Surface Topography of Heat-Set Whey Protein Gels: Effects of Added Salt and Xanthan Gum - Food Colloids: Self-Assembly and Material Science - page 482

Figure 7 Surface profile of the heat-set whey protein gel containing 0.05 wt% xanthan by
CLSM observation: (a) xanthan stain, (b) protein stain, and (c) dual stained
leading to xanthan- and protein-rich regions. Turgeon and Beaulieu 14 also
observed phase incompatibility between whey protein and polysaccharides and
postulated that such incompatibility could lead to spherical inclusion of whey
protein by polysaccharides. These observations seem broadly consistent with our
observations of the surface distribution profiles of whey protein and xanthan in
Figure 7: the protein and hydrocolloid appear to reside in separate local unmixed
domains at the surface. It would seem reasonable that one consequence of
thermodynamic incompatibility between protein aggregates and xanthan would
be exclusion of the latter from the aggregated protein network into an outer
polysaccharide-rich layer.
33.4 Concluding Remarks
This work has demonstrated that the topographical properties of heat-set
WPI gels are strongly influenced by the addition of either salt or hydrocol-
loid. Large differences can be clearly seen from both surface friction force
measurements and microstructural observations. The presence of 0.2 M NaCl
makes the protein gel surface much rougher and wetter, which is consistent
with the coarse microstructure of the bulk gel. However, the anisotropy in
the orientation of the protein aggregates at the surface would seem to
indicate a different mechanism of surface creation from that of bulk network
formation.