Crazy attenuation? Fermentis

[AsharaDayne]

Hi,

Assuming my readings and calculations are correct, I routinely get super strong attenuation out of my Fermentis dry yeasts (S-04 mainly, T-58 did it too), to the tune of 95% AA. I do think the hydrometer's functional. As for attenuation/ABV, I plugged formulas into an Excel sheet (not that the AA calculation is that complicated)...

I use extract with no more than 10% steepies, can that explain why it always goes way beyond the advertised 75% AA? Or is it just normal and the lab is giving a very conservative attenuation estimate? Not that I'm complaining about using less malt for my ABVs, but it does get me curious.

 

[GFHomebrew]

Wow 95% that's Crazy healthy fermentation if not maybe a little excessive. If I recorded that from a standard Ale yeast I'd think maybe I've got an infection in there? Your beers with these super high Attenuations taste ok?

 

[Hogarthe]

I'd check your hydrometer.... Extract usually isn't that fermentable and s04 usually isn't that attenuative. Something is going on there.

 

[The Brew Mentor]

Could you give us some examples of your OG/FG and the temperatures of the samples?

 

[J A]

You almost certainly aren't getting that actual level of attenuation from those yeasts. I've had T-58 go to 84% or so on a second pitch and S-04 might hit 80 with the right conditions but if you're actually getting that attenuation, you've got some help from you local micro-fauna.
You'd know if you were drinking something with attenuation in the 90s...very dry almost like a sparkling malt wine.
As Hogarthe says, a hydrometer check is in order.

 

[Nosybear]

I have a couple of hypotheses: Either your measuring equipment is wrong or you have an infected batch of beer. Measure some water with your hydrometer. It should come out near zero, which, given the results you reported, would tell you it's close enough for jazz. You don't have to use distilled water for this test, tap water will do. Then taste the beer for off flavors and thin mouthfeel. The attenuation you report is something like champagne and if real, should taste similar (very dry).

 

[AsharaDayne]

Thanks everybody, well the hydro does read 0 in water. I do like the taste of the beers and there's no obvious off flavour. So something might be wrong with the measurements. However they do line up with calculations from the recipe builder.

Now the hydrometer is in Plato and I convert to SG, but I feel like that shouldn't be an issue (using online calculators). Though I do think I'll get a new hydro soon.

A few examples:

Comet PA 1,05 1,005
Saaz-Gla-Cas 1,062 1,003
Ariana PA 1,057 1,0035
T-58 PeGlaCom 1,07 1,004
Hoppy Dark 1,048 1,002
SaazPerle-pecas 1,045 1,006

 

[J A]

Now the hydrometer is in Plato and I convert to SG, but I feel like that shouldn't be an issue (using online calculators). Though I do think I'll get a new hydro soon.

You can simply switch your recipe to Plato if you want. There's a setting in the "More" dropdown in the recipe calculator that allows you to toggle between SG and Plato.
I still suspect some sort of measurement error, either temperature or conversion or something. Extracts in particular are not known for high attenuation unless you're using a high percentage of simple sugar in the mix.

 

[Mark Farrall]

Current sitting at 110% AA for a US 05 kettle sour. It dropped 15 SG points to as low as 0.993 when I added the dry hop and is now slowly drifting back up a few points (thankfully, really prefer this one with the ABV closer to 3 than 4). Not that I routinely get that attentuation, but I do see it from time to time.

 

[AsharaDayne]

Temperatures of the samples aren't extreme enough to account for the difference, I should think.

Now that I look at my records, I do notice a FG dropoff at some point, which might coincide hydrometer switch. I'll get a new hydro and see if anything changes.

What's the maximum attenuation one can expect from S-04? Assuming a "normal" wort without added sugars?

 

[J A]

What's the maximum attenuation one can expect from S-04? Assuming a "normal" wort without added sugars?

My average is around 77 or 78 with that yeast. I've gotten as low as 75 or so and 81% seems to be the highest I've gotten with it.

 

[Ozarks Mountain Brewery]

any yeast that states higher than 78 I set it back to that, that's the common attenuation I get with most all yeasts unless it's a dud

 

[AsharaDayne]

So the last few batches, final gravity has magically gone up. I'm still at around 80% AA, but a 5% difference is no cause for concern.
Both old and new hydro concur on the readings.

