- The volatile flavor fraction of lightly milled wheat grown in
eastern Oregon was isolated for study by two methods: steam distillation
under vacuum and steam distillation at atmospheric pressure.
The sample obtained under vacuum was extracted with ether
which was then evaporated to yield the desired wheat essence.
Steam distillation at atmospheric pressure provided the headspace
vapors that were used for a portion of the gas chromatographic
Identification of the organic substances contained in the volatile
flavor fraction was made on the basis of chemical tests, paper
chromatography, gas-liquid chromatography, and mass spectrometry.
Preliminary testing for amines and carbonyls indicated the
presence of both of these functional groups, although in subsequent
research amines were not detected. Additional information as to the functional groups present was obtained by subjecting headspace
vapor samples to gas chromatography and directing the column effluent
into vials containing reagents selected to indicate the presence
of alcohols, amines, esters, carbonyls, and mercaptans. A separate
set of reagents was used for each eluting peak.
Formation of 2, 4-dinitrophenylhydrazone derivatives and determination
of their melting points provided one means of tentative
identification of carbonyl compounds.
Ascending paper chromatography was used to separate the
2, 4-dinitrophenylhydrazone derivatives of the carbonyls into classes
and to ultimately assist in the identification of these compounds.
A Barber-Colman gas-liquid chromatograph equipped with a
flame ionization detector was used as a means of separating the
components in the samples. Identification of some of the compounds
was possible through comparisons of retention times of the peaks on
these columns with retention times of known compounds. Column
packings used for gas-liquid chromatography were six percent
Apiezon M, six percent Diethylene Glycol Succinate, and three
percent Free Fatty Acid Phase, all on a solid support of Anakrom
ABS, 90 to 100 mesh. The column was heated isothermally at 75°C
with nitrogen as the carrier gas flowing at a pressure of five pounds
per square inch.
Mass spectra of the wheat essence compounds were obtained by use of an Atlas-MAT Ch-4 mass spectrometer using a two second
scan, coupled with a gas-liquid chromatograph.
Twelve compounds were identified and six were tentatively
identified in the headspace aroma or in the wheat flavor essence.
Those identified were acetaldehyde, isobutyraldehyde, butyraldehyde,
valeraldehyde, hexanal, heptanal, octanal, crotonaldehyde,
3-methyl-2-butanone, 2, 2-dimethyl-3-pentanone, diacetyl, and
ethyl acetate. The compounds tentatively identified included isoamyl
alcohol, amyl alcohol, butanone, isovaleraldehyde, cyclopentanone,