| Abstract: | Wheat flour non-starch lipids (lipids not bound to starch) were quantitatively extracted with water-saturated n-butanol (WSB), benzene-ethanol-water (10:10:1, by vol.) or ethanol-diethyl ether-water (2:2:1, by vol.) in 10min at 20 °C. Starch lipids (lipids bound to starch) were subsequently extracted with WSB at 90–100 °C. Carotenoid pigments were quantitatively extracted with the non-starch lipids. There was no significant hydrolysis of esterified fatty acids and no detectable autoxidation of unsaturated acids in the hot solvent extracts. Non-starch and starch lipids from a high grade spring wheat flour and three grades of winter wheat flour were separated by thin-layer chromatography and quantified as fatty acid methyl esters (FAME) by gas-liquid chromatography (g.l.c.) using heptadecanoic acid (or its methyl ester) as internal standard. Total flour and starch lipids after acid hydrolysis were also converted to FAME for quantitation by g.l.c. Non-starch lipids consisted of 59–63% non-polar (neutral) lipids, 22–27% polar glycolipids and 13–16% phospholipids. Steryl esters, triglycerides, and all the diacyl galactosylglycerides and phosphoglycerides were present only in non-starch lipids. Starch lipids consisted of 6–9% non-polar (neutral) lipids (mostly free fatty acids), 3–5 % polar glycolipids and 86–91 % phospholipids (mostly lysophosphatidyl choline). Starch lipids were almost exclusively monoacyl lipids. Factors are given for converting weight of FAME into weight of original lipid for all individual lipid classes in wheat which contain O-acyl groups. Factors for total lipids are: total starch lipids = FAME × 1.70, total non-starch lipids = FAME × 1.20, and total flour (non-starch + starch) lipids = FAME × 1.32. Similar factors could be used to convert weight of lipids obtained by conventional acid hydrolysis methods into weight of unhydrolysed lipids. Phospholipid contents are given by: total starch phospholipids = P × 16.51, total non-starch phospholipids = P × 23.90, total flour phospholipids = P × 17.91. |
