Alginates in Foods - Practical Food Rheology - page 127

application of alginate as a stabiliser in the food industry (Onsøyen,
2001). While alginate allows control of the ice cream's viscosity, it also
increases heat-shock resistance, reduces shrinkage and ice crystal for-
mation and enables ice cream to have a prolonged meltdown, which is a
desired characteristic (Onsøyen, 2001; Brownlee et al. , 2009). If calcium
ions are present in the food matrix, then alginate is usually mixed with
sodium phosphate, which binds excess calcium and prevents the precip-
itation of calcium alginate. Routine use of alginates in bakery creams
provides the cream with freeze/thaw stability and reduces separation of
the solid and liquid components (Brownlee et al. , 2009).
The esterified alginate derivative, PGA, is commonly used in acid-
based salad dressings, acidic fruit drinks and to maintain foam stability,
including applications in mousse and other desserts. This is due to its
higher solubility at low pH (Moe et al. , 1995). Another major use of
PGA is in the brewing industry, where it is added to different beers and
lagers to stabilise the froth head when poured, which also protects it
from foam-negative contaminants (Brownlee et al. , 2009).

6.6.7 Appetite control

The microstructure and bulk properties of food products are known
to influence the uptake of nutrients or other components of food and
can also influence satiety (Di Lorrenzo et al. , 1988; Bergmann et al. ,
1992). Of particular interest is research by several groups that suggests
that daily ingestion of a strong-gelling alginate reduces energy intake
by slowing gastric clearance and attenuating uptake from the small
intestine. This, in turn, modulates the human appetite (Pelkman et al. ,
2007; Paxman et al. , 2008). High viscosity or gel strength in the mouth is
associated with poor acceptability of foods. At the same time, however,
high viscosity in the stomach is linked to increased gastric distension
and thereby increased satiety (Pelkman et al. , 2007). Also, alginates
appear to have some inhibitory effects on a range of digestive enzymes
in vitro . This is likely to be due to their high viscosity, which in turn
reduces the availability of substrate for enzyme action (Rehm, 2009).
This has opened up an interesting and potentially lucrative application
of alginate as an appetite suppressor to control obesity. Unlike other
viscous polysaccharides which need to be administered in gel form
to exist as a gel in the stomach, alginates have the unique ability to
spontaneously form gels at low temperature in the presence of acid
or calcium ions. The nature of alginate gelation in the stomach and the
effect on satiety in human subjects has been investigated by Norton et al.
(2006), using NMR/MRI techniques. Alginate solutions were consumed
before MRIs of the stomach were taken at regular intervals over a two-
hour period. These images of the gels within the stomach were analysed