frosting on structured surfaces
Sman, R.G.M. van der - \ 2018
Food Structure 17 (2018). - ISSN 2213-3291 - p. 9 - 20.
Frosting - Frying - Structured surfaces

In this paper, we review the problem of clumping due to frost formation on frozen vegetables, like par-fried potato products. This problem has been very scarcely investigated in the scientific literature. Yet in the industry it is a significant problem, as evident by the various patents on this topic. Thanks to the enormous, recent growth of scientific literature on frost formation on engineered, structured surfaces, we have drawn a multitude of hypotheses of factors governing the clumping and frost formation of frozen foods, which can also be viewed as a structured surface.

Theoretical investigation of the swelling of polysaccharide microgels in sugar solutions
Sman, R.G.M. Van Der - \ 2018
Food & Function 9 (2018)5. - ISSN 2042-6496 - p. 2716 - 2724.

In this paper, we explain the increased swelling of crosslinked polysaccharide microgels by the increase of sugar concentration using a modified Flory-Rehner theory. This theory is validated via the investigation of the swelling of dextran microgels in sugar solutions, which can be viewed as a model system for crosslinked starch in sugar solution and custard. An essential part of our modified theory is that starch perceives the sugar solution as an effective solvent rendering a certain hydrogen bond density. Our simulations show that the often experimentally observed maximum in swelling of starch at 20% sugar concentration is probably due to the fact that equilibrium is not reached within practical time scales. Also, we discuss the use of our theory as a tool in sugar reformulation issues of custard. From simulation results one can produce a state diagram showing which formulations render a creamy, space-filling network.

In-situ Single Mode Dielectric Measurements of microwaveable snack pellets
Esveld, Erik ; Bows, John ; Vollebregt, Martijntje ; Sman, Ruud van der - \ 2018
Journal of Food Engineering 231 (2018). - ISSN 0260-8774 - p. 109 - 122.
Dielectric properties - Expansion - Microwave - Starch

The dielectric properties of starch based snack pellets have been measured in situ during microwave heating and expansion. The microwave setup consists of a single mode shorted waveguide, equipped with a six-port impedance analyser which measures the absorbed power and complex reflection coefficient during heating. The pellet is suspended in the electric field maximum, with an optic temperature sensor inserted in the centre. The dielectric properties of the pellet during heating and after expansion are obtained via an inverse mapping of the recorded reflection coefficient to dielectric properties, which are pre-computed via finite elements simulations. Experiments show that the dielectric properties of the starch pellets change significantly during heating, expansion and subsequent drying. The dielectric properties increase with increasing temperature up to the moment that the pellet starts expanding. Subsequently, the power absorption shows a sudden decline, which is mainly due to the sudden change in porosity. Addition of salt (2.5%) to the starch pellet composition results in a slight decrease of the dielectric constant and loss factor, as it apparently lowers the effective mobility of the dipoles. The dielectric properties as function of temperature and moisture content were fitted with a polynomial model. The strong effect of porosity for the dielectric properties of the expanded snack is well predicted with the effective medium mixing rule.

Critical factors in microwave expansion of starchy snacks
Sman, R.G.M. van der; Bows, J.R. - \ 2017
Journal of Food Engineering 211 (2017). - ISSN 0260-8774 - p. 69 - 84.
Expanded snacks - Microwave - Popcorn - Starch

Popping of starchy pellets in a domestic microwave oven has proven difficult compared to pellets expanded in frying oil, and even to microwave expanded popcorn. These pellets encounter problems like uneven popping, burning and the absence of an audible cue for the end of popping. The lack of a moisture barrier, like the pericarp of popcorn, leads to the development of an inverse temperature gradient in the pellets and a significant moisture loss before and after expansion. In this paper we review the hypotheses and solutions for the criticality of microwave popping of starchy pellets, as discussed in scientific and patent literature. We have found a large collection of critical factors and their associated hypotheses, which have been structured via linking them to specific steps in the physical expansion process. We conclude with a list of hypotheses that we view valuable for further investigation.

Model for electrical conductivity of muscle meat during Ohmic heating
Sman, R.G.M. van der - \ 2017
Journal of Food Engineering 208 (2017). - ISSN 0260-8774 - p. 37 - 47.
Electrical conductivity - Ohmic heating - Protein denaturation
A model is presented for predicting the electrical conductivity of muscle meat, which can be used for the evaluation of Ohmic heating. The model computes the conductivity as a function of composition, temperature and microstructure. The muscle meat is thought to be composed of protein, water, salt. Concerning the microstructure, the model takes into account the muscle fiber orientation with respect to the electric field, and the development of drip channels due to protein denaturation. The model includes a description of the protein denaturation kinetics. The model has been validated for different types of meat, varying in composition and heating rate. The submodel for protein denaturation is validated using independent DSC measurements. For meats heated faster than 20° per minute, the conductivity is a linear function of temperature - due to the absence of protein denaturation, and thus drip channel formation. If meat is heated slower than 10° per minute the conductivity is showing non-linear behaviour, with a significant decrease at temperatures above 70 degrees Celsius. This decrease is explained by the action of the complete protein denaturation. Our study shows that if Ohmic heating of meat is performed at fast rates, there is a large potential to retain most of its moisture during heating.
Predicting the solubility of mixtures of sugars and their replacers using the Flory-Huggins theory
Sman, R.G.M. van der - \ 2017
Food & Function 8 (2017)1. - ISSN 2042-6496 - p. 360 - 371.

In this paper we investigate whether the Flory-Huggins theory can describe the thermodynamics of solutions of simple carbohydrates, like sugars and polyols. In particular, we focus on the description of the solubility of the carbohydrates in water. This is investigated for both binary and ternary mixtures, having two types of these carbohydrates. This research question arises especially in the case of bakery products, where one seeks to replace sucrose with other simple carbohydrates-which are often polyols. Based on the model parameters obtained from fitting the theory to the experimental data of binary solutions, we show that the theory can predict (a) solubility data for ternary mixtures, over a broad range of concentrations and temperatures, and (b) the deliquescence point of binary mixtures of carbohydrate crystals as a function of temperature. The theory can even be applied to carbohydrates, which form hydrate crystals. Together with our earlier theories on the thermodynamics of complex food mixtures, we have now a complete thermodynamic framework to describe the phase and state transitions of food materials as confectionery and bakery products, where the question of sucrose replacement is urgent.

Flow through a filter plate backed by a packed bed of spheres
Sman, R.G.M. van der - \ 2017
Chemical Engineering Science 158 (2017). - ISSN 0009-2509 - p. 154 - 163.
Filtration - Fluid flow - Orifice - Simulation

In this paper we perform direct numerical simulation (DNS) on the problem of fluid flow through a filter plate backed by a packed bed of spheres, resembling a cake layer on top of a membrane. For both the complete problem, and its single components (the filter plate and a bed of spheres of finite height) we have observed three flow regimes, depending on the Reynolds number. In each regime the flow resistance is showing a different scaling with the Reynolds number. In the Stokes flow regime the total flow resistance can be decomposed in linear independent components. The interior flows inside the filter holes and inside the packed bed follow the same correlations as hold for the single component. However, at the transition zone between filter plate and packed bed, there is a diverging flow in the first row of the packed bed, whose contribution in the flow resistance scales with the fractional hole to the power −1.5. Similar scaling exponent has been found earlier for the viscous-inertial regime with Reynolds numbers larger than 10, which has been modelled using the porous medium approach. Our findings suggest that also in the Stokes flow and the weakly flow regime the problem can also be solved with the same porous medium approach using the Navier-Stokes equation having Darcy–Brinkman terms incorporated. This investigation provides a good basis for developing more accurate analytical models for the flow resistance of membrane filters with a cake layer on top.

More efficient mushroom canning through pinch and exergy analysis
Paudel, Ekaraj ; Sman, Ruud G.M. van der; Westerik, Nieke ; Awasthi, Ashutosh ; Dewi, Belinda P.C. ; Boom, Remko M. - \ 2017
Journal of Food Engineering 195 (2017). - ISSN 0260-8774 - p. 105 - 113.
Canned mushroom production - Exergy - Pinch analysis - Sustainability

Conventional production of canned mushrooms involves multiple processing steps as vacuum hydration, blanching, sterilization, etc. that are intensive in energy and water usage. We analyzed the current mushroom processing technique plus three alternative scenarios via pinch and exergy analysis. The product yield, utility use, exergy loss, and water use are used as sustainability indicators. Whilst re-arrangement of the production process could maximally save up to 28% of the heat input and up to 25% of the water usage, the most important improvement is obtained by re-using blanch water, which improves the overall yield of the preservation and canning process by 9%, also saving water and exergy use in the production.

Filler functionality in edible solid foams
Sman, R.G.M. van der - \ 2016
Advances in Colloid and Interface Science 231 (2016). - ISSN 0001-8686 - p. 23 - 35.

We review the functionality of particulate ingredients in edible brittle foams, such as expanded starchy snacks. In food science and industry there is not a complete awareness of the full functionality of these filler ingredients, which can be fibers, proteins, starch granules and whole grains. But, we show that much can be learned about that from the field of synthetic polymeric foams with (nano)fillers. For edible brittle foams the enhancement of mechanical strength by filler ingredients is less relevant compared to the additional functionalities such as 1) the promotion of bubble nucleation and 2) cell opening - which are much more relevant for the snack texture. The survey of particulate ingredients added to snack formulations shows that they cannot be viewed as inert fillers, because of their strong hygroscopic properties. Hence, these fillers will compete with starch for water, and that will modify the glass transition and boiling point, which are important factors for snack expansion. Filler properties can be modified via extrusion, but it is better if that processing step is decoupled from the subsequent processing steps as mixing and expansion. Several filler ingredients are also added because of their nutritional value, but can have adverse effect on snack expansion. These adverse effects can be reduced if the increase of nutritional value is decoupled from other filler functionality via compartmentalization using micropellets.

Effects of cellular structure and cell wall components on water holding capacity of mushrooms
Paudel, Ekaraj ; Boom, Remko M. ; Haaren, Els van; Siccama, Joanne ; Sman, Ruud G.M. van der - \ 2016
Journal of Food Engineering 187 (2016). - ISSN 0260-8774 - p. 106 - 113.
Cell membrane integrity - Cell wall components - Mushroom - Water holding capacity

In a sequel of papers we have investigated effects of different physical contributions to the water holding capacity of foods by considering the common white button mushroom (Agaricus bisporus). In the current paper of our sequel, we consider individual contributions of the cellular phase to water holding. The water holding capacity of hydrated mushroom is studied in relation to cell membrane integrity loss and change of state of structural polymers of the cell wall. We show that the loss in water holding capacity after heat treatment is closely correlated with cell membrane integrity loss. The intrinsic water holding capacity of the cell wall components, mostly chitin and proteins also play a role. The contribution of protein manifests largely via a significant response of WHC towards change in pH.

Phase field simulations of ice crystal growth in sugar solutions
Sman, R.G.M. Van Der - \ 2016
International Journal of Heat and Mass Transfer 95 (2016). - ISSN 0017-9310 - p. 153 - 161.
Computer simulation - Ice crystal growth - Phase field method - Sugar solution

We present the first model ever, that describes explicitly ice crystal growth in a sugar solution during freezing. This 2-D model uses the phase field method, supplemented with realistic, and predictive theories on the thermodynamics and (diffusion) kinetics of this food system. We have to make use of a novel type of phase field to obtain realistic, micron-sized ice crystals, and exclusion of sugar from the crystalline phase. Via simulation of a single ice crystal, we identify important time scales governing the growth. These times scales are also important for the coarsening of the ice morphology in freezing systems with multiple ice crystals. These simulations show that the average ice crystal size is governed by the freezing rate via a power law, similar to an empirical relation from literatures, which is deduced from experiment. The presented model is viewed as a good basis for even more realistic simulations of crystal growth in food.

