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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.

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Record number 355473
Title Structure-rheology relations in sodium caseinate containing systems
Author(s) Ruis, H.G.M.
Source Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Paul Venema. - [S.l.] : S.n. - ISBN 9789085046486 - 125
Department(s) Physics and Physical Chemistry of Foods
VLAG
Publication type Dissertation, internally prepared
Publication year 2007
Keyword(s) natriumcaseïnaat - reologische eigenschappen - afschuifkracht - gelering - emulsies - structuur - verzuring - spectroscopie - licht - verstrooiing - sodium caseinate - rheological properties - shear - gelation - emulsions - structure - acidification - spectroscopy - light - scattering
Categories Food Physics
Abstract The general aim of the work described in this thesis was to investigate structure-rheologyrelations for dairy related products, focusing on model systems containing sodium caseinate. The acid inducedgelationof sodium caseinate, of sodium caseinate stabilized emulsions, and the effect of shear on the structure formation was characterized. Special attention was given to the sol-gel transition point, which was defined by a frequency independent loss tangent. It was shown that the sol-gel transition point is completely controlled by the pH and the temperature, independent of the concentration sodium caseinate or the applied shear rate. Considering sodium caseinate solutions, increase of the temperature of acidification caused a decrease of the critical pH forgelationand a more dense gel structure. The formed gels were not in thermodynamicequilibrium,however, due to the slow kinetics of the system they were stable on the time scale of the experiment. At the gel point we have strong indications that the structure can not be characterized by a single fractal dimension. During the acid inducedgelationof sodium caseinate stabilized emulsions a single sol-gel transition was observed. Addition of an excess of sodium caseinate to the emulsion resulted in two sol-gel transitions upon acidification. Application of shear during the acidification of the emulsions showed a decreasing radius of the aggregates formed at thegelpointwith increasing shear rate. The aggregates formed becamemore densedue to the application of shear while the network that was formed by the aggregates became less compact. No shear induced alignment was observed of emulsion droplets dispersed in water or ina sodiumcaseinatesolution, while emulsion droplets dispersed in axanthansolution did align in a shear field. Addition of sodium inhibited the string formation of the emulsion droplets
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