Re-pitching on yeast cake over and over... is there a limit?

[planker101]

I am going to be making the exact same beverage over and over again. I have 3 kegs converted to fermenters that I want to cycle through. Since they are not conicals I have no way to collect the first yeast to fall out and will have to reuse ALL the yeast left in the keg.

I have heard that old/dead yeast cause off flavors. I have also heard that live yeast use dead yeast as food. So if I am constantly in a state of active fermentation will I ever experience off flavors? Are there any other concerns with doing this?

If all goes well I could easily be using the same yeast for a year or more...

My plan is pretty straight forward: Make wort. Ferment. Transfer to secondary at the same time I make another batch of wort. Dump new wort on old yeast cake. Repeat.

Thanks for any input.

 

[mredge73]

You will want to "wash" the yeast between every 2 batches to prevent off flavors from autolysis. Autolysis can start occurring as early as a month so you want to just reuse active yeast.
If consistency is paramount you will want to change the yeast every 6-8 batches or your first and last batch will have a different flavor profile due to mutations and population changes.
Yeast also have a budding limit, your older more hardy yeast cells will eventually get to the point where they cannot reproduce anymore.

 

[Jim311]

I've used the same yeast for 8-12 batches before but I never used ALL the yeast from the previous batch. I would pour out all but about a pint or a quart of yeast slurry, and then pitch my wort on that. I've done it that way a million times and it results in solid active fermentations every time. BUT.. you are going to be WAY overpitching after the first batch if you're not draining any of the old yeast out. Basically you're going to be making like a 2 gallon starter after the first batch and it's only going to get worse from there. While I've never tried it to verify, conventional wisdom says this is not ideal. I've read that overpitching is less of an issue on the homebrew scale than on the commercial scale, but you're going to be really pushing the limits to the extreme here. You're going to be overpitching by like 3500 billion cells or even more and that's just after the first batch.

 

[Yooper]

You generally don't want to pitch on an entire yeast cake, not even once. It's almost always a huge overpitch.

https://www.homebrewtalk.com/showthread.php?t=166221

 

[mredge73]

Biggest problem with over pitching at a homebrew scale is that we don't prepare for it.
You need to use fermcap and a vessel with large head space with a blow off tube.
Fermentation can finish in hours if the yeast is healthy and happy and can skip the lag/growth stage.

 

[flars]

You don't need to waste any time washing yeast with acid or rinsing yeast with sanitary water. Fill a couple of pint canning jars from your fermentor and estimate the number of cells per milliliter depending upon how much hop debris is present. Good read here.
https://www.homebrewtalk.com/showthread.php?t=579350

I will estimate 2 billion to 4 billion cells per milliliter depending upon which strain of yeast I'm using. I do strain hop debris during the pour into the fermentor.

Good calculators to use.
http://www.mrmalty.com/yeast-tools.php
http://www.brewunited.com/yeast_calculator.php
https://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

I stopped counting the times I've reused yeast. Could be well over 10 times for some of the harvested yeast. I have recently encountered a problem with the yeast not rinsing from the bottles using the jet washer. No noticeable difference in the taste of the beer though.

 

[Mainer]

Last summer as an experiment, I ran three saisons onto the same yeast cake of 3711 without washing in between. I went from light to dark, weak to strong, and none had more than a couple ounces of hops. Each one got an addition of some sort, but only after racking to secondary. I didn't notice any off-flavors. The yeast may have been a little stressed, as the second batch had very high peppery esters, but that suited the style. The third one was the best of the three.

 

[Mainer]

(To some extent, it may depend on what kind of beer you're brewing. Since I was making saisons with fruit additions or dry hops, I didn't mind a rustic profile. I wouldn't dare to try it with anything that depends on a clean profile, like a cream ale or any kind of lager.)

 

[planker101]

Probably should have mentioned this is for mead. I brew beer as well, but I was given over 100 gallons of honey and decided to make a crap load of mead. Not really worried about overpitching as my OGs are going to be high, like 1.1-1.3. Also, the yeast strain I'm using barely makes any foam and is a slower fermenting yeast. It is Cote des blancs yeast.

I am not a mead person. As long as it is drinkable I'm fine with it. Additionally, I have a set siphon depth so the yeast cake will be the same size after every run (of course it could get more concentrated, but only to a point). I'll be doing secondary, 3rd, 4th, maybe even fifth rackings so not concerned about pulling a bit too much yeast into secondary.

Any changes on inout based on the new info?

 

[Mainer]

Mead? I've exhausted my knowledge. I'm out.

 

[planker101]

Mead? I've exhausted my knowledge. I'm out.

Haha. Doesn't really matter that it is mead. Just takes out some
other variables. Your info about yeast is useful, thanks for taking the time to share your knowledge and experimentation

 

[DurtyChemist]

I'd say this is the best time to actually find out the real answer. You'll get to see how much "overpitching" changes the flavor of beer since you'll be making the same recipe.

EDIT: Oh you're making mead....yeah I think that takes a lot longer to ferment out than beer so this may take a while.

 

[planker101]

I'd say this is the best time to actually find out the real answer. You'll get to see how much "overpitching" changes the flavor of beer since you'll be making the same recipe.

EDIT: Oh you're making mead....yeah I think that takes a lot longer to ferment out than beer so this may take a while.

Yeah, that is the hard part. Supposed to let mead sit AT LEAST 6 months if not 1-3 years. I spent the last year making some test batches and found that I like this yeast best. However I won't know if the current batches are getting worse until it is too late. Aw well though, I'm pretty sure it will all be drinkable... ish, haha.

 

[mredge73]

So what does your fermentation schedule look like on your mead?
The first batch will need constant nutrient additions during the growth phase.
Ferment for 2 weeks and rack to secondary for 1-3 years.
"Wash" the yeast or siphon off only the white active yeast and use for the next batch.
The lag/growth stage will be really short with these guys so your nutrient schedule will not need to be very aggressive on the second batch.
You really don't want much of the dead yeast in there, the yeast will already be a bit stressed due to moving from a high alcohol environment to a high sugar environment.

Honestly yeast used for mead and wine is so cheap I would just use a new yeast packet for every batch.