The distribution of acyl lipids and tocopherols in flours millstreams

Abstract

AbstractKernels from a mixed hard wheat grist were dissected into germ, bran (pericarp, testa and aleurone), and starchy endosperm for direct analysis of tocopherols in lipid extracts by high‐performance liquid chromatography. α‐ and β‐tocopherols were almost exclusively in the germ, α‐tocotrienol was mostly in the bran, and β‐tocotrienol was equally distributed between the bran and the starchy endosperm. Acyl lipids and tocopherols were quantified in 23 millstreams obtained from this grist. Components related to germ and bran (triglyceride, diacylphospholipids, ã‐ and β‐tocopherols) and testa (flour colour) showed the highest coefficients of variation whereas endosperm components (glycolipids, N‐acylphospholipids and β‐T‐3) showed exceptionally low variation. The quantities of marker tocopherols in the streams were used to calculate the composition of the lipid transferred to the flour from germ and aleurone, and to predict the composition of the basic endosperm, free of aleurone and germ lipids. Low proportions of diacylphospholipids in the lipid transferred to high‐grade millstreams indicated the transfer of spherosome lipid. The low‐grade streams exhibited high proportions of phospholipids suggesting additional transfer of germ tissue and aleurone tissue containing membrane lipids. Protein and ash contents of the transferred fraction confirmed that a substantial proportion of the transferred lipid was probably accompanied by protein bodies or by tissue fragments. It is estimated that aleurone contributed less than one‐quarter of the transferred lipid in any stream. Hexane‐extractable free lipids in four representative streams consisted of almost all the non‐polar lipids, 40–67% of the glycolipids, 47–54% of the diacylphospholipids and 30–60% of the lysophospholipids.