# Getting Rid Of Acetaldehyde



## sinkas (16/10/07)

Hi all,
does anyone have any thoughts on how to get rid of Acetaldehyde from a force carbonated, belgian strong ale?
I have a full keg of it, and its nearly undrinkable. The flavour profile beneath the green apple is excellent, but the green apple just wont relent....

My thoughts:

1) reduce presure, and add a active yeast culture to the keg and see what happens?
2) totally decarbonate and then bulk prime and see what happens
2a) Send to fellow brewer to put through their water purification system.
3) use keg as water cannon against neighbours new labradoodle? 

I have asked around, but not even the pro brewers here seem to have any ideas.

Anyone?


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## kabooby (16/10/07)

I read somewhere that this should disipate with cold conditioning. Has the beer been cold conditioned? If so how long?

Kabooby


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## kirem (16/10/07)

SO2 will bind it up.


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## chovain (16/10/07)

According to Palmer (chapter 22.2), it should go away with time. He says that if you were to catch it in the fermenter, then you can clean it up by leaving it on the yeast longer, rousing the yeast for a bit, or conditioning at a higher temperature.

I reckon you should try bringing the temperature up for a few days, and see if that helps you. If that doesn't fix it, maybe you can repitch and recondition at a slightly elevated temperature in the hope the new yeast cleans it up.


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## Thirsty Boy (16/10/07)

kirem said:


> SO2 will bind it up.



Nice... any clues on ways to get the SO2 into the beer? Perhaps just a pinch or two of sodium or potassium met into the keg. Would you then need to leave the keg open to let any excess sulphur waft away? Would you need to let the compound formed by the SO2 and the Acetaldehyde fall out and then rack away from it?
or would it stay in solution as a flavour neutral?

Too many questions. Sorry

Thirsty


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## mika (16/10/07)

Bit about it in this Month's BYO mag. Apparently can be caused by overpitching (by a huge amount), underarating, fermenting too warm or separating the beer from the yeast too soon. They simply recommend leaving it on the yeast cake for a few more days at the upper end of the temperature range for the yeast (which kinda goes against the warm fermenting argument ?) and it should clear up.
If it's in a keg...bummer...maybe just add a fairly neutral yeast, US-05 ? and leave it to chew for a couple of days.


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## kirem (16/10/07)

Thirsty Boy said:


> Nice... any clues on ways to get the SO2 into the beer? Perhaps just a pinch or two of sodium or potassium met into the keg. Would you then need to leave the keg open to let any excess sulphur waft away? Would you need to let the compound formed by the SO2 and the Acetaldehyde fall out and then rack away from it?
> or would it stay in solution as a flavour neutral?
> 
> Too many questions. Sorry
> ...




PMS.
I would pour a glass add a pinch see if it does what you want and then treat a keg. If you do it at the correct or near correct rate there shouldn't be any 'excess' sulphur to 'waft' away. 

Not sure off the top of my head if it remains in solution or not.


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## Hargie (16/10/07)

....patience is the only answer now....put it at the back of the fridge and pretend its completely rooted....then in a month or two reward yourself...


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## Hargie (16/10/07)

....and i would not add anymore yeast or anything else you may just end up with a whole lot more grief than you've got now....


...I'm drinking a Schwartzbier right now that a month ago was Granny Smith City....it was already fined, filtered and carbonated before i detected it....so i left it in the fridge , no hasty decisions and now is scrubbed right out of the beer....it's getting judged this weekend at the ACT Champs and i guess i'll find out....i'll post the results if interested...


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## mfdes (17/10/07)

In my experience leaving the beer on the yeast for a while after fermentation appears finished is always a good policy and does mop up acetaldehyde, diacetyl, and other by-products.
Once it's been kegged or bottled, however, I'd say it's patience or nothing...

MFS.


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## ausdb (17/10/07)

sinkas said:


> Hi all,
> does anyone have any thoughts on how to get rid of Acetaldehyde from a force carbonated, belgian strong ale?
> I have a full keg of it, and its nearly undrinkable. The flavour profile beneath the green apple is excellent, but the green apple just wont relent....
> 
> ...


