More Beer Ultimate Yeast Harvester: Repitching question

[dermotstratton]

I have ~250 mL of yeast slurry that I harvested from my conical fermenter with the morebeer ultimate yeast harvester. The harvester has been sitting in my fridge for about a month or so.

From reading through lots of threads on here, I'm thinking I should probably make a starter with this yeast slurry since the yeast has been sitting in the fridge so long and the viability is really low. My other thought is that I have enough yeast slurry to compensate for that low viability?

Which makes more sense?

When I look on the Mr. Malty, you need to adjust the yeast concentration and non-yeast percentage. Is this assuming that you are using viable yeast that has not been sitting around? It doesn't have any way to adjust viability.

If I do need to wake up the yeast, I don't understand is how many mL of slurry I should pitch into my starter. I have a 2L flask and stir plate. Do I pitch the entire slurry into a liter or so of 1.040 wort? or should I just pitch part of the yeast slurry?

Thanks for helping me make sense of the best way to re-use a good quality yeast slurry that has been sitting around for a while!

 

[mbobhat]

From reading through lots of threads on here, I'm thinking I should probably make a starter with this yeast slurry since the yeast has been sitting in the fridge so long and the viability is really low. My other thought is that I have enough yeast slurry to compensate for that low viability?

Which makes more sense?

I would make a starter to wake it up at least, if its ready in 2 hrs then you know its good and you could maybe ditch the step next time.

When I look on the Mr. Malty, you need to adjust the yeast concentration and non-yeast percentage. Is this assuming that you are using viable yeast that has not been sitting around? It doesn't have any way to adjust viability.

Perhaps someone else can speak to that.

If I do need to wake up the yeast, I don't understand is how many mL of slurry I should pitch into my starter. I have a 2L flask and stir plate. Do I pitch the entire slurry into a liter or so of 1.040 wort? or should I just pitch part of the yeast slurry?

I usually let it settle in the fridge for a little bit, then decant off the liquid until most of it's gone, then swirl and pitch the yeasties...there a numerous pics on how to do this, but you want to get the whitish looking line of yeasties that are above all the trub, so you are shooting for that...good luck!

 

[dermotstratton]

Thanks. I guess I'll just throw most of it in a starter and see what happens.

 

[mbobhat]

From what I've read it is pretty difficult to overpitch, and breweries typically add a lot more than homebrewers are called to pitch because of viability and bacteria like you mentioned before.

 

[Jukas]

What process did you follow with collecting from your conical? This will help you guess how much viable yeast you have. You can also look at the yeast as it settled, if you see distinct layers you know you have trub/nonviable yeast with the creamier yeast on the top.

A lot of harvesting recommendations I've seen for a conical suggest dumping the trub about 30-60min after racking to the conical & before pitching yeast. Next dumping again at 3 days or so to get any additional trub and the early flocculating yeast. Then harvesting what's left.

Making some basic assumptions I plugged your slurry into Mr. Malty. The default slurry thickness & non yeast are fairly conservative which means that with 250ml of slurry, assuming it was harvested on 5/15/2012 would be good for a 6 gallon batch up to 1.115 OG. If we change the harvest date to 5/1/2012 to be safe you would still be good for a 6 gallon batch up to 1.085 OG.

I personally would probably have washed & split up that yeast. Taking half for next batch and splitting the remaining half into 2-4 washed jars for future batches.

I'm guessing you've already pitched into a starter and maybe a new batch so this is all academic at this point. Likely you'll have a very quick and vigorous ferment in your next batch. I personally like my starter wort around 1.020 - 1.030 as I want the yeast to be focusing on consuming & reproducing rather than converting to alcohol.

 

[dermotstratton]

Jukas, I dumped initial trub after 36 hours. I then dumped again on day 6. Then I hooked up yeast harvester and let it sit there for 15 more days. I took yeast harvester off and put in fridge. It has been sitting in fridge for 4 weeks now. I didn't get to brew this weekend, so it is still waiting for me.

I don't understand why I would wash this yeast. It has settled out nicely and it is mostly white creamy yeast with a thin layer of beer on top. I can't see the very bottom, but it does not look like there is much trub in there. My plan was t decant beer off top and then pitch most of yeast and leave the last bit to avoid pitching trub as well.

The thing I really don't understand is whether or not I need a starter to "wake up" yeast. Or if it will wake itself up quickly when pitched at appropriate cell count.

Thanks for your reply. I think I understand this much better now, but I still don't understand if viable cells need to be woken up.

 

[Jukas]

Jukas, I dumped initial trub after 36 hours. I then dumped again on day 6. Then I hooked up yeast harvester and let it sit there for 15 more days. I took yeast harvester off and put in fridge. It has been sitting in fridge for 4 weeks now. I didn't get to brew this weekend, so it is still waiting for me.

Altering the calc for a 4/15/2012 harvest date, with Yeast Slurry set to 3.0 and non yeast left at 15% (should be a baseline to err on the side of caution) you could still do up to a 6 gal batch of 1.060 just directly dumping the slurry.

I don't understand why I would wash this yeast. It has settled out nicely and it is mostly white creamy yeast with a thin layer of beer on top. I can't see the very bottom, but it does not look like there is much trub in there. My plan was t decant beer off top and then pitch most of yeast and leave the last bit to avoid pitching trub as well.

I would wash it solely to split up part of it into smaller storage to have a "yeast bank" for future batches of earlier generation yeast. You don't have to and it's certainly YMMV. You may have slanted some originally or prefer to just harvest & repitch through generation X and then start over with a new smack pack.

The thing I really don't understand is whether or not I need a starter to "wake up" yeast. Or if it will wake itself up quickly when pitched at appropriate cell count.

At four weeks old I would make a starter. You could probably warm the slurry to pitching temps, swirl it up a bit and dump it and it will still make beer, but will likely have a longer lag time. Making a 2L starter at 1.020 will get the yeast awake and reproducing. Then you can either dump the entire thing at high krausen, or cold crash, decant off the spent beer and pitch the slurry.

General rule of thumb is up to 1 week from harvesting you can direct pitch, anything longer and it's good to make a starter.