Acetaldehyde pt II

I posted a thread here a couple of weeks ago. I had a blonde ale that got dinged for acetaldehyde at a recent competition. I was pretty sure that my issue had been a combination of low fermentation temps making the beer ferment slower along with pulling the beer too soon. It was my first temp controlled ale and I used to be on a standard schedule of a 1 week primary, a week in secondary than straight into the keg or bottle.

Works ok mostly, if you're fermenting at room temp. But in a 60-65F fridge, not so much. I am pretty sure I burned myself again.

I had an IPA that had just hit the keg about the same time I got my scoresheets back on the blonde. I had done it with the same schedule. A week on the yeast in the primary, rack to the secondary and into the keg.

About 2 weeks in keg, I tasted it tonight. The hops cover up some of the flavor, but the taste that I finally learned was the green apples of acetaldehyde is there in this beer too. It's not overpowering. It's not horrid. But it is present.

Now I need to figure out how to make sure history doesn't repeat with the saison and porter I have fermenting now.

The saison should be OK. It's 17 days into primary and at about 70ish% attenuation. I am going to pitch a little WLP001 or Safeale 05 this weekend and try to dry it out some more. I figure the extra yeast and another 10 days or so in primary should help combat the acetaldehyde monster.

My porter is an odd duck though. It's 10 days in the primary now with a double-pitch of WLP001. I have been fermenting at right around 65F (the digi thermometer I have in it ranges from 61F-71F throughout the day. It's in a fridge in a hot garage with a controller). But 10 days in, I am still getting a bubble every 3 seconds through my blow off rig. Is that normal for temp controlled ferments? I was planning on 3 weeks in the primary then a week of dry hop in the same primary before kegging.

I have not taken a gravity reading but I still have about 1/2 inch of krausen. Is 001 known to ferment this slow at low temps? SHould I kick it up or just leave it at its current temp and wait it out?

1 week in primary really isn't quite enough. Let it sit for a week and a half to 3 weeks. When they start to slow down, you can increase the temperature to keep the yeast active.

The porter is likely pretty much finished. I'd increase fermentation temperatures to increase yeast activity to get them to clean up after themselves. Krausen on top after 10 days is a little weird, but it depends on a lot of factors. If you let it sit where it is for another few days it won't be a bad thing, but I would personally increase the temp.

If you're just leaving the fermenter in a fridge that's set to 65, the beer will be much warmer than that during the most active part of the ferment; then, just as the yeast are getting pooped out and the sugars are almost exhausted, the beer temp drops to your setpoint, putting your beasties into hibernation before they can finish metabolizing acetaldehyde into ethanol.

If you don't have a way to control the beer temp more directly, just set the fridge a couple ticks below the lower bound of the recommended range for whatever strain you're using. Watch for the kraeusen to start to fall, or beer temp to peak, then increase the setpoint a few degrees over the next couple days. Then, as the mind control crustacean says, leave it on the yeast a while, then cold crash and keg!

Had a bottle of Bud the other night....

944play said:

If you're just leaving the fermenter in a fridge that's set to 65, the beer will be much warmer than that during the most active part of the ferment; then, just as the yeast are getting pooped out and the sugars are almost exhausted, the beer temp drops to your setpoint, putting your beasties into hibernation before they can finish metabolizing acetaldehyde into ethanol.

If you don't have a way to control the beer temp more directly, just set the fridge a couple ticks below the lower bound of the recommended range for whatever strain you're using. Watch for the kraeusen to start to fall, or beer temp to peak, then increase the setpoint a few degrees over the next couple days. Then, as the mind control crustacean says, leave it on the yeast a while, then cold crash and keg!

Had a bottle of Bud the other night....

Click to expand...

The controller for the fridge my porter is in is set at 70F. The digi thermometer has a "hi"/"lo" functions that records the temp range it hits. The thermometer has registered temps between 71 and 63. Most of the time when I look at it and the fridge is turned off, it's reading 65F-68F.

