High gravity yeast question

[azazel1024]

So I brewed a Coffee Oatmeal Russian Imperial Stout the other month. I just went to bottle it yesterday.

The OG was 1.112, but the FG was only 1.039. Seems like the S-05 I used didn't get the job done very well. I was expecting it to be closer to 1.03. Is this simply because of the high ABV?

Solutions for the future? It was a 2.5 gallon batch and I pitched a full packet at 80F straight in to the wort and fermentation/Krausen was pretty active after about 5 hours. Fermentation was at 63-67F and I let it sit in primary for 6 weeks before adding coffee grounds and hops for 2 weeks of dry hopping before bottling yesterday (so 8wks total).

So, pitch more next time? Do a second pitching? Need to wake up the yeast first, before pitching into the wort? Or is the attenuation going to drop off with gravity no matter what I do and I need to expect low attenuation once I am getting up over 1.1 OG?

This is my first really big beer, with my previous record a 1.074 Belgian Dupple that ended up at 7.3% ABV (I forget the FG, but whatever that works out to, I think using S-33).

 

[flars]

You under pitched your batch of beer. Check out this calculator.

http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

Pitching directly into the wort without rehydrating the yeast is not a best practice. It is done, but the walls of the yeast cells are fragile. Without rehydration yeast cell viability is lost.

 

[azazel1024]

Would simple rehydration first be a good step forward?

And for a next time I assume doubling my yeast?

Also any chance these aren't going to carb up in bottle now (IE dead yeast)? Or should it still be viable, just underperformed?

Thanks!

 

[ACbrewer]

Would simple rehydration first be a good step forward?

And for a next time I assume doubling my yeast?

Also any chance these aren't going to carb up in bottle now (IE dead yeast)? Or should it still be viable, just underperformed?

Thanks!

It is probable that it will underperform. I've read that usually with a 1.080 or higher the recipes generally call for a 2nd pitch of yeast when bottling.

Additonaly the 'wait 3 weeks' for the carbonation is more like 'wait 8 weeks' when using the original yeast (ie no 2nd pitch) and a high gravity beer.

 

[afr0byte]

Would simple rehydration first be a good step forward?

And for a next time I assume doubling my yeast?

Also any chance these aren't going to carb up in bottle now (IE dead yeast)? Or should it still be viable, just underperformed?

Thanks!

You aren't, by chance, using a refractometer to measure the FG, are you?

 

[azazel1024]

Nope, regular hydrometer dropped in the neck of a bomber after filling it.

It's possible the OG is .001 lower than measured as the brew was around 64F not the calibrated 68F, but, still too high.

Good to know on how long to wait. I was planning on giving it a few months anyway. No issues with bottles busting though, right?

I could always get another packet of yeast, pop the bottles and sprinkle in a few grains, or would that be a bad idea, especially considering how much free sugar there might be?

I don't mind an extended wait on carbing. I figured this for a long aging process.

 

[ACbrewer]

Nope, regular hydrometer dropped in the neck of a bomber after filling it.

It's possible the OG is .001 lower than measured as the brew was around 64F not the calibrated 68F, but, still too high.

Good to know on how long to wait. I was planning on giving it a few months anyway. No issues with bottles busting though, right?

I could always get another packet of yeast, pop the bottles and sprinkle in a few grains, or would that be a bad idea, especially considering how much free sugar there might be?

I don't mind an extended wait on carbing. I figured this for a long aging process.

I would expect that you have pretty much exhausted the yeast from the initial pitch. I would be concerned with only a 65-66% attenuation (typical is usually 75% - hence your 1.030 expectation). Concerned enough to let it ride and not add more yeast to the bottles.

If after 2 months there is little to no carb, I'd probably try 1 or 2 bottles with some yeast and see what happens. Your ABV might be high enough that it would be ok and no bombs, but unless you had a lot of non fermentables, I think you have about 10 gravity points worth of fermenting that could occur.

for comparison, bottling sugar is usually about 1 to 2 gravity points of change. Thus new yeast could end up with about 5 to 10 times as much CO2 as desired and as you say - bombs.

 

[peterj]

You generally don't ever need a second pitch of yeast at bottling unless you've cold conditioned it for a long time or aged it for a very long time (like 6 months or so). With this beer coming out to under 10% I think US-05 can handle that pretty well. It should be fine even up to 12% or so though like others said it may take longer to carbonate.

Also, if you took the gravity reading after you had already mixed in your priming sugar (which it sounds like you did) then your actual FG is probably around 1.037. This would bring you in at about 67% attenuation.

