Pitching Rate for Harvested Yeast

[HollywoodTK]

Hi all,

I've recently begun harvesting yeast from some of my more frequently used yeasts, and have finally gotten around to deciding to use one. However, I'm looking for a little advise/insight into the pitching rate of this slurry and was hoping you folks could offer some advice/experience.
I am brewing another 2.5 G, 1.059 OG, iteration of my ESB using 1968 (London ESB). I have one mason jar mostly full of harvested yeast.

I would estimate that the jar has about 425 ml in it, 375 of which would be "compacted" yeast, and the rest the remainder of the previous beer. This yeast was harvested on Sept. 8, 2016 and has been kept in the refrigerator since.

Using most yeast calculators, I get a viability of around 60% given the harvest date. I have assumed a viability of 50% for the sake of conservativism.

Most of the information I have found shows that typical yeast concentrations of harvested slurry range from 1 to 5 billion cells per ml slurry. Assuming a slurry with 15% other trub material (Hops are strained just after chilling) and a concentration of 1.5 billion cells per ml slurry (again, for the sake of conservativism), MrMalty indicates that I only need 165 ml of this solution to pitch into a new 2.5 Gallon beer to pitch an adequate 100 billion cells.
Mathematically, this makes sense to me, but does this sound reasonable to you all?

The way I would pitch would be to let the solution warm up to room temperature prior to pitching, then pour the slurry into a measuring cup to the approximate required volume, then dump the rest down the drain; I will re-harvest after fermentation. Does this sound reasonable?

My alternatives are:
1) use this information to build a starter, then pitch as appropriate and pour the rest back into a re-sanitized jar

2) re-suspend the yeast into the solution to make it a slurry, then add a small amount of sugar in order to "proof" the yeast.
Thanks for any input you guys can provide. Cheers!

 

[TheMadKing]

I think all of your options sound good. You've clearly done your research and that is very refreshing for yeast harvesting questions!

Unless you have any concern about the yeast being dead (over heating, freezing, etc) I wouldn't worry about your alternative 1 and 2 options. The only thing those buy you are complete peace of mind that your yeast is viable, but they also introduce more opportunity for contamination/infection. If it were me, I would just pitch my 165 mL of slurry and call it good.

Your question is really opinion based, so you'll probably get different responses from different brewers. Good luck!

 

[Sadu]

For 7 week old yeast in a 1.059 beer you can get away with pitching as is. Personally I would do a vitality starter as insurance. I take a pH sample at 20 mins into the mash, then dilute boil and cool the sample wort and add it to my yeast so they have a couple of hours to get active before pitching to the full wort.

 

[Kampenken]

Interesting thread, and I hope it gets some legs, as I'd like to hear opinions, especially if backed by some empirical evidence (would be great).

I am unaware of any "proof" of over pitching and its impact on beer. I harvest somewhere in that volume, sometime less, sometimes more, some with more trub due to dry hops than others (most of my hops are filtered before they reach the fermenter thanks to the Grainfather, my hop basket and my use of a filter when filling.

I also tend to brew 5.5-6g batches. So, without having run any tests (or exBeeriments) and very much enjoying my beers, I do wonder if there would be a difference. Anyone have any knowledge of over-pitch issues? How much, what was your perceived impact? I am loathe to change my process if there is no upside, but am open to change, if there is a reasonable one to consider. Cheeers.

 

[HollywoodTK]

All good input, thanks all.

Regarding the vitality starter using some boiled mash, I like the idea, but is there any concern about just how much of this wort should be used? And, are you (Sadu) using the first runnings, or are you watering down prior to the quick boil? I don't want to toss the yeast into 1.08 gravity wort from the get go...

I will try pitching as is with roughly 200 mL. I feel that that is a safe estimate based on the factors involved, and I doubt that would run the risk of over pitching by a significant amount. I can see if I pitch a 3L starter into 1.04 wort there might be some issues with overpitching (though I haven't done enough reading on overpitching to be sure what) but throwing in a couple billion extra cells would be within any reasonable margin of error and cannot hurt as far as I'm concerned.

 

[shortyz]

the only thing i have found with overpitching is that yeast go wild producing a bit more heat... as long as you can keep that under control ive seen no real difference over throwing half a mason jar in versus a full one... To be honest i would rather overpitch because i find my beer finishes faster.

 

[Sadu]

With my vitality starters I take my pH sample, 100ml or whatever, add the same amount of water to dilute then boil 10 mins. This normally comes out at about 1.040 but I don't always measure. I do 1 gallon batches so typically I am pitching 20-50ml of slurry. I prefer to over pitch too though I try to keep it within reasonable distance of what the calculators say.

 

[thaefathan]

Chris White recommends making a starter to help the yeast out with the end of fermentation. Making alcohol isn't the only goal. He talks about it somewhere in here: [ame]https://www.youtube.com/watch?v=AbMedkH9_P0[/ame]

The general rule is that more yeast lead to less esters, but more fusels.

I would do your alternative number one, I consider that yeast you save as a cleaner 2nd generation, instead of re washing after your beer is done.

 

[RM-MN]

http://byo.com/bock/item/1967-pitching-rate-experiment