Stalled fermentation?

[The_Jester]

Hopefully you kids can help me with this one.

I'm fairly new to homebrewing, and I'm still doing partial mash. My first few batches were okay, but my last three have all been problematic, in that the fermentation seems to be stalling.

For example, in my most recent batch, a stout, it went into the pail at 1.074 and a double dose of Wyeast Irish Ale propogator. It looked good for the first couple of days, all scummy and foamy and such, then stopped and fell clear (after about 5 days) at 1.036. It should have dropped 20 more points!?!

Temperature shouldn't be a problem, as it stayed between 18-22 degrees. The yeast must have been healthy, since it started okay.

I'm at a loss. Any suggestions would be greatly appreciated.

[grub]

first question: what type of extract did you use? (ie: liquid vs dry, colour, etc). stopping high is not uncommon for extract, but even that seems a bit much. you'd likely get some kind of medal if you managed to get an extract batch down to 1.012, and something in the 1.020's is more realistic.

in general, liquid extract ends up being less fermentable than dry. it also usually goes bad faster, leading to off flavours and such. also, the darker the extract the less fermentable it is, which is why you should always use extra light dry malt extract (DME) and get any colour from your grain.

i can never remember, are "propagator" the small or big smack packs? either way, you likely underpitched, which can lead to stalled fermentation. this is even more of a problem as your gravity goes up (and yours is certainly above average).

save yourself some money and spend $1-2 on making a starter. you'll have far more healthy yeast cells and save most of the price of that second smack pack. i only ever buy the big ones and make a starter every single time. i can provide multiple links on the subject if you're curious to read further.

did you aerate the wort after cooling? which method did you use? for how long? with a big beer your best bet is pure oxygen for at least 60 seconds with a 0.5micron diffusion stone. other methods are less effective and take longer.

if anything your temperature is too high, though that won't cause it to stall. be aware that during active fermentation the temp inside the fermenter is usually about 5F higher than ambient, and can be 10F or higher if you use overpitch. so your 18-22F ambient temperature works out to 64-72F for an internal temp of 69-82F - well outside the 'happy' range of that irish ale yeast.

some yeast are more flocculant than others, meaning they drop out of suspension faster. the wyeast 1968 esb yeast even recommends occasionally rousing the yeast to make sure you hit your final gravity. grab your pail/carboy and gently rock it in a circular motion to get a nice swirling motion inside. that should help get some of the yeast back into suspension and perhaps coax it down a few more points.

5 days may be enough time for a small beer, but when you get up above 1.070 you need to give them more time, more yeast, more oxygen, and more love.

[Derek]

You may not be getting enough conversion in the mash as well, but with that OG, I'd leave it in the primary for 10-14 days (then probably 2 weeks or so in a secondary).

If that fails, Brett can break down more complex sugars that regular yeast can't. I had a similar issue with a stout... and the sediment from a couple bottles of Orval got me 10 more gravity points in 10 weeks (if I did it again, I'd leave it 3-4 months before bottling). I also threw in some oak cubes & got a pretty interesting brew! Afterwards you'll want to sterilize well, or leave that equipment for future funk.

[markaberrant]

I'll also add in that 1084 is not very attenuative anyways, I wouldn't expect it to get a 1.074 beer anywhere near 1.020.

[The_Jester]

Thanks, guys. Your help is greatly appreciated. There were many interesting points made, and many things learned. I need to do this more often, I think, because I don't know anyone else who homebrews.

Underpitching isn't the issue, because I did create a starter for this one, and I just had the same problem with a kolsch, which began at 1.046; certainly not a big beer.

One point in particular jumped out at me, and that is this:

did you aerate the wort after cooling? which method did you use? for how long? with a big beer your best bet is pure oxygen for at least 60 seconds with a 0.5micron diffusion stone. other methods are less effective and take longer.

All I do is stir for a minute or so. There is some splashing as the beer goes from the pot to the pail, so I figured that that was enough. So, here's my next question: How do you do this? Aquarium pump and stone?

