Big beers and attenuation

[pretzelb]

To "celebrate" being stuck at home I gave myself the project to brew high gravity beers each week to fill my kegs. Along the way I made some system adjustments on my 20g eBIAB system mainly where I discovered if I double crushed I could finally hit an OG in the 1.10 range. Normally I never come close but this is the first time I've done big beers back to back. Since I only have 2 fermenters I only give each batch 2 weeks before moving it. I've started to notice that nearly all of them are still in the 1.038 range after a few weeks and one, a Russian Imperial Stout, seems stuck there. So my questions are:

1. Is it normal for high gravity beers to take longer? I've rarely seen an ale need more than 2 weeks to finish. But I've never got my OG this high before.
2. If I find one of them is stuck in the 1.038 range, is there anything I can do to fix it? I was going to try Champagne yeast but I searched here and found quite a few posts saying to not do that.

 

[day_trippr]

Ok, so only because this comes up here so many times...are you checking gravity with a hydrometer - or a refractometer?
And if the latter...did you apply a correction algorithm given the presence of alcohol?

fwiw, I'm running a 10 gallon batch of my imperial chocolate honey stout - 48 hours in right now. Gravity dropped from 1.108 to 1.048 in that time.
It'll typically finish in the high 20s, but I've had at least one batch end up at 1.018 after 15 days. I mash low - 148 for 60 minutes, then step to 160 for 30 minutes, then raise to mash-out temp and fly sparge at a quart per minute.

Anyway, you can always try adding a teaspoon per 5 gallons of alpha amylase powder. It'll randomly chop up long chain sugars and some of the result will be fermentable. If you really want to bring out the drying hammer, try amyloglucosidase...carefully

Cheers!

 

[pretzelb]

Ok, so only because this comes up here so many times...are you checking gravity with a hydrometer - or a refractometer?
And if the latter...did you apply a correction algorithm given the presence of alcohol?

fwiw, I'm running a 10 gallon batch of my imperial chocolate honey stout - 48 hours in right now. Gravity dropped from 1.108 to 1.048 in that time.
It'll typically finish in the high 20s, but I've had at least one batch end up at 1.018 after 15 days. I mash low - 148 for 60 minutes, then step to 160 for 30 minutes, then raise to mash-out temp and fly sparge at a quart per minute.

Anyway, you can always try adding a teaspoon per 5 gallons of alpha amylase powder. It'll randomly chop up long chain sugars and some of the result will be fermentable. If you really want to bring out the drying hammer, try amyloglucosidase...carefully

Cheers!

I check my gravity readings during the brew day with both but after fermentation starts I've always relied on the hydrometer (though I read some posts saying the refractometer should be fine).

I've never used amylase powder, I will look into that.

 

[day_trippr]

Post-pitch fermentation readings with a refractometer require adjustment for the presence of alcohol and then can get pretty close to a hydrometer reading.
Without that adjustment it may appear beer always finish in the mid-30s hence my question (and it really does happen here - a lot).
Anyway, there are many such adjustment calculators on the internet.

As for the amylase, I've used it, it works, just have to give it time...

Cheers!

 

[madscientist451]

There are many variables to consider if the beer has not attenuated to the desired level.
What was the mash temperature?
How much and what kind of yeast was pitched?
What was the fermentation temperature?
Was any yeast nutrient added? (I've found this really helps with high gravity beers)
My experience has been that issues with high gravity beers usually comes down to how the yeast was handled. Making a big starter or re-pitching a yeast cake from a normal strength batch can make a huge difference.

 

[VikeMan]

To "celebrate" being stuck at home I gave myself the project to brew high gravity beers each week to fill my kegs. Along the way I made some system adjustments on my 20g eBIAB system mainly where I discovered if I double crushed I could finally hit an OG in the 1.10 range. Normally I never come close but this is the first time I've done big beers back to back. Since I only have 2 fermenters I only give each batch 2 weeks before moving it. I've started to notice that nearly all of them are still in the 1.038 range after a few weeks and one, a Russian Imperial Stout, seems stuck there. So my questions are:

1. Is it normal for high gravity beers to take longer? I've rarely seen an ale need more than 2 weeks to finish. But I've never got my OG this high before.
2. If I find one of them is stuck in the 1.038 range, is there anything I can do to fix it? I was going to try Champagne yeast but I searched here and found quite a few posts saying to not do that.

