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Saving & Reusing yeast

Updated 7/10/2012

Update:  For the last couple years, I've been "saving" yeast a little differently than previously mentioned on this site.  Both methods work great and save a ton of money on yeast, but I find my new method to be a good way to preserve the quality of the yeast in case you won't be re-pitching it for awhile.  Both methods are solid, so choose whatever best fits your brewing schedule/system.

Yeast Starter Method (New)

A friend of mine in the beer club mentioned using 2-liter plastic bottle blanks/preforms for saving yeast, and he knew someone at a plastic manufacturing plant that gave him a case of their "defects" which just means they didn't quite meet weight & size specifications.  I decided to try it out.  The nice thing about this method is that I feel much more comfortable saving yeast this way for extended periods of time.  Since there isn't as much trub/break material and no hops to worry about, you have a pretty clean specimen of yeast.  This method requires a little more thinking ahead since you should (need) to make a starter a day or two before your brew. I say "need" because 1 vial of saved yeast isn't really enough to pitch directly into a batch of anything higher than 1.030 starting gravity.  You could always pitch a couple vials if you don't have time to make a starter though.  If you don't want to make a starter, consult the yeast calculator on MrMalty.com.  I typically make a 800-1000ml starter using 1/2 cup DME for an average (1.040-1.060) batch of beer.

  1. Make a large (1500-2000ml with 1 cup DME) yeast starter, chill, and pitch your vial/smack-pack of yeast

  2. Allow the starter to ferment out completely. This usually takes 2-3 days, and you'll know it's done when the yeast drops out and your wort/beer clears up.

  3. Sanitize a small funnel and 5-6 yeast caps & vials***

  4. Position the sanitized vials in a container that allows them to sit upright for filling

  5. Pour out mostly all of your starter wort/beer, leaving only enough to swirl the yeast into suspension.  This usually takes a little getting used to, but you can eyeball it the first time.

  6. Sanitize the lip of your starter flask, swirl the slurry in the bottom to get everything into suspension, then funnel the slurry into your vials.

  7. Screw on your caps and label the vial with the strain of yeast it contains

Where to find the Vials?

I did a search for these vials online and they can be a little difficult to find.  The plastic caps can be purchased at several online homebrew stores like Northern Brewer, MoreBeer, and Midwest Supplies.  You can also save and reuse White Labs vials if you have some sitting around.  Here's a link Shawn P. sent me via email after reading through this tutorial of where to get vials:

- http://www.amazon.com/Soda-Bottle-Preforms-Caps-30/dp/B008MB1QNY/ref=pd_sim_indust_5

 

Shawn also tested out some 50ml centrifuge tubes that he said are easy to find and worked great.  Here's the link to those for anyone interested in giving them a try:

- http://www.novatech-usa.com/Products/Plastic-Centrifuge-Tubes

 

Harvesting Yeast Cake (My Older Method)

The question of how to save and reuse yeast gets brought up on a lot of online homebrew forums, so I thought that I'd write up a little how-to to show people what's worked for me.

Before You Start

Quick Tips:

  • *SAFETY TIP* I only use plastic containers to save yeast because they can withstand the pressure that sometimes builds up with saving yeast.  That way, I can have a completely sealed container and not worry about any funk getting in.  If you choose to go with glass, make sure you don't completely seal the vessel.  Use a stopper with an airlock or some other method that will allow pressure to escape.

  • Make a 6 gallon batch of beer when you know you're going to save the yeast cake.  When you transfer your beer into the fermenter, leave the last gallon of break material and hops behind so it doesn't end up in the saved yeast slurry.

  • Always pitch up in gravity

  • Only save yeast for 2 to 3 generations to avoid mutations

What's Needed to Save Yeast?  All you need to save yeast is a few 16 oz plastic beer bottles (as seen above), a funnel, some type of label, and an empty 6-pack holder.  The reason I use plastic bottles instead of glass is simple.  Even though the yeast will be stored in the refrigerator, they are still working and putting off CO2 at the lower temperature.  The plastic bottles can handle quite a bit of pressure without bursting.  When I pull the yeast out of the fridge on brew day, often times the bottle is under quite a lot of pressure and is very hard to press in on.

How Long Can the Yeast be Saved Before Use?  I typically try to reuse my yeast within a month or two, but I've heard of people using it several months later without any problems.  If you have saved yeast for longer than 2 or 3 months, it would probably be best to make a starter to check if the yeast is still viable (which it almost definitely should be).  I've had good luck pitching straight from the bottle at least 2 months after saving the yeast.

