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(a)
60
50
40
30
20
10
0
0.000
0.005
0.010
0.015
0.020
0.025
conc. Xanthan [%, w/w]
(b)
600
500
400
300
200
100
0
0.000
0.005
0.010
0.015
0.020
0.025
conc. Xanthan [%, w/w]
Figure 6 Effect of XG content on storage modulus G
0
of gels at pH 4.60 determined by
oscillatory rheometry for gel formation: (a) unheated skim milk and (b) pre-
heated skim milk
skim milk alone (Figure 7), which is in agreement with observations of Kalab
et al.;
26
but it was much more pronounced in gels formed with 0.015 or 0.025
wt.% XG. The aggregates were shaped like islands when formed in unheated
skim milk, but appeared like a web of causeways in gels made from pre-heated
skim milk. This morphological description implies a difference in connectivity
between the network-constituting entities. Connectivity between protein aggre-
gates appeared higher in the gels made from pre-heated skim milk. Moreover,
for an increase in XG concentration from 0.015 to 0.025 wt.%, the connectivity
remained quite high in the pre-heated skim milk, explaining the only moderate
decrease in G
0
, while the connectivity and modulus decreased dramatically in
the unheated skim milk.
The above results demonstrate that the inclusion of XG is an effective means
to tailor protein network microstructure. As can be seen in both the image
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