As brewers restart brewing operations after prolonged shutdown, one of the first considerations will be procuring pitchable quantities of viable yeast. The viability of yeast will suffer markedly when stored longer than 2-3 weeks. Using older stored yeast may result in potential off flavors from autolysis, sluggish or incomplete fermentation, delayed beer production, the presence of unwelcome microbes, and potentially unsaleable beer which translates to lost ingredients, energy, and revenue.

If you need to source new yeast:

• Order new yeast. Be sure to contact your supplier well in advance of anticipated need. Yeast suppliers are also restarting their businesses. Longer than usual wait times for fulfillment of orders and back orders may be common.
• Source fresh yeast from another trusted brewery until your usual supplier can fulfill your needs. Consider acid washing it before use, especially if your brewery doesn’t have the ability to run microbial lab testing, and as long as you are confident your particular chosen strain will tolerate acid washing without loss of viability. (See additional resources below for more information on yeast washing.)
• Consider using high quality dried yeast if your preferred strains are not available in liquid format.

Once you have new cultures:

• Consider brewing smaller batches of beer to ensure healthy pitchable quantities are on hand.
• When you restart with less yeast than needed to fill a production fermenter, consider serial wort additions to increase volume and cell count.
• Store the yeast at 34-38 degrees Fahrenheit for no more than two weeks.

Additional Resources:

• White Labs Resource on Yeast Washing
• Do’s and Don’ts of Yeast Washing