Freezing Yeast


Homebrewers often find they would like to have yeast at the ready, to defray costs or to be able to collect strains that are not readily available and grow them to a practical amount of yeast. I looked into yeast ranching with slants and decided the chore of sterilization and reculturing would be too much for me to handle. An excellent book on that subject is “First Steps in Yeast Culture” by Pierre Rajotte.

I decided to look for a different method and tried freezing yeast with glycerin based upon posts on rec.crafts.brewing. My results using a frost-free freezer were a total disaster. The freeze/thaw cycle of the fridge caused the yeast to die. The idea is when freezing/frozen the glycerin helps to keep the cell walls of the yeast from bursting. The freeze/thaw cycle can be the kiss of death depending upon how the yeast are stored.

 A few years later a brewer suggested I try a non-frost-free freezer and gave me a protocol. He used a lab freezer at –80ºF and a 15% glycerin solution. I had a regular upright freezer at work that ran about –5ºF and decided to give it a whirl.

 Here is the protocol I utilized (Many thanks go out to Brad Nicholson).

 Necessary materials and equipment:



Yeast slurry (from bottom of starter)

Pipette (or other measuring method)

Test tubes and caps (sterile, or sanitized)

Masking tape

Permanent marker

 The #1 thing to do is to have surfaces and equipment sanitized. Take nothing for granted.

 1)      Mix glycerin and water in the ratio of 30 ml glycerin to 70 ml water. This will yield a 30% glycerine solution.

2)      Microwave the mixture until boiling.

3)      Remove to the counter, cover with saran wrap and allow to mixture cool to room temp.

4)      Add equal amounts of the 30% glycerin solution and the yeast slurry to the test tube. (The amount will be dependent upon the volume of the tube.)

5)      Cap the tube and shake.

6)      Mark a piece of masking tape with the yeast type and label the tube.

7)      Freeze

 Glycerin can be purchased at most local drug stores, but can sometimes be difficult to locate in the store. Be diligent and you will find it. If in doubt, ask the pharmacist and they can point you to it.

 You now have a frozen tube that is 15% glycerine and yeast. When I get a new strain, I try to make at least 3 tubes from the starter slurry. My procedure is to hold my finger on the end of a pipette and stick into the slurry and remove my finger allowing the slurry to be sucked into the pipette. I transfer that into the test tube as many times as necessary.

 My yeast samples were kept frozen in the freezer, but eventually I had to remove them from my employer to the house. I put them into a cooler with ice packs and brought home. I then placed them into a thick foam cooler with frozen ice packs to prevent the freeze thaw cycle of the frost-free freezer from killing the yeast. Recently I revived the yeast by putting them on a stir plate with a small amount of starter wort and gradually adding more wort over time. The yeast revived perfectly after more than a year of frozen storage. The only caveat is the yeast had to grow so the results took longer than yeast abuse.


Another great page on freezing yeast is Mike D’Brewer’s entitled Yeast Harvesting and Freezing. I was going to take pictures for this page, but his are excellent.


Starters and Pressure Canning Wort

When I originally started brewing, I never made a starter. I had decent results, and whenever I made a beer with an original gravity higher than 1.060 I always tried to reuse yeast from a previous batch. The reason I didn’t make a starter was not because I didn’t think I needed to for proper fermentation and reduced lag times, it was because I HATE TO MAKE A STARTER. More on that in a second…

If you want to make a starter the traditional way, then Mike Uchima has an excellent page on that called Making Yeast Starters.

My problem was, I just could not stand spending 20 minutes to an hour getting yeast ready for the brew day. What I really wanted to be doing was brewing. Also, I hated being a slave to the smack pack. I always found that waiting on those things to swell was an absolute pain.

Then I found the “Confesions of a Yeast Abuser” page, although recently Domenick Venezia has renamed the page Yeast Starter – With Stirring Aeration.

I swapped a buddy some homebrew for a stir plate, and was off to the races. I modified the original procedure slightly. I figured if the outer pouch contains the yeast and the inner nutrients necessary for yeast growth, why am I adding YNB. So I just smack the pack and immediately put the package contents into the stirred starter.

Also the article refers to the stirring as aeration. I believe this to be true initially, but after the fermentation of the starter begins, the starter is giving off CO2, so with an outflow of CO2 from the starter container, I cannot see how much additional air can be getting in. I believe the stirring helps get the yeast in contact with the wort and adds air, which leads to a larger yeast population. Of course all this is conjecture on my part, but it works like a champ.

Here is a picture of my stirrer, an Erlenmeyer flask, and a mason jar.

Now I was no longer a slave to a smack pack, but I still had to make the dreaded starter. Very soon I tired of making the starter. I found it to be boring and tiresome.

So I searched a little more and read a few articles on Canning Wort. Unfermented beer wort pH is not low enough (4.6) to be considered safe for just water bath canning. A temperature of 240 F for 15 minutes is necessary to kill Botulism spores that could eventually produce deadly toxins. 240 F happens to be a pressure of 10 psi in the canner. In my own pressure canning of wort, I use 15 psi, 250 F, for 15 minutes. For more on canning you should check out the National Center for Home Food Preservation, and for more on botulism take a look at the CDC website.

This is my pressure canner.

It is an All American, and I obtained it off Ebay for $25 (a steal). It will hold 7 quarts, or 6 quarts and 2 pints, as shown in the picture below.

I like having some of both size canned, that way if I want to step up a starter while stirring, I can use more or less wort as needed. Wort will darken slightly in the canner, and will also undergo the boil. The picture below shows wort that has been pressure canned on the right, and on the left is wort awaiting canning.

It is a little difficult to tell the color difference, but you can definitely see the hot break in the bottom of the jars.

My procedure is to mash a grist of 100% Pils or Pale malt and after the sparge to can the unboiled wort. This gives me quite a few starters. The day I took these photos, I canned 22 quarts and 12 pints, as shown in the photo below.

So for starters, my procedure is to first use impeccable sanitation. The I smack the smack pack and dump the contents into a flask or mason jar and add the canned wort and the stir bar and place the starter on the magnetic stirrer. I then cover the top loosely with plastic wrap, or an airlock. Usually I have aerated the wort by splashing before and as I add it to the flask or jar. I really like the method because I am not tied to a smack, and I am not tied to a starter. Also when I pressure can starters I am brewing an entire batch of beer, which is what I wanted to do in the first place!