Sugar and polyol solutions as effective solvent for biopolymers
Sman, R.G.M. van der - \ 2016
Food Hydrocolloids 56 (2016). - ISSN 0268-005X - p. 144 - 149.
Biopolymer melting - Hydrogen bonding - Reformulation - State diagram

Ternary mixtures of biopolymers, sugars or polyols and water can be treated as a pseudo binary system with respect to melting of the biopolymer. Sugar and polyol solutions can be treated as an effective solvent, characterized by the density of hydroxyl groups available for intermolecular hydrogen bonding. Such a treatment has been shown earlier for the glass transitions of the ternary mixtures. Now we have analysed the melting behaviour of biopolymers in these ternary mixtures. If the melting points are plotted as function of the density of hydroxyl groups, all data for a variety of sugars and polyols collapse to a single curve. This master curve coincides with the prediction of the melting line for biopolymer/water mixtures as follows from Flory's theory. Such behaviour has been found for starch, gelatin, soy and sunflower proteins.

Effects of Porosity and Thermal Treatment on Hydration of Mushrooms
Paudel, Ekaraj ; Boom, R.M. ; Sman, R.G.M. van der - \ 2016
Food Bioprocess Technology 9 (2016)3. - ISSN 1935-5130 - p. 511 - 519.
Degree of hydration - Mushroom processing - Porosity - Water-holding capacity

In this study, hydration of mushroom as a porous food material has been studied considering their biphasic character. It consists of a solid phase that consists of intertwined hyphae and having cell walls with a swellable polymeric matrix and a pore phase made up by the space in between the hyphae. We have investigated the hydration of mushrooms as a function of initial porosity and thermal treatment. Variation in porosity is induced by the natural variation in the growth of mushroom. Porosity is measured by the weight gain during vacuum infiltration of mushroom caps with the mushroom isotonic solution. The hydration of the heat-treated mushroom shows a linear increase with the porosity of mushroom. Storage of mushroom increases the porosity with the number of storage days, which has also been confirmed with X-ray tomography(XRT) measurements. Finally, we show that the hydration of thermal-treated mushroom has two independent contributions, from porosity and temperature of the heat treatment. Current theories deal only with the latter contribution to the hydration of foods and need to be extended for accounting porosity of the food.

Analysis of improved Lattice Boltzmann phase field method for soluble surfactants
Sman, R.G.M. van der; Meinders, M.B.J. - \ 2016
Computer Physics Communications 199 (2016). - ISSN 0010-4655 - p. 12 - 21.
surfactants - phase field - lattice boltzmann
In this paper we present a novel Lattice Boltzmann model for immiscible fluids with soluble surfactants adsorbing at the interface with improved numerical and extended physical properties. The numerical improvements are based on the use of an analytical representation of a regularized delta-function in the surface free energy functional for the surfactant. Furthermore, the physics of the system have been extended to differential solubility of the surfactant combined with the use of Frumkin sorption behaviour. This enables the scheme to approach more realistic systems like foams and emulsions. This novel scheme is much superior in numerical stability than our previous scheme, based on a squared gradient approximation. Furthermore, we have observed the phenomenon of interface broadening under certain conditions. This phenomenon limits the surface pressure to about 30% of the capillary pressure of a bare droplet. It remains to be investigated whether this interface broadening reflects some physical
effect, as has been observed for proteins.
Mesoscale Lattice Boltzmann Model of Dispersions Stabilized by Surfactants
Meinders, M.B.J. ; Sman, R.G.M. van der - \ 2015
In: Computational Methods for Complex Liquid-Fluid Interfaces / Taeibi Rahni, Mohammad, Karbaschi, Mohsen, Miller, Reinhard, Boca Raton : CRC Press / Taylor & Francis - ISBN 9781498722087 - p. 295 - 308.
Modeling Foam Stability
Meinders, M.B.J. ; Sman, R.G.M. van der - \ 2015
In: Computational Methods for Complex Liquid-Fluid Interfaces / Taeibi Rahni, Mohammad, Karbaschi, Mohsen, Miller, Reinhard, CRC Press / Taylor & Francis (Progress in Colloid and Interface Science ) - ISBN 9781498722087 - p. 503 - 526.
Hyperelastic models for hydration of cellular tissue
Sman, R.G.M. Van Der - \ 2015
Soft Matter 11 (2015)38. - ISSN 1744-683X - p. 7579 - 7591.

In this paper we present hyperelastic models for swelling elastic shells, due to pressurization of the internal cavity. These shells serve as model systems for cells having cell walls, as can be found in bacteria, plants and fungi. The pressurized internal cavity represents the cell vacuole with intact membrane at a certain turgor pressure, and the elastic shell represents the hydrated cell wall. At pressurization the elastic shell undergoes inhomogeneous deformation. Its deformation is governed by a strain energy function. Using the scaling law of Cloizeaux for the osmotic pressure, we obtain approximate analytical expressions of the cell volume versus turgor pressure-which are quite comparable to numerical solutions of the problem. Subsequently, we have simulated the swelling of shells-where the cell wall material is embedded with microfibrils, leading to strain hardening and anisotropic cell expansion. The purpose of our investigations is to elucidate the contribution of cell membrane integrity and turgor to the water holding capacity (hydration) of plant foods. We conclude with a discussion of the impact of this work on the hydration of food material, and other fields like plant science and the soft matter physics of responsive gels.

Editorial overview : Food physics and material science
Sman, R.G.M. van der - \ 2015
Current Opinion in Food Science 3 (2015). - ISSN 2214-7993 - p. 6 - 8.
Comparison of first principles model of beer microfiltration to experiments via systematic parameter identification
Sman, R.G.M. van der; Willigenburg, G. van; Vollebregt, H.M. ; Eisner, V. ; Mepschen, A. - \ 2015
Journal of Membrane Science 484 (2015). - ISSN 0376-7388 - p. 64 - 79.
Beer - Fouling - Microfiltration - Shear-induced diffusion

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.

Biopolymer gel swelling analysed with scaling laws and Flory-Rehner theory
Sman, R.G.M. van der - \ 2015
Food Hydrocolloids 48 (2015). - ISSN 0268-005X - p. 94 - 101.
Gel - Swelling - Water holding capacity

The swelling of biopolymer gels is analysed with scaling laws from polymer physics, as an alternative for the classical Flory-Rehner theory. With these scaling laws, holding for polymer concentrations in the semi-dilute regime, experimental data on deswelling of gels can be collapsed to a single universal master curve. The predictions made with the scaling laws are similar to those made with the modified Flory-Rehner, where the osmotic pressure is described with a composition-dependent interaction parameter. For gels in the semi-dilute regime we recommend the use of the scaling laws, because their compact, and universal character.

Change in Water-Holding Capacity in Mushroom with Temperature Analyzed by Flory-Rehner Theory
Paudel, Ekaraj ; Boom, R.M. ; Sman, R.G.M. van der - \ 2015
Food Bioprocess Technology 8 (2015)5. - ISSN 1935-5130 - p. 960 - 970.
Gel compression - Mushroom processing - Thermodynamics - Water-holding capacity

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.

Water retention in mushroom during sustainable processing
Paudel, E. - \ 2015
Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Ruud van der Sman. - Wageningen : Wageningen University - ISBN 9789462575967 - 148
mushrooms - water holding capacity - physical properties - hydration - chemical composition - heat treatment - canning - process optimization - sustainability - paddestoelen - waterbergend vermogen - fysische eigenschappen - hydratatie - chemische samenstelling - warmtebehandeling - inblikken - procesoptimalisatie - duurzaamheid (sustainability)

This thesis deals with the understanding of the water holding capacity of mushroom, in the context of a redesign of their industrial processing. For designing food process the retention of food quality is of the utmost importance. Water holding capacity is an important quality aspect of mushrooms. A convenient process design methodology which accounts also for product quality is Conceptual Process Design (CPD). An approach to follow CPD methodology is first to explore, the material properties of the products to find optimal processing conditions. In this stage the constraints of (existing) processing equipment are not considered. Later in the second stage, suboptimal processing conditions are determined considering the constrains of equipment.

In mushroom canning, temperature induced loss of water holding capacity (WHC) of tissue manifests as a lower product yield. This loss of water is accompanied with the loss of nutrients, dissolved in the water. In addition to the loss of product quality like water holding capacity, mushroom canning (with alternating heating and cooling steps) also induces losses of useful resources as (potable) water. In terms of water use, water is added at several steps, and is discarded at other places. This shows that there is opportunity to improve the sustainability of the production system, but with the constraint that product quality is not impaired, or evenly improved.

The WHC is an important property that determines several aspects of foods. For example, it determines the juiciness of fruits, vegetables and meat products; the freshness (firmness, or crispiness) of green-leafy vegetables; and the calorie intake per serving for high calorie containing foods such as cheese. Despite being a widely used term in food science, there is no clear definition of water holding capacity and its thermodynamic nature is not fully acknowledged. The understanding of the WHC is even poorer in structured cellular foods such as mushroom, where different water fractions are present in various compartments. In a cellular system water is present as 1) a solution in the vacuoles, 2) water osmotically bound to the cytoplasmic and the cell wall materials and 3) capillary water in pores, which might be filled during processing. Because they have a distinct capillary phase, the mushroom is a good system to study the contributions of various water fraction on the total water retention.

The main aim of the current work is to provide insight for the development of canned mushroom processing where: 1) the resources of energy and water are efficiently used, and 2) the quality of mushroom is maintained. These two aims are related to the efficient use of raw materials and maintenance of full weight of mushroom during processing. The WHC is an important quality indicator of mushrooms. The analysis related to water retention of mushroom has been carried out at microscale where molecular and structural interactions in relation to water retention are studied. The micro scale analysis is discussed in chapter 2, chapter 3 and chapter 4. The sustainability analysis is carried out at mesoscale where analysis is carried out at the unit operation level which is described in chapter 5.