1.110 to 1.038 would be 65%+ attenuation. On an Imperial Stout, it may not be "stuck." It may be done. What were the grain bill, mash temp, mash length, and yeast strain?

Also, what FG were you expecting, and where did that expectation come from?

Edit: Oops. I see the OG was 1.100, not 1.110, which would put apparent attenuation at 62%. Still possible it's done, depending.

 

[pretzelb]

Sorry for not including the details. Let me try to cover what everyone asked. It also looked like I was off on the one recipe I was mentioning confusing it for another.

Russian Imperial Stout - Brewing Classic Styles
19 lbs pale 2 row
1.5 lb black barley
1 lb special b
.5 caramunich
.5 chocolate malt (350)
.5 pale chocolate malt (200)
Fermentis US-05 (2 packets)
Mash 154 for 60 minutes
Preboil gravity 1.071
Boil 1.5 hours
OG 1.097 (I got this wrong in my other comment)
Racked to secondary after 2 weeks - pitched another US-05 after reading gravity
FG 1.033 (more than 3 weeks now)
Estimated FG 1.018 (using 81% attenuation for yeast)

The book puts the estimated FG range at 1.018 to 1.030 but it also has the OG from 1.075 all the way up to 1.115.

My initial samples when racking to secondary were overly sweet. I didn't see any activity in the secondary. The last sample I took from the secondary was a small amount just to spot check with the refractometer which translated to nearly the same 1.033 value. The sample wasn't as sweet but still wasn't great.

Without going into the details on the other batches the reason I raised this question was due to the others trending in the same direction. Briefly here's some stats:

Imp Stout OG 1.097 FG 1.033 Estimate FG 1.018 (secondary)
Wee Heavy OG 1.103 FG 1.034 Estimate FG 1.031 (secondary)
Belgian Dark Strong OG 1.103 FG 1.038 Estimate FG 1.026 (primary)
Wheat Wine OG 1.090 --- still fermenting (primary)

Now that I've added the formula to estimate attenuation the stout might be the only one that is a bit high. I haven't taken the Wee Heavy reading again since racking since there was activity. The Belgian Dark Strong will be racked this weekend so at least I can see if it bubbles in the secondary.

I looked into amylase powder last night and might get some to test on the Imp Stout. Sorry for the long post.

 

[VikeMan]

Estimated FG 1.018 (using 81% attenuation for yeast)

Using your grain bill, mash temp, mash length, yeast strain, and an OG of 1.097, BrewCipher predicts an FG of 1.028, which a lot closer to your current 1.033 than an expectation of 1.018.

And just speculating a little here... how confident are you in the mash temperature/your thermometer? e.g. if you were at, say, 158F instead of 154F, the FG prediction changes to 1.031.

 

[pretzelb]

Using your grain bill, mash temp, mash length, yeast strain, and an OG of 1.097, BrewCipher predicts an FG of 1.028, which a lot closer to your current 1.033 than an expectation of 1.018.

And just speculating a little here... how confident are you in the mash temperature/your thermometer? e.g. if you were at, say, 158F instead of 154F, the FG prediction changes to 1.031.

I took my first look at BrewCipher and it's a bit much for me to handle right now - going to take some time later to review it. My estimate was just based on the OG and the estimated attenuation so mash temp wasn't in the equation. But I've added a column to my brew sheet for estimated attenuation so at least I should be in the ballpark now.

