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deformability. Measurements of the interfacial tension of the sub-phases
against n-hexadecane (Table 1) gave 15.8 mN m
1
for the protein-stabilized
system, but a much lower value of 8.4 mN m
1
for the Brij/SDS system. The
subsequent difference in the Laplace pressure would be expected to have a
significant effect on droplet deformability, leading to the protein system being
more elastic at the higher volume fractions.
The separation of the emulsions under gravity was followed non-invasively
using the ultrasonic technique described above. The results are shown in Figure 3
in terms of the disperse phase volume as a function of height for a series of time
intervals over a period of 45 h. Both systems show the development of a cream
layer at the top of the tube, whose thickness gradually increased with time. The
lack of a sharp boundary at the base of the creaming emulsion indicates a broad
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Height (mm)
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Figure 3 Dispersed phase volume as a function of height in creaming emulsions stabilized
by (a) WPI and (b) Brij35/SDS. Each line represents a set of measurements
taken 60 min apart over a period of 40 h. The arrows indicate the progression
with time
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