In chapter 2, the heat-induced change in water holding capacity of particular the gel phase of the mushroom is interpreted with the Flory-Rehner theory, commonly applied to polymer gels. As done earlier for meat, we have first assumed that WHC loss in mushroom can also be attributed to the protein denaturation. This assumption is based on the experimental observation that, like meat, mushroom also follows a typical sigmoid relation with change in temperature. In the theory, we have regarded mushroom as a homogeneous biopolymer hydrogel, in which salt and sugar are dissolved. The water holding capacity is then understood as the swelling capacity of the biopolymer gel. The thermodynamic state of this simplified system is characterized by the so-called swelling pressure, which is decomposed into three independent contributions: 1) the mixing pressure induced by sugars and polymers, 2) the ionic pressure induced by the salt, and 3) the elastic pressure induced by the polymers. An assumption was made that the heat treatment denatures mushroom protein, which is reflected in the change of the Flory Huggins interaction for protein. It follows the same temperature dependency as the WHC loss by mushroom under zero mechanical load. The assumption of the temperature dependency of the interaction parameter is tested with an independent sorption measurement. With the assumption, the sorption curve for mushroom sample which were preheated previously at 30, 60 and 90 °C could accurately be predicted. Curve fitting of WHC under various mechanical loads has shown that model parameters that are associated with the elastic pressure, the crosslink density and fraction of the polymer in the relaxed state, are temperature dependant. The values of increased in contrast to the decrease of upon heating of mushroom tissue up to temperature of 70°C. The result indicates that heat treatment increases the polymer chain length between the cross links as original conformation of mushroom is lost. At the same time, more crosslinks are formed by a polymer because of aggregation of polymers. However, in our fitting procedure, we have excluded WHC data at low external pressure values, as water is present in both gel phase as in in the capillaries. This is done as the pores in this range are not fully collapsed and the Flory Rehner theory is valid only for the gel phase

In chapter 2 mushroom is simplified in the sense that only compositional contribution is considered in WHC but not the structural contributions. In subsequent chapters we have acknowledged that mushroom has a cellular structure with a distinct pore phase. The pores are intentionally filled during processing via vacuum impregnation. The contribution of water present in the capillaries due to vacuum impregnation of mushroom has been discussed in chapter 3. Both the temperature of heat treatment and the initial porosity of mushroom contribute independently to water holding capacity of heat treated mushroom. The hydration of heat treated mushroom increases linearly with the initial porosity of mushroom for all the temperatures from 30 to 90 °C. The porosity of mushroom can also largely explain the increase in hydration of heat treated mushroom with storage as both porosity and the hydration increase simultaneously with the storage days. The fluid that filled in the capillaries acts against collapse of the hyphae which have inherent elastic force that works in the other direction. The initial porosity of mushroom is an important aspect that determines the hydration of the heat treated mushroom and therefore, cannot be ignored. In addition, the Flory-Rehner theory alone cannot capture the contribution of the capillary water. Hence an addition is needed in the theory to capture this effect.

The cellular phase in mushroom tissue is even more complicated because water is present in this phase in two other forms, as gel water and the intracellular water. Chapter 4 takes into account the role of structure in the WHC. The role of cell membrane integrity and the cell-wall structural components is investigated for retention of the water fraction. The cell membrane integrity is calculated from the conductivity measurement of the fluid that leaches out from the vacuole that has salts in it. The loss of the cell membrane integrity largely explains the water loss from heat treated mushroom sample. The loss of cell membrane integrity is also related with the water loss from frozen mushroom, but additional losses occur during freezing due to novel crosslinks formed during the growth of ice crystals compressing the unfrozen cell wall material. The enzymatic hydrolysis of mushroom cellular components shows that chitin and mushroom protein both contribute to the water holding capacity either via osmotic binding or by their role to provide the mechanical strength to the mushroom hyphae. In addition, proteins have additional contributions to water retention by mushroom because of their electrostatic interaction as polyelectrolyte. This is evident as the hydration of the mushroom increases with pH of mushroom.

In chapter 5, the efficiency of the use of the resources (raw materials, energy water) is investigated. The mass and exergy flow in the current production system is visualized with the Sankey diagrams. The sustainability of unit operations involved in the current production system of canned are analysed with the second law efficiency using exergy. Using ideas from Process Intensification three alternative routes are proposed for the production of canned mushrooms namely: 1). Slicing before vacuum hydration, and 2) Using hot water for vacuum hydration and 3) Using blanch water for vacuum hydration. Using hot water for vacuum hydration is not seen as a feasible option, since it consumed more resources. Slicing mushroom before their vacuum hydration and using blanch water for hydration of mushroom lowers the resources requirement for production. In addition, using blanch water for hydration also increases the final product yield.

Finally, the main findings of this thesis are summarized in the general discussion in chapter 6. The findings from previous chapters are combined to an overall description of water loss from heat treated mushroom. The overall description of water holding capacity in mushrooms is given in terms of the thermodynamic conditions for equilibrium between the different compartments holding water. The two dimensions of the thesis, the higher water retention of processed mushroom and more sustainable operation are discussed in the light of conceptual process design, using a micro/mesoscale approach. At the microscale material properties of mushroom are discussed. The biggest effect comes from cell membrane integrity loss. The porosity of fresh mushroom and the ionic interactions of polymers are the other effects that influence the WHC. Mesoscale analysis shows that shifting the sequence of unit operations and reusing the blanch water that is discarded in the current production process can improve the sustainability. Finally based on outcome of current work, future perspective of current work is discussed briefly.

Overall, this thesis demonstrated that there is substantial scope in improving the efficiency in the use of resources in producing preserved mushroom. Also scope in retention of water in the mushroom tissue is demonstrated. Thus this thesis shows that both aspects, product and process efficiency, can be improved at the same time.