Now I haven't left those recent batches as long as the previous ones. my current tackle is to consider them done when they're in the ballpark, a bit lower than predicted FG. During the high-attenuation phase they'd sit in the (primary) fermentor for at least a month and gravity would creep down over time. Does a longer sitting time allow for some kind of long-tail fermentation?

Elsewise it might be infection, but the beers didn't seem especially suspicious to me. *shrug*

 

[J A]

I used a re-pitch of S-04 on a couple of batches recently that really jumped in attenuation but only to about 84-85%. The first is an Irish Red/Strong Bitter 15 gallon batch and I pitched a good quantity of slurry and threw in a rehydrated packet of Nottingham just to be sure I had a big pitch. The Notty has an average of around the same as S-04 but it has a reputation for going lower. That could be a factor, but based just on averages, it's the same. The other batch is a DIPA that was supposed to get a slurry from a US-05 fermentation, but that went bad. The S-04 slurry from the Irish was the only yeast I had ready at pitch time so in it went. Last sample of that (day 4) was at 84% - not really what I wanted in a big beer like that but, we'll see how it turns out.
I attribute some of the extra attenuation to pro-level pitching and proper oxygenation. Maybe the first batch you mentioned was just a perfect storm of conditions for happy, healthy yeast cells.

 

[Nosybear]

So the last few batches, final gravity has magically gone up. I'm still at around 80% AA, but a 5% difference is no cause for concern.
Both old and new hydro concur on the readings.

Now I haven't left those recent batches as long as the previous ones. my current tackle is to consider them done when they're in the ballpark, a bit lower than predicted FG. During the high-attenuation phase they'd sit in the (primary) fermentor for at least a month and gravity would creep down over time. Does a longer sitting time allow for some kind of long-tail fermentation?

Elsewise it might be infection, but the beers didn't seem especially suspicious to me. *shrug*

If you're reusing yeast, you're likely leaving the least flocculant yeast behind in the beer, the ones that chew up the last few points of gravity. In essence, by reusing yeast, you're selecting for future generations of less flocculant yeast. Given what you say, your reused yeast would have a lower population of non-flocculant yeast that could build over time and produce the "long tail" fermentation you mention.

 

[GFHomebrew]

I recon the same would happen for those who decant their starters the least floculant go out with the bathwater.
As with packaging beer the least floculant continue into the serving vessel.
So maybe not a big difference how floculant yeast are ecept for what I hear as genetic vairiabilty from the mother culture. Meaning the more you reuse the yeast the further from it's original fermentation characteristics you go.

 

[J A]

I've been doing a lot of research on conical yeast harvesting and there's definitely an art to selecting the right yeast for re-use. Lowest layer is the stuff that quit too soon and dropped out, top layer is the stuff that didin't floculate and may have kept eating sugars, middle layer is the good stuff that's most likely to behave consistently through several generations. Hard to pick and choose with a bucket or carboy but since you're likely taking the whole slurry, it's probably a pretty good mix of all the different manifestations of the original reproduction.

 

[Nosybear]

I recon the same would happen for those who decant their starters the least floculant go out with the bathwater.
As with packaging beer the least floculant continue into the serving vessel.
So maybe not a big difference how floculant yeast are ecept for what I hear as genetic vairiabilty from the mother culture. Meaning the more you reuse the yeast the further from it's original fermentation characteristics you go.

Somewhat, but we're only talking about one generation. And yes, dumping the flocculant individuals is decreasing the genetic variability of the yeast (strange as it sounds). But even that, decreasing variability, would change the fermentation characteristics.

 

[Nosybear]

I've been doing a lot of research on conical yeast harvesting and there's definitely an art to selecting the right yeast for re-use. Lowest layer is the stuff that quit too soon and dropped out, top layer is the stuff that didin't floculate and may have kept eating sugars, middle layer is the good stuff that's most likely to behave consistently through several generations. Hard to pick and choose with a bucket or carboy but since you're likely taking the whole slurry, it's probably a pretty good mix of all the different manifestations of the original reproduction.

From what I can read, best way to harvest yeast is to skim at high krauesen.

 

[J A]

From what I can read, best way to harvest yeast is to skim at high krauesen.

For starters, yes. For full-pitch slurry, you won't get enough yeast that way. The top-cropping and splitting off fresh starters is probably the best way to keep a consistent colony going.