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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Sensorial analysis of polysaccharide-gelled protein particle dispersions in relation to lubrication and viscosity properties
Chojnicka-Paszun, A. ; Doussinault, S. ; Jongh, H.H.J. de - \ 2014
Food Research International 56 (2014). - ISSN 0963-9969 - p. 199 - 210.
oral perception - perceived texture - size - gels - hardness - systems - fluid - foods
In this work polysaccharide-protein gel particle dispersions were studied to identify relation between sensorial responses and their bulk rheological and tribological properties. Sensory analysis was performed by a trained panel using QDA to evaluate distinct mouth-feel perception. Attributes such as powdery, slipperiness, stickiness, and filmy were then correlated to tribological and rheological data of these dispersions. Since thickness perception masked scores of other attributes, all samples were tuned to obtain the same score in sensorial thickness to minimize its influence. The experimental survey presented in this work revealed an interesting set of correlations. The friction coefficient showed a negative correlation with slipperiness, while with other attributes the established relation was below a significant level. Attributes, such as stickiness, sliminess and filmy, correlated with viscosity data of the dispersions within a wide range of shear rates. In addition, a direct relation was found between the powdery attribute and the size of particles present in the dispersions. Moreover, the hardness of these particles seemed to have a strong influence on the steepness of this latter relation. (C) 2013 Elsevier Ltd. All rights reserved.
Equation of state and adsorption dynamics of soft microgel particles at an air-water interface
Deshmukh, O.S. ; Maestro, A. ; Duits, M.H.G. ; Ende, D.T.M. van den; Cohen Stuart, M.A. ; Mugele, F. - \ 2014
Soft Matter 10 (2014)36. - ISSN 1744-683X - p. 7045 - 7050.
cross-link density - poly(n-isopropylacrylamide) microgels - emulsion stabilizers - sensitive microgels - temperature - surfactants - scattering - kinetics - light - fluid
Understanding the adsorption dynamics of soft microgel particles is a key step in designing such particles for potential applications as stimuli-responsive Pickering stabilizers for foams or emulsions. In this study we experimentally determine an equation of state (EOS) for poly (N-isopropylacrylamide) (PNIPAM) microgel particles adsorbed onto an air–water interface using a Langmuir film balance. We detect a finite surface pressure at very low surface concentration of particles, for which standard theories based on hard disk models predict negligible pressures, implying that the particles must deform strongly upon adsorption to the interface. Furthermore, we study the evolution of the surface pressure due to the adsorption of PNIPAM particles as a function of time using pendant drop tensiometry. The equation of state determined in the equilibrium measurements allows us to extract the adsorbed amount as a function of time. We find a mixed-kinetic adsorption that is initially controlled by the diffusion of particles towards the interface. At later stages, a slow exponential relaxation indicates the presence of a coverage-dependent adsorption barrier related to crowding of particles at the interface.
Dynamics of multiphase systems with complex microstructure. I. Development of the governing equations through nonequilibrium thermodynamics
Sagis, L.M.C. ; Öttinger, H.C. - \ 2013
Physical Review. E, Statistical nonlinear, and soft matter physics 88 (2013)2. - ISSN 1539-3755 - 13 p.
scanning angle reflectometry - in-water emulsions - superficial viscosity - general formalism - bending rigidity - lipid-bilayers - interfaces - surface - fluid - rheology
In this paper we present a general model for the dynamic behavior of multiphase systems in which the bulk phases and interfaces have a complex microstructure (for example, immiscible polymer blends with added compatibilizers, or polymer stabilized emulsions with thickening agents dispersed in the continuous phase). The model is developed in the context of the GENERIC framework (general equation for the nonequilibrium reversible irreversible coupling). We incorporate scalar and tensorial structural variables in the set of independent bulk and surface excess variables, and these structural variables allow us to link the highly nonlinear rheological response typically observed in complex multiphase systems, directly to the time evolution of the microstructure of the bulk phases and phase interfaces. We present a general form of the Poisson and dissipative brackets for the chosen set of bulk and surface excess variables, and show that to satisfy the entropy degeneracy property, we need to add several contributions to the moving interface normal transfer term, involving the tensorial bulk and interfacial structural variables. We present the full set of balance equations, constitutive equations, and boundary conditions for the calculation of the time evolution of the bulk and interfacial variables, and this general set of equations can be used to develop specific models for a wide range of complex multiphase systems.
