Yeast Harvesting and reuse

for what?

 

Thanks - that's definitely a possibility.

 

Think about it like a car window thats been tinted. The film of the tint will keep that window together even if you throw a rock through it. Sure, there will be a hole in the glass and tint, but the area around the hole is still structurally sound.

 

Not sure I understand this . . . most mason jars are graduated in oz/ml and it's pretty easy to measure the slurry quantity once it has settled. With a little bit of interpolation you should have a reasonably accurate ml count of slurry.

Your problem is how to separate 76ml of slurry from a much larger quantity. Easiest way is to give the whole solution a hard shake and pour off XX% of the entire liquid and once it resettles you'll have that percentage of the original slurry amount. I don't know your time frame, but I wouldn't go two weeks without re-starting the yeast. I restart from slurry all the time. Essentially this is what you're doing when you make a starter from a commercial packet.

FWIW, I estimate my slurry at 2B/ml. Not saying your estimate of 4B is incorrect . . . it's just the way I've found works best for me. You will find nothing in Yeast about this.

 

We're using different terminology that's probably confusing. When I refer to ml's of yeast I'm talking about the solid sediment that collects in the bottom of the jar. The liquid above is basically void of any yeast and serves to just insulate/isolate the yeast solids.

When I restart yeast I pour off the liquid and add the yeast solids to a starter, just like I was starting a new commercial packet. If you have too much yeast solids you can separate by shaking and making the entire contents homogeneous . . . then pour off the percentage you need. This will require a couple of days to let it settle out again. Then pour off the liquid and you have YY% of yeast solids from your original amount. If you restart this you want a full blown starter; 1.040'ish wort, yeast nutrient, oxygen, stir-plate. Here is where you want to make an excess to pour off and save for your next brew cycle. Equally important to yeast quantity is yeast health and here's where a fresh starter pays off. This is addressed in Yeast, p133-44.

Lots of variables here: how many ml's of the solid are dead yeast? coagulated proteins? fats? You can eliminate some of these if you don't harvest from your trub, but there is still some guess work involved. My rules-of-thumb have evolved by repeating the process and measuring the results. Expect your process to differ from mine. Caveat: Lots of people post that they never make a starter, may use yeast that's months old . . . and they say their beer is good. Others will recommend just racking your new wort on an old yeast cake.

 

If I were to pour about 1L of say a 2L starter into a mason jar and stick it in the fridge for a future beer and then am told to decant about 90% of the liquid sitting atop the yeast layer before putting into my next starter, what would that decanting process involve? I guess I'm confused as to what decanting means and how to do it. Also once this process is complete, I assume I would build my new starter to 2L using DME and water as I usually would and then add the harvested yeast and begin the whole process over again?