Instant Emulsions - Food Colloids: Self-Assembly and Material Science - page 419

shaped 'gelled' particles. The CWS materials are not 'cooked out' as much in
the production process, i.e., only to the point of granular swelling, and are
subsequently spray dried. The granular integrity of the starch is retained; this is
due to cross-linking within the granule, and the fact that many of the CWSs are
waxy, i.e., they are low in amylose content. The agglomeration of granules
provides readily hydratable powders for dispersion directly into water.
Figure 4 shows the rates of hydration measured in this study, comparing
agglomerated and standard CWS with pre-gelatinized starch. The viscosity
traces were obtained using a Rapid Visco Analyser (RVA) 4 or Super4, with
mixtures of sunflower oil (12.5 g) + starch (4 g) + lecithin (2.5 g) (Bolec, MT),
to which water (11.25 g) was added. The mixture was immediately put into the
RVA and mixed for 10 min at 251C at 180 rpm. The relative viscosifying power
can be compared at constant starch level, along with the rates of hydration. It
seems that delivering these starches from an oil slurry provides no advantage to
using the more expensive agglomerated version of the CWS. Indeed, the non-
agglomerated sample thickens faster, reaching a plateau viscosity after 40 s,
which is reached by the agglomerated sample 20 s later.
Polymeric materials were also followed in a similar way. Xanthan gum is a
polyelectrolyte whose solution properties have been well described 21 because it
has been the polysaccharide of choice in many food applications since its
discovery and commercialization in the 1960s and 1970s. Figure 5 shows the
effect of hydrating the xanthan at different concentrations, in the presence or
absence of salt (NaCl) and emulsifier (lecithin). What can be clearly seen is that
the polyelectrolyte swells and solubilizes quickly in the absence of salt because
of charge repulsion. When hydrated in the presence of the emulsifier the onset
of the viscosity increase is also enhanced, presumably because small oil droplets

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Figure 4 Change in viscosity in a Rapid Visco Analyser for a mixture of 12.5 g oil, 4 g
starch, 0.3 g lecithin + 11.25 g water for cold-water-swelling starch (CWS)
( E ), agglomerated CWS ( ' ) and pre-gelatinized starch ( m )