3 Tips for Harvesting and Storing Yeast
Brewing.guru
3 Tips for Harvesting and Storing Yeast
Navigating the intricacies of yeast harvesting and storage can be daunting, but it's a game-changer for any brewer looking to elevate their craft. This article distills the collective wisdom of seasoned brewing professionals, offering pragmatic tips to ensure your yeast yields its fullest potential. Readers will discover the essentials of starting with quality wort, producing a viable yeast slurry, and implementing effective long-term storage solutions.
- Start With High Quality Wort
- Create a Yeast Slurry
- Freeze Yeast for Long-Term Storage
Start With High Quality Wort
A high quality yeast harvest begins with high quality wort. Proper levels of calcium, FAN (Free Amino Nitrogen) and zinc play important roles. Milling grain as close to brewing as possible ensures you'll get the FAN and minerals available from the grain. Zinc often has to be added at the end of boil, but don't go too far because zinc also assists in yeast flocculation, so too much can stall fermentation.
Whole careers and many books have been spent on this subject, so it can't be fully covered in a blog.
Proper pitching rates and oxygenation are the next layer to quality harvest. Too little of each and the yeast will underperform and perhaps create under-attenuated or off-flavor beer. Neither makes for a good harvest.
Getting to the best part of the yeast involves dumping early "spent" yeast and harvesting the creamy, light-colored center of the yeast cake. Typically, the right time is just as fermentation is slowing. Sometimes a soft crash helps fluffier yeast flocculate well enough to harvest. You don't want the yeast that stays in suspension. If all the above conditions are met, your yeast will have all the sterols and stamina for a week or so of storage before repitching.
An additional but optional layer of raising quality is to wash the yeast. We use a little dioxy-chlor for storing and feed with a little wort. This is a very important step if you have to store longer than a week. Best to use it before two weeks, but in a pinch we have successfully refed and repropagated yeast that gets a little older.
Create a Yeast Slurry
When harvesting yeast, my go-to method is to create a yeast slurry from the sediment at the bottom of a fermentation vessel. Nothing too revolutionary, but it tends to work well. The process is pretty simple. After siphoning off the beer, I sanitize jars and collect the remaining yeast and trub mixture. I then wash the yeast by adding sterilized water, allowing it to settle, and decanting the top layer to separate viable yeast from debris. Storing the washed yeast in an airtight jar in the refrigerator ensures it remains viable for weeks.
Freeze Yeast for Long-Term Storage
For long-term storage, freezing yeast is an effective method that has worked for me without any particular muss or fuss. I prepare a yeast slurry and add a cryoprotectant, glycerin in my case, at a ratio of 1:1 to protect cells from freezer damage. After thorough mixing, I divide the slurry into small, sterilized containers and freeze them at -4°F. To maintain viability, I label each container with the strain and date. Reviving frozen yeast involves careful thawing at room temperature and making a starter to ensure healthy fermentation activity before pitching.
