Volatile Constituents of Grass and Corn Silage. I. Steam Distillates

Summary Extracts of steam distillates from grass-legume and corn silages were analyzed to determine the identity of the volatile constituents in these feeds which may be responsible for feed flavor in milk. The normal C 2 –C 6 , isobutyric, and α- and β -methylbutyric acids were present in most of the distillates. The normal C 2 –C 6 aldehydes, 2- and 3-methylbutanal, 2-methylpropanal, acetone, butanone, benzaldehyde, phenylacetaldehyde, and furfural were detected in both types of silage. Traces of 3-(methylthio) propanal were found only in the grass silage. The acid- and carbonyl-free neutral fractions from the grass and corn silage distillates had odors charactetristic of the respective silages. The major portions of these fractions from the corn silages distilled from 35–100C and contained the normal C 2 –C 5 , secondary C 3 –C 5 , and the iso-C 4 and C 5 (2- and/or 3-methylbutanol) alcohols. The same alcohols were detected in similar fractions from the grass silages. In addition, hexanol, 2-hexanol, and cis-3-hexanol were detected in the high-boiling residues from the grass silage neutrals. Although several ethyl and propyl esters were identified in the neutral fractions from both silages, it was found that some of these could have been formed during extraction of the distillates. The volatiles of silages responsible for their characteristic aromas are concluded to be complex mixtures of alcohols, carbonyls, and probably esters of the alcohols and volatile acids present in silages.