The krausen had hit as high as the neck of the bottle, but has receded to where it is just the half inch of foam on top. You think I should push the whole thing up to 72-74F on my controller now?

Where's your temperature probe? I tape mine to the side of a fermenter "insulated" with a folded up paper towel, and it tracks with the stick-on thermometer on the side of the fermenter.

ksbrain said:

Where's your temperature probe? I tape mine to the side of a fermenter "insulated" with a folded up paper towel, and it tracks with the stick-on thermometer on the side of the fermenter.

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Mine is rolled up and sitting on a shelf, about 3 or 4 inches above the fermenter

You might consider investing in a temperature controller like the Johnson A419ABC-1C.
Just plug the fridge into the controller, and your controller into the fridge. Crank your fridge up to the max setting at let the Johnson figure out when to turn it on. Min maintains temps quite well and runs the fridge a lot less than if I use the built-in thermostat.


Also you really do want the probe to be stuck to the side of the fermenter if possible, and insulated from the surrounding air. Even better is if you can get a waterproof probe and stick it inside the fermenter...

weirdboy said:

You might consider investing in a temperature controller like the Johnson A419ABC-1C.
Just plug the fridge into the controller, and your controller into the fridge. Crank your fridge up to the max setting at let the Johnson figure out when to turn it on. Min maintains temps quite well and runs the fridge a lot less than if I use the built-in thermostat.


Also you really do want the probe to be stuck to the side of the fermenter if possible, and insulated from the surrounding air. Even better is if you can get a waterproof probe and stick it inside the fermenter...

Click to expand...

I am using the Johnson dial controller and currently have it set at 72F

I have the same issue on a brown ale fermented with US-05, which is very similar to 001. About 12 days in primary, fermentation is basically done, but I still have 1/2 of bubbly krausen mess on top. Weird.

I've read that the acetaldehyde flavor can disappear with age but does cooling/carbing the keg pretty much keep it in the beer?

Last batch tastes like cut grass, undrinkable. Usually leave 3-4 weeks in the primary but pulled off after 1 week this time. It's a light brown ale (OG 1.042) and already hit the FG so thought it might be ok. Never experienced this before but sounds like acetaldehyde is the culprit.

So what are my best options for refrigerated fermentation? I have not brewed a lager in years and I have just recently (last 3 beers) started using temperature controlled fermentation for ales. Based on the responses so far, here are my take aways:

1. Fermenting at 65 is OK. But after a week or so of primary, it is advisable to raise the temperature to the upper limits of the yeast range in order to keep them active and allow them to clean up

2. My digital thermometer is fine, but to get an accurate reading of where the beer is, I need to tape the probe to the side of the fermenter.

3. The same goes for my controller probe, taped to the side of the fermenter, insulated from the outside air if possible.

4. Pitch bigger starters (I bought a 2000ml flask at lunch today)

5. Acetaldehyde does not taste horrid, but it is sure out of character enough to make me wrinkle my nose at what is an otherwise decent IPA

One thing I am not entirely sure about now is how much longer to give the porter. It is 10 days in and I moved the dial on the fridge controller up to 72 at lunch as well. Like I said, no gravity reading yet but I was planning on leaving it on the yeast for 3 weeks.

I'd like to dry hop but I am not sure if I want to go to a secondary for that, or since I am just going a week, maybe drop the hops in the primary and keg after a total of 4 weeks on the yeast.

winvarin said:

I am using the Johnson dial controller and currently have it set at 72F

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Then why are you getting such huge temperature variations? There is no way you should be getting swings from 63 to 70+.

Also 72F is a bit high IMO for an American IPA. I prefer to ferment 65-68F (actual fermenter temp).

winvarin said:

Mine is rolled up and sitting on a shelf, about 3 or 4 inches above the fermenter

Click to expand...

