by Jamie Martin, Brewmaster, Dells Brewing Co.
What do you do if fermentation doesn’t start?
If this happens to you, here are a few places to look first:
Did you oxygenate enough? For those of us that don’t have the luxury of dissolved oxygen meters, oxygenation is a guessing game; this problem can be quickly resolved by bubbling oxygen in through the bottom of the tank.
Temperature is another good place to check when troubleshooting.
Temperature too high? – If the temperature was too high during wort transfer from the brew kettle to the fermenter then you could have cooked your yeast. To correct this problem, cool the fermenter down to optimal temperature for fermentation, and then pitch fresh active yeast slurry.
Too low? – If the temperature was too low during transfer, try draining the glycol from the fermenter jacket, then warm the vessel by running warm water through the jacket. This will warm the wort and yeast to a proper fermentation temperature.
Yeast any good? – If temperature is not the issue you might have dead or very unhealthy yeast. If this is the case:
Transfer your wort off the bad yeast. Filter it if necessary, you don’t want to take the chance of yeast autolysis which will produce off flavors in your beer and/or compromise the health of the new yeast.
Once the bad yeast has been removed from the wort, pitch fresh active and healthy yeast slurry.
It might not be stuck; it might just be done. If you had a high temperature during your mash it is likely you did not get the full extract you expected from your malt. This will, of course, affect your final gravity, resulting in a higher final gravity and a lower final alcohol content. There is really not much you can do to correct this but it’s not the end of the world. The beer will probably be a little sweeter due to the extra residual sugars, and the alcohol content will be a little lower. The change in taste will be so slight most people will not notice, and maybe you’ll find you like the beer better this way; you never know. The history of beer is filled with happy accidents.
Maybe it’s not stuck, just slow. Many Belgian & high gravity yeast strains work very slowly near the end of fermentation. If you think this is the case, wait two to three days more after you think the beer has reached terminal gravity. You’ll be surprised to see how much change in gravity those extra days can make. Sometimes it will continue like that for a week or two more, that’s just how some of those yeast strains work.
Tips for reusing yeast
- Don’t store yeast under pressure; they don’t like that; and it decreases its viability. Drop the temperature slowly after fermentation (I like to drop the temperature no more then 10 degrees a day) to avoid shocking the yeast.
- Make sure you regularly dump off dead yeast.
- Finally, taste your yeast; you should know your yeast better than anyone. If you don’t have a lab you need to rely on you palette and fermentation notes to know how healthy your yeast is.