Acetylaldehyde in Imperial IPA - Tastes Like Granny Smith Apple

[the75]

So, my 3rd beer ever was supposed to be a DIPA, but is very short of hop flavor & very strong in green apple flavor. From what I've read, that flavor is from acetylaldehyde. I'm trying to figure out where this came from in my process, so here is a quick rundown if anyone can help:

4 1/4 gallon batch in 5 gallon carboy
Water PH 5.6 Bottled (Used 4 gallon kettle - not full boil)
steeped 1 lbs Briess Pale Malt, 1/4 lbs Crystal 20 at 156 for 25 min
Boil, then added 7 lbs Pilsen Light LME & 2 lbs Golden Light Briess DME
2 oz columbus 60
2 oz columbus 45
1 oz warrior 30
1 oz chinook 30
1 oz centennial 15
1 teaspoon irish moss 15
1 teaspoon yeast nutrient 10
1 oz amarillo 5
1 oz simcoe 0
1.082 OG at 77
700 ML starter of Wyeast 1056 (decanted) & 1000ML starter of WLP008 (Briess Golden Light DME) not decanted (yeah, I know...LHBS was out of 1056 or WLP001)
Fermented at 70 Degrees for 21 days. Dryhopped for last 12 days (Too long?)
Gravity was at 1.024 at dryhop, finished at 1.019

I don't see anything blatantly obvious here, but maybe the yeast combo? Maybe oxidation? I think my bottling went pretty well, transfer seemed fine...

 

[twistr25]

Here is a wiki page about it, hope it helps. Assuming you've haven't already seen it...

 

[the75]

Here is a wiki page about it, hope it helps. Assuming you've haven't already seen it...

Definitely appreciate the response. Yes, I did take a look at that. I was hoping maybe someone here was able to offer insight from looking at my process. I took a look back & nothing really stands out to me, except maybe the combination of yeast...

 

[twistr25]

What was your FG supposed to be? The only thing I can think of is that the yeast were good enough to get started and create the alcohol, but couldn't fully finish the cleanup job leaving the acetyladehyde. Since it was reused yeast, looks like you got about 8.5% ABV, could have stressed the yeast a little at the end?

 

[Bithead]

Since acetaldehyde is a normal part of fermentation maybe this recipe / yeast combination just produced more. I'd let it sit and clean itself up more.

 

[the75]

What was your FG supposed to be? The only thing I can think of is that the yeast were good enough to get started and create the alcohol, but couldn't fully finish the cleanup job leaving the acetyladehyde. Since it was reused yeast, looks like you got about 8.5% ABV, could have stressed the yeast a little at the end?

That's a good possibility! I also did this one with little headspace, so I think I lost my most active yeast at krausen thru the blowoff. My final gravity finished where it was expected to, but is it still possible for me to reach final gravity & end up with this flavor? I'd assume final gravity doesn't fully dictate the yeast' health or their ability to clean things up...

 

[twistr25]

That's a good possibility! I also did this one with little headspace, so I think I lost my most active yeast at krausen thru the blowoff. My final gravity finished where it was expected to, but is it still possible for me to reach final gravity & end up with this flavor? I'd assume final gravity doesn't fully dictate the yeast' health or their ability to clean things up...

Correct, most beers take 4-7 days to ferment and the rest of the recommended time is to clean up. If they finished fermenting and were tuckered out, may not have had a chance to clean up even sitting for those additional 2 weeks

 

[pfgonzo]

Also, when you say fermented at 70, do you mean temp of the liquid or ambient? If ambient, the liquid temp was likely 74-78, which is a little high.

Chris White (White Labs) did an experiment for his Yeast book fermenting a 5ga batch at 68 and 75 (temp of wort), and tested for acetaldehyde. With a perception threshold of around 9ppm, the 68 degree batch only produced 7-10ppm, barely noticeable, and easily taken back up by the yeast during conditioning. The batch fermented at 75 produced something like 150ppm of acetaldehyde, quite a significant difference.

As others have said, give it some more time on the yeast to reduce levels if possible. Otherwise, you're stuck with the apple IPA this go-around, and should try fermenting a wee bit cooler next time.

Cheers.

 

[twistr25]

Also, when you say fermented at 70, do you mean temp of the liquid or ambient? If ambient, the liquid temp was likely 74-78, which is a little high.

Chris White (White Labs) did an experiment for his Yeast book fermenting a 5ga batch at 68 and 75 (temp of wort), and tested for acetaldehyde. With a perception threshold of around 9ppm, the 68 degree batch only produced 7-10ppm, barely noticeable, and easily taken back up by the yeast during conditioning. The batch fermented at 75 produced something like 150ppm of acetaldehyde, quite a significant difference.

As others have said, give it some more time on the yeast to reduce levels if possible. Otherwise, you're stuck with the apple IPA this go-around, and should try fermenting a wee bit cooler next time.

Cheers.

I think he's already bottled...

 

[Brandonovich]

I think you may want to be wary of your head space issue as well. The healthiest most viable yeast is going to be at the top during active fermentation, and if you blow it all out the top, you will not be left with enough healthy yeast at the end.

 

[the75]

I think he's already bottled...

Yup! Its almost gone too, lol. I just bottled another iipa, so if I get the same flavor, I'll know whether or not it was ferm temp.

 

[New Brew]

Also, when you say fermented at 70, do you mean temp of the liquid or ambient? If ambient, the liquid temp was likely 74-78, which is a little high.

I'd be curious about this too. Fermentation temp isn't usually listed as a contributor to acetaldehyde, but I have a couple small batches of ale I did & let ferment @ ambient (~72* air temp) that turned out to be real green apple bombs.

Nothing except the fermentation temperature was common between the batches (different malts, different (ale) yeasts, different hops), so I think that pretty much has to be the culprit.

One of them is a year old now, and I tried one last week. It still has strong green apple flavors, so conditioning really didn't do much to fix this problem for me. I think it's just one of those things you have to get right the first time around.

 

[the75]

Thanks everyone! My temp override was taped to the carboy in my fridge with some bubble wrap insulating it, so my temps should be right. The fermometer was reading what temp I was shooting for, but I didnt get an accurate internal temp outside of those two methods.