Waxes can be used to encapsulate water-solubleingredients for incorporation of some types of functional ingredients (289). Wax estersalso constitute another target molecule for lubricant applications. The highlinearity of wax esters enhances the viscosity index of the oil and impartsspecific desirable characteristics such as anti-rust, anti-foam, anti-wear andfriction reduction properties to the lubricant. These properties make wax estersexcellent feedstocks for production of high-temperature and pressure lubricantsas well as hydraulic fluids (290).
RBW has potential applications incosmetic, pharmaceutical, food, polymer, and leather industries. There are manyreports on the use of RBW in cosmetic preparations such as cold cream, drugs,and hair-conditioners and its performance was comparable to carnauba and otherwaxes. RBW is also a rich source of high molecular weight aliphatic alcoholsknown as policosanol. Beneficial therapeutic properties has been reported onpolicosanol intake, such as the lowering of blood lipids (291).
Determination of the wax estercontent has become more important in recent years. Wax esters are only slightlymore 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 ofdifferent qualities, such as extra virgin oils and pomace oils (292). For a longtime, wax contents were determined using crystallization procedures followed byfiltration and weighing of the solid residue. These methods were more accuratewhen applied to crude sunflower oils rich in crystallizable waxes than torefined and dewaxed oils (281). Among the various techniques availablefor the characterization of waxes, chromatographic and spectroscopic techniquesare very efficient (272). TLC isprobably the most useful method for isolating most single classes of waxconstituents for further study, and a separation of some wax constituents is illustratedschematically in Figure 18 to show the usual order of elution. An alternativeapproach is to pre-fractionate the wax components by SPE on a column of silicagel.
Elution with 2-chloropropane gives a fraction containing non-polar waxcomponents (alkanes, alkyl esters, benzyl esters and long-chain aldehydes),before more polar constituents (e.g. alkanols, alkanoic acids, alkyl coumaratesand triterpenoids) are recovered by elution with diethyl ether. Only the secondof these fractions is needed to be silylated.
It is claimed that much higheryields of the aldehyde constituents is obtained in this way (250). It is worthy to note that separation of phytosterolesters from wax esters in plants lipids by TLC and SPE, is yet to beresolved.