Optimal adaptive scheduling and control of beer membrane filtration
Willigenburg, L.G. van; Vollebregt, H.M. ; Sman, R.G.M. van der - \ 2015
Control Engineering Practice 34 (2015). - ISSN 0967-0661 - p. 77 - 87.
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.
Moisture transport in swelling media modelled with a Lattice Boltzmann scheme having a deforming lattice
Sman, R.G.M. van der - \ 2014
Journal of Food Engineering 124 (2014). - ISSN 0260-8774 - p. 54 - 63.
non-brownian suspensions - diffusion lattice - water transport - flow - simulations - profiles - kinetics - food - gels - validation
In this paper we present a novel numerical scheme for simulating the one-dimensional deformation of hydrogel material due to drying or rehydration. The scheme is based on the versatile Lattice Boltzmann method, which has been extended such that the computational grid (lattice) deforms due to shrinkage or swelling. This property of a deforming grid is new to the lattice Boltzmann method, and a detailed description of this new method is given. Via simulations we show that self-similar moisture concentration profiles occur in two periods in both drying and swelling processes: the penetration period and the regular regime. Given the property of self-similarity, we have been able to formulate a reduced-order model for the regular regime of swelling.
Multiscale analysis of structure development in expanded starch snacks
Sman, R.G.M. van der; Broeze, J. - \ 2014
Journal of Physics-Condensed Matter 26 (2014)46. - ISSN 0953-8984
mass-transfer - food materials - bubble-growth - porous-media - systems - polymer - phase - model - simulation - extrusion
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.
Effects of salt on the expansion of starchy snacks: a multiscale analysis
Sman, R.G.M. van der; Broeze, J. - \ 2014
Food & Function 5 (2014)12. - ISSN 2042-6496 - p. 3076 - 3082.
glass-transition - sodium-chloride - aqueous-solutions - mass-transfer - sucrose - extrusion - potato - water - trehalose - mixtures
We investigate the effect of salt on the expansion of starchy snacks during frying by means of a multiscale simulation model. This model has been developed earlier for starchy snacks without salt. The simulation results are analysed by means of the supplemented state diagram. We have found that the optimal expansion for salty snacks occurs under the same conditions as for snacks without salt. This occurs at the moisture content where the 4 bar boiling line intersects the critical isoviscosity line of 1 MPa s. Salt is shown to influence both the boiling line and the critical isoviscosity line, via a change of the glass transition. The optimal moisture content for salty snacks is lower than that of unsalted snacks. We view our findings as important for reformulations of starchy snacks with lower salt levels. Furthermore, the presented tools of the multiscale simulations and supplemented state diagram can generally be used for reformulation problems in structured foods.
Lattice Boltzmann simulation of the stability of thin films in foams
Sman, R.G.M. van der - \ 2014
Chips in hete lucht gebakken
Jong, M. de; Meinders, M.B.J. ; Sman, R.G.M. van der - \ 2014
Voedingsmiddelentechnologie 2014 (2014)13. - ISSN 0042-7934 - p. 20 - 21.
Mesoscale models of dispersions stabilized by surfactants and colloids
Sman, R.G.M. van der; Meinders, M.B.J. - \ 2014
Advances in Colloid and Interface Science 211 (2014). - ISSN 0001-8686 - p. 63 - 76.
dissipative particle dynamics - fluid-fluid interfaces - lattice-boltzmann simulations - phase-separation dynamics - pickering emulsions - soluble surfactants - amphiphilic fluids - binary fluids - adsorption - flows
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.
Computational physics of edible soft matter
Sman, Ruud van der - \ 2014
Rehydration kinetics of freeze-dried carrots
Vergeldt, F.J. ; Dalen, G. van; Duijster, A.J. ; Voda, A. ; Khalloufi, S. ; Vliet, L.J. van; As, H. van; Duynhoven, J.P.M. van; Sman, R.G.M. van der - \ 2014
Innovative Food Science and Emerging Technologies 24 (2014). - ISSN 1466-8564 - p. 40 - 47.
fruits - foods - microstructure - vegetables - quality - impact - nmr
Rehydration kinetics by two modes of imbibition is studied in pieces of freeze-dried winter carrot, after different thermal pre-treatments. Water ingress at room temperature is measured in real time by in situ MRI and NMR relaxometry. Blanched samples rehydrate substantially faster compared to non-blanched samples, independent of their porous microstructure. It is proposed that for non-blanched tissues immobilized sugars result in nearly complete swelling of the solid matrix, hindering the ingress of water through the porous network. Nonblanched carrot pieces frozen at-28 °C rehydrate faster compared to those frozen at-150 °C, due to blocking of smaller pores by swelling. In blanched tissues themobilization of sugars results in amore homogeneous Sugar distribution, leading to less swelling of the solid matrix and allowing fast ingress of water via capillary suction. Industrial relevance: The dried fruits and vegetables that are currently available on the market are a poor compromise between convenience (rehydration kinetics) and sensorial quality. This is a major bottleneck for consumers to “Make the Healthy Choice the Easy Choice” and this also negatively impacts market growth. Currently, rational optimization of drying processes is impeded by lack of insight which structural features determine rehydration kinetics (convenience) and texture (sensorial quality) upon rehydration. We therefore started a program to quantitatively assess and model microstructural features and rehydration behavior of freeze-dried carrots as a model system.
Impact of different drying trajectories on degradation of nutritional compounds in broccoli (Brassica oleracea var. italica)
Jin, X. ; Oliviero, T. ; Sman, R.G.M. van der; Verkerk, R. ; Dekker, M. ; Boxtel, A.J.B. van - \ 2014
Food Science and Technology = Lebensmittel-Wissenschaft und Technologie 59 (2014)1. - ISSN 0023-6438 - p. 189 - 195.
ascorbic-acid - antioxidant capacity - cooking methods - tomato halves - red cabbage - vitamin-c - temperature - vegetables - myrosinase - retention
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 30e60 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.
Energy efficient drying strategies to retain nutritional components in broccoli broccoli (Brassica oleracea var. italica)
Jin, X. ; Sman, R.G.M. van der; Straten, G. van; Boom, R.M. ; Boxtel, A.J.B. van - \ 2014
Journal of Food Engineering 123 (2014). - ISSN 0260-8774 - p. 172 - 178.
ascorbic-acid - tomato halves - vitamin-c - optimization - heat - temperature - consumption - degradation - health - trends
This work concerns the combined optimization of the retention of bioactive components and energy efficiency during drying of broccoli. Kinetics for the degradation of glucosinolates, vitamin C and drying of broccoli are used to calculate optimal drying trajectories for the control variables air flow rate and temperature. It is shown from plots of the optimal drying trajectories in moisture–temperature state diagrams with degradation and drying rates, that areas with high degradation rates are circumvented. The optimized drying strategies result in significant improvement of energy efficiency (65%) and vitamin C retention of 55%.
Multiphysics pore-scale model for the rehydration of porous foods
Sman, R.G.M. van der; Vergeldt, F.J. ; As, H. van; Dalen, G. van; Voda, A. ; Duynhoven, J.P.M. van - \ 2014
Innovative Food Science and Emerging Technologies 24 (2014). - ISSN 1466-8564 - p. 69 - 79.
moisture transport - mass-transfer - water - imbibition - quality - media - pressure - lattice - liquid - fruits
In this paper we present a pore-scale model describing the multiphysics occurring during the rehydration of freeze-dried vegetables. This pore-scale model is part of a multiscale simulation model, which should explain the effect of microstructure and pre-treatments on the rehydration rate. Simulation results are compared to experimental data, obtained by MRI and XRT. Time scale estimates based on the pore-scale model formulation agree with the experimental observations. Furthermore, the pore-scale simulation model provides a plausible explanation for the strongly increased rehydration rate, induced by the blanching pre-treatment. Industrial relevance The increased insight in the physical processes governing the rehydration of porous or freeze-dried foods gives more rationale for optimizing all processing steps. Industry is seeking for means to give dried fruits and vegetables more convenience, but also higher quality concerning health and texture. This study shows that blanching pretreatment prior to freeze-drying strongly enhances the rehydration, while the loss of nutrients is hardly affected.
Measuring and modelling of diffusivities in carbohydrate-rich matrices during thin film drying
Perdana, J.A. ; Sman, R.G.M. van der; Fox, M.B. ; Boom, R.M. ; Schutyser, M.A.I. - \ 2014
Journal of Food Engineering 122 (2014). - ISSN 0260-8774 - p. 38 - 47.
glass-transition temperature - free-volume theory - lactobacillus-plantarum - diffusion-coefficients - sucrose solutions - moisture-content - solvent systems - sugar solutions - water - droplet
Knowledge about moisture diffusivity in solid matrices is a key for understanding drying behaviour of for example probiotic or enzymatic formulations. This paper presents an experimental procedure to determine moisture diffusivity on the basis of thin film drying and gravimetric analysis in a Dynamic Vapour Sorption (DVS) system. The extraction of moisture diffusivity is based on the “regular regime approach”. The method was explored and verified for its assumptions. It provided insight in the effect of moisture content and temperature on moisture diffusivity. Moreover, it was found that moisture diffusivity in different carbohydrate systems was similar and decreased with moisture content. The latter was explained by similar molecular interactions in carbohydrate systems and formation of a percolating network at low moisture content that affects water mobility. Subsequently, measured moisture diffusivities were compared to model predictions based on the generalised Darken relation. It was found that predicted moisture diffusivities were in fair agreement with these, including the effect of moisture content and temperature on moisture diffusivity. At low moisture content the model overestimated the sensitivity of moisture diffusivity towards temperature. This was explained by the fact that the different water–solid interactions at lower moisture content (including relaxation behaviour in the glassy state) are not considered in the modelling. Finally, the methodology was successfully evaluated to other solid matrices such as glycerol, skimmed milk and casein, providing different moisture diffusivities as function of moisture content.
Moisture Sorption Isotherms of Broccoli Interpreted with the Flory-Huggins Free Volume Theory
Jin, X. ; Sman, R.G.M. van der; Maanen, J.F.C. van; Deventer, H.C. van; Straten, G. van; Boom, R.M. ; Boxtel, A.J.B. van - \ 2014
Food Biophysics 9 (2014)1. - ISSN 1557-1858 - p. 1 - 9.
water activity - glassy-polymers - drying methods - carrot slices - tissue-damage - quality - vegetables - mixtures - heat - pretreatment
In this work, the Flory Huggins Free Volume theory is used to interpret the sorption isotherms of broccoli from its composition and using physical properties of the components. This theory considers the mixing properties of water, biopolymers and solutes and has the potential to describe the sorption isotherms for varying product moisture content, composition and temperature. The required physical properties of the pure components in food became available in recent years and allow now the prediction of the sorption isotherms with this theory. Sorption isotherm experiments have been performed for broccoli florets and stalks, at two temperatures. Experimental data shows that the Flory Huggins Free Volume (FHFV) theory represents the sorption isotherm of fresh and blanched broccoli samples accurately. The results also show that blanching affects the sorption isotherm due to the change of composition via leaching solutes and the change of interaction parameter due to protein denaturation
