Chemistry Reference
In-Depth Information
Fig. 10.17
Viscosity verses shear rate for mixtures of LBG/caseinate for different phase
volumes of the two phases (adapted from Spyropoulos et al., 2010).
starts to invert, resulting in an effective increased phase volume of the
included phase, as would be expected, giving a higher overall viscosity
to the system. On further increasing the applied forces, the materials
totally phase invert so that the viscosity is seen to decrease significantly.
In this inverted form, the included phase now has a greater phase volume
than the continuous phase, although the continuous phase has a lower
viscosity. This results in the overall system having a viscosity close to
the non-inverted state for this particular mixture of biopolymers.
The remaining question, which is by and large still unanswered,
is, can these systems be emulsified using a molecule or a particle as an
interfacial material? Although this is not as yet clear, there has been some
work (Simon
et al
., 2007; Firoozmand
et al
., 2009) to investigate this.
The suggestion at the moment is that low molecular weight materials
(e.g. oligosaccharides) probably go to the interface as a consequence of
their increased solubility (over the polymers) in the second phase. There
is a need to investigate this further, as the use of molecular surfactants,
if available, will make the design of different structures possible.
Water-in-water emulsions constructed in the right way have been
shown to have all the rheological properties of spreads and margarines.
This means that they can be used to produce products that are not just
low in fat, but are zero fat. Again, the design strategy is to create a mi-
crostructure that mimics that of the high-fat product and thus gives the