Dynamics of multiphase systems with complex microstructure. II. Particle-stabilized interfaces
Sagis, L.M.C. - \ 2013
Physical Review. E, Statistical nonlinear, and soft matter physics 88 (2013)2. - ISSN 1539-3755 - 9 p.
fourier-transform rheology - in-water emulsions - superficial viscosity - bending rigidity - surface - liquid - viscoelasticity - liquid/liquid - fluid - gas/liquid
In this paper we use the GENERIC (general equation for nonequilibrium reversible-irreversible coupling) nonequilibrium thermodynamics framework to derive constitutive equations for the surface extra stress tensor of an interface stabilized by a two-dimensional suspension of anisotropic colloidal particles. The dependence of the surface stress tensor on the microstructure of the interface is incorporated through a dependence on a single tensorial structural variable, characterizing the average orientation of the particles. The constitutive equation for the stress tensor is combined with a time-evolution equation describing the changes in the orientation tensor as a result of the applied deformation field. We examine the predictions of the model in in-plane steady shear flow, in-plane oscillatory shear flow, and oscillatory dilatational flow. The model is able to predict the experimentally observed shear thinning behavior in surface shear flow, and also the experimentally observed emergence of even harmonics in the frequency spectrum of the surface stress in oscillatory dilatational flow. Our results show that the highly nonlinear stress-deformation behavior of interfaces with a complex microstructure can be modeled well using simple structural models like the one presented here.
Generalized surface momentum balances for the analysis of surface dilatational data
Sagis, L.M.C. - \ 2013
The European Physical Journal. Special Topics 222 (2013)1. - ISSN 1951-6355 - p. 31 - 38.
in-water emulsions - interfacial permeability - superficial viscosity - bending rigidity - lipid-bilayers - fluid - dynamics - liquid - microbubbles - mixtures
Dilatational rheological properties of interfaces are often determined using drop tensiometers, in which the interface of the droplet is subjected to oscillatory area changes. A dynamic surface tension is determined either by image analysis of the droplet profile or by measuring the capillary pressure. Both analysis modes tend to use the Young-Laplace equation for determining the dynamic surface tension. For complex fluid-fluid interfaces there is experimental evidence that this equation does not describe the response of the interface to deformations adequately. Generalizations of this equation are available, and in this comment we will discuss these generalizations, and the conditions for which they reduce to the Young-Laplace equation.
Behaviour of silver nanoparticles and silver ions in an in vitro human gastrointestinal digestion model
Walczak, A.P. ; Fokkink, R.G. ; Peters, R.J.B. ; Tromp, P. ; Herrera Rivera, Z.E. ; Rietjens, I.M.C.M. ; Hendriksen, P.J.M. ; Bouwmeester, H. - \ 2013
Nanotoxicology 7 (2013)7. - ISSN 1743-5390 - p. 1198 - 1210.