Stability of foam films investigated by Lattice-Bolzmann phase-field method
Sman, R.G.M. van der; Meinders, M.B.J. - \ 2013
Water dynamics in solid foams
Sman, Ruud van der - \ 2013
Multiscale modeling in food engineering
Ho, Q.T. ; Carmeliet, J. ; Datta, A.K. ; Defraeye, T. ; Delele, M.A. ; Herremans, E. ; Opara, L. ; Ramon, H. ; Tijskens, E. ; Sman, R.G.M. van der; Liedekerke, P. Van; Verboven, P. ; Nicolai, B.M. - \ 2013
Journal of Food Engineering 114 (2013)3. - ISSN 0260-8774 - p. 279 - 291.
dissipative particle dynamics - lattice-boltzmann simulations - ray computed-tomography - random-field parameters - subsp mitis wallr. - mass-transfer - porous-media - moisture transport - discrete element - air-flow
Since many years food engineers have attempted to describe physical phenomena such as heat and mass transfer that occur in food during unit operations by means of mathematical models. Foods are hierarchically structured and have features that extend from the molecular scale to the food plant scale. In order to reduce computational complexity, food features at the fine scale are usually not modeled explicitly but incorporated through averaging procedures into models that operate at the coarse scale. As a consequence, detailed insight into the processes at the microscale is lost, and the coarse scale model parameters are apparent rather than physical parameters. As it is impractical to measure these parameters for the large number of foods that exist, the use of advanced mathematical models in the food industry is still limited. A new modeling paradigm - multiscale modeling - has appeared that may alleviate these problems. Multiscale models are essentially a hierarchy of sub-models which describe the material behavior at different spatial scales in such a way that the sub-models are interconnected. In this article we will introduce the underlying physical and computational concepts. We will give an overview of applications of multiscale modeling in food engineering, and discuss future prospects. (C) 2012 Elsevier Ltd. All rights reserved.
Moisture sorption in mixtures of biopolymer, disaccharides and water
Sman, R.G.M. van der - \ 2013
Food Hydrocolloids 32 (2013)1. - ISSN 0268-005X - p. 186 - 194.
glass-transition temperature - frozen state transitions - vapor sorption - poly(ethylene glycol) - amorphous mixtures - sucrose - behavior - prediction - polymers - crystallization
The moisture sorption of ternary mixtures of biopolymer, sugar and water is investigated by means of the Free-Volume-Flory-Huggins (FVFH) theory. The earlier FVFH theory developed for binary mixtures of biopolymer/water and sugar/water has to be modified to account for two effects: 1) the change in the glass temperature due to the non-ideal mixing of biopolymer and 2) inhibition of self-association of the polymer if the mixture is quenched very fast into the glassy state. The modified FVFH theory forms a good basis for predicting moisture sorption for quaternary mixtures of biopolymers, di-, mono-saccharides and water - which can be viewed as a model for vegetables and fruits. (c) 2013 Elsevier Ltd. All rights reserved.
Modeling cooking of chicken meat in industrial tunnel ovens with the Flory-Rehner theory
Sman, R.G.M. van der - \ 2013
Meat Science 95 (2013)4. - ISSN 0309-1740 - p. 940 - 957.
water-holding capacity - protein cross-linking - cod gadus-morhua - mass-transfer - moisture transport - porous-media - heat-transfer - theoretical aspects - capillary-pressure - structural-changes
In this paper we present a numerical model describing the heat and mass transport during the cooking of chicken meat in industrial tunnels. The mass transport is driven by gradients in the swelling pressure, which is described by the Flory-Rehner theory, which relates to the water holding capacity (WHC). For cooking temperatures up to boiling point and practical relevant cooking times, the model renders good prediction of heat and mass transport and the total loss of moisture. We have shown that for cooking temperatures above boiling point, the model has to be extended with the dynamic growth of capillary water (drip) channels. Furthermore, we discuss that the Flory-Rehner theory provides the proper physical basis for describing the change of the WHC by a wide variety of factors like salt and pH. (C) 2013 Elsevier Ltd. All rights reserved.
Predictions of Glass Transition Temperature for Hydrogen Bonding Biomaterials
Sman, R.G.M. van der - \ 2013
The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 117 (2013)50. - ISSN 1520-6106 - p. 16303 - 16313.
molecular-dynamics simulations - gel sol transition - aqueous-solutions - free-volume - glycerol-water - physical-properties - positron lifetime - light-scattering - phase-behavior - starch gels
We show that the glass transition of a multitude of mixtures containing hydrogen bonding materials correlates strongly with the effective number of hydroxyl groups per molecule, which are available for intermolecular hydrogen bonding. This correlation is in compliance with the topological constraint theory, wherein the intermolecular hydrogen bonds constrain the mobility of the hydrogen bonded network. The finding that the glass transition relates to hydrogen bonding rather than free volume agrees with our recent finding that there is little difference in free volume among carbohydrates and polysaccharides. For binary and ternary mixtures of sugars, polyols, or biopolymers with water, our correlation states that the glass transition temperature is linear with the inverse of the number of effective hydroxyl groups per molecule. Only for dry biopolymer/sugar or sugar/polyol mixtures do we find deviations due to nonideal mixing, imposed by microheterogeneity.
Investigation of Lattice Boltzmann wetting boundary conditions for capillaries with irregular polygonal cross-section
Sman, R.G.M. van der - \ 2013
Computer Physics Communications 184 (2013)12. - ISSN 0010-4655 - p. 2751 - 2760.
binary fluids - porous-media - simulations - flows - model - equation - configurations - dynamics - schemes
We have investigated the performance of an alternative wetting boundary condition for complex geometries in a phase field Lattice Boltzmann scheme, which is an alternative to the commonly used formulation by Yeomans and coworkers. Though our boundary condition is much simpler in its implementation, all investigated schemes show proper droplet spreading behaviour following the Cox-Voinov law. Still, numerical artefacts like spurious velocities or chequer board effects in the pressure field can be significantly reduced by the use of a two-relaxation-time (TRT) scheme, likewise recent studies by the Yeomans group. The outstanding property of our implementation is the presence of an (artificial) thin wetting layer, which influences the relation between the saturation (S-w) and capillary pressure p(cap) in channels with irregular polygonal cross section. The p(cap) (S-w) relation from our simulation follows the shifted-Young-Laplace (sYL) law, showing that the physics of this wetting layer is similar to precursor films due to Van der Waals forces. With the knowledge of the thickness of the wetting layer, simulation results can be translated back to realistic pore configurations with thinner wetting layers. (C) 2013 Elsevier B.V. All rights reserved.
Ice crystal interspacing in frozen foods
Sman, R.G.M. van der; Voda, A. ; Dalen, G. van; Duijster, A. - \ 2013
Journal of Food Engineering 116 (2013)2. - ISSN 0260-8774 - p. 622 - 626.
directional-solidification - apple tissue - part ii - texture - growth - cream - crystallization - transport - model - microstructure
In this paper we show that the ice crystal growth in food and biomaterials is a function of the freezing rate. Our experimental data and literature data on other biomaterials collapse to a single curve, if plotted against the freezing rate. The fitted correlation is compared to scaling rules developed for dendrite interspacing during directional solidification of alloys. We argue that the food freezing process is reasonably comparable to the solidification process in alloys, as is apparent in the comparable exponent in our fitted scaling rule with the one commonly used in alloy solidification. (C) 2013 Elsevier Ltd. All rights reserved.
Hydration properties of vegetable foods explained by Flory-Rehner theory
Sman, R.G.M. van der; Paudel, E. ; Voda, A. ; Khalloufi, S. - \ 2013
Food Research International 54 (2013)1. - ISSN 0963-9969 - p. 804 - 811.
water-holding capacity - dietary fiber content - cell-wall components - glass-transition - meat-products - nutritional-value - aqueous-solutions - freezing-point - carrot tissue - wheat bran
In this paper we have analyzed the hydration properties of vegetable materials, namely carrots and mushrooms, by means of the Flory-Rehner theory. This is done to circumvent problems with the ill-defined concept of water holding capacity. Via this thermodynamic theory one can predict the hydration properties for a wide range of mechanical loads. The theory is compared to measurements on the hydration of the vegetable samples in centrifugation experiments. The theory predicts two contributions to the hydration properties, which are due to 1) mixing free energy of water and food ingredients, and 2) the elastic energy of the crosslinked network of cell wall materials (i.e. the dietary fibers). Via independent measurements of the moisture sorption isotherms, we have quantified of the mixing contribution, which can be described by the volume-averaged Flory-Huggins Free Volume theory. From combined analysis of centrifugation and sorption experiments, we have obtained the elastic contribution, which is shown to follows the Flory-Rehner theory. Remarkably, the cell wall materials of carrots and mushrooms show very similar elastic behavior. (C) 2013 Elsevier Ltd. All rights reserved.
A Paradigm Shift in Drying of Food Materials via Free-Volume Concepts
Sman, R.G.M. van der; Jin, X. ; Meinders, M.B.J. - \ 2013
Drying Technology 31 (2013)15. - ISSN 0737-3937 - p. 1817 - 1825.
water-vapor absorption - moisture transport - simultaneous heat - mass-transfer - porous-media - meat - polymers - behavior - sorption - models
We give an overview of the prediction of thermodynamics of food materials, and the kinetics of water transport in them using universal theories based on free volume concepts. These material properties are highly relevant to the prediction of food drying. These presented theories are shown to hold for a large class of polysaccharides and proteins. These different food materials apparently follow the soft matter paradigm that materials' behavior at length scales larger than the molecular scale are dominantly determined by physical characteristics rather than their chemical details. We pose that for food and other bio-materials hydrogen-bonding is largely determining their physical behavior, as in drying. [Supplementary materials are available for this article. Go to the publisher's online edition of Drying Technology for the following free supplemental resource(s): Data sets.]
Describing dewatering during mushrom blanching with Flory Rehner's theory (online)
Paudel, E. ; Boom, R.M. ; Sman, R.G.M. van der - \ 2013
Drying of healthy foods : from mechanism to optimization
Jin, X. - \ 2013
Wageningen 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 - broccoli - 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.

