By Chris Jennings
For the Oregon Beer Growler
Now that the new year is upon us, we should make some beer resolutions to continue to enhance our brewing skills. No recipe is complete without the perfect yeast, but what happens if the yeast that we love doesn’t get produced again? Not only can we as homebrewers harvest yeast from bottles and the world around us; we can also save a few dollars by keeping our favorite strain going for several yeast generations.
After your tasty homebrew’s primary fermentation period, the yeast will fall to the bottom of the fermenter and form a cake. Usually we would just discard this cake, but it‘s still a viable yeast pitch. As long as you were careful not to introduce anything foreign into it, you can use the cake as a new pitch for your next brew. The fastest and easiest way to reuse the cake is to brew the same day you empty your fermenter, then just put the new wort into the bucket with the yeast. You can only use this method a few times before you may notice some off-flavors beginning to develop. This is because there is protein and even some beer left from the previous brew. If you are planning to use this strain for much longer than a few brews, you can wash the yeast.
In order to wash the yeast, put about 3 gallons of cold water into your fermenter. Transfer as much of the sludge into a glass carboy or other clear vessel. Make sure there is plenty of liquid and that most of the sludge is stirred into the solution. You need to then put the carboy into a chilled area around 50 F. This will force the proteins and dead yeast cells to fall back into the cake and should only take a few minutes. Once most of the cake has re-formed, the live yeast cells will be floating in the water, so rack the water with the living cells into a separate sanitized container. After this is complete, you have a fresh yeast pitch with minimal impurities. You can continue to wash the same strain of yeast for several generations with very low levels of flavor change. Eventually the yeast will mutate and it may take on a completely new flavor. As long as it still tastes good, there’s no reason to stop using it when it can save you money.
Capturing New Strains
Purchasing yeast at your local homebrew shop is the safest guaranteed way to get the flavors that you are looking for in your homebrew. But sometimes you can harvest yeast out of an empty beer bottle and have your very own Duvel strain. If you are going to attempt this, you need to be sure that the beer has not been filtered or pasteurized. When you have found the beer with the yeast that you want, decant as much of the beer out of the bottle as possible. Add some cold water and transfer the remaining contents of the bottle into a flask or growler to begin making a starter.
To make a starter, cook up a small amount of wort by using dry malt extract and boil it with some water. Once the wort is chilled, add it to your flask or growler and allow it to begin fermentation. Be sure to incorporate air into the solution as well because it will help the yeast grow. You can do this by swirling the container every few hours or every time you walk past it. Another option would be to use a stir plate with a stir bar like the kind you might remember from high school chemistry class. Either way, in a few days your yeast should have enough cell growth for you to pitch it into your next tasty experiment.
Though it is cost-effective to save yeast and begin your own yeast bank, it can be a daunting task. Starting small and getting a few of the different techniques mastered can help to start the new year off right and ensure a successful brew year.
Killer Winter White [Extract]
Killer Winter White [AG]
Stories from the print edition of the Oregon Beer Growler.