Funny you should mention the mash temp because I'm actually considering replacing my current rig with a new eBIAB from Ss Brewtech and one of the main reasons is frustration with the mash temps. I don't have any notes that mash temp was an issue with the imperial stout. I did have a massive temp issue on the wee heavy but oddly enough it seems close to the expected FG. I do check with an instant thermometer while I re-circulate so the mash temp at the top should be what I expect. Does that mean it's also the same around the element? I'm not so sure. Switching to a new system should solve some issues I have with my current setup, but I just hate have to find a buyer for my current stuff.

I still think the imperial stout had further to go but the others might be fine with more time over 2 weeks. The wee heavy did show some decent airlock activity after being moved but I haven't retested it yet. I'm curious to see if the Belgian dark strong also shows activity after I move it.

Except for the stout, I'm wondering if expecting them to finish in 2 weeks is a bad assumption on my part. I never brewed so many big beers back to back before so these stats are new to me.

 

[smata67]

Failing to reach an acceptable-to-me finished gravity is one of the reasons I have shied away from high gravity beers over the years. The only RIS I have brewed was 10 years ago, a 6 gallon batch using an astounding 15# of dark LME, OG of 1.091. In a moment of utter, inexperienced insanity, I pitched a single packet of S04 (per the recipe) (Note: I just checked this recipe again online and the recommendation is now 2 packets- now they tell me!) Of course, I know better now and that took it down to 1.036 and stopped. Subsequently skimmed the high krausen off my next brew, a Wee Heavy, a quart of fermenting wort, and a packet of S05 and dumped into the RIS. I roused for several days and ended up at 1.031. This was in secondary and I ended up bottling at this FG, about 2 months after the initial pitch. So, some suggestions:

1. Do your best to NOT accept 1.03X as the finish gravity. Have doubts about this? Scoop out some of that wort and swirl it around in a glass. Does it remind you of motor oil? Because mine- with a lower starting OG- went to 1.031 and that's exactly what it looked like. It was one of my least satisfying brews, took me 4 years to finish the 60 or so bottles, it was a chore to choke those down, though I eventually did. Much too thick and sweet. So do everything possible to get that FG down to 1.025 or so, there are a number of techniques out there that MIGHT accomplish this. Probably a near impossible task at this point, but I can't think of a better man to give it a go. If you keg/bottle at above 1.030 you will regret it. Ask me how I know.

2. In the future, resolve to shoot for lower mash temps when high ABV is the goal. 154F is too high. 148F would be ideal, but certainly 150F or below. A 154F mash temperature will not get you down to where you need to be FG-wise. Read the BJCP guide for the style: full body, but not overly sweet. That's where people get the idea to mash higher. You will end up stalled and unsatisfied. Simple sugars will give you an early boost, but they are mostly a head fake, won't tell you where you will end up. A difficult style to nail, so don't be disappointed if the first try falls short.

 

[Craiginthecorn]

Most likely, your yeast gave up due to the presence of alcohol and/or insufficient reserves of unsaturated fatty acids due to insufficient oxygenation . With big beers, the rule is more yeast and more oxygen. It can be a good idea to oxygenate a second time about 12 hours after pitching to give the yeast everything it needs.

Adding a packet of dry yeast at this point may not have much effect. I think you must make a starter with some yeast nutrients and pitch that instead. It might even be a good idea to put a drop of olive oil in the yeast slurry about four hours before pitching. The olive oil will help supplement the missing source of oxygen in the partially fermented beer. There have been some reasonable successful experiments with substituting oxygenation with a miniscule amount of olive oil to minimize oxidation in the primary. At this point, you don't want to oxygenate, so I'm thinking the olive oil might be appropriate here.

https://beersmith.com/blog/2015/09/14/olive-oil-instead-of-aeration-for-beer-brewing/

 

[TheMadKing]

I for one intentionally finish my RIS at 1.030. I also increase the hop levels above the style guidelines close to a 1:1 OG/IBU ratio.

That leaves you with a beer that's still balanced, has a massively thick mouthfeel, and after 6 months to a year ends up with some of the best dried fruit/raisin/date/port wine flavors. Those come from slow oxidation of residual sugar and help to smooth out the beer.