Have you ran that by Randall? he touched on it during the talk he gave at WCB but I can't remember it :-(


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## sinkas (17/10/07)

He doesnt reply to pm's


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## Trev (18/10/07)

At the risk of straying slightly off topic...

There's lots of good advice given above about methods of hopefully decreasing the Acetaldehyde but maybe the question should also be asked about how it got there in the first place.

Are you happy that the yeast was in good health and you pitched sufficient quantity?

Was the wort well aerated?

Did you leave it long enough in the fermenter for the yeast to finish the job?

Trev


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## sinkas (18/10/07)

Hi there,
Yes the yeast is probably to blame, or moreso the brewer punishing the yeast, after they had already succefully fermented a pale aale and a 8.5% Triple, maybe its was too much for them.......
The beer sat on the yeast for over 8 weeks, 4 of them at room temperature post cessation of fermentation.

To be honest I'm not likely to drink a keg of big belgian until next winter, so I think I will add some fresh yeast, and see what happens.

This topic does sem to highlight a definite weakpoint in the knowledge base.


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## mika (18/10/07)

Your just ahead of your time Case....just like with that SaisonWeizen thingo <_<


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## Andyd (19/10/07)

mika_lika said:


> They simply recommend leaving it on the yeast cake for a few more days at the upper end of the temperature range for the yeast (which kinda goes against the warm fermenting argument ?) and it should clear up.




My understanding is that in the last stages of fermentation, the yeast are just cleaning up some of the crap that gets generated earlier on, so the raise in temperature has little or no effect on the production of esters etc.

Andy


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## OneEye (18/6/12)

I've been having some problems with Acetaldehyde lately. My last 3 brews have been an apple cidery mess. My fermentation is Temp controlled, I always use an appropriate yeast starter (via mr.malty calcs) and I've been leaving the beers in primary for around 12-14 days. Should I be leaving it on the cake longer? Could it be an infection rather than a yeast by-product?


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## mattyra (18/6/12)

It is possible that it is an infection. Give all of your equipment a good clean. I used bleach a little while ago when i detected an infection. I left the fermenter and equipment in a bleach solution for 24 hours. After that I rinsed out thoroughly (you will need to otherwise the bleach can add flavours to your beer) and haven't had the issue since. I also use starsan as a no rinse sanitiser.

I also had a problem with Acetaldehyde at one point and how I solved it was to use less simple sugars. More malts and less dextrose.


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## OneEye (18/6/12)

Yeah I have my kettle and fermenters soaking in PBW now. I don't use and simple sugars, like dextrose, in my beers. AG beers here.


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## mika (18/6/12)

Tell us more about your yeast handling. Acetaldehyde is mostly about poor yeast health/performance.


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## Greg.L (18/6/12)

mika said:


> Tell us more about your yeast handling. Acetaldehyde is mostly about poor yeast health/performance.



I don't know where you got this. Acetaldehyde is produced by the oxidation of ethanol. If you get acetaldehyde you are letting too much oxygen into your fermentation vessel after fermentation finishes. Acetaldehyde production from ethanol is a purely chemical reaction, it doesn't need any microbiological action. To reverse acetaldehyde you can try adding SO2 in the form of metabisulfite, SO2 bonds strongly to acetaldehyde (but if there is a strong smell it is usually too late). Mainly you need a good seal to keep out air.


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## OneEye (18/6/12)

I've just been doing the old glad wrap trick, using the gasket from the fermenter lid. The lid + airlock doesn't quite fit in my ferm chamber. The latest batch definitely has a stronger smell to it that a few days ago.

Should I throw it into a keg with some priming sugar and hope the yeast can clean it up a bit?


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## MHB (18/6/12)

Both Diacetyl and Acetaldehyde are made by yeast (not saying that there arent other ways to make them) but enough oxygen ingress to make a lot of acetaldehyde would have enough other affects on the beer to be very noticeable.
Having a read of German Brewing Techniques, especially the last bit on maturation should give you most of what you need. I did flick Kunze open and there is a fairly obvious amount of cribbing going on in the Lager page, including the diagrams, but thats where I would go first for information on making Lager so no big suprise.
Mark


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## dr K (18/6/12)

> QUOTE (mika @ Jun 18 2012, 05:18 PM) *
> Tell us more about your yeast handling. Acetaldehyde is mostly about poor yeast health/performance.
> 
> 
> I don't know where you got this. Acetaldehyde is produced by the oxidation of ethanol. If you get acetaldehyde you are letting too much oxygen into your fermentation vessel after fermentation finishes.



