Studies are reported on changes in fatty acid and lipid class composition in developing soybeans picked at intervals from ca. nine days after flowering to maturity. In the early stages of development of the

SUMMARY Studies were carried out on the fractionation and analysis of egg lipid by several new techniques employing thin‐layer chromatography. The fatty acid composition of the major lipid classes and subfractions thereof was determined by a combination of alkali‐isomerization and gas‐liquid chromatography. The positional arrangements of the fatty acids in the glycerides and lecithin fraction were determined. The fatty acids in lecithin were distributed mainly in one type, the α‐saturated β‐unsaturated type, in contrast to the fatty acids of triglycerides.

The autoxidation of polyunsaturated lipids is initiated by a discrete reaction occurring prior to the formation ofstable hydroperoxides. The products of the initiating reaction were detected by thin‐layer chromatography and by ultraviolet spectral analysis. The reaction initiating autoxidation does not necessarily involve interactions with metals, although it is catalyzed by some heavy metals when these are present in sufficient concentrations. ॅ‐Tocopherol does not inhibit the initiation reaction, and in general, the stability of preparations of esters of polyunsaturated fatty acids is related to the content of prooxygenic substances resulting from this reaction. By taking special precautions to remove these prooxygenic substances, methyl esters containing as many as six double bonds were prepared having significant induction periods at 40C during which there was no measurable uptake of oxygen.