aggregation kinetics - aqueous-solution - toxicity - dissolution - exposure - fluid - food - nanotechnologies - fabrication - nanosilver
Oral ingestion is an important exposure route for silver nanoparticles (AgNPs), but their fate during gastrointestinal digestion is unknown. This was studied for 60 nm AgNPs and silver ions (AgNO3) using in vitro human digestion model. Samples after saliva, gastric and intestinal digestion were analysed with SP-ICPMS, DLS and SEM-EDX. In presence of proteins, after gastric digestion the number of particles dropped significantly, to rise back to original values after the intestinal digestion. SEM-EDX revealed that reduction in number of particles was caused by their clustering. These clusters were composed of AgNPs and chlorine. During intestinal digestion, these clusters disintegrated back into single 60 nm AgNPs. The authors conclude that these AgNPs under physiological conditions can reach the intestinal wall in their initial size and composition. Importantly, intestinal digestion of AgNO3 in presence of proteins resulted in particle formation. These nanoparticles (of 20–30 nm) were composed of silver, sulphur and chlorine
Structures, stresses, and fluctuations in the delayed failure of colloidal gel
Lindstrom, S.B. ; Kodger, T.E. ; Sprakel, J.H.B. ; Weitz, D.A. - \ 2012
Soft Matter 8 (2012)13. - ISSN 1744-683X - p. 3657 - 3664.
fracture - force - suspensions - particles - adhesion - lifetime - strength - network - fluid - bonds
Sample-spanning networks of aggregated colloidal particles have a finite stiffness and deform elastically when subjected to a small shear stress. After some period of creep, these gels ultimately suffer catastrophic failure. This delayed yielding is governed by the association and dissociation dynamics of interparticle bonds and the strand structure of the gel. We derive a model which connects the kinetics of the colloids to the erosion of the strand structure and ultimately to macroscopic failure. Importantly, this model relates time-to-failure of the gel to an applied static stress. Model predictions are in quantitative agreement with experiments. It is predicted that the strand structure, characterized by its mesh size and strand coarseness, has a significant impact on delay time. Decreasing the mesh size or increasing the strand thickness makes colloidal gels more resilient to delayed yielding. The quench and flow history of gels modifies their microstructures. Our experiments show that a slow quenching increases the delay time due to the coarsening of the strands; by contrast, preshear reduces the delay time, which we explain by the increased mesh size as a result of shear-induced fracture of strands.
Starch source in high concentrate rations does not affect rumen pH, histamine and lipopolysaccharide concentrations in dairy cows
Pilachai, R. ; Schonewille, J.T. ; Thamrongyoswittayakul, C. ; Aiumlamai, S. ; Wachirapakom, C. ; Everts, H. ; Hendriks, W.H. - \ 2012
Livestock Science 150 (2012)1-3. - ISSN 1871-1413 - p. 135 - 142.
subacute ruminal acidosis - induced lactic-acidosis - inflammatory response - cattle - fermentation - endotoxin - degradation - performance - steers - fluid
The replacement of ground corn by cassava meal on rumen pH, lipopolysaccharide (LPS) and histamine concentrations under typical Thai feeding conditions (high concentrate diets and rice straw as the sole source of roughage) was investigated. Four rumen-fistulated crossbred Holstein, non-pregnant, dry cows were randomly assigned to the four experimental rations in a 4×4 Latin square design with 21-d periods. Each period consisted of a 14-d run-in/wash out period, followed by a 7-d experimental period. During the run-in/wash out period, the cows were offered 5.4 kg DM of concentrate containing 4.6% cassava meal and rice straw was provided ad libitum. During the 7 day of each experimental period, cows were offered 10.5 kg DM of concentrate containing either 4.6% or 18.3% or 32.4% or 46.2% cassava meal and 1.5 kg of rice straw. Irrespective of dietary treatments, rumen total VFA and lactate concentrations were significantly affected by sampling day, which were significantly higher on day 1 versus days 3 and 7 of the experimental periods. Mean postprandial rumen pH was reduced to values
Coalescence of oil droplets in plasticized starch matrix in simple shear flow
Emin, M.A. ; Schmidt, U. ; Goot, A.J. van der; Schuchmann, H.P. - \ 2012
Journal of Food Engineering 113 (2012)3. - ISSN 0260-8774 - p. 453 - 460.
