Fast Ferment Test

The fast ferment test is a fermentation test designed to expose the attenuation limit of a given wort. A sample of wort is pitched with yeast at a high pitching rate and fermented at relatively high temperatures (70-80F, 20-25C) with intermittent or constant agitation. These conditions allow the yeast to ferment all the wort sugars that it can ferment and the resulting final extract of the sample is an indication of the amount of unfermentable extract that was present in the wort.

The completion of this test takes from 2-4 days and it can therefore be used to predict the final extract that can be expected from a fermenting batch of beer. Depending on the yeast and the actual fermentation conditions during that fermentation the actual attenuation may be lower than the attenuation limit that was established with the fast ferment test. The difference is caused by residual fermentable sugars and their desired amount depends on the style of beer and contributes to the balance of that beer.