SOP Series Part 2 of 10 (Forced Fermentation)

The second thing I want to implement, costs us nothing, yet can ensure that a batch of beer is ready when we release it. The technique is called Forced Fermentation, and is done by very few breweries of our size, but is an essential QC step to ensure consistently excellent beer.

A forced fermentation should be done with each batch of beer. Especially when we are re-using yeast, as this is a good indicator of whether or not the yeast has reached the end of its life span, and can no longer be re-pitched.

We draw a liter of wort from the fermentor and add some yeast slurry to that, putting it in a sanitized container, like a 2L bottle. Then leaving that to ferment at room temp while the mother batch does its thing as well.

Within a few days, due to the high pitching rate (the number of yeast cells per liter of wort) and the higher fermentation temperature, the yeast will fully attenuate, or eat up all the available sugar within the wort, which lets us know the maximum attenuation of that yeast strain during this pitch. The smaller, over pitched, beer will finish before the mother beer letting us know where we should be gravity-wise with the mother beer. We can check this against the recipe, which has the final gravity of the beer as a target.

What this tells us is a few things; if the yeast has been pitched too many times, it will not reach final gravity, which allows us some time to add some more yeast to the batch and properly finish out the beer. Also, if we have a bad batch of yeast, we can also adjust (Although this should be checked by SOP 3, but it still occasionally occurs) This step, which costs us a few 2L plastic bottles and a couple of blow off tubes, can save batches of beer, and maintain flavor consistency.

Here is a link to an article that likely more eloquently explains the process, and has some photos.

Forced Fermentation