title: Scanning force microscopy as a tool to investigate the properties of polyglycerol ester foams.
abstract: Foamed products are a popular class of food products. The mechanism of stabilization of the air bubbles is often only partially understood. The current study aims at better understanding the stabilization of air-water interfaces through the low molecular weight surfactant polyglycerol ester (PGE). We chose PGE films as an exemplary case for a non-equilibrium situation at an air-water interface--a situation that requires the development of new experimental techniques. Several different film preparation and transfer methods onto solid substrates have been tested. The films were then investigated by scanning force microscopy, and structural artifacts associated to the sample preparation were identified and discussed. In addition to the study of Langmuir monolayers and Gibbs adsorption layers, we have proposed a new approach to investigate the skins of foam bubbles. We thereby were able to determine that PGE indeed covers bubbles by a multilayer structure and that the pH plays a role in the structuring of the films. We show that a combination of different film preparation methods allows us to get an insight into the aggregation behavior of PGE at the air-water interface and thereby better understand the stabilization mechanism of this particular surfactant.
authors.affiliation: Laboratory of Food Process Engineering, ETH Zürich, Schmelzbergstrasse 9, CH-8092 Zürich, Switzerland. corina.curschellas@hest.ethz.ch
authors.forename: Corina
authors.initials: C
authors.lastname: Curschellas
authors.forename: Rabea
authors.initials: R
authors.lastname: Keller
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Berger
authors.forename: Uwe
authors.initials: U
authors.lastname: Rietzler
authors.forename: Daniela
authors.initials: D
authors.lastname: Fell
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.forename: Hans Jörg
authors.initials: HJ
authors.lastname: Limbach
mesh_terms: D000327:Adsorption; D000388:Air; D004952:Esters / Q000737:chemistry*; D005990:Glycerol / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D008970:Molecular Weight; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D004952:Esters; D011108:Polymers; D013501:Surface-Active Agents; D014867:Water; C043941:polyglycerol; D005990:Glycerol