immiscible polymer blends - 2-dimensional linear flow - equal-sized drops - viscosity ratio - fluid - emulsions - hysteresis - components - extrusion - breakup
The formation of oil droplets in plasticized starch matrices is studied by using well-defined conditions similar to extrusion. A method based on double staining and confocal scanning microscopy was developed to investigate the role of coalescence during droplet formation. The results indicate that coalescence takes place at all process conditions studied. The apparent critical capillary number was used to quantify the coalescence intensity and to separate the influence of interdependent process parameters on the coalescence. The intensity of coalescence increased with shear rate and oil content whereas an increase in blend viscosity reduced the extent of coalescence. Besides, the results showed that the critical dispersed phase concentration (Fc), below which no coalescence takes place, depends on applied shear rate and decreases with increasing shear rate.
A microfluidic method to study demulsification kinetics
Krebs, T. ; Schroën, C.G.P.H. ; Boom, R.M. - \ 2012
Lab on a Chip 12 (2012)6. - ISSN 1473-0197 - p. 1060 - 1070.
simple shear-flow - size distributions - oil-emulsions - break-up - coalescence - drops - droplets - fluid - surfactants - suspensions
We present the results of experiments studying droplet coalescence in a dense layer of emulsion droplets using microfluidic circuits. The microfluidic structure allows direct observation of collisions and coalescence events between oil droplets dispersed in water. The coalescence rate of a flowing hexadecane-in-water emulsion was measured as a function of the droplet velocity and droplet concentration from image sequences measured with a high-speed camera. A trajectory analysis of colliding droplet pairs allows evaluation of the film drainage profile and coalescence time t(c.) The coalescence times obtained for thousands of droplet pairs enable us to calculate coalescence time distributions for each set of experimental parameters, which are the mean droplet approach velocity (v(0)), the mean dispersed phase fraction (f) and the mean hydraulic diameter of a droplet pair (d(p)). The expected value E(t(c)) of the coalescence time distributions scales as E(t(c)) is proportional to (v(0))(-0.105±0.043)(d(p))(0.562±0.287), but is independent of f. We discuss the potential of the procedure for the prediction of emulsion stability in industrial applications
Deconjugation Kinetics of Glucuronidated Phase II Flavonoid Metabolites by B-glucuronidase from Neutrophils
Bartholomé, R. ; Haenen, G. ; Hollman, P.C.H. ; Bast, A. ; Dagnelie, P.C. ; Roos, D. ; Keijer, J. ; Kroon, P.A. ; Needs, P.W. ; Arts, I.C.W. - \ 2010
Drug Metabolism and Pharmacokinetics 25 (2010)4. - ISSN 1347-4367 - p. 379 - 387.
quercetin glucuronides - grain dust - inflammation - dietary - ph - tissue - cells - fluid - quercetin-4'-glucoside - quercetin-3-glucoside
Flavonoids are inactivated by phase II metabolism and occur in the body as glucuronides. Mammalian ß-glucuronidase released from neutrophils at inflammatory sites may be able to deconjugate and thus activate flavonoid glucuronides. We have studied deconjugation kinetics and pH optimum for four sources of ß-glucuronidase (human neutrophil, human recombinant, myeloid PLB-985 cells, Helix pomatia) with five flavonoid glucuronides (quercetin-3-glucuronide, quercetin-3'-glucuronide, quercetin-4'-glucuronide, quercetin-7-glucuronide, 3'-methylquercetin-3-glucuronide), 4-methylumbelliferyl-ß-D-glucuronide, and para-nitrophenol-glucuronide. All substrate-enzyme combinations tested exhibited first order kinetics. The optimum pH for hydrolysis was between 3.5-5, with appreciable hydrolysis activities up to pH 5.5. At pH 4, the Km ranged 44-fold from 22 µM for quercetin-4'-glucuronide with Helix pomatia ß-glucuronidase, to 981 µM for para-nitrophenol-glucuronide with recombinant ß-glucuronidase. Vmax (range: 0.735-24.012 µmol·min-1·unit-1 [1 unit is defined as the release of 1 µM 4-methylumbelliferyl-ß-D-glucuronide per min]) and the reaction rate constants at low substrate concentrations (k) (range: 0.002-0.062 min-1·(unit/L)-1 were similar for all substrates-enzyme combinations tested. In conclusion, we show that ß-glucuronidase from four different sources, including human neutrophils, is able to deconjugate flavonoid glucuronides and non-flavonoid substrates at fairly similar kinetic rates. At inflammatory sites in vivo the pH, neutrophil and flavonoid glucuronide concentrations seem favorable for deconjugation. However, it remains to be confirmed whether this is actually the case.
