Bioactive Lipids in Cereals and Cereal Products

Abstract

Cereal grains, belonging to the plant family Poaceae, are mainly composed of starch and contain much smaller amounts of lipids compared to the oilseeds. The seven major cereals are common wheat, rye, barley, oats, rice, maize, sorghum, and pearl millet (Figure 11.1). Cereal lipids are mainly located in the germ, the bran, and/or the endosperm, depending on the cereal. Lipids associated with the starch can be divided into surface lipids and internal lipids according to their extractability in cold or hot n-propanol (Morrison 1981). Surface lipids, which exist on the surface of starch granules (Galliard and Bowler 1987), resembles the rest of kernel lipids while internal lipids consist mainly of monoacyl lipids (lysophospholipids) and free fatty acids that form inclusion complexes with amylase (Morrison and Coventry 1985). In these amylolipid inclusion complexes, the hydrocarbon chain of the lipid lies within the hydrophobic amylose tube while the polar ends stay outside the helix (Morrison 1988; Morrison et al. 1993). Although the amount of starch for internal lipids is limited, for example, about 1% of the starch in barley (Becker and Acker 1971; Morrison 1995), they in‹uence the swelling and gelatinization of these starched affecting properties such as the baking quality (Morrison et al. 1993). In oats, a considerable amount of lipids exist in the starchy endosperm as surface lipids.