Prediction of the time evolution of pH in meat
Hamoen, J.R. ; Vollebregt, H.M. ; Sman, R.G.M. van der - \ 2013
Food Chemistry 141 (2013)3. - ISSN 0308-8146 - p. 2363 - 2372.
water-holding capacity - electrical-stimulation - ultimate ph - moisture transport - rigor temperature - postmortem muscle - beef longissimus - sensory quality - state diagram - mass-transfer
In this paper we compare experimental data on pH decline in carcasses and predictions using a model, based on earlier work of Vetharaniam and coworkers. This model is extended in order to cope with the varying temperatures in the slaughterhouse. We have measured initial glycogen, and the pH and temperature at multiple times in the production chain. We have obtained good comparison between model predictions and our measurements. Fur-thermore, the correlation between initial glycogen content and ultimate pH as predicted by the model, follows closely experimental data reported earlierin literature. Being able to predict pH decline and ultimate pH, one can obtain reliable indications of final meat quality.
Transient critical flux due to coupling of fouling mechanisms during crossflow microfiltration of beer
Sman, R.G.M. van der; Vollebregt, H.M. - \ 2013
Journal of Membrane Science 435 (2013). - ISSN 0376-7388 - p. 21 - 37.
pressure-driven flow - concentration polarization - concentrated suspensions - colloidal suspensions - particle migration - yeast suspensions - model - filtration - shear - simulations
Models of fouling during beer clarification, previously validated for dead-end filtration, are combined with a model describing the build-up of the cake layer of yeast cells via shear-induced diffusion induced by crossflow. For describing shear-induced diffusion, we have taken the most recent model, which is based on the effective temperature concept. Via scale analysis we show that (1) effects of polydispersity are negligible and (2) the cake layer growth model still be reduced to the earlier model of Romero and Davis, albeit with different parameter values. The adapted Romero and Davis model has been coupled to the earlier reviewed models of fouling by aggregates and macromolecules, for which we have performed computer simulations. In this paper we report on striking results on the downstream movement of the critical point, xcr, where the cake layer starts building up. We show that this is due to strong coupling between the cake layer build-up and the other fouling modes. Hence, this means that the concept of critical flux can not be viewed any more as a time-invariant value. This finding has implications beyond the application of beer, and especially for biotechnological broths which have similar composition of beer.
Moisture diffusivity in food materials
Sman, R.G.M. van der; Meinders, M.B.J. - \ 2013
Food Chemistry 138 (2013)2-3. - ISSN 0308-8146 - p. 1265 - 1274.
glass-transition temperatures - free-volume theory - polymer-polymer diffusion - field gradient nmr - self-diffusion - molecular-weight - aqueous-solutions - concentrated sucrose - sugar solutions - maltose-water
This paper investigates whether moisture diffusion can be predicted for food materials. We focus especially on mixtures of glucose homopolymers and water. The predictions are based on three theories: (1) the Darken relation, linking the mutual diffusivity to the self diffusivities, (2) the generalised Stokes–Einstein relation for the solute self diffusivity, and (3) the free volume theory for water self diffusivity. Using literature data obtained for the whole class of glucose homopolymer, we show that these theories predict the moisture diffusivity for the whole range of volume fractions, from zero to one, and a broad range of temperatures. Furthermore, we show that the theories equally holds for other hydrophilic biopolymers one finds in food. In the concentrated regime, all experimental data collapse to a single curve. This universal behaviour arises because these biopolymers form a hydrogen bonded network, where water molecules move via rearrangement of the free volume.
Structuring of expanded snacks based on patato ingredients : a review
Sman, R.G.M. van der; Broeze, J. - \ 2013
Journal of Food Engineering 114 (2013)4. - ISSN 0260-8774 - p. 413 - 425.
glass-transition temperature - damaged starch granules - physical-properties - extruded products - bubble-growth - semicrystalline polymers - rheological properties - extrusion behavior - sodium-chloride - foaming process
In this paper we review the current knowledge on the structuring via bubble expansion of starchy snacks, which are formulated on the basis of potato ingredients. These snacks are rarely discussed in scientific literature, but there are a scant number of patents dealing with various formulations and process descriptions. The general trends in the snack processing, we have described in a formal way using the Complex Dispersed Systems notation, augmented with a depiction of the processing pathway in the supplemented state diagram of starch. With this general framework in mind, we have compared the information given in the patents with scientific literature on cereal-based snacks. Based on this comparison we have formulated hypotheses about the functionality of the various ingredients with respect to the structuring of the potato snacks.
Soft matter approaches as enablers for food macroscale simulation
Datta, A.K. ; Sman, R.G.M. van der; Gulati, T. ; Warning, A. - \ 2012
Faraday Discussions 158 (2012). - ISSN 1359-6640 - p. 435 - 459.
multiphase porous-media - free-volume theory - moisture transport - mechanical-properties - mass-transfer - hydraulic conductance - model development - large-deformation - fluid transport - wetting liquid
Macroscopic deformable multiphase porous media models have been successful in describing many complex food processes. However, the properties needed for such detailed physics-based models are scarce and consist of primarily empirical models obtained from experiment. Likewise, driving forces such as swelling pressure have also been approached empirically, without physics-based explanations or prediction capabilities. Soft matter based prediction of properties will provide an additional avenue to obtaining properties and also provide a deeper and critical understanding of how these properties change with composition, temperature and other process variables.
The effect of structure and imbibition mode on the rehydration kinetics of freeze-dried carrots
Vergeldt, F.J. ; Duijster, A.J. ; Sman, R.G.M. van der; Voda, A. ; Khallouffi, S. ; Dalen, G. van; Vliet, L.J. van; Duynhoven, J.P.M. van; As, H. van - \ 2012
In: Magnetic Resonance in Food Science – Food for Thought / Belton, P., Webb, G., London : RSC Books
Change in Water Holding Capacity (WHC) of Mushroom during Processing: An Analysis Based on Flory Rehner’s Apprroach
Paudel, E. ; Sman, R.G.M. van der; Boom, R.M. - \ 2012
Conceptual Process Design of Mushroom Processing
Paudel, E. ; Sman, R.G.M. van der; Boom, R.M. - \ 2012
Anomalies in moisture transport during broccoli drying monitored by MRI?
Jin, X. ; Boxtel, A.J.B. van; Gerkema, E. ; Vergeldt, F.J. ; As, H. van; Straten, G. van; Boom, R.M. ; Sman, R.G.M. van der - \ 2012
Faraday Discussions 158 (2012). - ISSN 1359-6640 - p. 65 - 75.
viscoelastic behavior - cooking - model - nmr - simulation - carrot - grain - food - meat
Magnetic resonance imaging (MRI) offers unique opportunities to monitor moisture transport during drying or heating of food, which can render unexpected insights. Here, we report about MRI observations made during the drying of broccoli stalks indicating anomalous drying behaviour. In fresh broccoli samples the moisture content in the core of the sample increases during drying, which conflicts with Fickian diffusion. We have put the hypothesis that this increase of moisture is due to the stress diffusion induced by the elastic impermeable skin. Pre-treatments that change skin and bulk elastic properties of broccoli show that our hypothesis of stress-diffusion is plausible.
The impact of freeze-drying on microstructure and rehydration properties of carrot
Voda, A. ; Homan, N. ; Witek, M. ; Duijster, A. ; Dalen, G. van; Sman, R.G.M. van der; Nijsse, J. ; Vliet, L.J. van; As, H. van; Duynhoven, J.P.M. van - \ 2012
Food Research International 49 (2012)2. - ISSN 0963-9969 - p. 687 - 693.
integral-equations - apple tissue - ice crystals - tip radius - frozen - nmr - fruit - crystallization - dehydration - mechanisms
The impact of freeze-drying, blanching and freezing rate pre-treatments on the microstructure and on the rehydration properties of winter carrots were studied by µCT, SEM, MRI and NMR techniques. The freezing rate determines the size of ice crystals being formed that leave pores upon drying. Their average size (determined by µCT) can be predicted in a quantitative manner by considering dendritic growth and freezing rates. Blanching as a pre-treatment, however, did not affect pore size distribution induced by freeze-drying. Upon rehydration of the freeze-dried carrots, PFG NMR and MRI show that cellular compartments were not restored and instead a porous network with permeable barriers is formed. Blanching pre-treatment introduced a less connected and more anisotropic porous network if followed by fast freezing, indicating that more of the native cell wall morphology is preserved.
Review of hypotheses for fouling during beer clarification using membranes
Mepschen, A. ; Sman, R.G.M. van der; Vollebregt, H.M. ; Noordman, T.R. - \ 2012
Journal of Membrane Science 396 (2012). - ISSN 0376-7388 - p. 22 - 31.
cross-flow microfiltration - governing permeate flux - pressure-driven flow - beta-glucans - transmembrane pressure - colloidal suspensions - ceramic membranes - protein rejection - self-diffusion - model
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.
Effects of confinement on hydrodynamic interactions between a suspended sphere and stationary obstacles
Sman, R.G.M. van der - \ 2012
Computers & Fluids 58 (2012). - ISSN 0045-7930 - p. 63 - 69.
deterministic lateral displacement - microfluidic devices - flow - separation - simulations - particles - fractionation
Via Lattice Boltzmann simulations we have derived an empirical relation for the hydrodynamic interaction between a sedimenting sphere and an obstacle in narrow confining flow channels. This relation is of importance for particle tracking in microfluidic devices used for fractionation of suspensions. The hydrodynamic interaction is a function of the dimensionless gap, the degree of confinement, and the ratio of the principal curvatures of the sphere and obstacle. The degree of confinement is defined as the ratio of particle diameter and the length scale, which enters the mobility of the confined sphere, and is described by a generalisation of the Haberman–Sayre correlation. For gaps larger than a certain the screening length, the hydrodynamic interaction changes over from a 1/¿ to a 1/¿2 scaling. The screening length is dependent on the degree of confinement.
Soft matter approaches to food structuring
Sman, R.G.M. van der - \ 2012
Advances in Colloid and Interface Science 176-177 (2012). - ISSN 0001-8686 - p. 18 - 30.
lattice-boltzmann simulations - protein-polysaccharide interactions - brownian dynamics simulation - free-volume theory - glass-transition - phase-transitions - mass-transfer - rheological properties - beta-lactoglobulin - casein micelles
We give an overview of the many opportunities that arise from approaching food structuring from the perspective of soft matter physics. This branch of physics employs concepts that build upon the seminal work of van der Waals, such as free volume, the mean field, and effective temperatures. All these concepts aid scientists in understanding and controlling the thermodynamics and (slow) dynamics of structured foods. We discuss the use of these concepts in four topics, which will also be addressed in a forthcoming Faraday Discussion on food structuring.
Modeling migration in sheared bidisperse suspensions using an effective termperature
Sman, R.G.M. van der; Vollebregt, H.M. ; Boom, R.M. - \ 2012
Faraday Discussions 158 (2012). - ISSN 1359-6640 - p. 89 - 103.
pressure-driven flow - concentrated suspensions - polydisperse suspensions - numerical simulations - self-diffusion - fluidized beds - shear-flow - spheres - sedimentation - instabilities
A model for the particle migration in a bidisperse flowing suspension is proposed and compared to experimental data. A mixture formulation, describing the suspension velocity and pressure and the concentrations of two solid fractions is derived from a multi-fluid model. In the multi-fluid model the liquid phase and both dispersed phases are interpenetrating phases. The closure relations are based on a mean field approach extending closure relations of a monodisperse suspension. The model is used to predict segregation based on particle size in channel flow where the particles are subjected to Brownian motion and shear-induced migration. The comparison of the model results with experimental data shows that particle migration is predicted well by the given formulation.
Suspension flow in microfluidic devices - a review of experimental techniques focussing on concentration and velocity gradients
Dinther, A.M.C. van; Schroën, C.G.P.H. ; Vergeldt, F. ; Sman, R.G.M. van der; Boom, R.M. - \ 2012
Advances in Colloid and Interface Science 173 (2012). - ISSN 0001-8686 - p. 23 - 34.
fluorescence correlation spectroscopy - particle image velocimetry - electrical-impedance tomography - pressure-driven flow - nuclear-magnetic-resonance - laser-doppler anemometry - multiphase flows - neutron-radiography - confocal microscopy - brownian suspension
Microfluidic devices are an emerging technology for processing suspensions in e.g. medical applications, pharmaceutics and food. Compared to larger scales, particles will be more influenced by migration in microfluidic devices, and this may even be used to facilitate segregation and separation. In order to get most out of these completely new technologies, methods to experimentally measure (or compute) particle migration are needed to gain sufficient insights for rational design. However, the currently available methods only allow limited access to particle behaviour. In this review we compare experimental methods to investigate migration phenomena that can occur in microfluidic systems when operated with natural suspensions, having typical particle diameters of 0.1 to 10 µm. The methods are used to monitor concentration and velocity profiles of bidisperse and polydisperse suspensions, which are notoriously difficult to measure due to the small dimensions of channels and particles. Various methods have been proposed in literature: tomography, ultrasound, and optical analysis, and here we review and evaluate them on general dimensionless numbers related to process conditions and channel dimensions. Besides, eleven practical criteria chosen such that they can also be used for various applications, are used to evaluate the performance of the methods. We found that NMR and CSLM, although expensive, are the most promising techniques to investigate flowing suspensions in microfluidic devices, where one may be preferred over the other depending on the size, concentration and nature of the suspension, the dimensions of the channel, and the information that has to be obtained. The paper concludes with an outlook on future developments of measurement techniques.
Thermodynamics of meat proteins
Sman, R.G.M. van der - \ 2012
Food Hydrocolloids 27 (2012)2. - ISSN 0268-005X - p. 529 - 535.
water-vapor absorption - glass-transition - sodium-chloride - polyelectrolyte networks - desorption isotherms - moisture transport - polymer-solutions - phase-separation - pork meat - temperature
We describe the water activity of meat, being a mixture of proteins, salts and water, by the Free-Volume-Flory–Huggins (FVFH) theory augmented with the equation. Earlier, the FVFH theory is successfully applied to describe the thermodynamics to glucose homopolymers like starch, dextrans and maltodextrins. We have estimated parameter values from sorption isotherms of unsalted, lean meat products and model proteins like elastin and gelatin. These parameter values are quite similar to those found for glucose homopolymers. Moist meat products are also characterized with a water holding capacity, which we can describe with the Flory–Rehner theory. Subsequently, we have been able to predict very accurately the sorption isotherms of salted meat products and gelatin gels. Hence, the thermodynamics of foods can be described without the use of the controversial concept of bound/unfreezable water. Comparison of FVFH theory combined with Flory–Rehner theory to concentrated systems shows that the theory contains terms that are double counting for elastic effects – which makes us conclude that the validity of the Flory–Rehner theory is restricted to the (semi)-dilute regime. A complete thermodynamic description is proposed via mathematical matching of the FVFH and Flory–Rehner theory.