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.
In vitro digestibility of b-casein and b-lactoglobulin under simulated human gastric and duodenal conditions
Mandalari, G. ; Adel-Patient, K. ; Barkholt, V. ; Baro, C. ; Bennett, L. ; Bublin, M. ; Gaier, S. ; Graser, G. ; Ladics, G.S. ; Mierzejewska, D. ; Vassilopoulou, E. ; Vissers, Y.M. ; Zuidmeer, L. ; Rigby, N.M. ; Salt, L.J. ; Defernez, M. ; Mulholland, F. ; Mackie, A.R. ; Wickham, M.S.J. ; Mills, E.N.C. - \ 2009
Regulatory Toxicology and Pharmacology 55 (2009)3. - ISSN 0273-2300 - p. 372 - 381.
human pancreatic-juice - food allergens - gastrointestinal proteolysis - protein digestibility - pepsin digestion - stability - fluid - hydrolysis - resistance - ph
Initially the resistance to digestion of two cow's milk allergens, beta-casein, and beta-lactoglobulin (beta-Lg), was compared using a "high-protease assay" and a "low-protease assay" in a single laboratory. The low-protease assay represents an alternative standardised protocol mimicking conditions found in the gastrointestinal tract. For the high-protease assay, both proteins were incubated with either pepsin or pancreatin and digestion monitored by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and reverse phase-high performance liquid chromatography. The low-protease assay involved gastroduodenal digestion in the presence or absence of phosphatidylcholine (PC). Both beta-casein and beta-Lg were susceptible to hydrolysis by pepsin and pancreatin in the high-protease assay. In contrast, the kinetics of beta-casein digestion in the low-protease assay were slower, beta-Lg being pepsin resistant. During duodenal digestion, beta-Lg was gradually degraded and addition of PC slowed digestion. Subsequently, the reproducibility of the low-protease assay was assessed in 12 independent laboratories by visual assessment of the gels and densitometric analysis: the inter- and intra-laboratory variability was affected by sampling and electrophoresis method employed. The low-protease assay was shown to be reproducible. Future studies will extend these findings using a broader panel of proteins
Relationship between in situ degradation kinetics and in vitro gas production fermentation using different mathematical models
Rodrigues, M.A.M. ; Cone, J.W. ; Ferreira, L.M.M. ; Blok, M.C. ; Guedes, C. - \ 2009
Animal Feed Science and Technology 151 (2009)1-2. - ISSN 0377-8401 - p. 86 - 96.
