Back End Fermentation

Am reading a lot here about concerns about front-end fermentation, my newbie concern is a little different - although the answer may be the same - patience .

Am brewing my first batch - a 1 gallon all grain milk stout. Started it a week ago Sunday - fermentation right from the getgo - a full two inch krauzen - starting gravity 1055 (a little lower than the 1060 target) and within 4 days had a reading down to 1030. That's the good news. The bad news is that it is still at 1030 today (my target is 1016). I have tried warming it a bit, doing a little sloshing around, and no change. No real airlock activity (a bit after each warming or slosh) and no surface bubbles. Initially pitched a full Wyeast pack (more than enough for my gallon). There are no surface bubbles. Do I have to be more patient - give it a week and test again or just accept that this is the end of the line as far as gravity reduction and just wait for some more cleanup and bottle my 3% abv milk stout? It does taste good, but would like a bit more.

What temperature was it at? Did you feed it some oxygen? Which yeast strand?

Give it a few more days, though, and check again, I'd be surprised if it isn't lower than 30.

libeerty said:

What temperature was it at? Did you feed it some oxygen? Which yeast strand?

Give it a few more days, though, and check again, I'd be surprised if it isn't lower than 30.

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Irish Ale Yeast. Some pre-pitching shaking but no "real" oxygen. We have a pretty cool house, so it spent most of its early time around 64 degrees (maybe a little cooler at night). After the first couple of 1030 readings I brought out a heating pad and boosted the temp into the 70s (briefly was in the upper 70s but backed right off that) - this additional warmth brought on obvious signs of active fermentation but no further drop from the 1030 - and that was a few days ago. Since then the temp has been between 66 and 68. Have been considering a return to the heating pad but on a lower setting (have had some concern about taste artifacts from the heat, but have been reading that maybe this far into fermentation that is less of a concern - is that so?). It hasn't dropped a bit in 6 days.

What temp did you mash at?

libeerty said:

What temp did you mash at?

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Target was 158. Had some difficulty maintaining that temperature during the early portion so added an extra 15 minutes. As I said, my initial density was 1055 rather than the 1060 target.

MBuck said:

Target was 158. Had some difficulty maintaining that temperature during the early portion so added an extra 15 minutes. As I said, my initial density was 1055 rather than the 1060 target.

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Hmm... well, honestly, you aren't that far away from the high end of that range, only 5-6 points, so I bet it is still going to taste great. You've already tried stirring the yeast, at some point all of the stirring isn't going to help you and might risk oxidation, so If I were you, I'd leave it alone for another week or more, try to keep it around ~70-72, see if it drops further. And if it doesn't, then it is definitely done, and you are ready to drink it.

Can't speak to why the yeast didn't do its job, though, maybe someone with more knowledge might be able to help you out?

I have a few questions:
How did the sample taste? You said it tasted good, but you wanted a bit more. A bit more of what? Was it overly sweet? How was the mouthfeel? How much lactose did you use?

In my experience with milk stouts, I've not gotten the FG below 1.020, mostly because I use a fair amount of lactose (one pound per 5 gallons). My last milk stout finished at 1.028 and I thought it was going to taste cloyingly sweet and under attenuated. To my delight, the beer was excellent. The gravity numbers don't always tell the full story.

libeerty said:

Hmm... well, honestly, you aren't that far away from the high end of that range, only 5-6 points, so I bet it is still going to taste great. You've already tried stirring the yeast, at some point all of the stirring isn't going to help you and might risk oxidation, so If I were you, I'd leave it alone for another week or more, try to keep it around ~70-72, see if it drops further. And if it doesn't, then it is definitely done, and you are ready to drink it.

Can't speak to why the yeast didn't do its job, though, maybe someone with more knowledge might be able to help you out?

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Yeah, I'm far more concerned with the difference between the 1016 and the 1030 than the narrower 1055/1060 gap. So, you think there is no problem (off favors, etc) with moving the temperature up to the 70-72 range?

MBuck said:

Yeah, I'm far more concerned with the difference between the 1016 and the 1030 than the narrower 1055/1060 gap. So, you think there is no problem (off favors, etc) with moving the temperature up to the 70-72 range?

