Kee** properties of edible oils. III. identity of trace materials adsorbed from peanut oil by chromatography on alumina

Abstract

A peanut oil of improved quality was obtained by replacing active earth bleaching in the refining process by treatment with alumina. To determine which components of the oil were removed and modified by this treatment, the material adsorbed on the alumina was examined. Off-flavor precursors were not concentrated, but chemical modification of precursors had taken place. Alumina treatment probably owes its effectiveness in part to removal of off-flavor precursors and pro-oxidants, and in part to suppression of undesirable side reactions which occur in bleaching earths. Hydroperoxides originally present in the oil were almost entirely destroyed on the alumina, and the adsorbate was found to be enriched in oxidized, hydroxylated, and unsaponifiable material. The presence of glycer-ides containing both saturated and α,β unsat-urated (and possibly traces of a,β, γ, δ diunsat-urated) aldehyde groups was demonstrated. The adsorbate also contained a considerable proportion of glycerides containing polar groups, e.g. hydroxyl, in the fatty acid radicals ; the bulk of these appeared to be hydroxydienoic acid. Gas liquid chromatography (GLC) of the methyl esters of the fatty acids of the adsorbate was used to detect simple oxidized fatty acids such as keto, epoxy, and hydroxy acids. Adsorption on alumina may prove to be a powerful tool for the isolation of aldehydoglycerides and glycerides of hydroxy-acids from oils and fats.