nylon bag degradability - production profiles - ruminant feeds - rumen fermentation - dairy-cows - extent - fluid - digestibility - disappearance - prediction
In vitro and in situ studies were conducted to evaluate the influence of different mathematical models, used to fit gas production profiles of 15 feedstuffs, on estimates of nylon bag organic matter (OM) degradation kinetics. The gas production data were fitted to Exponential, Logistic, Gompertz and a Sigmoidal model. Using only gas production parameters allowed poor prediction of in situ degradation. It was not possible to estimate the washout (W) and degradable (D) in situ fractions for all models, with the exception of the Sigmoidal model with which the D fraction was poorly estimated (R2 = 0.28). The Exponential model did not show any estimation capability, and the Logistic and Gompertz models best predicted in situ degradation rate of OM (kd) with R2 values of 0.65 and 0.62, respectively. The transformation of the in situ rate of degradation (kd) to its half-life value of degradation ((ln 2/kd)100) provided an improvement of kd prediction in the Sigmoidal model, with R2 changing from 0.35 to 0.64. As to kd and fermentable organic matter (FOM) all estimations improved upon inclusion of chemical composition characteristics, such as sugars, crude protein (CP), neutral detergent fibre (NDFom) and crude fat (CFat). The Logistic and Gompertz models continued to better predict kd, with R2 values of 0.79 and 0.88, respectively, while the Sigmoidal model showed a higher capability to estimate FOM (R2 = 0.90). It should also be noticed that the estimation of the washout fraction (W) estimation was obtained with only sugar and starch contents (R2 = 0.62). There were only moderate relationships between in situ and gas production indicating that the methods do not describe the degradation of these feedstuffs in a similar way
Membrane protein frustration: protein incorporation into hydrophobic mismatched binary lipid mixtures
Stopar, D. ; Spruijt, R.B. ; Hemminga, M.A. - \ 2009
Biophysical Journal 96 (2009)4. - ISSN 0006-3495 - p. 1408 - 1414.
major coat protein - bacteriophage m13 - phase-transitions - acyl-chain - bilayers - fluid - phosphatidylcholines - spectroscopy - domain - solubilization
Bacteriophage M13 major coat protein was reconstituted in different nonmatching binary lipid mixtures composed of 14:1PC and 22:1PC lipid bilayers. Challenged by this lose-lose situation of hydrophobic mismatch, the protein-lipid interactions are monitored by CD and site-directed spin-label electron spin resonance spectroscopy of spin-labeled site-specific single cysteine mutants located in the C-terminal protein domain embedded in the hydrophobic core of the membrane (I39C) and at the lipid-water interface (T46C). The CD spectra indicate an overall ¿-helical conformation irrespective of the composition of the binary lipid mixture. Spin-labeled protein mutant I39C senses the phase transition in 22:1PC, in contrast to spin-labeled protein mutant T46C, which is not affected by the transition. The results of both CD and electron spin resonance spectroscopy clearly indicate that the protein preferentially partitions into the shorter 14:1PC both above and below the gel-to-liquid crystalline phase transition temperature of 22:1PC. This preference is related to the protein tilt angle and energy penalty the protein has to pay in the thicker 22:1PC. Given the fact that in Escherichia coli, which is the host for M13 bacteriophage, it is easier to find shorter 14 carbon acyl chains than longer 22 carbon acyl chains, the choice the M13 coat protein makes seems to be evolutionary justified
Effects of Different Tastants on Parotid Saliva Flow and Composition
Neyraud, E. ; Heinzerling, C.I. ; Bult, J.H.F. ; Mesmin, C. ; Dransfield, E. - \ 2009
Chemosensory Perception 2 (2009)2. - ISSN 1936-5802 - p. 108 - 116.
gustatory stimuli - human whole - secretion - protein - gland - taste - amylase - fluid
Saliva from parotid glands plays a role in taste perception. Parotid saliva is also stimulated by tastants. The aim of this work is to investigate the effects of different tastants on the parotid salivary response in six subjects. Five tastants were given in different concentrations in solution and held in the mouth for 10 s. The flow rate, protein concentration, and pH of secreted parotid saliva were monitored continuously for 5 min. Stimulation by tastants on flow rate response consists of an immediate rise in flow followed by a plateau and a rapid return to prestimulus flow. Response of pH results in a slower increase while protein concentration consists in a slower decrease, both followed by a return to prestimulus levels in about 4 min. From a resting flow rate of about 140¿L/min, an increase in flow rate to 370¿L/min was caused by stimulation for 10 s with 10 mL of solutions of 0.01 M citric acid, 0.13 M MgSO4, 0.25 M monosodium glutamate, 0.5 M NaCl, or 0.5 M sucrose. Comparisons of the different tastants showed that the pH of stimulated parotid saliva increased linearly (r=-0.9), irrespective of the nature of the tastant. Protein concentration decreased (r=-0.45) and protein amount increases (r=-0.58) with increase in flow rate for all tastants. Corrected for the effects of flow rate, protein amount depended on the nature of the tastant with the greatest secretion after stimulation by citric acid. Flow rate was largely responsible for pH but tastant appears to play an additional role with flow rate on protein secretion.
