Formation of Methyl Ketones from Milk Fat during Steam Distillation or Saponification

Abstract

An homologous series of methyl ketones was identified, by means of their 2,4-dinitrophonylhydrazones, in both the steam distillate and the unsaponifiable matter from milk fat. This series contains the n-alkyl members with odd numbers of carbons from C3 (acetone) through C15 (pentadecanone-2). Evidence is presented that fresh un-heated milk fat is devoid of such ketones, with the exception of acetone, but that it does contain carbonyl functions as suggested by its reaction with 2,4-dinitrophenylhydrazine reagent. The capacity of milk fat to generate methyl ketones is discussed in terms of origin and flavor significance. A means of overcoming anomalous melting-point behavior of certain 2,4-dinitrophenylhydrazones is presented.