STIRRING IT UP
To disperse an oil in water, or vice verse, requires that the droplets be small enough
to remain in suspension. Without emulsifiers all such mixtures would eventually settle
out.
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STABILISERS AND THICKENERS
Texture - both for the feel of food and for digestion - is maintained by thickening and
stabilising agents
ANTICAKING AGENTS
The substances that keep food flowing.
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We all love smooth foods and they get that
way through the use of emulsifiers The smoothness and homogeneity of many
foodstuffs are central to their appeal. Take mayonnaise or ice cream; if we find globs of
oil separating out of mayonnaise sauce or chunks of ice in ice cream, we feel that
something has gone wrong. But such smoothness doesn't happen 'naturally'; it is a result
of the process of emulsification, in which the two great legendary incompatibles; oil and
water; are persuaded to resolve their differences. An emulsifier is a molecule with one
oil-friendly end and one water-friendly. In this way droplets of oil are surrounded by the
emulsifier molecule, with the oil core hidden by the water-friendly tails of the
emulsifier.
So, what is an emulsifier? Many living systems use emulsifiers, because life itself is
a mixture of oil and water. The classic emulsion is milk, a complex mixture of fat
droplets suspended in an aqueous solution. Nature's emulsifiers are proteins and
phospholipids. The word lipid means fat-soluble. In a phospholipid the phosphate end of
the molecule is water-soluble and the lipid fat-soluble. In cooking, one of the most
versatile emulsifiers is egg phospholipid (lecithin: E322). In many sauces, such as
mayonnaise or béarnaise sauce, it is the egg yolks that do the binding and
homogenisation. Mayonnaise is still one of the most impressive emulsions: 80% oil
dispersed into an acidified aqueous phase. The humble ice cream is actually one of the
most complex foods we encounter; both a foam and an emulsion, it contains ice crystals and
an unfrozen aqueous phase.
As with many food additives, the emulsifiers used in food production are sometimes
purified natural products and sometimes synthetic chemicals that have very similar
structures to the natural products. Typical emulsifiers are lecithins (E322) (mixtures of
phospholipids, e.g. phosphatidylcholine and phosphatidylethanolamine, usually from soya),
mono- and di-glycerides of fatty acids (E471), esters of monoglycerides of fatty acids
(E472a-f) and phosphated monoglycerides.
It isn't only creamy sauces that use emulsifiers. Bread and other baked products, in
which solid particles are dispersed in an airy foam, are enhanced by emulsifiers.
Emulsifiers are generally bland chemicals; which is not surprising, since smoothness is
the quality they impart. Their reactivity is confined to the process of joining oil to
water. This is not a category in which major health scares are likely. |
