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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Record number 334202
Title Scaling Behavior of Delayed Demixing, Rheology, and Microstructure of Emulsions Flocculated by Depletion and Bridging
Author(s) Blijdenstein, T.B.J.; Linden, E. van der; Vliet, T. van; Aken, G.A. van
Source Langmuir 20 (2004)26. - ISSN 0743-7463 - p. 11321 - 11328.
Department(s) Physics and Physical Chemistry of Foods
Publication type Refereed Article in a scientific journal
Publication year 2004
Keyword(s) diffusing-wave spectroscopy - in-water emulsions - colloid-polymer mixtures - confocal microscopy - beta-lactoglobulin - disordered solids - elastic networks - transient gels - particle gels - casein gels
Abstract Abstract: This paper describes an experimental comparison of microstructure, rheology, and demixing of bridging- and depletion-flocculated oil-in-water emulsions. Confocal scanning laser microscopy imaging showed that bridging-flocculated emulsions were heterogeneous over larger length scales than depletion-flocculated emulsions. As a consequence, G' as determined from diffusing wave spectroscopy (DWS) corresponded well with G' as measured macroscopically for the depletion-flocculated emulsions, but this correspondence was not found for the bridging-flocculated emulsions. The heterogeneity of bridging-flocculated emulsions was confirmed by DWS-echo measurements, indicating that their structure breaks up into large fragments upon oscillatory shear deformation larger than 1%. Depletion- and bridging-flocculated emulsions showed a different scaling of the storage modulus with the volume fraction of oil and a difference in percolation threshold volume fraction. These differences will be discussed on the basis of the two types of droplet-droplet interactions studied. Gravity-induced demixing occurred in both emulsions, but the demixing processes differed. After preparation of bridging-flocculated emulsions, serum immediately starts to separate, whereas depletion-flocculated systems at polysaccharide concentrations in the overlap regime usually showed a delay time before demixing. The delay time was found to scale with the network permeability, B; the viscosity, , of the aqueous phase; and the density difference between oil and water, , as tdelay ~ B-1-1. The results are in line with the mechanism proposed by Starrs et al. (J. Phys.: Condens. Matter 2002, 14, 2485-2505), where erosion of the droplet network leads to widening of the channels within the droplet networks, facilitating drainage of liquid.
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