Chemistry Reference
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Figure 5 Dispersed phase volume contour plots for emulsions containing 40% glycerol
stabilized by (a) protein and (b) surfactant. Height is plotted as a function of
time. The contours are in phase volume steps of 0.02
In order to investigate these differences more fully, a similar experiment was
undertaken in the presence of 40% glycerol, which increased the viscosity of the
continuous phase and thus slowed down the creaming by a factor of around 20.
The data from this experiment are shown in Figure 5, in the form of contour
plots of height against time. The contours represent lines of equal oil phase
volume in 2% intervals up to around 80%, depending on the final phase
volume at the top of the cream layer. This type of plot allows the determination
of the aggregation state of the droplets as they rise. The linearity of the contour
lines below the cream layer shows that the droplets have ascended with fixed
velocities. This means that the droplets did not aggregate in the sub-cream
region. These Stokes velocities can also be used to calculate a size distribution,
which was found to be in good agreement with that measured by light
scattering at the start of the experiment. Again there was a 'pseudo' plateau
at the base of the cream layer in the protein sample [Figure 5(a)]; this persisted
until very near the end of the experiment, and it had a depth of some 30 mm at
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