Instant Emulsions - Food Colloids: Self-Assembly and Material Science - page 421

28.5 Competitive Hydration
In large-scale food manufacturing, blends of biopolymers are used to supply
the requisite product properties. In ice-cream manufacture, mixtures of locust
bean gum + k-carrageenan are used in combination with milk proteins to
provide the correct product stability and eating quality. And in the manufac-
ture of low-fat emulsions such as mayonnaise, mixtures of starch with gums
such as xanthan are employed effectively to replace the fat-structuring prop-
erties. The previous section has highlighted the fast hydration and structuring
potential of two different biopolymers. Now let us consider what happens when
blends of these two biopolymers are used in this 'instant' structuring route.
Figure 6 shows the effect of changing the level of xanthan in blends with
starch in the presence and absence of salt. All experiments were carried out in
the presence of an emulsifier (lecithin), to aid the hydration process. The blend
with the lowest xanthan content hydrates at slightly later time, but yet it reaches
a slightly higher end viscosity when compared to starch alone. As the concen-
tration of xanthan increases, however, it dominates the hydration to such an
extent that the swelling and viscosifying potential of the starch is reduced, so
that the viscosity of the blend of 0.5 g of xanthan + 3.5 g of starch only
achieves the same viscosity as for xanthan alone (see Figure 5). The sample
containing 0.25 g of xanthan + 3.5 g of starch hydrates in a two-stage process,
whereby the xanthan first enhances the viscosity and afterwards the swelling
potential of the starch emerges. In the presence of salt the hydration of the same
mixture is delayed, and the onset of the viscosity increase seems to match that
of starch alone. The value rises and then falls to a level similar to that of starch
alone, indicating a complex competition between xanthan and starch for the

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Figure 6 Change in viscosity in a Rapid Visco Analyser for 12.5 g oil, 11.25 g water and
0.3 g lecithin, and also containing: K , J , 4 g CWS; , 0.125 g xanthan + 3.5 g
CWS; ' , & , 0.25 g xanthan + 3.5 g CWS; E , 0.5 g xanthan + 3.5 g CWS.
Closed and open symbols indicate absence and presence of NaCl