Effective temperature for sheared suspensions: A route towards closures for migration in bidisperse suspension
Vollebregt, H.M. ; Sman, R.G.M. van der - \ 2012
Advances in Colloid and Interface Science 185-186 (2012). - ISSN 0001-8686 - p. 1 - 13.
pressure-driven flow - lattice-boltzmann simulations - induced particle migration - non-brownian suspensions - induced self-diffusion - concentrated suspensions - colloidal suspensions - kinetic-theory - polydisperse suspensions - deterministic ratchets
By extending the concept of an effective temperature, earlier introduced for sheared monodisperse suspensions, we propose a continuum theory for sheared bidisperse suspensions. We show the theory for sheared suspensions can be constructed from the theory for Brownian suspensions by replacing the temperature with the effective temperature. Furthermore, we explore the validity of closure relations based on mean field/free volume theory, by comparison with experimental data obtained for Brownian bidisperse suspensions. In a recent paper, we have shown that the new theory, combined with the discussed closure relations, is indeed a predictive theory.
Prediction of post-harvest firmness of apples using biological switch model
Sman, R.G.M. van der; Sanders, M. - \ 2012
Journal of Theoretical Biology 310 (2012). - ISSN 0022-5193 - p. 239 - 248.
controlled-atmosphere storage - carbon-dioxide - ethylene biosynthesis - climacteric fruit - pattern-formation - systems biology - braeburn apples - generic model - tomato fruit - cell
In this paper we present a model that predicts the softening of apple during ripening in the postharvest phase. Apple ripening starts with an autocatalytic production of ethylene, which triggers a multitude of biochemical processes like the degradation of cell wall material. This triggering of the ripening process has been modelled as a biological switch—using the activator-depleted substrate model, which is proposed earlier by Meinhardt in the field of developmental biology. The model has been calibrated using storage experiments using various apple cultivars. Furthermore, the model is proven to be valid using independent experimental data of Elstar apple under dynamic storage conditions.
On the prediction of the remaining vase life of cut roses
Tromp, S.O. ; Sman, R.G.M. van der; Vollebregt, H.M. ; Woltering, E.J. - \ 2012
Postharvest Biology and Technology 70 (2012)aug.. - ISSN 0925-5214 - p. 42 - 50.
vascular blockage - keeping quality - flowers - water - temperature - sucrose - storage - model
The objective of the present paper was to examine the hypothesis that the time–temperature sum built up during storage and transport at constant as well as stepwise changing temperatures is a good predictor of the remaining vase life of cut roses. Theoretical calculations and graphing of functions showed that the time–temperature sum closely approximated the more common approach to quality loss, involving first order reaction kinetics with an Arrhenius temperature dependency. The time–temperature sum approximation failed at temperatures below 2 °C, especially in the case of long storage times. The time–temperature sum approximation succeeded in the range 2–6 °C. For temperatures above 6 °C, the degree-days model will underestimate the remaining vase life, depending on the storage time. The current experiment confirms these expectations from theory about the performance of the time–temperature sum. In the experiment not only constant storage temperatures but also stepwise changing storage temperatures were applied. Because of its simple principle, the time–temperature sum has practical value, but we are now aware of its limitations.
Effect of morphology on water sorption in cellular solid foods. Part I: Pore scale network model
Esveld, D.C. ; Sman, R.G.M. van der; Dalen, G. van; Duynhoven, J.P.M. van; Meinders, M.B.J. - \ 2012
Journal of Food Engineering 109 (2012)2. - ISSN 0260-8774 - p. 301 - 310.
moisture diffusivity - porous product - composite food - transport - prediction - media
A pore scale network model is developed to predict the dynamics of moisture diffusion into complex cellular solid foods like bread, crackers, and cereals. The morphological characteristics of the sample, including the characteristics of each cellular void and the open pore connections between them are determined from X-ray micro-tomography (XRT) data by means of 3D image analysis techniques. The 3D network allows to simulate the water vapor transport between the air cells through the open pores and the local sorption kinetics in the lamellae that separate them. In this way realistic moisture ingress profiles can be simulated in complex morphologies without need of unknown effective parameters. It is shown that the fine structure related transport characteristics embedded in the cell discretized network can be volume averaged to obtain a steady state relative vapor conductivity and a quasi-steady-state sorption time constant. These essential morphology related parameters can be used for an equivalent continuous two-equation description for a homogeneous product.
Effect of morphology on water sorption in cellular solid foods. Part II: sorption in cereal crackers
Esveld, D.C. ; Sman, R.G.M. van der; Witek, M.M. ; Windt, C.W. ; As, H. van; Duynhoven, J.P.M. van; Meinders, M.B.J. - \ 2012
Journal of Food Engineering 109 (2012)2. - ISSN 0260-8774 - p. 311 - 320.
moisture diffusivity - porous product - composite food - tortuosity - migration
Experimental dynamical moisture profiles of crackers with a fine and coarse morphology are successfully predicted using a pore scale network model. Experimental profiles are obtained using a single point imaging (SPI) NMR technique that enables 3D mapping of the moisture content of relatively immobile water at low water activity. The relative vapor conductivity trough the structure is 33% and 64% for the fine and coarse structured crackers, respectively. It can be argued that this is due to their difference in cell connectivity and not directly related to their difference in average cell diameter (0.33 and 0.75 mm, respectively). It was found that the retarded local sorption dynamics of the solid matrix has a noticeable influence on the moisture profiles that arise in the first hours. This is crucial for the moisture sorption dynamics of sub centimeter size samples, for which there is a distinct non-equilibrium between the vapor and the sorbed water phase. The local sorption at low water activity is a factor 3 faster for the fine structure cracker compared to the coarse one. This is due to their differences in average lamellae thickness (54 and 93 µm, respectively). However, for the description of the overall moisture sorption dynamics of the few cm thick samples, on a time scale of days, it valid to assume local equilibrium and to use an effective diffusivity model. The relative vapor conductivity together with the porosity and the derivative of the sorption isotherm determines the effective moisture diffusivity for these open structures, which is a factor 3 lower for the fine structured cracker compared to the coarse one. The single sided moisture sorption in the 2.5 thick cracker samples is not even completed after 5 days, mainly because at higher water content (near 20%) there is very little gradient in relative humidity to drive the vapor transport. This is reflected in the predicted effective moisture diffusivities which for the coarse cracker decrease from 16 × 10-9 m/s2 (at 1% MC, 16% aw) to 7.6 × 10-10 m/s2 (at 20% MC, 86% aw). --------------------------------------------------------------------------------
Moisture distribution in broccoli: measurements by MRI hot air drying experiments
Jin, X. ; Sman, R.G.M. van der; Gerkema, E. ; Vergeldt, F.J. ; As, H. van; Boxtel, A.J.B. van - \ 2011
Procedia Food Science 1 (2011). - ISSN 2211-601X - p. 640 - 646.
profiles - nmr - diffusivity - model - food - gel
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.
Evaluation of the Free Volume Theory to Predict Moisture Transport and Quality Changes During Broccoli Drying
Jin, X. ; Sman, R.G.M. van der; Boxtel, A.J.B. van - \ 2011
Drying Technology 29 (2011)16. - ISSN 0737-3937 - p. 1963 - 1971.
polymer-solvent systems - self-diffusion - coefficients
Moisture diffusion in porous broccoli florets and stalks is modeled using the free volume and Maxwell-Eucken theories. These theories are based on the mobility of water and concern the variation of the effective diffusion coefficient for a wide range of temperature and moisture content during product drying. Mass and heat transport, shrinkage, and vitamin C degradation during drying of broccoli are simulated by a spatial model. The effective diffusion coefficient varies strongly with product moisture content and temperature. Vitamin C degradation is high at moisture contents around 2 kg water/kg dry matter. The influence of the size of broccoli on the drying rate is evaluated for several types of broccoli florets and stalks
Moisture Distribution in Broccoli: Measurements by MRI Hot Air Drying Experiments
Jin, X. ; Sman, R.G.M. van der; Gerkema, E. ; Vergeldt, F.J. ; As, H. van; Boxtel, A.J.B. van - \ 2011
ABSTRACT 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. Keywords: diffusion properties; MRI; convective drying; moisture profiles
Investigation on the influence of pre-treatments on drying behaviour of broccoli by MRI experiments
Jin, X. ; Sman, R.G.M. van der; Gerkema, E. ; Vergeldt, F.J. ; As, H. van; Straten, G. van; Boom, R.M. ; Boxtel, A.J.B. van - \ 2011
Abstract: Magnetic Resonance Imaging (MRI) allows the monitoring of internal moisture content of food products during drying non-destructively. In an experimental set-up with continuous and controlled hot air supply, the internal moisture distribution of broccoli with different pre-treatments are measured during drying. Moisture distribution, drying rate and shrinkage are compared and analyzed quantitatively. MRI results indicated that for fresh broccoli stalks the moisture content in the core of the sample increased after some hours of drying. With pre-treatments as peeling, blanching or freezing the moisture transport barrier in the skin of the broccoli sample was reduced. Shrinkage was uniform for most of the pre-treated samples and the moisture increment in the core did not occur. It was also found that with these pre-treatments progress of drying enhanced significantly. Therefore, from an drying efficiency and economic point of view, pre-treatments prior to drying offer important opportunities. Keywords: MRI, hot air drying, broccoli stalk, increased moisture content, pre-treatments
Effectiviteit van ervarend leren op de boerderij
Hassink, J. ; Meyer, R. de; Sman, P. van de; Veerman, J.W. - \ 2011
Orthopedagogiek: Onderzoek en Praktijk 50 (2011)2. - ISSN 2211-6273 - p. 51 - 63.
gedragsstoornissen - gedragsproblemen - jeugd - jeugdzorg - zorgboerderijen - geestelijke gezondheid - effecten - multifunctionele landbouw - behaviour disorders - behaviour problems - youth - child welfare - social care farms - mental health - effects - multifunctional agriculture
In Noord-Brabant zijn individuele woon-werktrajecten op boerderijen ontwikkeld voor jongeren tussen de 16 en 20 jaar met ernstige problemen. Er is sprake van problemen en ruzie in het gezin, de jongeren gaan niet meer naar school en ze hebben geen goede vrijetijdsinvulling. De jongeren verblijven een half jaar op de boerderij. Daarna volgt nog een nabegeleiding van een half jaar. De resultaten van de door de jongeren ingevulde vragenlijsten laten zien dat het traject met name een positief effect heeft op probleemgedrag en zelfwaardering en in iets mindere mate op het copinggedrag. De positieve veranderingen zijn ook een half jaar na afsluiting van het nabegeleidingstraject nog zichtbaar. Uit de scores van de begeleiders blijkt dat er verbeteringen opgetreden zijn in het contact met het gezin, schooluitval, politiecontact, drugsgebruik, vrijetijdsbesteding, welzijn, gedragsproblemen en zelfvertrouwen.
Prediction of the state diagram of starch water mixtures using the Flory--Huggins free volume theory
Sman, R.G.M. van der; Meinders, M.B.J. - \ 2011
Soft Matter 7 (2011)2. - ISSN 1744-683X - p. 429 - 442.
glass-transition temperatures - phase-transitions - aqueous-solutions - physicochemical properties - light-scattering - molecular-weight - corn starch - thermal characterization - crystalline polymorph - scanning calorimetry
In this paper we analyse the phase and state transitions of starch and other glucose homopolymers and oligomers using the free volume extension of the Flory–Huggins theory by Vrentas and Vrentas, combined with the Couchman–Karasz theory for the glass transition. Using scaling relations of model parameters with molar weight we have obtained accurate predictions of moisture sorption and the freezing, boiling, and melting data obtained from literature for starch, dextrans, pullulan and maltodextrins. With the estimated model parameters we can construct the complete state diagram for starch, which can now be used as a quantitative tool for design and analysis of food structuring processes.
Analysis of mixed motion in deterministic ratchets via experiment and particle simulation
Kulrattanarak, T. ; Sman, R.G.M. van der; Schroën, C.G.P.H. ; Boom, R.M. - \ 2011
Microfluidics and Nanofluidics 10 (2011)4. - ISSN 1613-4982 - p. 843 - 853.
lattice-boltzmann simulations - lateral displacement - periodic arrays - fractionation - flow - suspensions - separation - equation - models - size
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 (Kulrattanarak et al. 2010b). 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
Mixed motion in deterministic ratchets due to anisotropic permeability
Kulrattanarak, T. ; Sman, R.G.M. van der; Lubbersen, Y.S. ; Schroën, C.G.P.H. ; Pham, H.T.M. ; Sarro, P.M. ; Boom, R.M. - \ 2011
Journal of Colloid and Interface Science 354 (2011)1. - ISSN 0021-9797 - p. 7 - 14.
continuous particle separation - lattice-boltzmann simulations - lateral displacement - microfluidic devices - periodic arrays - heat-transfer - blood-plasma - flow - fractionation - classification
Nowadays microfluidic devices are becoming popular for cell/DNA sorting and fractionation. One class of these devices, namely deterministic ratchets, seems most promising for continuous fractionation applications of suspensions (Kulrattanarak et al., 2008 [1]). Next to the two main types of particle behavior, zigzag and displacement motion as noted by the inventors (Huang et al., 2004 [2]) and (Inglis et al., 2006 [3]), we have shown recently the existence of a intermediate particle behavior, which we named ‘mixed motion’. In this paper we formulate the hypothesis that the occurrence of mixed motion is correlated with anisotropy in the permeability of the obstacle array. This hypothesis we base on the comparison of experimental observations of mixed motion and the flow lane distribution as obtained from 2-D flow simulations.
Characterization of water diffusion in food products for MRI experiments
Jin, X. ; Sman, R.G.M. van der; Gerkema, E. ; Vergeldt, F.J. ; As, H. van; Boxtel, A.J.B. van - \ 2010
Characterization of water diffusion in food products from MRI experiments
Jin, X. ; Sman, R.G.M. van der; Gerkema, E. ; As, H. van; Boxtel, A.J.B. van - \ 2010
Evaluation of the free volume theory to predict moisture transport and quality changes during broccoli drying
Jin, X. ; Sman, R.G.M. van der; Boxtel, A.J.B. van - \ 2010
Abstract: Moisture diffusion in porous broccoli florets and stalks is modeled by using the free volume and Maxwell-Eucken theories. These theories are based on the mobility of water and show the variation of the effective diffusion coefficient for a wide range of temperatures and moisture content of the product during drying. Mass and heat transport, shrinkage and vitamin C degradation during drying of broccoli are simulated by a spatial model. The effective diffusion coefficient varies strongly with product moisture content and temperature. Vitamin C degradation is strong at oisture contents below 4 kg water per kg dry matter.
Suspension flow modelling in particle migration and microfiltration
Vollebregt, H.M. ; Sman, R.G.M. van der; Boom, R.M. - \ 2010
Soft Matter 6 (2010)24. - ISSN 1744-683X - p. 6052 - 6064.
pressure-driven flow - shear-induced diffusion - concentrated colloidal dispersions - induced self-diffusion - fluidized-beds - hard-spheres - bidisperse suspensions - viscous resuspension - concentration polarization - spherical-particles