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I meant the milk stout FG range goes up to ~.1025 or so, so you are not that far off. I know the recipe called for .1016, but it should still be very tasty. At this point, where you are trying to just knock off a few points, I think that temp. is good. It's probably not going to hop down to .1020 all of the sudden, but it can easily crawl to .1024 or so.

Why no focus on aeration? A one gallon batch should be pretty easy to aerate and initial yeast nutrients in wort (oxygen being one of the most important) really sort of "predetermine" your attenuation. 158 is a pretty high rest temp and will certainly reduce attenuation, but only a few percent. Unless you were way heavy handed with the lactose 1.030 is only 44% attenuation from 1.055 and indicative of a problem. The temperatures mentioned are in the ballpark and should not be a problem.
As for the 1 smack pack pitch, it should be plenty ASSUMING GOOD VIABILITY, but how do you really know? Did the pouch swell up tight in a reasonable amount of time? What strain was it?

Pie_Man said:

I have a few questions:
How did the sample taste? You said it tasted good, but you wanted a bit more. A bit more of what? Was it overly sweet? How was the mouthfeel? How much lactose did you use?

In my experience with milk stouts, I've not gotten the FG below 1.020, mostly because I use a fair amount of lactose (one pound per 5 gallons). My last milk stout finished at 1.028 and I thought it was going to taste cloyingly sweet and under attenuated. To my delight, the beer was excellent. The gravity numbers don't always tell the full story.

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Tastes very good. Smoother/mellower in the most recent sample than earlier ones. Also less hoppy (fuggles) than previously as well - maybe something lost there. Not overly sweet and good mouth feel. When I referred to something more I was talking about attenuation - I don't want/need my socks knocked off, but there is no sense of alcohol presence (the numbers say 3%, but who knows ). I used 3.2 oz of lactose - scaled down from a 5 gallon recipe - pretty consistent with yours. If I could get to 1020 would give me 4.6 percent - would be tolerable. . Not totally disappointed for my first time out, but good to strive for perfection. So, you think I should let it be and wait and see? Bump up the temperature? Anything else?

libeerty said:

I meant the milk stout FG range goes up to ~.1025 or so, so you are not that far off. I know the recipe called for .1016, but it should still be very tasty. At this point, where you are trying to just knock off a few points, I think that temp. is good. It's probably not going to hop down to .1020 all of the sudden, but it can easily crawl to .1024 or so.

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Ok, will give the temp bump a try. Thanks

Demus said:

Why no focus on aeration? A one gallon batch should be pretty easy to aerate and initial yeast nutrients in wort (oxygen being one of the most important) really sort of "predetermine" your attenuation. 158 is a pretty high rest temp and will certainly reduce attenuation, but only a few percent. Unless you were way heavy handed with the lactose 1.030 is only 44% attenuation from 1.055 and indicative of a problem. The temperatures mentioned are in the ballpark and should not be a problem.
As for the 1 smack pack pitch, it should be plenty ASSUMING GOOD VIABILITY, but how do you really know? Did the pouch swell up tight in a reasonable amount of time? What strain was it?

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Not really no focus, but new to this and wasn't as aware two weeks ago of the importance of aeration as I am now. Did some initial swirling, but not the vigorous shake that I would now. (did do some shaking since opening day, but not early in the process).

Only 3.2 oz lactose. It was Irish Ale and did swell up tight in just under 3 hours.

The comment on no focus on aeration was really for everyone. None of your variables seem very far except your aeration, which is WAY off. I was surprised no one else commented on it. Where there's smoke there's fire; poor aeration is the smoke, sub-50% attenuation is the fire....

MBuck said:

So, you think I should let it be and wait and see? Bump up the temperature? Anything else?

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At this point in fermentation, it won't hurt, but I don't think you'll get much more attentuation.

Demus said:

The comment on no focus on aeration was really for everyone. None of your variables seem very far except your aeration, which is WAY off. I was surprised no one else commented on it. Where there's smoke there's fire; poor aeration is the smoke, sub-50% attenuation is the fire....

