Immediately re-using yeast

[MrHadack]

I have a bock that is ready to be racked to secondary and put into cold storage. I also plan to make another bock-type beer tomorrow using the exact same yeast strain. I have never harvested yeast before, but it seems silly not to use the bountiful supply that is sitting at the bottom of the existing beer's bucket.

My initial plan is:
1. Rack the finished batch to secondary tonight.
2. Harvest a lot of the yeast to an Erlenmeyer flask with some boiled and cooled DME to essentially make a really big starter with it, and wake it up
3. Brew the new batch tomorrow and pour the flask in.

My other thought is:
1. Brew the new batch of beer
2. While the new batch is cooling, rack the finished batch to secondary, leaving the yeast at the bottom of the brew bucket.
3. Drain the cooled wort directly into the brew bucket with the yeast cake already at the bottom.

What's the best way to do it?

 

[Hammy71]

I would suggest a combination of both. I routinely rack my beer to keg or secondary the same day as brew day. Then, using a sanitized measuring cup I pour some of the yeast/trub into it. I use Mr. Malty to determine how much I want to use. There is a tab that says "Repitching from slurry". No need to make a starter or wash the yeast if your making essentially the same brew. Some will take offense to that, but it's what the big boys do. They take the proper amount of yeast from one fermenter and put it in a new one.

http://www.mrmalty.com/calc/calc.html

 

[MrHadack]

Perfect, thanks. I just used the Mr. Malty calculator and it says I will need about 1 cup (250 ml) of yeast. So I'll just scoop that out, plop it into the new batch, and off I go. Thanks!

 

[BigFloyd]

Perfect, thanks. I just used the Mr. Malty calculator and it says I will need about 1 cup (250 ml) of yeast. So I'll just scoop that out, plop it into the new batch, and off I go. Thanks!

I would tend to (and do) lean on the side of a more fresh slurry for a bock (closer to a pint).

Since it's a higher gravity lager, you should up the pitch rate from the base lager rate of 1.50 to make it closer to 2.00. Also, pitch it into wort that's in the mid-40's and well-oxygenated. That will help you achieve the sort of clean ferment profile that you want in this kind of beer.

I've come to prefer this yeast calculator over Mr. Malty- http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

 

[Cyclman]

I would not re-pitch a yeast from a high gravity beer, especially a lager- they are worn out from high osmotic pressure and high alcohol. You could get a stuck fermentation.

Better to take the initial yeast, grow it in huge / stepped starters, and pitch fresh yeast into each batch.

 

[MrHadack]

Hey all,
Just reporting back. I did as I planned (8oz cup) and the airlock was bubbling furiously within 3-4 hours. After 7 days it was already down to 1.016 from 1.066 while fermenting at 50F. I sampled when taking the gravity and I'm very happy with it. I think I will try to time more brews this way and re-use the yeast (or learn to wash and save it.)

 

[MrHadack]

Cyclman and BigFloyd:

Thanks for the advice. I wasn't ignoring your posts, I just had already gone ahead with my plan. I'll check the other yeast calculation web site, and I plan to read up more on re-using yeast to get a better idea how I can do it efficiently going forward.