Derek, you said that I may not be getting enough conversion in the mash. Does that mean that my OG should be even higher? My efficiency is only at about 65%, and I have trouble holding the temp in the appropriate range. I am looking into a cylindrical cooler to help with this. I just need to make a false bottom.

And finally markaberrant: Is there a better choice of yeast for a big stout, or do I just need to get my OG higher?

Thanks again, guys.

[grub]

Underpitching isn't the issue, because I did create a starter for this one, and I just had the same problem with a kolsch, which began at 1.046; certainly not a big beer.

did they use the same extract? i'd start to worry about its fermentability. you didn't answer the question of whether it was dry vs liquid extract and on the colour. that's where my suspicion is.

All I do is stir for a minute or so. There is some splashing as the beer goes from the pot to the pail, so I figured that that was enough. So, here's my next question: How do you do this? Aquarium pump and stone?

that's certainly not enough. i use 60-120 sec (depending on the gravity) of pure oxygen through a 0.5 micron diffusion stone. i also use a stir plate for my starters to keep them aerated and propagating as fast as possible.

an aquarium stone uses air, which obviously isn't pure oxygen, and uses a much coarser stone. as a result you need 5-10x longer to get the same amount of oxygen in the solution. dumping/shaking/splashing is even worse, and you need to do it for at least 20min before you're even close to what you get from pure oxygen.

for anyone else reading (since you seem to be doing this right), you only ever want to aerate your wort when it is cool and unfermented, never when hot ("hot side aeration") or post-fermentation.

everything you ever wanted to know about yeast propagation

great article+discussion on aeration

Derek, you said that I may not be getting enough conversion in the mash. Does that mean that my OG should be even higher? My efficiency is only at about 65%, and I have trouble holding the temp in the appropriate range. I am looking into a cylindrical cooler to help with this. I just need to make a false bottom.

no, if you're not getting enough conversion, your OG would be lower. the conversion he's talking about is from starch to sugar. temp could be a factor in conversion, but generally lower temp = more fermentable wort.

And finally markaberrant: Is there a better choice of yeast for a big stout, or do I just need to get my OG higher?

that yeast is probably fine if you want a big stout. that yeast should be able to hit 71-75% attenuation, but you're just under 50%. i think it's more a matter of fermentability than the yeast at this point.

[The_Jester]

did they use the same extract? i'd start to worry about its fermentability. you didn't answer the question of whether it was dry vs liquid extract and on the colour. that's where my suspicion is.

Sorry. With the stout, I used both light LME and light DME. The LME may have been a little elderly, and wasn't really light any more. (I don't have much choice here in Peterborough.) The DME isn't labelled with a date, but I know that it's only been in my local shop for about a month. I think it's from UCM (just down the street).

i use 60-120 sec (depending on the gravity) of pure oxygen through a 0.5 micron diffusion stone. i also use a stir plate for my starters to keep them aerated and propagating as fast as possible.

an aquarium stone uses air, which obviously isn't pure oxygen, and uses a much coarser stone. as a result you need 5-10x longer to get the same amount of oxygen in the solution. dumping/shaking/splashing is even worse, and you need to do it for at least 20min before you're even close to what you get from pure oxygen.

So, either I need to get the oxygen/diffuser setup (any ideas as to where?) or run an aquarium pump for half an hour. And I never even considered aerating the starter. Live and learn.

everything you ever wanted to know about yeast propagation

great article+discussion on aeration

Thank-you. Quite helpful.

... if you're not getting enough conversion, your OG would be lower. the conversion he's talking about is from starch to sugar. temp could be a factor in conversion, but generally lower temp = more fermentable wort.

This is something I need to work on. I'm trying to work my way toward all-grain. As I mentioned, I'm going to give the big igloo cooler a go, rather than my converted food-grade pail.

