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Food Lipids: Chemistry, Nutrition, and Biotechnology

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4<br />

The <strong>Chemistry</strong> of Waxes <strong>and</strong> Sterols<br />

EDWARD J. PARISH, TERRENCE L. BOOS, <strong>and</strong> SHENGRONG LI<br />

Auburn University, Auburn, Alabama<br />

I. CHEMISTRY OF WAXES<br />

A. Introduction<br />

The term waxes commonly refers to the mixtures of long chain apolar compounds<br />

found on the surface of plants <strong>and</strong> animals. By a strict chemical definition, a wax is<br />

the ester of a long chain acid <strong>and</strong> a long chain alcohol. However, this academic<br />

definition is much too narrow both for the wax chemist <strong>and</strong> for the requirements of<br />

industry. The following description from the German Society for Fat Technology [1]<br />

better fits the reality:<br />

Wax is the collective term for a series of natural or synthetically produced substances<br />

that normally possess the following properties: kneadable at 20�C, brittle to solid, coarse<br />

to finely crystalline, translucent to opaque, relatively low viscosity even slightly above<br />

the melting point, not tending to stinginess, consistency <strong>and</strong> solubility depending on<br />

the temperature <strong>and</strong> capable of being polished by slight pressure.<br />

The collective properties of wax as just defined clearly distinguish waxes from other<br />

articles of commerce. Chemically, waxes constitute a large array of different chemical<br />

classes, including hydrocarbons, wax esters, sterol esters, ketones, aldehydes, alcohols,<br />

<strong>and</strong> sterols. The chain length of these compounds may vary from C 2,asinthe<br />

acetate of a long chain ester, to C 62 in the case of some hydrocarbons [2,3].<br />

Waxes can be classified according to their origins as naturally occurring or<br />

synthetic. The naturally occurring waxes can be subclassified into animal, vegetable,<br />

<strong>and</strong> mineral waxes. Beeswax, spermaceti, wool grease, <strong>and</strong> lanolin are important<br />

animal waxes. Beeswax, wool grease, <strong>and</strong> lanolin are by-products of other industries.<br />

The vegetable waxes include carnauba wax, the so-called queen of waxes, ouricouri<br />

(another palm wax), <strong>and</strong> c<strong>and</strong>elilla. These three waxes account for the major pro-<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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