Characterization of key aroma compounds in distiller's grains from wheat as a basis for utilization in the food industry.

The limited use of distiller's grains (DG) in the food industry depends occasionally on the characteristic odor of DG. For a better understanding of this typical odor, a sensory evaluation was performed first. The impressions seasoninglike, roasty/breadlike, and malty/caramellike were revealed as the most intensive odors. Furthermore, analysis of volatile flavor compounds was applied on dried DG from wheat. Isolation was performed by means of headspace solid-phase microextraction, solvent-assisted flavor evaporation (SAFE), and simultaneous distillation/extraction and identification with gas chromatography-olfactometry/mass spectrometry. As a result, 42 odor-active compounds could be identified in total. Among 24 of the 42 odor-active compounds obtained by SAFE, 3-hydroxy-4,5-dimethyl-2(5H)-furanone (seasoninglike) showed the highest flavor dilution (FD) factor, and 7 compounds (3-methylbutanioc acid, dimethyl trisulfide, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 2-ethyl-3,5-dimethylpyrazine, 2-phenylethanol, 2,6-nonadienal, and 5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone) with a FD factor ≥ 32 were identified as key aroma compounds in DG from wheat.

Identification of volatile forms of methyl groups released by Halobacterium salinarium.

halobacterium salinarium (formerly H. halobium) is a chemotactic and phototactic archaeon from which volatile methyl groups are released continually, a phenomenon related to its sensory system. We found that released methyl groups comprised two different chemical species, methanol and methanethiol, the sulfur analog of methanol. Radiolabeling experiments showed that the methyl groups of both compounds, as well as the sulfur of methanethiol, were derived from methionine but were donated to cellular components and subsequently cleaved to produce the respective volatile compounds. Previous work had shown that chemostimuli and photostimuli result in transient increases in the rate of release of volatile methyl groups. We found that these increases reflected increased release of methanol but not of methanethiol. Thus, the methyl group chemistry of the H. salinarium sensory system is analogous to the well-studied chemotactic system of Escherichia coli. The reactions that result in methanethiol release are of unknown function and have unusual features. They may involve a methionine-gamma-lyase activity we detected in H. salinarium. Sulfur derived from methionine was found attached to specific proteins in reduction-sensitive disulfide linkages.