Acetaldehyde In Aroma

[The King of Spain]

Two of the judges at the Nats commented that they could detect acetaldehyde in the aroma of my Brown Ale. My thinking is that I should be able to fix this by raising the temps once fermentation is finished so the yeast can finsh all its work. I do this for my lagers but not ales.

Am I on the right track here?

Thanks
KOS

 

[browndog]

Two of the judges at the Nats commented that they could detect acetaldehyde in the aroma of my Brown Ale. My thinking is that I should be able to fix this by raising the temps once fermentation is finished so the yeast can finsh all its work. I do this for my lagers but not ales.

Am I on the right track here?

Thanks
KOS

I've had similar comments in some of my dark beers at BABBs minicomps, since I have never had this problem with pale beers (with similar yeast and fermentation conditions) and after having other brewers try the beer and saying it was fine, I put it down to an incorrect perception from the judges. If you are concerned, you could leave the beer for a day or two after teminal gravity is reached.

cheers

Browndog

 

[manticle]

Two of the judges at the Nats commented that they could detect acetaldehyde in the aroma of my Brown Ale. My thinking is that I should be able to fix this by raising the temps once fermentation is finished so the yeast can finsh all its work. I do this for my lagers but not ales.

Am I on the right track here?

Thanks
KOS

I thought (and I could be wrong) that raising temps helped remove diacetyl rather than acetylaldehyde.

I also have the impression that acetylaldehyde will settle down with extended conditioning. Presumably that's also yeast cleaning its own byproducts but whether or not it can do it in that small timeframe is the question.

Can you detect it or do you think they may have been talking through their respective sphincters? If it is there what do you think is causing it? Underpitching or something else? If you can work it out it's probably better to prevent it happening in the first place.

 

[Nick JD]

How careful are you when you rack to secondary that no oxygen is introduced?

Yeast munch the ethanal (acetylaldehyde) and turn it into ethanol during fermentation, but it never is completly gone (tasteable over 20ppm). Getting a lot of oxygen into your beer will change the ethanol back into ethanal.

How old was the beer? Did they describe it as cidery or grassy?

 

[The King of Spain]

I cannot detect it so I am going to agree with Browndog. I just did my first brown since the QABC comp and wanted to improve it. The beer that I entered was cutting things fine, I had it temp sitting at 25C to get it propery carbed in time. I've tweaked my recipe a bit as well using 100g of choc wheat for the first time, tastes good out of the fermenter.

Was certainly not cidery or grassy, in my opinion one of the niced beers i have made. Scored a place at the QABC so can't have been too bad.

Thanks
KOS

 

[Thirsty Boy]

I find that I perceive acetylaldehyde quite differently in dark beers to light beers....

In light beers I get the Bruised Apple thing going, but in Dark beers I get no apple at all, I detect it as red currant/grape undertones. But acetylaldehyde it most certainly is.

Could be the judges misperception - or - it could be that they know their palates well enough so they recognize it where you don't?

Either way its usually caused by pre-mature yeast seperation, so a bit longer contact with your yeast and care with oxygen ingress should nullify the issue if it exists.

TB

 

[berapnopod]

Three common ways to get acetaldehyde:

1. oxidation - too much oxygen gets into the beer and effectively reverses the fermentation one step

2. Young beer - yeast has not quite finished the job yet, so just be patient and it should subside after a few weeks

3. Too high a fermentation temperature - yeast gets stressed when fermenting too warm and produces more acetaldehyde than it can consume later.

Based on whats been said so far, I would guess number 3 is the most likely culprit.

Berp.

 

[Fourstar]

In light beers I get the Bruised Apple thing going

Yeah i dont get the 'green apple thing' i seem to fall into the same cat as you thirsty. It reminds me of rotting apples in the bottom of a schoolbag with the slighty winey/cider aroma it has. The 1st thing i usually notice is a mildy solvent like sharpness followed by a deep old apple aroma as you pointed out.

 

[Ross]

I've had similar comments in some of my dark beers at BABBs minicomps, since I have never had this problem with pale beers (with similar yeast and fermentation conditions) and after having other brewers try the beer and saying it was fine, I put it down to an incorrect perception from the judges. If you are concerned, you could leave the beer for a day or two after teminal gravity is reached.

cheers

Browndog

Tony,

Judges won't (in my experience) make things up. If the judge is picking up acetaldehyde I'd be pretty sure that's what he's found.
For an example, I have a mild in the shop at the moment, that pretty well everyone says is great, but to me it has a taste that is not quite right (having made it many times before) & I couldn't put my finger on it. Berapnopod was in the shop picking up some beers & I got him to taste it, & he picked up acetaldehyde straight way. Once I knew what it was I could pick it easily, whereas my manager Anthony who has a fantastic pallette, couldn't detect it at all.
We all have different taste thresholds to different things, which is why it's important to have more than one judge on a flight.

cheers Ross

 

[browndog]

Tony,

Judges won't (in my experience) make things up. If the judge is picking up acetaldehyde I'd be pretty sure that's what he's found.
For an example, I have a mild in the shop at the moment, that pretty well everyone says is great, but to me it has a taste that is not quite right (having made it many times before) & I couldn't put my finger on it. Berapnopod was in the shop picking up some beers & I got him to taste it, & he picked up acetaldehyde straight way. Once I knew what it was I could pick it easily, whereas my manager Anthony who has a fantastic pallette, couldn't detect it at all.
We all have different taste thresholds to different things, which is why it's important to have more than one judge on a flight.

cheers Ross

I certainly don't think judges make things up Ross and didn't imply that either. I was of the opinion that the combination of the dark grains and hops used gave the impression of a slight green apple aroma. As I said, when I got other brewers to try the said beer, they could not pick it up.

cheers

Tony

 

[O-beer-wan-kenobi]

I have recently had some of my beers judged and on my Bohemian Pills, all 3 judges commented Acetaldehyde. It is feint but now it is pointed out I can tell it is there.

