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0.01
25
20
0.008
0.006
15
0.004
10
0.002
5
0
0
0.025
0.035
0.045
0.055
0.065
0.075
C
xanthan
(% w/v)
Figure 4 Effect of xanthan concentration on zero shear rate viscosity of emulsions (30
vol.% oil, 1.4 wt.% sodium caseinate) (left ordinate scale,
D
) and aqueous
solutions (right ordinate scale,
m
)
10
1
0.1
0.01
0.1
1
10
Time lag
τ
(s)
Figure 5 Normalized MSD of two kinds of probe particles in emulsions (30 vol.% oil, 1.4
wt.% sodium caseinate, pH 6.8) at 201C without added xanthan:
m
, 0.5
m
m
microspheres;
J
, 0.89
m
m microspheres. The quantity a
h
D
r
2
(
t
)
i
is plotted as a
function of time
t
, where a is the particle radius
drove the elongated shapes of the phase-separating xanthan-rich domains into
more circular shapes.
14
With increasing xanthan concentration, the rate of this
relaxation process was increasingly retarded; and for Z 0.06 wt.% xanthan
there was complete inhibition of the microstructural evolution.
When incorporated into the xanthan-containing emulsions, the microspheres
were seen to be well dispersed within both the oil-droplet-rich and the xanthan-
rich regions. Figure 6 shows two images for a system with 0.05 wt.% xanthan
containing 0.21 mm diameter microspheres. The oil phase was stained with Nile
Red. Image (a) was recorded soon after the stirring had stopped: clearly visible
are the deformed and elongated xanthan-rich blobs (depleted of oil droplets).
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