Acetaldehyde in an ordinary bitter

[AerationStation]

I've been working on my ordinary bitter for a little while but I keep getting an acetaldehyde aroma in the nose. The flavor isn't really there so much but it smells pretty strongly of the stuff. The recipe is from brewing classic styles

I'm using wlp007 ( one vial ) at a controlled 68°f , I was wondering if anyone had any ideas about where this is coming from?

 

[afr0byte]

How long are you keeping the beer on the yeast? Also, are you sure it's not just fruitiness from the British yeast?

 

[AerationStation]

Beers stays on for two weeks, and I brought to a brew club comp yesterday and got a resounding "that's green apple" response. Think it could just be esters getting a bad rap?

 

[afr0byte]

If multiple people pegged it as green apple it's probably not esters. You don't get any cidery/vineger-like flavor along with it, do you? Also, were these kegged/bottled? If kegging, did you purge the keg of CO2 first? Did you accidentally splash the wort around a lot while kegging/bottling?

 

[BigFloyd]

Try pitching it at 62, starting it fermenting at 64 (beer temp) for the first 4-5 days then slowly ramping it up to finish around 68-70*F. Leave it at least 2 weeks in the primary before bottling.

Make a yeast starter. Your underpitch with one vial may be contributing to yeast stress leading to the unwanted flavor.

 

[afr0byte]

Oh, and how old was the vial? An ordinary bitter could probably get by without a starter, assuming the yeast was fresh.

 

[progmac]

https://www.homebrewtalk.com/f163/b...on-temps-profiles-cybi-other-thoughts-221817/

i think i've linked to that thread a few times in the past couple weeks, but it is full of valuable information for creating your british beers.

i got strong acetaldehyde from a bitter that i started around 64 and bumped to 68 and then all the way to over 70 for the last 30% of fermentation (having had success with this method with other yeasts). i get much better results keeping in the 60s, even lowering the temp a bit towards the end.

if your ambient is 68, the beer could be fermenting at 72+. wlp007 works hot and fast if you let it.

how long are your fermentation times?

 

[AerationStation]

If multiple people pegged it as green apple it's probably not esters. You don't get any cidery/vineger-like flavor along with it, do you? Also, were these kegged/bottled? If kegging, did you purge the keg of CO2 first? Did you accidentally splash the wort around a lot while kegging/bottling?

No cider/vinegar flavors but it might be that I forgot to purge the keg. The only shaking that happened was carrying the fermentor up from the basement.

A club member did say to ferment around 63°F to remove the green apple but I thought acetaldehyde was the consequence of an incomplete fermentation, not an off flavor from a hot fermentation (ie fusels)?

 

[IL1kebeer]

A club member did say to ferment around 63°F to remove the green apple but I thought acetaldehyde was the consequence of an incomplete fermentation, not an off flavor from a hot fermentation (ie fusels)?

Acetaldehyde is in intermediate compound in the creation of ethanol. In healthy fermentations, your yeast will clean up the acetaldehyde before they go dormant. According the book "Yeast", causes of excessive acetaldehyde are (not quoted word for word):

1. Removing the beer from the yeast too early, before it has completed fermentation
2. The oxidation of ethanol after fermentation is complete
3. Acetic acid bacterial infection
4. Fermentation parameters that encourage excessively fast fermentation, such as over pitching and high fermentation temps

Elsewhere in the book it says that under pitching and low temps at the end of fermentation could also cause acetaldehyde. At any rate, if you had one or more of these issues then acetaldehyde could be present in your beer. If not then maybe a combination of hops and English esters are being mistaken for acetaldehyde by your club members. Just curious, how well do you trust their palates?

 

[AerationStation]

Ahhh ok and so by decreasing the temp(like down to 63-64) you could slow down the ferment and allow the yeast to clean up? Does the english yeast's tendency to floc easy and tightly contribute to them not cleaning up like a less flocculant yeast (ie wlp001) would at the same higher temp?

 

[afr0byte]

Ahhh ok and so by decreasing the temp(like down to 63-64) you could slow down the ferment and allow the yeast to clean up? Does the english yeast's tendency to floc easy and tightly contribute to them not cleaning up like a less flocculant yeast (ie wlp001) would at the same higher temp?

I'd say the most important part is to let the temperature rise throughout fermentation, especially with flocculant yeasts. You could start at 64, let it go for 3 days, and then ramp the temperature up to 68-70 at a rate of 1 degree a day.

 

[IL1kebeer]

i'd say the most important part is to let the temperature rise throughout fermentation, especially with flocculant yeasts. You could start at 64, let it go for 3 days, and then ramp the temperature up to 68-70 at a rate of 1 degree a day.

+1

 

[AerationStation]

Cool, thanks for the info guys. I'll report back on the results for the next bitter, I'm excited to give this another shot!

 

[Yooper]

Cool, thanks for the info guys. I'll report back on the results for the next bitter, I'm excited to give this another shot!

Make sure you pitch the proper amount of yeast. Consult the yeast pitching calculator on mrmalty.com, or use yeastcalc.com, and make sure to pitch the optimum amount of yeast at the proper temperature. You haven't pitched warmer and cooled the fermenter, I assume, but make sure to pitch at something like 62 or so, and then allow it to raise up to the ideal fermentation temperature. Pitching the proper amount of yeast at the proper temperature should minimize or eliminate acetaldehyde.

 

[progmac]

I'd say the most important part is to let the temperature rise throughout fermentation, especially with flocculant yeasts. You could start at 64, let it go for 3 days, and then ramp the temperature up to 68-70 at a rate of 1 degree a day.

allegedly fullers ferments at 64, bumps to 68, then cools down to 64 to finish out. the idea is to not let the yeast cleanup too much after itself. in the thread i linked on page 1, some people have had success with this method. this is strictly in the context of english ales and english yeasts.

 

[IL1kebeer]

allegedly fullers ferments at 64, bumps to 68, then cools down to 64 to finish out. the idea is to not let the yeast cleanup too much after itself. in the thread i linked on page 1, some people have had success with this method. this is strictly in the context of english ales and english yeasts.

That might be to keep a bit of diacetyl around since very small amounts are part of the style and acceptable. On the other hand, I haven't read about many styles where detectable acetaldehyde is acceptable, American lagers come to mind first. I don't think they are trying to purposely keep acetaldehyde around, and it might not matter anyway since it should have been cleaned up with a healthy ferment anyway.