Is it acetaldehyde?

[seanppp]

I've been brewing for 10 years and have been happy with my beers for the last 8 years or so. I have done over 150 batches and feel like I have a good grasp on what I'm doing. One thing, though, that I've never gotten around to doing is learning off-flavors. I know the names and causes of off-flavors, and have tasted eight or ten different off-flavors, but I don't know if I can assign each flavor with each word. So, I'm sure I know what diacityl tastes like but I don't know that it's diacityl instead of, say acetaldehyde. Hope that makes sense.

I live in Denmark now and before I left I planned on getting one of those off-flavor wheels to put this problem to bed once and for all. Never got around to it.

Anyway, I brewed a black IPA recently and I *think* it's suffering from acetaldehyde. I have a temperature controlled fermentation, here are the gravities (when I took them) and temperatures each day during the fermentation:
Day Grav Temp
Pitch 1.077 59F
1 64F
2 66F
3 66F
4 66F
5 1.024 68F
6 68F
7 69F
8 70F
9 71F
10 72F
11 73F
12 1.021 48F (began to crash)
13 40F
14 35F
15 1.021 35F (racked to keg)

I pitched with Safale US-05 and was expecting a 1.016 FG.

Do you think it's probably acetaldehyde that this beer is suffering from? Should I have kept it on the yeast longer?

I have since bottled (bottle carbonating) and am wondering whether I should pour them out or wait a while and hope the yeast cleans it up.

What do you think?!

 

[flars]

the taste you are experiencing could be just a green, unfinished beer. it looks like you stopped the fermentation by cold crashing. another week in the primary may have allowed the yeast to finish.

 

[seanppp]

I don't think it's just green beer. I think it's something more. Anyone else have a guess?

 

[Beernik]

I didn't see where you described the flavor.

Acetaldehyde is like a green apple, Granny Smith apple, or I have even heard it described as a lawnmower that ran across a green apple flavor.

Diacetyl is like artificial butter, butterscotch, or just a pronounced slickness.

Are you getting either of these?

 

[EternalStudent]

Are those temperatures in the 100s? I may be reading it wrong? If you ferment above 80 F your going to have a lot of phenol = band aid.


Sent from my iPhone using Home Brew

 

[mkeckjr]

Acetaldehyde is an off-flavor that tastes like green apple, as Beernik said. It is a natural product during the fermentation process that is eventually turned into alcohol. One common cause of acetaldehyde in the finished product is racking young beer off of the yeast cake, because then the yeast don't finish up their job of converting acetaldehyde into alcohol. If you crashed the beer a bit too early, which you may have in this case, or fermentation stalled out for some other reason, then the same result may occur. However, again, as Beernik has already pointed out, if you could describe the flavor you're getting, that would help us assess it.

 

[khillian]

How are you crashing? I have noticed on higher alcohol beers, combined with the suck back effect of oxygen with cold crashing can reverse ethanol back into acetaldehyde. I normally skip cold crash or do it in a sealed keg then jump into a sealed keg.

 

[khillian]

Didn't mean to post on this old thread