Differential saliva-induced breakdown of starch filled protein gels in relation to sensory perception
Janssen, A.M. ; Pijpekamp, A.M. van de; Labiausse, D. - \ 2009
Food Hydrocolloids 23 (2009)3. - ISSN 0268-005X - p. 795 - 805.
proteins/polysaccharide mixed gels - whey - microstructure - texture - custards - release - amylase - flavor - fluid - food
In this study, the differential breakdown of protein gels containing four types of high and low cross-linked starch granules were studied. Susceptibility to saliva-induced breakdown of starch granules and the consequences of these for overall breakdown of the gel matrix were captured using a multiple extrusion cell (MEC). Gels filled with two types of starch were used for sensorial evaluation by a QDA panel and the mechanical impact of the starch granules on these latter gels was characterized using uniaxial compression measurements. These data were used to better understand differences in sensory mouth feel attributes. MEC measurements indicated that the low cross-linked starches were more susceptible to saliva-induced breakdown compared to their highly cross-linked counterparts. The sensory space of starch filled gels was divided into three dimensions. Protein content of the gel matrix determined one dimension, resulting in high sensory ratings for separating and slippery mouth feel. The distinction into the two other dimensions, one being dominated by grainy/spreadable/sticky and the other by crumbly/crumbly effort, originates mainly from different starch types used: larger starch granules from the low cross-linked potato starch were perceived as more grainy and gels filled with these granules were more spreadable with a lower rating for crumbly and crumbly effort. Surprisingly, in most cases ratings for firm for both starch types were more or less comparable, indicating that these granules behave as inert fillers in a rather similar way, as also suggested by compression measurements. This work indicates that low cross-linked potato starch displays a higher susceptibility for digestion by amylase present in saliva. This is possibly the reason for the larger spreadability and lower rating for crumbly effort of the gel containing this type of starch.
Complexity of Lipid Domains and Rafts in Giant Unilamellar Vesicles Revealed by Combining Imaging and Microscopic and Macroscopic Time-Resolved Fluorescence
Almeida, R.F.M. de; Borst, J.W. ; Federov, A. ; Prieto, M. ; Visser, A.J.W.G. - \ 2007
Biophysical Journal 93 (2007). - ISSN 0006-3495 - p. 539 - 553.
differential scanning calorimetry - resonance energy-transfer - model membranes - correlation spectroscopy - cell-membranes - phase-equilibria - cholesterol - fluid - phosphatidylcholine - mixtures
The application of fluorescence lifetime imaging microscopy to study gel/fluid and raftlike lipid domains in giant unilamellar vesicles (GUVs) is demonstrated here. Different regions of the ternary dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine/cholesterol phase diagram were studied. The head-labeled phospholipid Rhodamine-dioleoylphosphatidylethanolamine (Rhod-DOPE) was used as a fluorescent probe. Gel/fluid and liquid-ordered (lo)/liquid-disordered (ld) phase separation were clearly visualized upon two-photon excitation. Fluorescence intensity decays in different regions of a GUV were also obtained with the microscope in fixed laser-beam configuration. The ensemble behavior of the system was studied by obtaining fluorescence intensity decays of Rhod-DOPE in nongiant vesicle suspensions. The fingerprints for gel/fluid coexistence and for the presence of lo raftlike phase, based on fluorescence lifetime imaging microscopy histograms and images, and on the fluorescence intensity decay parameters of Rhod-DOPE, are presented. The presence of three lipid phases in one single GUV is detected unequivocally. From the comparison of lifetime parameters, it can be concluded that the lo phase is formed in the binary dipalmitoylphosphatidylcholine/cholesterol but not in the dioleoylphosphatidylcholine/cholesterol mixture. The domains apparent in fluorescence intensity images have a more complex substructure revealed by analysis of the lifetime data. The potential applications of this combined imaging/microscopic/macroscopic methodology are discussed.