We review existing mixture models for shear-induced migration (SIM) in flowing viscous, concentrated particle suspensions via an analysis of the models from the perspective of a two-fluid formulation. Our analysis shows that particle suspensions in strong non-linear shear fields are a prime example of a driven soft matter system. The driving forces for particle migration can be expressed in terms of non-equilibrium osmotic pressure and chemical potential. Using the linear scaling of the effective temperature with the shear stress, we show that the osmotic pressure and shear-induced diffusion coefficients can be written in identical equations. This is similar to the equations for Brownian motion - with the temperature replaced by the effective temperature. As a guiding application we have taken crossflow microfiltration, where the driving is very strong and there is formation of a jammed state, cake layer, coexisting with the fluid state. The question whether the SIM mixture models holds for this application is investigated. Another questions is how SIM models can be extended for bidisperse suspensions, which is relevant for microfiltration applications involving particle fractionation. Analysis of existing closures of SIM mixture models from the two-fluid perspective learns us that the theory seems to be extendable towards bidisperse suspensions by means of the effective medium theory
MRT Lattice Boltzmann schemes for confined suspension flows
Sman, R.G.M. van der - \ 2010
Computer Physics Communications 181 (2010)9. - ISSN 0010-4655 - p. 1562 - 1569.
boundary-conditions - simulations - fluid - equation - relaxation - resistance - diffusion - membrane - particle - spheres
We introduce a novel multiple-relaxation time (modified MRT) Lattice Boltzmann scheme for simulation of confined suspension flow. Via careful tuning of the free eigenvalues of the collision operator we can substantially reduce the error in the so-called hydrodynamic radius. Its performance has been compared to that of the TRT scheme for several benchmark problems. We have found that the optimal value of the free eigenvalue depends on the curvature of the solid–fluid interfaces. Hence, we have investigated suspension flow problems, with confining boundaries of different curvatures. We have found that the modified MRT scheme is better suited for suspension flow in curved confining walls, while the TRT scheme is better for suspension flow confined between planar walls. With both schemes we have investigated problems for confined suspension flows, namely 1) drag forces experienced by spheres flowing in confining flow channels of different cross sections, and 2) the lubrication force between a sedimenting sphere and the end cap of a confining cylindrical capillary.
Drag force on spheres confined on the center line of rectangular microchannels
Sman, R.G.M. van der - \ 2010
Journal of Colloid and Interface Science 351 (2010)1. - ISSN 0021-9797 - p. 43 - 49.
low-reynolds-number - parallel plane walls - microfluidic devices - flow - square - simulations - separation - particle - motion - conduits
Via Lattice Boltzmann simulations we show there is a great deal of universality in the reduced mobility of spheres moving along the centre line of capillaries or rectangular microchannels. The reduced mobility follows a generalization of the Haberman–Sayre correlation, which is a function of the degree of confinement, e. This quantity e = dp/De, is defined as the ratio of the particle diameter and the length scale De, which is a weighted mean of the square root of the cross section area DA, and the hydraulic diameter Dh. The force experienced by spheres in pressure driven flow can be described by a generalized Faxen theorem, combined with effective medium theory. This force can be decomposed in a drag force and a pressure gradient force, both inversely proportional to the reduced mobility.
Deterministic ratchets for suspension fractionation
Kulrattanarak, T. - \ 2010
Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Ruud van der Sman; Karin Schroen. - [S.l. : S.n. - ISBN 9789085856146 - 141
suspensies - fractionering - vloeistofmechanica - simulatiemodellen - tweedimensionale stroming - deeltjes - scheidingstechnologie - suspensions - fractionation - fluid mechanics - simulation models - two dimensional flow - particles - separation technology
Driven by the current insights in sustainability and technological development in
biorefining natural renewable resources, the food industry has taken an interest in
fractionation of agrofood materials, like milk and cereal crops. The purpose of fractionation
is to split the raw material in several functional ingredients. For example,
milk can be split in fractions containing milk fat, casein micelles, and whey proteins.
Traditionally, separation processes in food industry are mainly aimed at separating
fluid from a suspension stream. Frequently membrane technology is used this type of
separation; membranes seem an obvious choice because they are able to sieve components
during mild fractionation of many foods, which are suspensions by nature,
like milk, or are suspended in liquid during processing (such as starch granule suspensions).
However, membrane separation is hindered by fouling of the pores by the
food ingredients and accumulation of these components in front of the pore, which
makes fractionation with membranes more challenging than plain separation of fluid
and solids. That is why we have investigated the possibilities of alternative technologies
such as microfluidic devices, and evaluated them under conditions required for
food applications.
Microfluidic devices are currently investigated for fractionation in biological applications,
like sorting of DNA or cells. Due to the large degree of freedom in design,
these devices are very suited for innovative fractionation technologies. First, we have
evaluated various designs available in literature in chapter 2, which concludes that
so-called deterministic ratchets are the most promising technology for fractionation of
food suspensions. This conclusion is based on the high yield, compactness of equipment,
and high selectivity that can be reached with such devices. In chapters 3 6,
we report on detailed investigations on deterministic ratchets through 2D simulation
(chapter 3), image analysis in comparison with simulation results (chapter 4), and full
3D simulations in combination with the previously mentioned methods (chapter 5).
In the last chapter, our findings are summarized in classification and design rules, and
an outlook for future developments is given.
Deterministic ratchets are microchannels, containing a regularly spaced array of
obstacles, through which the particle suspension flows. The essential property of
these ratchets is that each obstacle row is displaced slightly laterally with respect
to the previous row. Small particles follow the streamlines of the fluid, and zigzag
around the obstacles, while particles larger than a certain critical size bump into the
obstacles, and are consequently displaced from their streamline. The larger particles
will continuously be displaced in a direction in which the obstacles are placed, and
have a certain angle with the flow direction. The small particles are moving in the
direction of the liquid flow, which implies under an angle of zero degrees. Via the
difference in migration angle of the zigzag and displacement motion, particles can be
fractionated, and collected from different outlets.
An important property of deterministic ratchets is the size of the particles relative
to the width of the so-called flow lane, which determines whether it will show zigzag
motion or not. This we have investigated intensively in chapter 3 by means of 2-D
flow field simulation. The critical particle size is related to the width of the flow lanes,
within which the zigzagging particles will move, and we have determined the flow lane
widths for various designs. The distribution of the flow lane width is found to depend
strongly on the design of the ratchets. For a limited number of designs the original
hypothesis of the inventors of the deterministic ratchets holds, and the flow lanes are
symmetrically distributed over the space in between obstacles in one single row. In
general, ratchets have an asymmetric flow lane distribution, and typically, ratchet
designs suitable for food applications show a strong asymmetric flow lane distribution.
An asymmetric flow lane distribution implies that there is not one critical flow lane
width but two that determine the type of motion of particles inside the ratchets. As a
first approach we have taken these as the first and last (and largest) flow lane width,
df,1 and df,N. Consequently, particles are expected to show alternative motions that
are in between zigzag and displacement motion. Its existence has become evident in
the experiments described in chapter 4, and we have named it mixed motion. The
mixed motion is irregular, in contrast to the zigzag and displacement motion, and has
a migration angle which is intermediate between the angles corresponding to zigzag
and displacement motion, 0 < _ < _max. The particles moving in the ratchets we have
tracked by high speed recording, and the migration angle were quantified through tailor-made image analysis. As expected, the transitions between the different types
of particle motion seem to occur on the basis of the critical length scales, df,1 and df,N.
However, this conclusion can not be stated with high certainty because of the large
experimental error due to the wide particle size distribution of the used suspensions.
Because the ratchets used in chapter 4 has not been specifically designed to investigate
various particle behaviors, we have designed new ratchets based on the critical
length scales, df,1 and df,N, via 2D flow simulations, in order to allow detailed investigation.
Although these critical length scales do not take all aspects that play a
role during particle movement in a ratchet into account, we have stated that they can
be used as an initial guideline for ratchet designs. Next, we have performed detailed
and computationally intensive, 3D simulations, that include the particles. These 3D
simulations are performed to check the validity of the classification rules, derived from
the 2D simulations, that only include fluid flow. The simulation results show that the
transition between zigzag and mixed motion occurs indeed at the critical length scale,
df,1, being the width of the first flow lane. However, the length scale determining the
occurrence of displacement motion is larger than the last lane width, df,N, and might
even be uncorrelated with it. We have concluded that this second critical length scale,
df,c, can only be determined via 3D simulations. The thus obtained classification rules
are investigated experimentally and we have been able to correlate the migration angle
of many observed particles exhibiting mixed motion, to the critical length scales. This
makes us confident, that we now have identified the relevant critical length scales in
deterministic ratchets.
In the concluding chapter, we discuss the approach that we chose to ultimately derive
the classification rules, and discuss the implications of the corrected length scales
on the key performance indicators of ratchets, that are relevant to food applications.
We find that obtaining the correct critical length scales requires computationally intensive
3D simulations. Specifically for compact ratchet designs, which are relevant for
food application, the critical lane width df,c is not much different from df,N, obtained
via 2D flow simulations - and 2D simulation may thus offer a more time-efficient way
of estimating df,c. Further, we have discussed the existence of mixed motion in terms
of selectivity during fractionation for polydisperse suspensions, and have found that
the yield, compactness, and selectivity, all decrease, but at the same time it also opens
possibilities for fractionation in multiple streams in one step.
Simulations of confined suspension flow at multiple length scales
Sman, R.G.M. van der - \ 2009
Soft Matter 5 (2009). - ISSN 1744-683X - p. 4376 - 4387.
lattice-boltzmann method - dissipative particle dynamics - low-reynolds-number - immersed boundary method - shear-induced diffusion - pressure-driven flow - non-brownian suspensions - induced self-diffusion - particulate flows - numerical-simulation
In this paper we review simulation methods, which address suspension flows at different length scales. Taking the multiscale problem of confined suspension flow in fractionation and sorting applications as a guiding example, we discuss these numerical methods for use in a multiscale simulation framework. We have classified the methods in terms of dimensionless numbers, governing the physics of confined suspension flows, and the resolution of particles on the computation grid. From our literature review, we conclude, that for suspension flows at Peclet numbers larger than unity, Lattice Boltzmann is a good method to implement for all levels of the multiscale simulation framework
Deterministic Ratchets for Particle Separation Fabricated With Si MEMS Technology
Hoa Pham, ; Kulrattanarak, T. ; Sman, R.G.M. van der; Schroën, C.G.P.H. ; Boom, R.M. ; Sarro, P.M. - \ 2009
In: Proceedings of the Eurosensors XXIII conference, Lausanne, Switzerland, 6-9 September 2009. - - p. 345 - 346.
This paper presents the design, fabrication and testing of deterministic ratchets which are used for fractionation purpose. Ratchets with different configuration are prepared to determine particle trajectories with different sizes. Silicon based MEMS technology is used to fabricate devices containing arrays of obstacles with varying size, spacing and number. The arrays of high aspect ratio, 7-20um wide, silicon pillars are defined and etched in 60 to 80¿ deep microchannels using Deep Reactive Ion Etching (DRIE). The working modes of the ratchets are demonstrated using colloidal suspensions of latex particles which have an average diameter ranging between 2 and 6um
Lattice Boltzmann simulations of droplet formation during microchannel emulsification
Zwan, E.A. van der; Sman, R.G.M. van der; Schroën, C.G.P.H. ; Boom, R.M. - \ 2009
Journal of Colloid and Interface Science 335 (2009)1. - ISSN 0021-9797 - p. 112 - 122.
t-shaped microchannel - simple shear-flow - of-fluid method - membrane emulsification - numerical-simulation - model - deformation - breakup - surfactants - pressure
In this study, we compared microchannel droplet formation in a microfluidics device with a two phase lattice Boltzmann simulation. The droplet formation was found to be qualitatively described, with a slightly smaller droplet in the simulation. This was due to the finite thickness of the interface in the simulations. Dependence on dispersed flow rate could be very nicely predicted by the model, while a better insight was obtained on the internal pressures and flow velocities during droplet formation. These were found to be well described by simple relations; (1) the pressure inside the dispersed phase was predicted very well by the Laplace pressure while (2) the flow rate through the neck could be estimated by the flow through an orifice. These insights simplify the development of design rules for new microchannel devices
Deterministic ratchets for continuous suspension fractionation
Sman, Ruud van der - \ 2009
The science of food structuring
Sman, R.G.M. van der; Goot, A.J. van der - \ 2009
Soft Matter 5 (2009). - ISSN 1744-683X - p. 501 - 510.
condensed matter physics - glass-transition - molecular gastronomy - moisture transport - state diagrams - phase-transitions - double emulsions - droplet breakup - polymer science - cereal proteins
Food structuring is discussed from the viewpoints of soft matter physics and molecular gastronomy. Food is one of the most complex types of soft matter, with multiple dispersed phases and even hierarchical structure. Food structuring seems to be a kind of art, comprising a careful balance between forces driving the system towards equilibrium and arresting forces. A more scientific approach to this complex matter is desirable, using (1) concepts from soft matter physics, e.g. free energy and jamming, and (2) complex disperse system (CDS) notation as developed for molecular gastronomy. Combining CDS with state diagrams renders a new tool for the qualitative description of the complex process of making structured foods.
Lift force on a spherical particle in a couette and poiseuille flow
Kassa, S.B. ; Sman, R.G.M. van der; Schroën, C.G.P.H. ; Boom, R.M. - \ 2008
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