[grub]

Sorry. With the stout, I used both light LME and light DME. The LME may have been a little elderly, and wasn't really light any more. (I don't have much choice here in Peterborough.) The DME isn't labelled with a date, but I know that it's only been in my local shop for about a month. I think it's from UCM (just down the street).

ok, using light is good as it's generally more fermentable than the dark stuff. though i suspect the old LME may be the issue. i'd be curious to see what happend if you brewed only using the DME.

So, either I need to get the oxygen/diffuser setup (any ideas as to where?) or run an aquarium pump for half an hour. And I never even considered aerating the starter. Live and learn.

here's one from the place i shop at in detroit. call/email to find out what it'd cost to ship to you. pretty small and light, so it should be reasonable.

This is something I need to work on. I'm trying to work my way toward all-grain. As I mentioned, I'm going to give the big igloo cooler a go, rather than my converted food-grade pail.

if you have a spare pot, you can just mash there. allows you to turn on the heat if you lose a bit of temp (just stir it well while heating, and don't go overboard with the burner temp). transfer it to your tun at the end of the mash using a spare pot or something like the 2qt scoop i use. just make sure not to splash it around when transferring. i do all my mashing in the kettle then transfer to one of the tuns (6gal bucket tun for small batches, big rectangular cooler for everything else) after for the sparge.

[The_Jester]

here's one from the place i shop at in detroit. call/email to find out what it'd cost to ship to you. pretty small and light, so it should be reasonable.

Thanks, again, grub.
Okay. My last question. For now.
Where does one go about getting oxygen.? (No jokes please.)

[Derek]

This is something I need to work on. I'm trying to work my way toward all-grain. As I mentioned, I'm going to give the big igloo cooler a go, rather than my converted food-grade pail.

if you have a spare pot, you can just mash there. allows you to turn on the heat if you lose a bit of temp (just stir it well while heating, and don't go overboard with the burner temp). transfer it to your tun at the end of the mash using a spare pot or something like the 2qt scoop i use. just make sure not to splash it around when transferring. i do all my mashing in the kettle then transfer to one of the tuns (6gal bucket tun for small batches, big rectangular cooler for everything else) after for the sparge.

You could also try decoction mashing... take out 1/4-1/3 of the denser mash (not the wort with enzymes in it), heat that on the stove-top to around 160F & mix it back in. If you do it just to maintain temperature (and not a proper step-mash), it's really not that hard... just time consuming. But some more mash time at the right temperature should really help you out.

Also, heat rises. So if your measuring the temp at the top of the pail, it could be over 5 degrees lower at the bottom (I noticed this when I checked the run-off from my igloo). With your non-insulated setup, I'd definitely aim high (probably 155F to start). The enzymes won't all shut down at 160F, but you definitely have to keep it warm (or mash a lot longer... like maybe 2 hrs at 140F?).

You can also do testing for starch conversion... but I've never done it.

[Derek]

Also, crystal malt isn't as fermentable (the complex starches are crystalized & untouchable, plus it doesn't have the enzymes to convert on its own). So if your partial mash is mainly 'specialty' malts, this could be holding you back.

You can get diastatic LME to help conversion. I've never mashed with it, but perhaps it helped me a little as the wort came up to a boil in the brewpot?

[grub]

Okay. My last question. For now.
Where does one go about getting oxygen.? (No jokes please.)

something like $10 at your local rona/home depot/canadian tire. hit canadiantire.ca and search for 58-7558-6 and you'll even get a picture. one bottle lasts me about a year.

[markaberrant]

that yeast is probably fine if you want a big stout. that yeast should be able to hit 71-75% attenuation, but you're just under 50%. i think it's more a matter of fermentability than the yeast at this point.

I'm not saying it is the yeast either, but you have to take it into account when formulating a recipe. I typically want a highly attenuative yeast for my bigger beers, there is already going to be a ton of body and residual sweetness.

[The_Jester]

Thanks, guys.

Taking your advice, I picked up an Igloo with a tap, and an O2 stone.

My most recent batch (a dunkelweizen) surpassed the target FG, and got down to 1.011.

So again, thank you.