It'll definitely help to get your probe measuring the temp of the beer rather than the temp of the fridge. As was said before, getting the probe up against the fermenter and then insulating it with something works pretty well. That way when the yeast is really active and generating a lot of heat, the fridge will run colder to counteract it. Then, when the yeast slow down and the beer isn't generating as much heat, your fridge will automatically warm up a little. That way it keeps the beer at the same temp rather than the air in the fridge since it's the beer you want to control temperature on after all.

weirdboy said:

Then why are you getting such huge temperature variations? There is no way you should be getting swings from 63 to 70+.

Also 72F is a bit high IMO for an American IPA. I prefer to ferment 65-68F (actual fermenter temp).

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My opinion is the same as the post right above this. My controller probe is hanging in the air just inside the door. The digital thermometer's probe us rolled up and laying on a shelf (metal wire shelf) above the fermenter.

My assumption, and I may be way off, is that the actual temp is closer to the upper 60s (66-69F) but the fact that it's laying on the metal shelf actually makes the low readings seem lower than the actual air temp inside the box (the fan for the inside of the fridge blows right against the shelf).

The highs may seem higher because the refrigerator is in a hot garage and I am sure the air around it is being warmed when I open the door to check on the beer.

Most of the time when I look at the temp readout with the door closed (intermittently when I walk by) it reads in the 66-69 range. But there is no telling actual beer temp because the probe for the digi thermometer is not touching the fermenter and there is no thermometer strip on the fermenter.

ChshreCat said:

It'll definitely help to get your probe measuring the temp of the beer rather than the temp of the fridge. As was said before, getting the probe up against the fermenter and then insulating it with something works pretty well. That way when the yeast is really active and generating a lot of heat, the fridge will run colder to counteract it. Then, when the yeast slow down and the beer isn't generating as much heat, your fridge will automatically warm up a little. That way it keeps the beer at the same temp rather than the air in the fridge since it's the beer you want to control temperature on after all.

Click to expand...

So do you actually ramp up the temp on your fridge as the fermentation goes on or just let the probe against the fermenter keep it in the yeast's target temp range?

And what do you do to insulate the probe? Would just tape against the fermenter do it? Or do you need to press the probe against the side of the fermenter, then place something over the outside, then tape it in place?

winvarin said:

My opinion is the same as the post right above this. My controller probe is hanging in the air just inside the door. The digital thermometer's probe us rolled up and laying on a shelf (metal wire shelf) above the fermenter.

My assumption, and I may be way off, is that the actual temp is closer to the upper 60s (66-69F) but the fact that it's laying on the metal shelf actually makes the low readings seem lower than the actual air temp inside the box (the fan for the inside of the fridge blows right against the shelf).

The highs may seem higher because the refrigerator is in a hot garage and I am sure the air around it is being warmed when I open the door to check on the beer.

Most of the time when I look at the temp readout with the door closed (intermittently when I walk by) it reads in the 66-69 range. But there is no telling actual beer temp because the probe for the digi thermometer is not touching the fermenter and there is no thermometer strip on the fermenter.

Click to expand...

And as to the temp question for the style, I went through most of week 1 with the beer in the mid 60s. It was only after I noticed that I still had a half inch krausen and bubbles in the airlock at day 10 that I ramped up the temperature to 72F in order to keep from stalling fermentation

winvarin said:

So do you actually ramp up the temp on your fridge as the fermentation goes on or just let the probe against the fermenter keep it in the yeast's target temp range?

Click to expand...

No need to change the temp of the fridge. It adjusts as the temp of your beer changes and keeps things right at your target range.

winvarin said:

And what do you do to insulate the probe? Would just tape against the fermenter do it? Or do you need to press the probe against the side of the fermenter, then place something over the outside, then tape it in place?

Click to expand...

Tape the probe to the fermenter, then tape something over it. Jamil talks about using bubble wrap. You could use some foam, an old oven mitt, whatever you have around that'll insulate the probe from the outside air so it reads the temp of your beer more than the temp of the air in the fridge.

stop doing a secondary. People who secondary end up with acetaldehyde because they take the beer off of the yeast before the yeast is finished cleaning up....