I began washing and harvesting my own yeast about a year ago. I got excited and harvested 4 jars from 4 batches in the first month, leaving me with 16 jars of 4 different yeasts. Since I usually brew twice per month, I had a ton of yeast just sitting in my fridge. After using some of this stored (aka old) yeast in beers that came out less than perfect, I began tossing it – hours of work, down the drain. Then I had an idea – why can’t I just harvest clean yeast directly from my starter? After trying out a few techniques, here’s the process that seems most efficient:
Step 1: Make a starter (3 days prior to brewing) that is .5 liter larger than you need for your beer. Since the majority of 5 gallon batches require no more than a 1 liter starter, a standard 2000 mL flask or even gallon growler will work great. In the photo below, I needed a 2 L starter for a 10 gallon batch, so I made 2.5 L.
Step 2: A couple days after making your starter, sanitize a 500 mL (1 pint) mason jar using the sanitizer of your choice. I prefer Iodophor.
Step 3: Fill the sanitized mason jar directly from the starter – if you use a stir plate everything will be in suspension, otherwise shake it up a bit prior to pouring.
As you can see, I poured about 500 mL of wort/slurry from my starter into the mason jar. After just a few minutes, you can already see the creamy white and very clean yeast settling to the bottom of the jar.
Step 4: Place the capped jar in the fridge over night to crash the yeast.
If you plan to use the yeast within a week or so, you can decant the “beer” and pitch directly from this jar. However, if you like to use different yeasts and won’t be returning to your freshly harvested yeast for awhile, you will want to store it in a more hospitable environment. Steps 5 and 6 address how to do this.
Step 5: Fill a 250 mL (1/2 pint) mason jar halfway with tap water then microwave it (without the lid!) for 2 minutes to sterilize and de-oxygenate the water.
Remove the very hot jar and put the lid on (using pot holders… it’s HOT!), then shake it up to sanitize the lid with the boiling water. Let this sit over night to chill to room temp. I usually do this right after harvesting my yeast from the starter.
Step 6: The next day, decant about 80% of the beer off of the pre-harvested yeast in the larger mason jar, making sure to agitate to release the yeast from the bottom of the jar. Then simply pour the yeast directly into the previously boiled water in the smaller mason jar.
Cap tightly and place in the fridge. Within a couple days you will have very clear water on top of a clean and compact yeast cake. When you want to use this yeast, make a starter as usual, decanting most of the water off the yeast, leaving just enough to help break up the cake.
Some of the benefits I see to this method include:
- The yeast is un-hopped and as clean as it’s ever going to be. In fact, this is basically how White Labs and Wyeast grow their yeast.
- Since you’re only making one jar of yeast, you won’t have to store a ton of yeast (some people won’t like this point).
- You don’t have to go through the “washing” process, which is a pain in the arse if you ask me.
- You can brew any beer you want, even a barley wine or RIS, and still harvest yeast, as you’re getting the yeast prior to it fermenting the beer you will ultimately brew. I guess you will need a pretty large flask, though.