In homebrewing, you can wash your yeast in order to reuse it from batch to batch.
Washing your yeast will save you money. At $6-$10 per vial of liquid yeast, the savings add up significantly over time.
It is also a great way to reuse a yeast that performs well for you. If you like the qualities you are getting out of a certain stock of yeast, you can save it for more batches of beer.
The process is simple and can be performed on your bottling day or when you're transferring your beer to a secondary fermenter.
- A batch of beer from the primary or secondary fermenter (I recommend the primary; see below)
- A large glass jar between 1/2 – 1 gallon
- A pot capable of boiling 1 gallon of water
- 4 pint size mason jars
Yeast Washing Steps
- Boil one gallon of water for 15 minutes.
- During the boil, sanitize the glass jars and funnel.
- Let the water cool for a couple minutes on the stove, and then pour into the large glass jar.
- Place the large jar in the refrigerator to cool.
- Siphon the beer off the yeast, either to bottle it or transfer to a secondary fermenter. Place the airlock back on the empty fermenter while it waits.
- Take the large jar of water out of the refrigerator and let it come up to room temperature.
- Pour the large jar of water into the fermenter, place the airlock back on, and shake it.
- Let the fermenter sit for 20 minutes so the trub can separate from the yeast and fall to the bottom. The yeast will be a milky white color, while the trub will be a darker brown.
- Pour the top layer (yeast and some beer) back into the large jar, trying to leave the bottom layer of trub behind.
- Cap the large jar and shake. Let it sit for 20 minutes.
- Similar to the pour from the fermenter, carefully pour the liquid from the large jar into the four pint size mason jars, trying to leave behind the dark matter on the bottom.
- Cap the mason jars and place them in the refrigerator. The yeast will settle to the bottom over the next few days.
Yeast Washing Questions
What do I do with the harvested yeast? Make beer with it! On brew day, take it out of the refrigerator and pour off the liquid on top, leaving a little bit behind. When you're ready to pitch, swirl up the yeast and pour it into the wort. This method will work, but you're better off making a yeast starter, especially if the yeast is stored for a while. Which leads us into our next question…
How long can I store the washed yeast? I don't have a scientific answer for this one, but Bernie Brewer mentioned he has used yeast one year later. I've never gone more than 3 months. Here's my best advice – if you wait more than a week, make a yeast starter. In fact, you should make a yeast starter for every batch.
How many generations can I harvest? I typically don't go more than 5, but some people go more than 10. If your sanitization is solid, you should be able to get many generations out of it. Once you notice something is off though, it's time for a fresh vial.
Do I harvest from the primary or the secondary? You can do both, but I recommend the primary. The yeast from the primary is more flocculant and not as stressed out as the yeast in the secondary, which has been exposed to alcohol for a longer period of time. It is more work to separate out the trub, but it is worth it in my opinion.
Can I pour my fresh batch of beer onto the yeast cake to ferment it? I don't recommend it. It is the easier way to go, but if your goal is to make the best beer possible, you are better off washing it. The cake is full of dead yeast and other particles that can contribute off-flavors to your new beer.