I have had this problem on most of my lagers and some you can smell a mile off. The thing is my ales and dark beers don't have this problem so I am trying to work out the issue. Would it be my process or infection?

With the lagers I keep fermentation temperatures steady at 10 degrees and pitch good sized starters. After fermenting for 2 - 3 weeks I then I give them a d rest for 2 days or so before cold conditioning.
I have reused the yeast from these beers and it seems the resulting beer from the re pitched yeast has an even stronger green apple/pumpkin smell.

I don't transfer to secondary and I purge my kegs first. I bottle no differently with the ales so I don't think its oxidisation.

 

[Audion]

FWIW,

One further observation on acetaldehyde development..

I have seen serious acetaldehyde issues in lagers that have been insufficiently oxgenated/ aerated at wort transfer stage. I am sure there is textbook rationale for this but the explanation escapes me atm

Postscript: Hough and Briggs.." Reducing wort dissolved oxygen from 8 mg/L to 3 mg/L can cause a seven fold increase in the production of acetaldehyde by the yeast..."

Cheers,

 

[O-beer-wan-kenobi]

Thanks Audion

I have been looking into this and my process. The wort aeration is the area I will be looking at.
I read in The Yeast book that acetaldehyde can be caused by low aeration, and interestingly affects the yeast for future brews when re using the yeast. This rings true with my experience because the future brews from the re-pitched yeast had a much more acetaldehyde than the original.

 

[Screwtop]

I find all of the above interesting. Been chasing acetaldehyde in my beers (pale and dark) for over 12 months. Tried all manner of things, temp, extra time on yeast, oxygenation etc. Both myself and son Joel are supersensitive to acetaldehyle whereas most others don't notice it in our beers. Kegged a batch this morning and think I have finally nailed the source of the very slight green apple aroma/flavour. Have always used plastic fermenters in the past, for beer, cider ginger beer etc. Bought a glass fermenter and split the last batch. The beer fermented in the plastic fermenter tastes the same as most others have out of the fermenter over the pst 12 months, a slight yeasty apple flavour, like green beer, which slowly morphs into the acetaldehyde aroma over a few days in the keg. The other half of the batch fermented in the glass fermenter has a totally different flavour/aroma, this beer is nice and malty without any detectable acetaldehyde.

Interesting to see how these age in the keg.

Screwy

 

[O-beer-wan-kenobi]

I find all of the above interesting. Been chasing acetaldehyde in my beers (pale and dark) for over 12 months. Tried all manner of things, temp, extra time on yeast, oxygenation etc. Both myself and son Joel are supersensitive to acetaldehyle whereas most others don't notice it in our beers. Kegged a batch this morning and think I have finally nailed the source of the very slight green apple aroma/flavour. Have always used plastic fermenters in the past, for beer, cider ginger beer etc. Bought a glass fermenter and split the last batch. The beer fermented in the plastic fermenter tastes the same as most others have out of the fermenter over the pst 12 months, a slight yeasty apple flavour, like green beer, which slowly morphs into the acetaldehyde aroma over a few days in the keg. The other half of the batch fermented in the glass fermenter has a totally different flavour/aroma, this beer is nice and malty without any detectable acetaldehyde.

Interesting to see how these age in the keg.

Screwy

So you think it is the plastic fermenter that could be the cause? Would like to know how the glass one turns out.
I wonder if the betta bottle type fermenters would make a difference?

My experience is similar to yours where there is a slight green apple flavour when kegged and then over a few days it develops into a much stronger smell and flavour.

 

[Screwtop]

So you think it is the plastic fermenter that could be the cause? Would like to know how the glass one turns out.
I wonder if the betta bottle type fermenters would make a difference?

My experience is similar to yours where there is a slight green apple flavour when kegged and then over a few days it develops into a much stronger smell and flavour.

Exactly the same here, thought it was an infection in the lines/taps. Everything cleaned and disinfected, replaced the taps, still the same.

Just split another batch brewed today. Half into plastic, half into glass.

Screwy

 

[manticle]

Reckon slight oxygen intake during conditioning Screwy or something else?

 

[GABBA110360]

To start i'll admit I don't know what the taste is your all on about.
but for the average joe blow it's about wether your Home brewed beer tastes like you reckon it should?
I'm relatively new to all grain and i'm learning every day.
I realise this a craft but i'll bet it's not rocket sience
most of us I suppose will just drink out mistakes as I will
cheers
ken

 

[HBHB]

To start i'll admit I don't know what the taste is your all on about.
but for the average joe blow it's about wether your Home brewed beer tastes like you reckon it should?
I'm relatively new to all grain and i'm learning every day.
I realise this a craft but i'll bet it's not rocket sience
most of us I suppose will just drink out mistakes as I will
cheers
ken

Acetaldehyde is perceived by most people as that taste you get when you sink your teeth into a granny smith apple.

With that in mind, you'll know it when you taste it.

Martin

 

[GABBA110360]

Acetaldehyde is perceived by most people as that taste you get when you sink your teeth into a granny smith apple.

With that in mind, you'll know it when you taste it.

Martin

thanks martin