Reusing Yeast Harvested from a Conical

[dermotstratton]

So, I've listened to a few podcasts by Jamil and John Palmer and read as many threads as I could about harvesting and reusing yeast, but I haven't been able to find an answer to my question.

I brew ~ every 3 weeks. I have one conical fermenter that I just started using. I dumped the trub after 4 days of primary fermentation and then harvested yeast ~ 4-5 days later. I have the yeast sitting in a my refrigerator right now.

I would ideally like to use that yeast 2-3 weeks from now. From what I gather, if you are using the yeast within a week, you just just pitch the whole slurry into you next batch, but I need to wait 2-3 weeks. Should I make a starter or can I still just dump the slurry into the next batch?

Do I let the yeast come back up to room temperature if I am pitching it directly into my next batch? or if I'm making a starter?

I'm trying to assess how well my yeast will perform in its 2nd, 3rd, 4th, etc. generation. Everything I read is that yeast hits its prime after a few generations and is actually much better than just using a fresh white labs tube.

Does this still hold true if the yeast sits waiting for 2-3 weeks to be used?

Thanks!

 

[osagedr]

You can use it after a few weeks. You typically will not need to use the whole yeast cake. Use a pitching rate calculator like the one at www.mrmalty.com that takes harvesting date into account for calculating viability to help you get the right number of cells into your next batch.

If you are storing your yeast longer than a few weeks before re-using, you may as well just rinse it (see the yeast washing sticky thread in the fermentation and yeast forum) then make a starter. May as well give your batch the best chance you can. Everyone has their own guideline on how long they will store slurry before repitching it without a starter. Personally I think 2 or 3 weeks is okay but YMMV.

 

[dermotstratton]

So assuming I keep everything clean and sanatized, storin my yeast for 3 weeks will not have a negative impact on subsequent generations of yeast? I should still be able to pitch yeast that is "better" than a first pitch from a WL tube?

 

[osagedr]

I really would check the mrmalty.com calculator to see how your viability is affected. According to Mr. Malty if you harvested it yesterday your slurry is 92% viable. A week ago is 82%; two weeks ago is 71%; three weeks ago is 60%. So you might need 100 ml (four-tenths of a cup) of a yeast harvested yesterday to inoculate 5.25 gallons of a 1.055 ale. If you harvested it three weeks ago you need 154 ml which isn't much more (except in percentage terms). People tend to dump a lot more slurry than they need into their brews--it's a little thing, why not do it right?

But yeah, keep it in a sanitized jar with as little air as possible and you are pitching something that IMO will give you a great fermentation.