Saving Money: Simple Yeast Culturing

A few members of the family

I just finished racking my English IPA to a secondary fermentor. As part of the process, I saved some of the yeast in the primary for future use. Here then, is the start of a series of articles on yeast culturing.

Back in the "good old days," homebrewers didn't have a ton of yeast choices. In some cases, brewers would even use bread yeast from the baking section of the grocery store. In practice, you hydrated the packet of dry yeast you got at the homebrew or grocery store and pitched it. The packets were cheap and worked, but there wasn't much variety to be had.

Nowadays, there are several dozen strains available. While a few strains are still dry, most are liquids that come in pitchable tubes, or smack-packs. The liquid yeasts give consistent results and provide tremendous variety to finished beers, but are pricey. If you only use each pack, or tube once, you will quickly discover that yeast makes up 15%, or more of the cost of a batch. Thankfully, reusing yeast is simple and doesn't require a degree in Molecular Biology. With proper sanitation, you can get 4-5 batches of beer from one packet of yeast.

I won't discuss how to pitch your original yeast packet. The manufacturer happily puts that info on the label. What I care about is what to do after the yeast is done fermenting its latest batch of beer. To start, you'll need some spare beer bottles, extra fermentation locks with stoppers small enough to fit your bottles, a funnel, a lighter, rubbing alcohol and free space in your refrigerator. Keeping things sterile is very important. Be sure to sterilize anything that's going to touch the yeast to avoid unwanted visitors.

With that out of the way, it's time to start culturing. When you transfer your beer from the primary fermentor, there will be a thick layer of goop (slurry) at the bottom. Put your sterilized funnel into a sterilized bottle and pour some of the slurry in. I usually try and get 6-8oz of the stuff, but you can get more, or less.

Once the slurry is in the bottle, I like to take a cloth dipped in rubbing alcohol to the bottle rim. Once you feel you've wiped the rim fully, take a lighter and burn off the excess. This will make sure that nothing that was on the rim gets in. When you've finished playing with fire, put on your fermentation lock and stick the bottle in the fridge. After a few days, you should see a layer of liquid on top of your slurry. At this point, the yeast is hibernating and waiting for new food to munch on.

Burning away possible contaminants

To reuse your yeast, remove the bottle from the refrigerator and let it warm to room temperature. When you're ready to pitch into your aerated wort, carefully remove the fermentation lock, wipe the bottle rim with alcohol and then use your lighter to burn it away. Next, pour the layer of liquid on top of the yeast into the sink. Then swirl the bottle to loosen the slurry up. Finally, pour the slurry into your wort. You'll have to do a bit of shaking to get everything out, because the slurry at the bottom has the consistency of ketchup.

Yeast stored for up to four weeks can be reused using this method. If you let it sit longer, you'll need to perform some extra work to rouse it. I'll be covering that, as well as culturing from bottle-conditioned beers in a future article.