Combination of thin layer chromatography and gas chromatography in the analysis on a microgram scale of lipids from wheat flour and wheat flour doughs

Lipids were extacted on a microgram scale from 3 to 6 mg flour or from freeze-dried dough by percolation. The impure extract was separated into 12 nonpolar and 14 polar lipids by TLC. Then the fatty acid composition of most of these lipids was determined by gas chromatography. The microscale method renders possible qualitative and quantitative determination of the composition of the lipids in minute quantities of flour and dough. The selectivity of different extraction solvents was studied. In both flour and dough the fatty acid composition of a given component is identical in the free and bound lipid fractions. In dough, the quantity of free lipids is less than in flour; the extent of the decrease depends on the atmosphere in which it is mixed. During mixing, the carotenoid pigments, α-monoglycerides and the free linoleic acid and linolenic acid are oxidized. Oxidation is apparently a function of the concentration of oxygen and of lipoxidase.