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SUMMARY:Emulsion stabilized by proteins – surfactant-covered drops or ca
 psules? - Dr Peter Fischer\, Institute of Food Science and Nutrition\, ETH
  Zurich\, Schmelzbergstrasse 9\,\n                         8092 Zurich\, S
 witzerland
DTSTART:20070309T141500Z
DTEND:20070309T151500Z
UID:TALK6097@talks.cam.ac.uk
CONTACT:Jurij Kotar
DESCRIPTION:The deformation of emulsion drops covered with a globular prot
 ein layer (β-lactoglobulin\,\nlysozyme) show i) that the adsorption layer
  restricts the ease of deformation\, rather than\nfacilitating it and ii) 
 that shape fluctuations (tank-treading) are caused by the elastic\ndeforma
 tion of the (visco-)elastic skin. The obtained data are compared to\npredi
 ctions of the Flumerfeld model inwhich interfacial viscosities and Marango
 ni stresses\nare incorporated. We see that the experimental values cannot 
 be reached with the\nFlumerfelt model if the interfacial rheological model
  parameters are varied in a realistic range\nand all other parameters are 
 kept constant. All parameter necessary to compute the\ninterfacial stress 
 boundary condition are characterized by i) interfacial tension or interfac
 ial\npressure\, ii) interfacial shear rheology\, and iii) interfacial dila
 tational rheology.\nAlternatively\, the data are compared to a model by Ba
 rthès-Biesel and Sgaier for the\ndeformation of capsules surrounded by a 
 solid membrane. It is found that for strongly\nviscoelastic interfacial la
 yer of adsorbed lysozyme and β-lactoglobulin\, only the capsule\nmodel ca
 n give a satisfactory description of the data. In comparison the response 
 of\nthe structurally different protein β-casein (flexible random coil) is
  briefly discussed. This result\nsuggests that globular protein layer shou
 ld be seen as “soft elastic membranes“ with\ninterfacial tension prope
 rties\, i.e. as a hybrid between elastic membranes (no interfacial\ntensio
 n properties) and of soluble emulsifier layers with interfacial tension.
LOCATION:IRC in Superconductivity Seminar Room\, Cavendish Laboratory
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