Components of the hardening flavor present in hardened linseed oil and soybean oil

Abstract

Abstract The characteristic hardening flavor which develops in hardened linseed and soybean oils during storage has been coned from hardened linseed oil by stripping with nitrogen. After separating the volatile substances by adsorption chromatography on silica, the fraction containing the hardening flavor has been converted into 2,4‐dinitrophenylhydrazones (DNPHs) and separated by means of partition chromatography. On regeneration of the fractions of DNPSs obtained, the characteristic hardening flavor was observed in one specific band. Both by hydrogenation and by oxidation of the free carbonyl the carrier of the flavor was found to be an unsaturated aldehyde; however, not of the ॅ‐ॆ unsaturated type. Further separation of the regenerated carbonyls by means of gas‐liquid chromatography (GLC) points to a C 9 ‐aldehyde. After synthesis of the 4‐,5‐ and 6‐ cis ‐ and trans ‐nonenals, comparison made it probable that the carrier of the hardening flavor is a mixture of 6‐ cis and 6‐ trans ‐nonenal, the latter of which has the greatest share in the hardening flavor. In order to confirm the location of the double bond in the carrier of the hardening flavor a recent isolation technique was applied. The volatile substances from hardened linseed oil were first separated via GLC. After conversion of the carbonyls in question into their DNPHs, the latter have been separated by means of thin‐layer chromatography (TLC). By means of IR‐analysis and oxidation with osmium tetroxide of the pure derivative, the principal carrier of the hardening flavor has been identified as 6‐ trans ‐nonenal.