Food Lipids: Chemistry, Nutrition, and Biotechnology

portion of the consumption of vegetable waxes. The mineral waxes are further classified
into the petroleum waxes, ozokerite, and montan. Based on their chemical
structure, waxes represent a very broad spectrum of chemical types from polyethylene,
polymers of ethylene oxide, derivatives of montan wax, alkyl esters of monocarboxylic
acids, alkyl esters of hydroxy acids, polyhydric alcohol esters of hydroxy
acids, Fisher–Tropsch waxes, and hydrogenated waxes, to long chain amide waxes.
We begin with an overview of the diverse class of lipids known as waxes. The
discussion presented that follows, which touches on source, structure, function, and
biosynthesis, is intended to serve as an entry to the literature, enabling the reader to
pursue this topic in greater detail.
B. Properties and Characteristics of Waxes
The ancient Egyptians used beeswax to make writing tablets and models, and waxes
are now described as man’s first plastic. Indeed, the plastic property of waxes and
cold-flow yield values allow manual working at room temperature, corresponding to
the practices of the Egyptians. The melting points of waxes usually vary within the
range 40–120�C.
Waxes dissolve in fat solvents, and their solubility is dependent on temperature.
They can also wet and disperse pigments, and they can be emulsified with water,
which makes them useful in the furniture, pharmaceutical, and food industries. Their
combustibility, associated with a low ash content, is important in candle manufacture
and solid fuel preparation. Waxes also find application in industry as lubricants and
insulators, where their properties as natural plastics, their high flash points, and their
high dielectric constants are advantageous.
The physical and technical properties of waxes depend more on molecular
structure than on molecular size and chemical constitution. The chemical components
of waxes range from hydrocarbons, esters, ketones, aldehydes, and alcohols to acids,
mostly as aliphatic long chain molecules. The hydrocarbons in petroleum waxes are
mainly alkanes, though some unsaturated and branched chain compounds are found.
The common esters are those of saturated acids with 12–28 carbon atoms combining
with saturated alcohols of similar chain length. Primary alcohols, acids, and esters
have been characterized and have been found to contain an even straight chain of
carbon atoms. By contrast, most ketones, secondary alcohols, and hydrocarbons have
odd numbers of carbon atoms. The chemical constitution of waxes varies in great
degree depending on the origin of the material. A high proportion of cholesterol and
lanosterol is found in wool wax. Commercial waxes are characterized by a number
of properties. These properties are used in wax grading [4].
1. Physical Properties of Waxes
Color and odor are determined by comparison with standard samples in a molten
state. In the National Petroleum Association scale, the palest color is rated 0, while
amber colors are rated 8. Refined waxes are usually free from taste, this property
being especially important in products such as candelilla when it is used in chewing
gum. Melting and softening points are important physical properties. The melting
points can be determined by the capillary tube method or the drop point method.
The softening point of a wax is the temperature at which the solid wax begins to
soften. The penetration property measures the depth to which a needle with a definite
top load penetrates the wax sample.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.