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I suspect there are several factors contributing to the low attenuation in this case. I agree, the lack of aeration reducted the yeast attenuation. Also, milk stouts are not very fermentable by design because of the addition of lactose sugar which is unfermentable by brewer's yeast. The milk stout I last brewed finished at 1.028 and had 57% attentuation even though I used a starter and oxygenated well. I thought it should have been a little higher, but not too much.

Next milk stout, if you aerate well, pitch enough yeast, and maintain good temperature control, you should be in the high 50%, or low to mid 60% range for attenuation which is a little below the normal attenuation for Irish ale yeast due to the lactose sugar addition.

Demus said:

The comment on no focus on aeration was really for everyone. None of your variables seem very far except your aeration, which is WAY off. I was surprised no one else commented on it. Where there's smoke there's fire; poor aeration is the smoke, sub-50% attenuation is the fire....

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Ahhhh. Well, newbie lesson learned. Haven't mentioned it, but so hooked by the brewing bug that went out a bought a second gallon plus carboy the weekend after starting the milk stout and started a pale ale. This time well and thoroughly shaken/aerated before pitching (and did maintain a more consistent mash temp as well). The result was a kraeusen at least double the volume of the milk stout's and more persistent - just starting to diminish on day 5 - despite using only a half tube of White California Ale yeast. So, unless there is something about the formulation of pale ales that leads to this result, it looks like I'm doing better this time.

One last thing has occurred to me. The baster that I'm using to draw my samples isn't as long as I might like, so all my samples are taken right from the surface - and I guess you have to figure that the least dense liquid is floating there. How different would you think these surface samples are from those taken from the center of the carboy? Have been thinking about picking up a thief to address this issue and ease testing without the need to transfer liquid to testing tube. (Of course, have to see if that will fit my carboy neck).

Pie_Man said:

At this point in fermentation, it won't hurt, but I don't think you'll get much more attentuation.

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Thanks, we'll have to see how it turns out.

That high of a mash temp, combined with lactose is going to yield a fairly unfermentable (relatively speaking) wort. Aeration, or lack thereof, may very well be playing a role here too, but I'm leaning towards mash temp. 158 will create a lot of dextrines (unfermentable sugars), and if you were +1 or 2 degrees (always a possibility), even more so.

NordeastBrewer77 said:

That high of a mash temp, combined with lactose is going to yield a fairly unfermentable (relatively speaking) wort. Aeration, or lack thereof, may very well be playing a role here too, but I'm leaning towards mash temp. 158 will create a lot of dextrines (unfermentable sugars), and if you were +1 or 2 degrees (always a possibility), even more so.

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Hmmmm. I've been reporting rookie mistakes, but this one may owe something to old age (failure to put on reading glasses) - went back and looked at recipe and it calls for 153 not 158. I guess the good news is that I had a lot of trouble maintaining my mash temperature (mashed in my stockpot) so I'm pretty sure I didn't exceed my target, but I did extend my mash period by 15 minutes to an hour and a quarter.

MBuck said:

Hmmmm. I've been reporting rookie mistakes, but this one may owe something to old age (failure to put on reading glasses) - went back and looked at recipe and it calls for 153 not 158. I guess the good news is that I had a lot of trouble maintaining my mash temperature (mashed in my stockpot) so I'm pretty sure I didn't exceed my target, but I did extend my mash period by 15 minutes to an hour and a quarter.

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That could easily do it, the temp, not the time. 158 is about the top end for an Alpha rest, so you'd be creating a lot of unfermentables. 153 is right at the lower end of alpha, high high end of beta and would create a much more fermentable wort.

Try rousing the fermenter gently and keeping it warm, but considering the recipe and mash temp, you may very well be done. Like others pointed out, 1.030 is not an insanely high FG for a milk stout, it may be a bit sweet but it'll still be good. Mash temps are pretty important, from one 4 eyed dude to another, always wear your glasses when reading a recipe.

