The Aroma Components Produced by Yeast in Nitrogen-Free Sugar Solution

Abstract

In nitrogen-free sugar fermentation yeast produces several other volatile com pounds in addition to ethanol. Most of these compounds are distilled over with the ethanol. When the aroma components obtained from the ethanol fraction of a nitrogen-free sugar fermentation were compared with the aroma components of whisky, they showed a qualitatively striking similarity. There was a clear difference in the proportions of the components, however, a fact for which the distillation procedure might be at least partly responsible. The distillate obtained from the fermented sugar solution contained iso-amyl alcohol and /3-phenethyl alcohol as well as the ethyl esters of caproic, caprylic, capric, lauric and palmitic acids in considerable amounts. The same acids also appeared as main components among the free acids and, further, isobutyric and isovaleric acid were found quite abundantly. The similarity between the aroma compounds formed in nitrogen-free sugar fermentation and the aroma fraction of alcoholic beverages indicates that the yeast is responsible for the bulk of the aroma compounds produced.