The yellow pigments in wheat grain and flour are primarily carotenoids (carotene and xanthophylls) of which the predominant species is lutein. This is present mainly in the free form at harvest-ripeness but generally becomes esterified with fatty acids during storage. The factors and mechanisms involved in esterification of lutein in wheat are still unclear but the reaction probably depends on the interaction of several factors such as the amount of free fatty acid present (Kaneko et al, 1995), genotype (Lepage and Sims, 1968) and environmental conditions (Kaneko et al, 1995). The conversion of free lutein to its esters may have a significant impact on the'quality of the end-product and the bioavailability of lutein since esterification decreases the polarity of the free form making it more hydrophobic and therefore, more difficult to solubilise in aqueous systems. In addition to its role in determining the creamy and yellow colours of wheat-based products (Mares and Campbell, 2001), lutein is absorbed from the human gut and accumulates in the eye where it is reputed to reduce the likelihood of macular degeneration and possibly cataracts (Fraser and Bramley, 2004). As a strong antioxidant, it may also assist in lowering the risk of cancer and cardiovascular disease (Ziegler, 1989). Research at the University of Adelaide is focused on the development of high lutein bread wheats, particularly for yellow alkaline noodles, to reduce the need for colour additives and as a functional food capable of supplying a significant proportion of the suggested daily intake. The aims of the work reported here were to optimise the extraction and quantification of lutein and lutein esters, to determine the tissue location of these compounds and to confirm which fatty acids are involved in esterification.
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