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Feb
28
2012

How To Reuse Home Brew Yeast From a Previous Batch of Home Brew

Yeast Bed

If you're new to home brewing, you might think that when fermentation is over, the home brew yeast that you pitched into your wort has done it's job and died off.  Actually, the yeast consumes the sugars in your wort, and when it can't do that any longer, settles down at the bottom of the carboy. Lucky for us, we can extract it and reuse it in another batch of delicious home brew.  

In this blog post, I'm going to walk you through the steps needed to get the yeast out of the carboy, wash it, and reuse it.

Equipment Needed:

  • Carboy with home brew ready to be bottled or put into a keg system
  • Auto Siphon or other mechanism for removing home brew from a carboy
  • Sanitizing Solution
  • Small stove pot
  • 2 Cups of Water
  • 2 large jars with lids
  • 1 small jar with lid for storage

Step 1: Siphon Your Beer

Before you can get at the yeast, you need to siphon the home brew out of the carboy.  That sludgy tan colored nastiness at the bottom of the carboy is the yeast cake or yeast bed.  It may have some home brew, hops or other miscellaneous things in it, but don't worry, you'll take care of that later.

 Siphon Beer

 

Step 2: Boil and Cool 2 Cups of Water

Boil two cups of water for 10 minutes to sterilize the water. Cover the pot with a lid and allow the water to cool to room temperature.  You can use an ice bath if you are in a hurry, but don't fret...why not sit back and enjoy a home brew while you're waiting.  You're going to combine this water with the yeast cake in a few steps.

 Stove Pot

 

Step 3: Prepare the Jars

While the boiled water is cooling, wash the jars and lids if needed and sanitize them.  Set them aside for later, making sure they aren't able to collect any bacteria or wild yeast while you're waiting. 

 

Step 4: Pour the Water Onto the Yeast Cake and Shake It!

Once the water that you boiled in step 2 has cooled down to room temperature, you're going to pour the cooled water directly onto the yeast cake inside the carboy.  Next, you want to shake and swirl the carboy...juggle it if you like, just don't drop it or spill it. The goal is to dislodge all of the yeast, trub and other gunk at the bottom of the carboy and mix it into the water, forming a thick tan colored concoction. There may be some larger particles in there...don't worry.

Water and Funnel

 

Step 5: Pour the Yeast Mixture

Once you have thoroughly mixed the water and yeast cake and most of the yeast cake has combined with the water, pour the yeast mixture into one of the sanitized jars.  Secure the lid on the jar and shake the mixture as much as you can for a good 2 to 5 minutes.  This will help break up the larger particles and mix everything together.

Sludge in Jar

 

Step 6: Wait 10 Minutes

After shaking, set the jar down somewhere and let it rest for 10 minutes or more.  You should start seeing distinct separation of layers in the jar with the sludge and other gunk collecting at the bottom, yeast in the middle and water on top.  Depending on the type of beer you made, how much you shook the jar and how long you let it rest will affect the distinction between the yeast and water layers.

Separation

 

Step 7: Pour off Yeast and Water

After everything has settled fairly well, slowly pour the top layers of the jar into the other sanitized jar.  As you do this, the layers will mostly remain intact and you can watch the water and yeast layers getting smaller as you pour.  Stop pouring just before the sludge layer starts getting transferred.  Discard the sludge that is left over in the first jar then clean and re-sanitize the jar. Cover and seal the jar that now has the yeast and liquid.   Continue to shake, wait and pour as many times as you need to to get rid of the bulk of the sludge. In this process, you're simply moving the the yeast back and fourth between jars and getting rid of more sludge with each transfer.  Typically, doing this 2 to 3 times is sufficient.

Yeast Pour Off

Layers 

Step 8: Label and Refrigerate

Once you are satisfied with how much sludge has been eliminated, you're going to transfer the remaining yeast and water into a small jar or other vessel that will hold the yeast until you decide to use it in another batch of home brew.  Make sure the jar or vessel is sanitized, pour in the yeast water mixture and seal with a lid.  Label the jar or vessel of yeast, making sure to include the yeast strain as well as the number of times it has been reused.  You don't want to reuse your yeast more than 4 or 5 times as it will begin to mutate and no longer produce predictable flavors in your home brew.  After the yeast has been in the refrigerator for a few days, the yeast will solidify at the bottom and the liquid will be on top.  You can now take this out and use it in a batch of home brew, though I recommend using a yeast starter to get the yeast active before pitching into your wort.  Yeast that is stored in the refrigerator should keep for a few months, but using it sooner than later is always recommended.

 

Harvested Home Brew Yeast

If you have any tips or comments on how to reuse home brew yeast, please leave a comment.