In my experience a RIS finishing much below 1.025 will end up harsh and won't smooth out as well.

 

[Brewmasher]

I’m just discovering Kveik now, which is by far the easiest fix to big beers finishing fast. Before that I would use a finishing yeast like WY3711 that has diatastic enzyme ability.

 

[JimRausch]

Except for the stout, I'm wondering if expecting them to finish in 2 weeks is a bad assumption on my part.

I think this may be your key. A high starting gravity is quite a stressor for most yeast. As someone above mentioned, you really have to pamper the yeast- pitch heavy, pitch active, add nutrients, and maybe again a couple days in (something mead folks do all the time), and give it more time than you normally would. You may have taken it away from the yeast too soon.
You may have to pitch a big, active fermenting starter. But I would try the amylase first.

 

[Craiginthecorn]

I don't think the amylase or any other enzymes would help. The implication is that the yeast has exhausted the fermentable sugars. I doubt that's the case here. It won't hurt, though.

 

[Craiginthecorn]

You may have taken it away from the yeast too soon.

Agreed. Big beers take longer to finish. Plus, racking to a secondary is rarely useful and anytime you can eliminate a transfer, you're avoiding another chance for oxidation and contamination. Now, if you need to reintroduce a starter, you'll probably need to move it back to a larger vessel with substantial headspace.

 

[pretzelb]

Agreed. Big beers take longer to finish. Plus, racking to a secondary is rarely useful and anytime you can eliminate a transfer, you're avoiding another chance for oxidation and contamination. Now, if you need to reintroduce a starter, you'll probably need to move it back to a larger vessel with substantial headspace.

And time might be the main factor with maybe the imperial stout that is an outlier. The Belgian strong ale that I just moved to secondary was very active so I hope if it gets 3 or 4 weeks it might reach an expected FG. I've never tried this weekly big beer "experiment" before so it's been eye opening. If I had unlimited space for primary fermentation it might give different results. Since I can only handle two 5g batches at a time for the primary it's revealed some stats that I may have never realized.

I will say I'm very paranoid of contamination after I did have a great wee heavy batch go bad on me last year due to something wrong with my sampling from secondary process. To try and avoid the risk I've bought a few keg lids with stoppers so that they can act as secondary fermenters and also go straight to dispensing once done. The trick is to make sure I don't contaminate them while getting readings. I'm going to work on that but for now I'm happy they are in kegs and hopefully fermenting while outside my chest freezer for the primary fermenters.

 

[TheMadKing]

You may have taken it away from the yeast too soon.

Unless you centrifuge or filter your beer, racking it off the cake won't make any difference. Yeast that has flocculated is effectively out of action and is no longer doing anything. Only the yeast in suspension are still working. So simply racking off the cake will no affect the finished beer other than to possibly prevent off flavors from autolyzed yeast (but this takes a long time on the cake).

 

[VikeMan]

Yeast that has flocculated is effectively out of action and is no longer doing anything.

You may well be correct. However, I've never been able to find any confirmation of this. Do you have any sources for it?

 

[TheMadKing]

You may well be correct. However, I've never been able to find any confirmation of this. Do you have any sources for it?

https://sfamjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2010.04897.x
Here's one good link if you scroll down to the Sugars section below figure 3.

One of the primary theories of why/how yeast flocculate is based on the cells generating lectin proteins on their cell walls. Lectin proteins and sugars occupy the same receptors, so it is reasonable to infer that yeast that have flocculated and remain settled are no longer in the presence of a sufficient quantity of of sugar to inhibit the lectin production, and are therefore incapable of being metabolically active until the lectin production can be inhibited via the addition of fresh sugars.

https://www.cmbe.engr.uga.edu/bche4520/Other/Ch3/Verstrepen et al 2003 Appl Microbiol Biotechnol.pdf
This link is also a good read, and on page 199 it states that flocculation is induced by starvation and stress conditions and

"absence of glucose, sucrose and maltose in the growth medium is an absolute prerequisite for flocculation, as these sugars block the NewFlo flocculin binding sites and thus inhibit flocculation"

Which again infers that yeast which have flocculated are no longer metabolically active because they are physically incapable of passing sugars through their cell walls.

