Waxes These properties make wax esters excellent feedstocks for

Waxes can be used to encapsulate water-soluble
ingredients for incorporation of some types of functional ingredients (289). Wax esters
also constitute another target molecule for lubricant applications. The high
linearity of wax esters enhances the viscosity index of the oil and imparts
specific desirable characteristics such as anti-rust, anti-foam, anti-wear and
friction reduction properties to the lubricant. These properties make wax esters
excellent feedstocks for production of high-temperature and pressure lubricants
as well as hydraulic fluids (290).

RBW has potential applications in
cosmetic, pharmaceutical, food, polymer, and leather industries. There are many
reports on the use of RBW in cosmetic preparations such as cold cream, drugs,
and hair-conditioners and its performance was comparable to carnauba and other
waxes. RBW is also a rich source of high molecular weight aliphatic alcohols
known as policosanol. Beneficial therapeutic properties has been reported on
policosanol intake, such as the lowering of blood lipids (291).

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Determination of the wax ester
content has become more important in recent years. Wax esters are only slightly
more polar than cholesterol esters from which they are not easily separated (250). In olive oils,
the analysis of wax esters is used for distinguishing between olive oils of
different qualities, such as extra virgin oils and pomace oils (292). For a long
time, wax contents were determined using crystallization procedures followed by
filtration and weighing of the solid residue. These methods were more accurate
when applied to crude sunflower oils rich in crystallizable waxes than to
refined and dewaxed oils (281).

Among the various techniques available
for the characterization of waxes, chromatographic and spectroscopic techniques
are very efficient (272). TLC is
probably the most useful method for isolating most single classes of wax
constituents for further study, and a separation of some wax constituents is illustrated
schematically in Figure 18 to show the usual order of elution. An alternative
approach is to pre-fractionate the wax components by SPE on a column of silica
gel. Elution with 2-chloropropane gives a fraction containing non-polar wax
components (alkanes, alkyl esters, benzyl esters and long-chain aldehydes),
before more polar constituents (e.g. alkanols, alkanoic acids, alkyl coumarates
and triterpenoids) are recovered by elution with diethyl ether. Only the second
of these fractions is needed to be silylated. It is claimed that much higher
yields of the aldehyde constituents is obtained in this way (250). It is worthy to note that separation of phytosterol
esters from  wax esters in  plants lipids by TLC and SPE, is yet to be
resolved.

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