Characterization of the carbonyl compounds in reverted soybean oil1,2,3

Abstract

AbstractTwenty‐one mono‐carbonyl compounds were identified in a reverted but not rancid soybean oil with a peroxide number of 2.7 meq/kg and a flavor score of 6.0. Six of the carbonyl compounds were saturated methyl ketones, ten were saturated aldehydes and five were 2‐enals. The amount of 2,4‐dienals in the reverted soybean oil was too small to be fractionated and identified. One fraction of the 2,4‐dinitrophenylhydrazones of mono‐carbonyl compounds obtained was different in chemical properties from those of the four known classes of compounds; viz. saturated aldehydes, saturated ketones, 2‐enals, and 2,4‐dienals. The chemical identity of this fraction has not been completely established.The technique used for the identification of the mono‐carbonyl compounds consisted of essentially five steps: (a) passing a hexane solution of the soybean oil through a celite column, which was homogeneously impregnated with 2,4‐dinitrophenylhydrazine and phosphoric acid, in order to convert quantitatively all the carbonyl compounds in the oil into their 2,4‐dinitrophenylhydrazones; (b) removing the soybean oil from the solution with a Seasorb‐Celite Column; (c) removing decomposition products and 2,4‐dinitrophenylhydrazones of ketoglycerides with an Alumnia Column; (d) separating, by adsorption chromatography, the 2,4‐dinitrophenylhydrazones of mono‐carbonyl compounds into four classes; viz. saturated ketones, saturated aldehydes, 2‐enals, and 2,4‐dienals; and (e) identifying the individual components in each class of compounds by the Rf values of liquid‐liquid partition chromatography.