Shear localisation in stirred yoghurt

Raudsepp, Allan; Feindel, Kirk W.; Hémar, Yacine

doi:10.1007/s00397-010-0438-9

Cited by 9 publications

(8 citation statements)

References 21 publications

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“…Rheo‐NMR was successfully used to study both types of material behavior; yield stress as well as shear banding and any progress in instrumentation and advances in methodology may benefit equally the investigation of both material classes. With this in mind, it may not be too surprising if the remainder of this review will be concerned with properties of surfactant systems, reporting on their shear banding behavior and shear‐induced structural changes, although yield stress behavior is more prevalent in food materials and, indeed, has been investigated in the past using Rheo‐NMR techniques . Moreover, certain observations common in surfactant systems may have a similar counterpart in complex food materials such as the transient formation and degradation of colloidal networks or the gap size dependence if colloidal particles are not much smaller as compared with the gap width.…”

Section: Introductionmentioning

confidence: 99%

“…Based on the reviews discussed above and a selection of original research publications, this article will focus on recent developments in Rheo‐NMR instrumentation and methodology, thus offering new opportunities for material characterization. Although the progress will be demonstrated using model surfactant systems, its capabilities are equally relevant for yield stress materials and may therefore be of interest in food science.…”

Section: Introductionmentioning

confidence: 99%

“…With this in mind, it may not be too surprising if the remainder of this review will be concerned with properties of surfactant systems, reporting on their shear banding behavior [22] and shear-induced structural changes, [23] although yield stress behavior is more prevalent in food materials and, indeed, has been investigated in the past using Rheo-NMR techniques. [24][25][26] Moreover, certain observations common in surfactant systems may have a similar counterpart in complex food materials such as the transient formation and degradation of colloidal networks or the gap size dependence if colloidal particles are not much smaller as compared with the gap width. More examples (such as the shear banding like behavior of microfibril suspensions) and further discussions can be found in de Kort et al [19] Thus, from a phenomenological point of view, colloidal systems and surfactant systems may behave in a similar way, [27] and new experimental approaches will therefore be equally beneficial for the investigation of food materials.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, there is a recent interest to study food materials using large amplitude oscillatory shear (LAOS) [28] that will be the experimental method used for the study reviewed in the second part of this article. [23] Based on the reviews discussed above [2,[15][16][17][18][19][20][21] and a selection of original research publications, [24][25][26][29][30][31] this article will focus on recent developments in Rheo-NMR instrumentation and methodology, thus offering new opportunities for material characterization. Although the progress will be demonstrated using model surfactant systems, its capabilities are equally relevant for yield stress materials and may therefore be of interest in food science.…”

Section: Introductionmentioning

confidence: 99%

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Rheo‐NMR in food science—Recent opportunities

Galvosas

Brox

Kuczera

2019

Magnetic Reson in Chemistry

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For over 25 years, nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) techniques have been used to study materials under mechanical deformation. Collectively, these methods are referred to as Rheo‐NMR. In many cases, it provides spatially and temporally resolved maps of NMR spectra, intrinsic NMR parameters (such as relaxation times), or motion (such as diffusion or flow). Therefore, Rheo‐NMR is complementary to conventional rheological measurements. This review will briefly summarize current capabilities and limitations of Rheo‐NMR in the context of material science and food science in particular. It will report on recent advances such as the incorporation of torque sensors or the implementation of large amplitude oscillatory shear and point out future opportunities for Rheo‐NMR in food science.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Rheo‐NMR in food science—Recent opportunities

Galvosas

Brox

Kuczera

2019

Magnetic Reson in Chemistry

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“…This immediately suggests shear banding of the form expected for a yield stress fluid. These data are discussed along with NMR velocimetry in [118]. Fig.…”

Section: Chapter 7 Flow-dwsmentioning

confidence: 92%

A Rheo-Optic Study of Wormlike Micelles Solutions

Raudsepp¹

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<p>Shear banding, where a fluid spatially partitions into strain rate or shear bands in steadystate simple shear flow conditions, was first observed in wormlike micelles solutions and has since been observed in many other complex fluids. These solutions have been used extensively to explore the relationship between shear (or stress) banding and microstructure in complex fluids. This relationship is difficult to study because of its dynamic nature and there is still no clear consensus as to how banding relates to microstructural changes in wormlike micelles solutions. In this thesis, the rheology of a number of wormlike micelles solutions is examined using both conventional and novel techniques with the view to developing a better understanding of this relationship. The rheology of three wormlike micelles solutions composed of a surfactant cetylpyridinium chloride (CPCl) and counterion sodium salicylate in water with or without the salt sodium chloride were examined using mechanical rheometry and the rheo-optical techniques: homodyne photo-correlation spectroscopy (PCS), diffusing wave spectroscopy (DWS) and ellipsometry. Rheo-mechanical measurements were largely consistent with the predictions of the reptation-reaction model. While signi cant stress fluctuations were noted in one particular flow geometry, they were generally not observed in most rheomechanical measurements presented here, indicating that these fluctuations are not universal and that they are geometry dependent. Shear induced turbidity was directly observed in the cone-plate and parallel-plate geometries with turbid rings forming in samples that showed a stress plateau. The Poisson-renewal model, which extends the reptationreaction model to include the influence of high frequency modes on the linear rheology, was tested experimentally using mechanical rheometry, DWS microrheology and literature data. In most cases the data fitted the model behaviour quite well, giving a physically reasonable estimate of the average length of the micelles. DWS's spatial sensitivity to shear induced relative motion was then used to probe the flow behaviour of selected wormlike micelles solutions in the cylindrical-Couette, cone-plate and parallel-plate geometries. In the cylindrical-Couette, the 'flow-DWS' measurements were largely consistent with rheo-mechanical measurements and indicated that some wormlike micelles solutions were partitioning into apparently stable high and low strain rate bands in the vicinity of the stress plateau. While measurements in the cone-plate and parallel-plate geometries also suggested shear banding in samples that showed a stress plateau, the interpretation was less clear-cut. Homodyne PCS was combined with ellipsometry to examine the spatial relationship between strain rate and birefringence banding in selected wormlike micelles solutions in a cylindrical-Couette geometry. In contrast to the observations of previous workers, it was found here that the birefringence and strain rate bands did coincide. Furthermore, the high strain rate band was observed to be more turbid than the lower strain rate band suggesting a connection between strain rate, optical anisotropy and turbidity.</p>

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