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Leon E. Govaert, Han E.H. Meijer
DYFP2006, the 13th int. conference on deformation, yield and fracture of polymers

Appl. Rheol. 16:5 (2006) 290-291

Since its start in 1970, the international conference on Deformation, Yield and Fracture of Polymers has been held every three years in Churchill College, Cambridge, UK. Amongst the 'mechanical properties of polymers' aficionados these meetings have become known as the 'Churchill' conferences, an event that has been established as the leading conference on its subject world wide. ...

Cite this publication as follows:
Govaert LE, Meijer HEH: DYFP2006, the 13th int. conference on deformation, yield and fracture of polymers, Appl. Rheol. 16 (2006) 290.

Peggy Courtois, Rammile Ettelaie, Jianshe Chen
Numerical Studies of Transport Properties in Heterogeneous Food Systems

Appl. Rheol. 16:5 (2006) 275-286

The current computer simulation based study aims to elucidate the complex role that the state of aggregation and morphology of the food materials plays in determining their transport behaviour. Using Brownian dynamic simulations, applied to colloidal systems, we simulate the compression of two different dense layers of nanoparticles (with reversible and irreversible bonds), at interface, at three different compression rates. We determine the desired transport coefficient for these structures using a novel technique, originally proposed by Torquato and Kim (1990). This method allows us to consider complex structures in our study, for which calculations of effective transport coefficients using conventional methods, like finite elements and finite difference, would be relatively difficult. We first validate our algorithm by comparing its results with those of exact calculations, for different regular lattices. Our results are in excellent agreement with the theory. The variation in the transport coefficient of nano-particle monolayers during the compression, are also correlated with the build up of stress and changes in the structure of the films.

Cite this publication as follows:
Courtois P, Ettelaie R, Chen J: Numerical Studies of Transport Properties in Heterogeneous Food Systems, Appl. Rheol. 16 (2006) 275.

Trevor S.K. Ng, Gareth H. McKinley, Mahesh Padmanabhan
Linear to Non-linear Rheology of Wheat Flour Dough

Appl. Rheol. 16:5 (2006) 265-274

We provide an overview of transient extensional rheometry techniques for wheat flour doughs in which the deformation and material response is well defined. The behavior of a range of model doughs was explored with a Filament Stretching Extensional Rheometer (FISER). The measurements were also compared to data obtained with a new windup extensional rheometer; the SER universal testing platform. A simple empirical constitutive equation, which allows characterization of the experimental results with a small number of parameters, is presented to describe the resulting measurements. To characterize the relaxation modulus of the doughs, small amplitude shear tests were performed on samples that have been shear-mixed in a mixograph for varying lengths of time. The linear viscoelastic properties were found to exhibit a broad power-law dependence on the imposed oscillatory frequency that is very reminiscent of that exhibited by a critical gel. The critical gel model of Winter and Chambon was used as the basis for constructing a non-linear constitutive equation for the material stress by combining the relaxation modulus for the critical gel with a Lodge rubber-like liquid form for the kinematics. Transient uniaxial extensional data recorded from the FISER and SER instruments were then compared to the predictions of the constitutive equation. The model captures the initial powerlaw response and subsequent strain-hardening; however additional physics is required to describe the rheological phenomena at very large Hencky strains, including finite extensibility effects and filament rupture in extensional flows.

Cite this publication as follows:
Ng TS, McKinley GH, Padmanabhan M: Linear to Non-linear Rheology of Wheat Flour Dough, Appl. Rheol. 16 (2006) 265.

Suzanne Bolder, Hanneke Hendrickx, Leonard Sagis, Erik van der Linden
Ca2+-induced cold-set gelation of whey protein isolate fibrils

Appl. Rheol. 16:5 (2006) 258-264

In this paper we describe the rheological behaviour of Ca2+-induced cold-set gels of whey protein mixtures. Coldset gels are important applications for products with a low thermal stability. In previous work [J. Agric. Food Chem. 54 (2006) 4229], we determined the state diagram for whey protein mixtures that were heated for 10 h at pH 2 at 80°C. Under these conditions, the major whey protein, β-lactoglobulin (β-lg), forms fibrils. When whey protein mixtures are heated at protein concentrations in the liquid solution regime of the state diagram, cold-set gels can be formed by adding Ca2+ ions at pH 7. We studied the rheological behaviour of cold-set gels for various sample compositions for whey protein mixtures. When keeping the total whey protein concentration constant, the elastic modulus, G., for the cold-set gels decreased for increasing α-lactalbumin and bovine serum albumin ratios, because less material (blg fibrils) was available to form a gel network. In the cold-set gels the interactions between the β-lg fibrils induced by the calcium ions are dominant. The β-lg fibrils are forming the cold-set gel network and therefore determine the gel strength. α-Lactalbumin and bovine serum albumin are not incorporated in the stress-bearing structure of the gels.

Cite this publication as follows:
Bolder S, Hendrickx H, Sagis L, vanderLinden E: Ca2+-induced cold-set gelation of whey protein isolate fibrils, Appl. Rheol. 16 (2006) 258.

Chrystel Loret, William Frith, Peter Fryer
Mechanical and structural properties of maltodextrin/agarose gel composites

Appl. Rheol. 16:5 (2006) 248-257

When two biopolymers are mixed together, they will normally phase separate to give two distinct phases. If the biopolymers are gelled during this phase separation, for instance by reducing the temperature, one phase is trapped in this other one and an emulsion-like composite structure is obtained. In this study, we investigated the effect of volume fraction and droplet size of this dispersed phase on the mechanical properties of maltodextrin/ agarose gel composites, where agarose is the dispersed phase. Mechanical properties of the different composites were investigated under large deformation using a rheometer with a vane geometry. These composites were also observed by confocal microscopy, allowing conclusions to be drawn regarding the microstructural origins of the observed mechanical behaviour.

Cite this publication as follows:
Loret C, Frith WJ, Fryer PJ: Mechanical and structural properties of maltodextrin/agarose gel composites, Appl. Rheol. 16 (2006) 248.

Anja Vananroye, Peter Van Puyvelde, Paula Moldenaers
Morphology development during microconfined flow of viscous emulsions

Appl. Rheol. 16:5 (2006) 242-247

In this contribution, a brief review is given of the dynamics of emulsions in microconfined shear flow. The interest in confined flow is triggered by the increasing importance of microfluidic applications in the processing industries. In a first part, some important aspects of confinement on single droplet dynamics are highlighted. The validity of the conclusions drawn from this part are subsequently applied to more concentrated systems. It is shown that microconfined emulsions can exhibit rich dynamics, and can display some peculiar morphologies.

Cite this publication as follows:
Vananroye A, VanPuyvelde P, Moldenaers P: Morphology development during microconfined flow of viscous emulsions, Appl. Rheol. 16 (2006) 242.

Thomas Schweizer
Rheology. Concepts, Methods, and Applications (A. Ya. Malkin, A.I. Isayev)

Appl. Rheol. 16:5 (2006) 240-241

Cite this publication as follows:
Schweizer T: Rheology. Concepts, Methods, and Applications (A. Ya. Malkin, A.I. Isayev), Appl. Rheol. 16 (2006) 240.

Peter Fischer, Martin Kroger
Patents Review (October 2006)

Appl. Rheol. 16:5 (2006) 287-289

Cite this publication as follows:
Fischer P, Kroger M: Patents Review (October 2006), Appl. Rheol. 16 (2006) 287.

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