When Should the Yeast be Saved?  I like to keep mostly all of my beers in the primary fermenter for at least 2 weeks.  This gives the yeast plenty of time to eat through the sugars and clean up any of their byproducts.  It also allows the yeast to drop out of suspension so you can be sure you're getting most of the yeast at the bottom of the fermenter.

What Type of Beers Can Yeast be Saved From?  I typically save yeast from lower gravity beers like English Bitters, Scottish 60 /-, American Wheat, Cream Ales, Blond Ales, etc.  By saving yeast from lower gravity beers, you are putting less stress on the yeast and ensuring that what you end up with will be fresh and won't produce any off-flavors. NOTE:  Always try to pitch up when saving yeast.  For example, don't pitch a yeast slurry from a 1.060 beer onto one that's 1.040.  You may experience some off-flavors when doing this.  Also, I usually don't save any yeast from beers over 1.060 as a general rule.  By that point, the yeast may start producing undesirable flavor characteristics.  I also only usually save 2 or 3 generations of yeast before starting over.  When saving yeast at home you can only be so clean and will likely cause some yeast mutation down the road.  I remember having a slurry of WLP002 that was a few generations old and the beer I made with it tasted more like a Belgian.  It wasn't infected, but the flavor profile of the yeast had definitely mutated.

Yeast Saving Procedure

Now that I've given you a little background on what you need to get started, here's my procedure for saving yeast:

Sanitize three 16 oz plastic beer bottles along with the other equipment you use to transfer your beer.

Siphon your beer off the yeast cake, but be sure to leave about 1/2 inch of beer behind to help get the yeast back into suspension.

Once the beer has been siphoned off the yeast cake, arrange the sanitized beer bottles in the empty 6-pack holder.  You can see how I distribute them above.  With the lid on your fermenter, swirl the bucket to get the yeast back into suspension with the little bit of beer you have left.  If you still have chunks of yeast sticking to the bottom, use a sanitized spoon to stir them into your slurry.  If you're using a bucket for a fermenter, be careful not the scratch it with the spoon.  A plastic spoon would be your best bet here.

When you have gotten your beer and yeast mixed up into a slurry, place your sanitized funnel into the plastic beer bottles and begin filling them up.  I find that I can fill three 16 oz beer bottles from a standard yeast cake.  You may want to sanitize an extra bottle if it's your first time saving yeast.  I typically will fill each bottle about 3/4 of the way and then go back if I have any yeast slurry left over.  Once the bottles are filled, screw down the sanitized cap fairly tight to ensure a proper seal.  Dry off the top of the cap and apply a label that gives the strain of yeast and the date it was saved.  I like to use the little round garage sale stickers that come in a variety of colors.  This helps me keep track of the different strains easily.

The above pictures show what the yeast slurry looks like after it's settled and been in the fridge for awhile.  You can distinctly see the yeast on the bottom of the bottles.  The pictures on the right show the different strains of yeast that are stored in my kegerator. 

Reusing Saved Yeast

UPDATE (2/7/2014) - I've had a few people email me about how long the saved yeast lasts in the fridge.  I typically like to use the yeast within a few months in an ideal world.  That being said, the longest amount of time I've held the yeast for has been about 6 months.  After that, I'd probably just get a new yeast packet from the homebrew shop and start over.  Also, the bottles can build up a good amount of pressure and it can be hard to get them open without the yeast spraying all over the place.

On brew day, take your yeast slurry out of the refrigerator and slowly unscrew the lid.  Depending on the yeast you saved, it may just sit there or it could try to explode out of the bottle.  I've had both happen to me.  If you want, you can pour off some of the beer that's sitting on top of the yeast, but I usually pour the whole thing into the new wort.

Let the yeast warm up to around room temperature so you don't shock it when pitching it into your fresh wort.  I've actually forgotten to take the yeast slurry out of the fridge until right before I pitched, and I didn't notice any off-flavors by pitching cold.  It's just better for the overall yeast health if the slurry is close to the temperature of the wort.

For beers with a medium starting gravity (1.050 to 1.065 or so) I will pitch one of my saved slurries, or 1/3 of a yeast cake.  There's a really nice yeast calculator on Mr. Malty (Jamil Zainasheff's Website) that calculates how much yeast you should pitch depending on your starting gravity.  Personally, I don't use this website but several people do with great success.  If a beer is over 1.075, I typically pitch 2 slurries and call it a day.

Before I pitch the yeast, I'll give the bottle a good shake.  This gets everything suspended and makes it easier to get all the yeast into your new batch of wort.  After that, just follow your normal fermentation procedure.

If you have any questions about saving yeast or anything else, please feel free to contact me at the email address listed on the bottom of this page.  Thanks for looking and happy brewing!

 

 


Contact Information:  mikeyounghb at gmail.com

 
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