AMI seminar: Peter Fischer

Room 170.048, Adolphe Merkle Institute, Marly

Thursday, June 17th, 2010  16:00 h

Interfacial rheology and its role in emulsion science

Peter Fischer

Institute of Food, Nutrition and Health

ETH Zurich

Abstract:

Interfacial rheology as a tool to study the structure and deformation behavior of two-dimensional surfactant, surface-active hydrocolloid, and particle layers is introduced [1, 2]. In particular, techniques and devices to apply shear and dilatational deformation to air-water and oil-water interfaces (oscillatory shear rheometry, oscillating pendant drop method, Langmuir trough methods) will be discussed. In a second step the interfacial rheologicial response function of e.g. milk proteins, plant protein-polysaccharide complexes such as Gum Arabic, and polyglycerol ester forming interfacial aggregates are summarized [3-5]. Utilizing the obtained knowledge in two-dimensions the deformation behavior of emulsion droplets as well as diluted emulsions will be reviewed: The deformation of emulsion drops covered with a globular protein layer shows i) that the adsorption layer restricts the ease of deformation, rather than facilitating it and ii) that shape fluctuations (tank-treading) are caused by the elastic deformation of the viscoelastic skin (Figure 1) [6-8]. This result suggests that globular protein layer should be seen as soft elastic membranes with interfacial tension properties, i.e. as a hybrid between elastic membranes with no interfacial tension properties and of soluble emulsifier layers with interfacial tension.

Figure 1: a) Deformation experiments performed with a clean drop and with the identical drop covered with a lysozyme layer, b) Deformation for b-lactoglobulin-covered drops described with the capsule deformation model.

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