Which brings me to my next point which is that your yeast might not have underperformed at all. There's no way to tell without knowing the recipe. Attenuation is heavily dependent on recipe and mash temp. Was this extract or all grain? What was your mash temp? How much of the grain bill was specialty malts (crystal, roasted, etc.)? If you used extract or mashed high (i.e. above 152 or so) and used a lot of crystal and roasted malts (which I would expect in an Imperial Stout) then I would say 67% sounds about right. You may have gotten a little more out of it if you would have rehydrated, but probably not too much more. Actually your pitch rate looks to be right on if you had rehydrated. When you pitch directly on the wort a number of the cells will die or lose viability, so you might have underpitched by a little but probably not enough to be noticeable. But I really don't think you need to worry about bottle bombs.

Also, you said you pitched the yeast at 80F? That's a lot higher than I would ever pitch. I always pitch at or slightly under the temperature I'm going to ferment at, especially with high gravity beers.

This beer sounds delicious though! I hope it turns out well. I just did an RIS that went from 1.099 to 1.032 and it tastes awesome!

 

[azazel1024]

DOH!

You are right, I did take the gravity reading after mixing in the priming sugar. I never measure precisely on how much water I mix in, but I generally mix about 50/50 priming sugar to water in a bowl and microwave to a boil and then let it cool off before mixing in.

So you are probably right that the actual gravity was a couple of points less (2 ounces priming sugar mixed to 2G of beer I think changes the gravity by about .002 or a little more).

It never occured to me about taking the gravity readings after mixing in the priming sugar...but actually, I think I general do that, though sometimes I take the reading right out of the bucket before mixing in and sometimes I manage to fill a bomber, take a reading, cap it and a bottle or two later remember I didn't mix in the priming sugar and have to uncap and pour back in.

For this one, yeah, lots of crystal and speciality. Recipe was

2.5 Gallon
3.25 Gallon boil
3lb mild
3lb US 2-row
1lb flaked oats
.5lb crystal 120l
.5lb Chocolate malt
.5lb roasted barley
.6oz cascade 90 min
.5oz challenger 15 min
.25oz challenger flame out
S-05

6 weeks primary then .25oz challenger, .25oz cascade, 2oz rough ground trader joe's coffee dry hop for 2 weeks in primary

All grain, BiaB.

Biggest yeast cake I've ever seen. The 2.5 Gallons in primary ended up with basically 2 gallons in the bottle. I didn't quite expect the yeast and torb to eat up quite so much of the final volume.

Next time, 3.75G batch I think. It tastes amazing, even room temperature and flat. I think this one is going to be best servered around cellar temps.

My only questions are, will it carb up and will any bottles explode, but you've put my mind at ease on both of those accounts.

Thanks!

Now I just need to brew up my Duclaw Euphoria clone (Caramel nut brown ale) and bottle my Oktoberfest/Marzen and see if I should brew a larger batch to stash away from Oktoberfest. Then I might look at doing either a Triple or a Quadruple before I switch over to spring/summer beers.

Big beers have me hooked.

 

[azazel1024]

Oh, I forgot to mention, for mashing, since it was BiaB, I mashed in the flaked oats first at 130F and then raised the temp over about 15 minutes to 162F before cutting the heat and mixing in the rest of the grains. Final mash temp was about 156F for 75 minutes before I raised the temp to 165F to mash out and do a second dunking in another pot at 165F for 20 minutes, then mixed the two pots and squeezed every last drop of wort out of the grains I could.

The bit with the oats first starting at 130F is I had read that a bit of a protien rest is a good idea with oats for clarity, though as dark as this is, I don't know that the clarity really matters, but it was pretty clear at bottling time (I also mixed in a half tsp of irish moss with 15 minutes left. I pretty much use Irish moss in all my beers except wheat beers, because nothing seems to really clarify those and I like my wheats cloudy).

 

[hottpeper13]

I think 2oz for 2.5 gal is a bit much for priming a stout. I am in secondary with a RIS and plan on carbing 5 gal with 2.5 oz. Also without oxygenating a big beer like this one your asking for underatenuation.

 

[azazel1024]

Yeah, the over carbing is something I think I've been running in to. Its not often, but maybe 1 in 8 beers I have with foam over. Just this past weekend I had all 4 beers I brought to a club meeting foam over when I opened them, though there I'll grant they had been carried loose on my front seat rattling together and then warmed up from 45F to maybe 65F before opening.

Less than ideal circumstances. I think I need to try .75oz per gallon instead of my 1oz per gallon. For stouts, I think I need to cut it further.