Incidentally, the oxygen section on that same page is interesting from a big beer perspective.

"No flocculation can be monitored during the exponential growth phase, but as soon as the cells stop dividing, flocculence gradually reappears (Soares and Mota 1996; Straver et al. 1993). As the oxygen content of the pitching wort is a major determinant of cell growth, Straver et al. (1993) investigated whether the timepoint at which cells start to flocculate could be altered by modifying the initial wort oxygen content. It was found that poor wort aeration resulted in early and incomplete flocculation, while normal saturation with oxygen both delayed and intensified flocculation. Remarkably, the poor growth and flocculation characteristics of yeast grown in de-aerated medium could be restored by addition of ergosterol and oleic acid to the medium. This indicates that oxygen probably does not act directly on flocculation, but rather indirectly through its importance for the synthesis of unsaturated fatty acids and sterols (Straver et al. 1993)."

I wonder if that means a couple drops of olive oil will get your beer going again OP

 

[VikeMan]

https://sfamjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2672.2010.04897.x
Here's one good link if you scroll down to the Sugars section below figure 3.

One of the primary theories of why/how yeast flocculate is based on the cells generating lectin proteins on their cell walls. Lectin proteins and sugars occupy the same receptors, so it is reasonable to infer that yeast that have flocculated and remain settled are no longer in the presence of a sufficient quantity of of sugar to inhibit the lectin production, and are therefore incapable of being metabolically active until the lectin production can be inhibited via the addition of fresh sugars.

https://www.cmbe.engr.uga.edu/bche4520/Other/Ch3/Verstrepen et al 2003 Appl Microbiol Biotechnol.pdf
This link is also a good read, and on page 199 it states that flocculation is induced by starvation and stress conditions and

"absence of glucose, sucrose and maltose in the growth medium is an absolute prerequisite for flocculation, as these sugars block the NewFlo flocculin binding sites and thus inhibit flocculation"

Which again infers that yeast which have flocculated are no longer metabolically active because they are physically incapable of passing sugars through their cell walls.

Incidentally, the oxygen section on that same page is interesting from a big beer perspective.

"No flocculation can be monitored during the exponential growth phase, but as soon as the cells stop dividing, flocculence gradually reappears (Soares and Mota 1996; Straver et al. 1993). As the oxygen content of the pitching wort is a major determinant of cell growth, Straver et al. (1993) investigated whether the timepoint at which cells start to flocculate could be altered by modifying the initial wort oxygen content. It was found that poor wort aeration resulted in early and incomplete flocculation, while normal saturation with oxygen both delayed and intensified flocculation. Remarkably, the poor growth and flocculation characteristics of yeast grown in de-aerated medium could be restored by addition of ergosterol and oleic acid to the medium. This indicates that oxygen probably does not act directly on flocculation, but rather indirectly through its importance for the synthesis of unsaturated fatty acids and sterols (Straver et al. 1993)."

I wonder if that means a couple drops of olive oil will get your beer going again OP

Thanks for the links! There's a lot to digest there.

In the meantime, I find this statement interesting...
"absence of glucose, sucrose and maltose in the growth medium is an absolute prerequisite for flocculation, as these sugars block the NewFlo flocculin binding sites and thus inhibit flocculation"

Notably, fructose and maltotriose were not included. This seems to imply that (NewFlo strain, at least) yeast begin to flocculate only after the three listed sugars are eliminated, but that some of the cells remain in suspension to utilize maltotriose. Will definitely give it a closer read later.

 

[day_trippr]

fwiw, this batch is following the typical curve for the recipe. Sitting at 1.026 SG, 11.1% abv and a scoche under 75% attenuation now, it's at the top of Fermentis' spec for S04, but I'll give it a few more days ramping another degree or two just to see if it's got anything left in the tank. I never hurry the stout

Cheers!