Effect of Acetaldehyde, Acetal, and Ethyl Acetate upon Alcoholic Fermentation

¹ Department of Viticulture and Enology University of California, Davis

1. The influence of acetaldehyde, acetal and ethyl acetate upon the fermentation of grape musts under various conditions was studied. Quantities of acetaldehyde added at the beginning of fermentation in excess of about 0.1 percent produced important delays in fermentation, but grape musts with acetaldehyde concentrations as high as 0.3 percent were readily fermented after the necessary lag period. The effect of acetal measured as the acetaldehyde equivalent was essentially the same. Both compounds are readily utilized without significant effect on fermentation rates when added during a state of vigorous fermentation in amounts up to 0.35 per cent acetaldehyde or 0.9 per cent acetal. Ethyl acetate added prior to fermentation in amounts up to 3 per cent also caused large delays but did not prevent normal fermentation once it was started. Added during fermentation, 2 to 3 per cent ethyl acetate produced sluggishness.

2. The reduction of both acetaldehyde and acetal is about 100 per cent when added to grape must under conditions in which the fermentation of sugar is essentially complete. This utilization of aldehydes resulted in a complement of alcohol approximately equivalent to the aldehyde metabolized.

3. During the course of a fermentation added acetaldehyde decreased rapidly even while the sugar utilization was momentarily slowed. An accumulation of acids occurred during the period of rapid acetaldehyde reduction, which in turn later mostly disappeared.