Lipid Composition of Wheat Germ and Wheat Germ Oil

Abstract Information available in the literature concerning the composition of lipids in wheat germ and in wheat germ oil is critically reviewed. After a brief introduction to the botanical and technological aspects of wheat germ, the yield of oil and its physico‐chemical properties are described followed by the composition of fatty acids, acyl lipids and non‐saponifiable components. The importance of distinguishing between dissected germ and commercial wheat germ and between germ oil and germ lipids is emphasised. The triglycerides account for the major part of the fatty acids, of which linoleic acid is the principal component, and the content of free fatty acids depends on the rancidity of the germ and also on possible post‐extraction processing in the case of commercial oil. Polar lipids consist mainly of phospholipids and available information suggests that glycolipids are present only at very low concentration and that galactosyl glycerides may be absent from the embryo of the quiescent wheat grain. Most reports of tocopherol composition concern wheat germ oil and there is less information about the tocopherols of dissected wheat germ. α‐ and β‐tocopherols are found in wheat germ but tocotrienols are probably absent from dissected germ and only occur in commercial germ as a result of bran and endosperm contamination. Wheat germ oil exhibits a range of sterols. 4‐methyl sterols and triterpenoid alcohols, and β‐sitosterol and campesterol are the major components. The hydrocarbon composition of wheat germ oil has been reported but the significance of the results is uncertain. Flavonoid pigments, xanthophyll and xanthophyll esters have been shown to be present in wheat germ. Most of the studies of the non‐saponifiable fraction were based on germ oil and commercial wheat germ and little is known of the nature of this fraction in dissected wheat germ.