Lattice Boltzmann simulation of 2D and 3D non-Brownian suspensions in Couette flow
Kromkamp, J. ; Ende, D. van den; Kandhai, D. ; Sman, R.G.M. van der; Boom, R.M. - \ 2006
Chemical Engineering Science 61 (2006)2. - ISSN 0009-2509 - p. 858 - 873.
navier-stokes equation - shear-induced particle - induced self-diffusion - concentrated suspensions - particulate suspensions - numerical simulations - spheres - fluid - migration - viscosity
In this study, the Lattice Boltzmann (LB) method is applied for computer simulation of suspension flow in Couette systems. Typical aspects of Couette flow such as wall effects and non-zero Reynolds numbers can be studied well with the LB method because of its time-dependent character. Couette flow of single, two and multi-particle systems was studied, where two-dimensional (2D) systems were compared with three-dimensional (3D) systems. Computations on multi-particle 3D suspensions, for instance to assess the viscosity or shear-induced diffusivity, were found to be very intensive. This was only partly a consequence of the 3D system size. The critical particle grid size, necessary for accurate results, was found to be relatively large, increasing the system to impractical sizes. It is however demonstrated that it is possible to carry out computer simulations on 2D suspensions and use relatively simple, linear scaling relations to translate these results to 3D suspensions, in this way avoiding intensive computations. By doing so, the LB method is shown to be well-suited for study of suspension flow in Couette systems, particularly for aspects as particle layering near solid walls, hydrodynanmic particle interactions and viscous stresses at non-zero Reynolds numbers, which cannot be easily solved with alternative methods. It also opens the way to employ the LB method for other unexplored aspects, such as particle polydispersity and high Reynolds number flow, with large relevance to practical processing of suspensions.
Adaptation of the rumen microbial population to native potato starch degradation determined with the gas production technique and the nylon bag technique
Cone, J.W. ; Gelder, A.H. van - \ 2006
Journal of Animal Physiology and Animal Nutrition 90 (2006)11-12. - ISSN 0931-2439 - p. 511 - 518.
in-situ - dairy-cows - production profiles - inoculum source - digestion - fermentation - fluid - kinetics - enzymes - tract
Experiments were conducted to investigate the influence of the adaptation of rumen micro-organisms on the degradation of native potato starch (PS) in the rumen. Cows were fed with rations used for gas production (GP) analysis (dry cows, 1.6% starch) and for the nylon bag (NB) technique (lactating cows, 23% starch, mainly maize starch) and a ration containing 19% native PS (lactating cows). Fermentation characteristics of 13 samples were investigated with the GP technique using rumen fluid from cows fed each of the three rations. The same samples were investigated with the NB technique in the cows obtaining the NB ration and the PS ration. The results showed that the rate of GP was influenced by the source of the rumen fluid. The fermentation rate of PS was considerably enhanced by using rumen fluid adapted to the fermentation of native PS instead of using the other rumen fluids. Incubating in cows fed the PS ration, the rate of PS degradation determined with the NB technique, was higher compared with cows fed other rations. Using the PS ration the observed lag period for PS was shorter. The results show a clear influence of ration on the degradation characteristics of starch, determined with both the GP technique and the NB technique. However, these changes in behaviour did not explain observed differences in amounts of rumen escape PS measured in vivo in animal experiments and in situ, using the NB technique.
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