NordeastBrewer77 said:

That could easily do it, the temp, not the time. 158 is about the top end for an Alpha rest, so you'd be creating a lot of unfermentables. 153 is right at the lower end of alpha, high high end of beta and would create a much more fermentable wort.

Try rousing the fermenter gently and keeping it warm, but considering the recipe and mash temp, you may very well be done. Like others pointed out, 1.030 is not an insanely high FG for a milk stout, it may be a bit sweet but it'll still be good. Mash temps are pretty important, from one 4 eyed dude to another, always wear your glasses when reading a recipe.

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Thanks. Things to bear in mind for future brews.

I know higher mash temps produce more unfermentable sugars, but 45% attenuation from 75%??? I doubt just the higher mash temp could make that much of a difference...

Demus said:

I know higher mash temps produce more unfermentable sugars, but 45% attenuation from 75%??? I doubt just the higher mash temp could make that much of a difference...

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Combine those temps with no real aeration.... could easily stick. I have a dude in my club who's participating in a 12 man brew (5 gal each) for a wine barrel. High grav Scottish ale. All of us besides him got ~70% attenuation, he got ~40% (in 5 weeks). Why? Because he thought pouring the wort from kettle to bucket would sufficiently aerate a ~1.090 OG brew. Silly brewer.

Exactly my point...

NordeastBrewer77 said:

Combine those temps with no real aeration.... could easily stick. I have a dude in my club who's participating in a 12 man brew (5 gal each) for a wine barrel. High grav Scottish ale. All of us besides him got ~70% attenuation, he got ~40% (in 5 weeks). Why? Because he thought pouring the wort from kettle to bucket would sufficiently aerate a ~1.090 OG brew. Silly brewer.

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Have been thinking more about this. Does aeration become that much more important because I pitched a full packet (5 gallons worth) for only a 1 gallon brew? Or does the yeast adjust (sufficient "die off" to allow the proper amount to thrive under existing conditions)? I have been reading about its flexibility and natural adaptability, but wondering if this just puts too much stress on its capability.

Going to test gravity again today and will report progress. The pale ale I started last Sunday still sporting lots of foam - dramatic difference from the milk stout.

I don't think it becomes any more or less important. O2 is necessary for yeast to reproduce, and even though you pitched a lot, they needed to reproduce, it's what they do. Low O2 levels = stressed yeast = funny flavors, stuck ferments, etc.

NordeastBrewer77 said:

I don't think it becomes any more or less important. O2 is necessary for yeast to reproduce, and even though you pitched a lot, they needed to reproduce, it's what they do. Low O2 levels = stressed yeast = funny flavors, stuck ferments, etc.

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So,milk stout still at 130. Tastes great. A little smoother, sweetness diminished a bit and hops more prominent. It's been two weeks. Do I bottle tomorrow or give the yeast another week to work its magic?

Pale ale started last Sunday with a half tube of White California Ale, but better aeration, already down to 1024 great taste - a little sweetness and nice citrusy Crystal

MBuck said:

So,milk stout still at 130. Tastes great. A little smoother, sweetness diminished a bit and hops more prominent. It's been two weeks. Do I bottle tomorrow or give the yeast another week to work its magic?

Pale ale started last Sunday with a half tube of White California Ale, but better aeration, already down to 1024 great taste - a little sweetness and nice citrusy Crystal

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Typed Crystal but meant Cascade (although is also Crystal 20 in the grain bill).

NordeastBrewer77 said:

I don't think it becomes any more or less important. O2 is necessary for yeast to reproduce, and even though you pitched a lot, they needed to reproduce, it's what they do. Low O2 levels = stressed yeast = funny flavors, stuck ferments, etc.

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So I gave the milk stout another week to cleanup and bottled today. Gravity still 1030. Taste was even smoother and a touch less sweet. Now a little more waiting.

My Pale Ale only progressed a tiny bit to 1024 - think it may be stuck there. Giving it another week too

Tomorrow trying my first designed recipe. 2-row, crystal 20, Dingeman's Special B with Chinook early and Saaz late and Bunton Ale Yeast and a vanilla bean added after turning off the boil. We'll see how that goes.