The application of natural hydrocolloids to foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 176

or bursting of reformed products such as potato croquettes. Because they return to
liquid state at temperatures above normal eating temperatures, the consumer does
not notice a difference in the product texture.
MEC has high surface activity, and is excellent at forming and stabilising
foams, making it an effi cient replacement for egg white. Unlike egg white, it is
able to stabilise foams in the presence of fat and so can be used to stabilise egg
white foams when fat is present. Typical applications are whipped toppings,
aerated desserts and meringues (Emerton and Choi 2008).
Last but not least is CMC, a good general thickener and stabiliser, used in a
wide range of applications. It is unusual in its ability to interact with proteins such
as casein and soya, and protect them from precipitation at their isoelectric point
(Murray 2009). This has application in low pH milk products. However, pectin
can also perform this function.
One other commonly used food additive based on cellulose is microcrystalline
cellulose (MCC). Since it is not chemically modifi ed, it can be viewed as natural
(Hazen 2004), but its chemical sounding name still makes it unpopular in clean
label products. MCC is not soluble and is therefore used mainly as a fi bre source
and anti-caking agent. MCC is mainly used in its colloidal form where it is
mechanically processed and mixed with another hydrocolloid, commonly guar
gum or CMC (Krawczyk et al. 2009). Like most hydrocolloids, colloidal MCC
has found many applications due to its multifunctionality, but two of its key
properties are emulsion stabilisation and fat replacement, giving a rich creamy
texture in low fat sauces and dressings, and good stability to dairy or soya
beverages (neutral and acid).
Another category of gums are those produced by microbial fermentation. The
best known of these is xanthan gum, which is an extracellular polysaccharide
secreted by the micro-organism Xanthomonas campestris . While the name
xanthan seems logical given its origins, allegedly current consumers are suspicious
of ingredients starting with the letter 'x'! Xanthan gum is a cold soluble stabiliser,
widely used in the food industry. Its unusual property is its pseudoplastic rheology,
which means that it is very viscous at low shear, but very low viscosity at high
shear, and the viscosity is recovered as soon as shearing stops (Sworn 2009a).
This means that xanthan is very good at holding particles in suspension during
storage and transport, but it will fl ow easily on stirring and pumping. Xanthan also
has very good acid, heat and enzyme stability, ensuring no loss in viscosity over
the shelf life of the product. All these factors make xanthan the ideal stabiliser for
sauces and dressings. Another major use is in baking, where it increases the
volume and moisture of the baked goods and suspends particles (e.g. chocolate
chips, fruit) in the batter prior to baking.
Gellan gum is the other key fermentation gum, this time using the microorganism
Sphingomonas elodea . Gellan gum is a highly effi cient gelling agent, forming
gels at low concentrations. The type of gel depends on the degree of acyl
substitution along the polymer chain; the high acyl form produces soft, elastic
gels, while the low acyl form produces hard brittle gels (Sworn 2009b). As well as
its use as the sole gelling agent, gellan gum is often used in conjunction with other

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