The liquid phase consists of Whey Protein Isolate (WPI) (Lactalis
Ingredients, Bourbarré, France) with 95 wt% protein as surfaceactive
agent and Xanthan Gum (XG) (Cargill, Baupte, France) acting
as a thickener. Two WPI-XG solutions are prepared from 3 wt%
WPI, and 0.35 and 0.6 wt% xanthan gum, referred to as WPI3XG35
and WPI3XG06 respectively. A third solution is obtained by adding
NaCl (0.2 M) to WPI3XG035 to test the eventual effect of the ionic
strength on the conformation of the protein and/or xanthan gum.
These concentrations correspond to the ones used in the milk
industry (Fox and McSweeney, 2003; Simon, 2001). For these concentrations,
the two biopolymers are non-interacting and mutually
soluble in the water (Benichou et al., 2007).