Planning a brew day is one of the joys of summer.  And nobody wants their brew day canceled or rescheduled due to dead yeast.  

"Is My Yeast Dead?"

As one of the leaders in homebrewing, we get asked this question a lot.  To ensure we are giving the best answer, we decided to do some experiments to see just how well liquid yeast holds up, while in the hands of the delivery service.  Here are the results of those experiments.

For all 3 versions of our experiment, we started off by ordering 3 ordinary White Labs California Ale Yeasts, directly from White Labs.  White Labs is located in California, so our yeast was delivered about two days later to our main homebrew shop, in Ann Arbor, Michigan.

We stored all 3 packs in our shop refrigerator for 6 weeks.

Yeast Viability: Experiment #1 - Box With Ice Pack

For Yeast Viability: Experiment #1, we mailed one package of White Labs California Ale yeast all the way back to California.  Remember, the yeast package that we shipped back was 6 weeks old.  The shipping department at Adventures in Homebrewing packed the yeast in a regular cardboard box, with an ice pack.  Now, you are probably wondering about the temperature.  This shipment, as well as Experiment #2 and Experiment #3, took place during the first week of July,   Hot in Michigan, hot in California, and hot everywhere in between.  The yeast was shipped out on Monday and arrived in California on Friday.

Yeast Viability: Experiment #2 - Box Without an Ice Pack

Again, for Yeast Viability: Experiment #2, we mailed our 6 weeks old White Labs, California Ale, all the way back to California, during the first week of July.  This yeast was shipped the exact same way as Experiment #1, but this time we left out the ice pack.  The yeast was shipped out on Monday and arrived in California on Friday.


Yeast Viability: Experiment #3 - Mailing Envelope With Ice Pack

For Yeast Viability: Experiment #3, we again sent our 6 weeks old White Labs California Ale all the way back to California, during the first week of July.   This time, we did not use a box but packed the yeast into a mailing envelope lined with bubble wrap.  The yeast was shipped out on Monday and arrived in California on Friday.


Results

We partnered with White Labs to complete a set of viability tests on each of the yeasts that we sent.  Each of the yeasts arrived on Friday to their California location.  This means, that our 3 packs of yeast toured the country for 5 days on the back of various delivery trucks.  On any given day of deliveries, the temperature in the back of a traditional UPS or USPS truck can soar to 140° and higher.  This does not seem like a fair fight for the lonely little package of California Ale Yeast.

However, once the yeast was given to the Analytical Lab Supervisor at White Labs, they were able to look at and test each package for viability.  Here is how they did.

Yeast Viability: Experiment #1 - Box With Ice Pack
  • This package of California Ale Yeast was tested to be 93.8% viable.  
Yeast Viability: Experiment #2 - Box Without an Ice Pack
  • The California Ale Yeast sent without an ice pack was tested to be 93.3% viable.
Yeast Viability: Experiment #3 - Mailing Envelope With Ice Pack
  • The yeast mailed in an envelope tested to be 91.4% viable.