Acetaldehyde in aged bottles.

[Truman42]

Gday brewers,
I have had a couple of brews now that were fine when they were young and as they have aged (4-5 months) they have developed what I think is a acetaldehyde. The first was an amber ale which tasted fine for the first few months and now that it's about 4-5 months old I can taste a cidery green apple taste to it.

Then tonight I opened a porter which was fine at first with no off flavours at all. When I opened the bottle it gushed and it too had a really bad green apple taste that I had to tip it down the sink as it was Undrinkable.

About a year ago my BIL told me that a Raison D'être clone I had given him and that had been left in his cupboard had exploded. Normally I drink a batch within 3 months so haven't really noticed this before. But lately I've been brewing a lot so have had a lot of beers aging in milk crates in my hallway cupboard and some of them have been there 5 months or so.
From what I've read about acetaldehyde it's created by fermentation and often through not pitching enough yeast. I always do nice big starters and the beer has no green apple taste at all when it's young.
I bulk prime and seem to have no problems with overcarbonation with the young beers so I'm guessing this is an infection issue. But how is it that this beer can be fine for 3-4 months then after that start to develop an infection and end up over carbonated and cause a green apple taste?

Wouldn't an infection be obvious even in a beer that's 1-3 months old as well? And if this is an infection why am I continually getting this happen to all of my beers once they age? I sanitize and clean really well to the point of going overboard sometimes. Everything cold side and on bottling day gets starsanned and I have never had this problem with my kegged beer even when I've had a keg sit for 4 + months in the fridge.

 

[manticle]

Acetaldehyde is a halfway point in the formation of ethanol. It's a chemical pathway that can go either direction. Oxidation/reduction reactions can cause ethanol to move back towards acetaldehyde so its presence in older/aged beer is indicative of oxidation/staling

 

[Truman42]

How am I getting oxidation issues if that's the cause then? I bulk prime so transfer to a bulk priming fermenter but I lay the hose in the bottom of the fermenter and tip the fermenter on its side so the hose is completely covered with wort quicker. I don't open the tap fully until the bottom of the priming vessel has around an inch of wort.
I bottle with a bottling wand and other than that I don't know of any other time I could get oxidation. Any thoughts?

OT. That grainy huskiness taste I mentioned in another post with my stout from a keg actually went away and it now tastes really good. So can't work that one out.

 

[JDW81]

What type of bottles do you use? I have heard of a few brewers having trouble with long term storage when they use VB style long neck bottles. I have been told that the screw top doesn't seal as well as the coopers style (although I don't know how true this is as I've only ever used coopers, grolsch and champagne bottles).

JD

 

[manticle]

Oxidation and staling reactions are an inevitable part of beer making and packaging. Just putting a hose at the bottom of the fermenter and slowing the flow decreases the likelihood and rate of certain reactions - it isn't a surefire protection against all of them.

Some reactions are natural pathways that occur as part of fermentation, both forwards and backwards (formation of acetaldehyde and conversion of acetaldehyde to ethanol is one of those) while others are slow but irreversible. It's a part of the process - what we do is try and reduce the likelihood and speed of those reactions. Even maturing a rich dark beer is utilising some of that oxidation/staling for a result that is desirable..

You could try adding an active starter to a test sample to see if that removes the acetaldehyde flavour. You also may be experiencing a flavour that is misdiagnosed as acetaldehyde.

 

[Truman42]

That's the problem I'm not good at diagnosing flavours in my beer. The acetaldehyde detected in the amber ale was first brought to my attention by fat ******* as I sent him one in the lotto comp. then as I drank more of them from the bottle I could taste it also. I had served this same beer when it was younger from the keg at a brew club meet and everyone said it was fine with no off flavours.

The porter I drank tonight was possibly not acetaldehyde. Hard to describe the taste, a bit sour perhaps, may be a touch of vinegar but also had lost all of its flavour, almost like a cidery soda water if that makes sense.
I had a similar taste in an out of date bottle of stone and wood pacific ale once.

So your saying add a starter to a sample of the porter? Won't it not ferment as there is no sugars left?

Thanks for the help on this btw. Much appreciated.

@ JDW81.. The Porter was in a brown PET but I use a variety of 330 ml 600ml and 750 ml bottles. I have tasted the acetaldehyde from the amber ale in all of these bottles.

When I try some stouts that I've aged they often seem to have a vegemite yeast taste to them. I don't mind it at all but no doubt I would lose points if it were entered into a competition.

 

[manticle]

Not about fermenting. It's about reversing the reaction using active yeast. Think of it as extra conditioning. It's a long shot but I've known it to work and it is a good test.

 

[Truman42]

Not about fermenting. It's about reversing the reaction using active yeast. Think of it as extra conditioning. It's a long shot but I've known it to work and it is a good test.

ok ill give it a try. But how much yeast should I use for just a 700ml bottle? And what should we conclude if it works?

 

[manticle]

Really just for your own curiousity. Next time you make an active starter, reserve a bit, pour a bottle gently into a sanitised container and add a wee bit of the active starter. See if the flavour profile changes over a few days.

If the beer were in a keg, you could try salvaging the whole batch, less easy in bottles.