GregL, I suggest you google a bit more accurately. Acetaldehyde is just about the last thing that happens in fermentation before Ethanol,it both natural and a chemical reaction, now if you add too much oxygen after fermenation has completed you may get acetaldehyde but as Mark points out a whole bucket load of other crap (especially diacetyl) as well..on top you may get ethyl acetate which makes acetaldehyde smell like a walk in the orchard...

Acetaldehyde (well lack of it) is one of the reasons you manage your fermentation, and there is plenty written about that.

K


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## Greg.L (18/6/12)

dr K said:


> GregL, I suggest you google a bit more accurately. Acetaldehyde is just about the last thing that happens in fermentation before Ethanol,it both natural and a chemical reaction, now if you add too much oxygen after fermenation has completed you may get acetaldehyde but as Mark points out a whole bucket load of other crap (especially diacetyl) as well..on top you may get ethyl acetate which makes acetaldehyde smell like a walk in the orchard...
> 
> Acetaldehyde (well lack of it) is one of the reasons you manage your fermentation, and there is plenty written about that.
> 
> K



Hey, I didn't get this from google, it's just basic science. This gladwrap thing is just weird - is it so hard to put a lid on your fermenter? Acetaldehyde is a part of normal fermentation, but only as a step in the process. If you leave ethanol exposed to oxygen you will get either acetaldehyde or acetic acid, it's inevitable. It is hard to believe I am even having this discussion, this is such basic science. You only need a day or 2 of exposure to air to generate acetaldehyde, it will overwhelm all other flavours. Just put a lid on your beer and forget the gladwrap, that is really the stupidest idea i have ever seen, there is no reason to use gladwrap, every fermenter comes with a lid, why would you want to run the risk of getting air in there? I just can't believe some of the stuff on this forum, grumble grumble mutter mutter.


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## DJR (18/6/12)

Greg.L said:


> Hey, I didn't get this from google, it's just basic science. This gladwrap thing is just weird - is it so hard to put a lid on your fermenter? Acetaldehyde is a part of normal fermentation, but only as a step in the process. If you leave ethanol exposed to oxygen you will get either acetaldehyde or acetic acid, it's inevitable. It is hard to believe I am even having this discussion, this is such basic science. You only need a day or 2 of exposure to air to generate acetaldehyde, it will overwhelm all other flavours. Just put a lid on your beer and forget the gladwrap, that is really the stupidest idea i have ever seen, there is no reason to use gladwrap, every fermenter comes with a lid, why would you want to run the risk of getting air in there? I just can't believe some of the stuff on this forum, grumble grumble mutter mutter.



Yes, ethanol oxidation will cause acetaldehyde but poor yeast health may do the same. Acetaldehyde is an intermediate in the yeast metabolic pathway on the road to ethanol, if the yeast is stressed or in poor health it may not convert all the acetaldehyde into ethanol and your beer may taste like cloudy apple juice.

What MHB was getting at was if it was from oxidation there would be plenty more wrong (like sherry/wet cardboard)


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## mxd (18/6/12)

Greg.L said:


> Hey, I didn't get this from google, it's just basic science. This gladwrap thing is just weird - is it so hard to put a lid on your fermenter? Acetaldehyde is a part of normal fermentation, but only as a step in the process. If you leave ethanol exposed to oxygen you will get either acetaldehyde or acetic acid, it's inevitable. It is hard to believe I am even having this discussion, this is such basic science. You only need a day or 2 of exposure to air to generate acetaldehyde, it will overwhelm all other flavours. Just put a lid on your beer and forget the gladwrap, that is really the stupidest idea i have ever seen, there is no reason to use gladwrap, every fermenter comes with a lid, why would you want to run the risk of getting air in there? I just can't believe some of the stuff on this forum, grumble grumble mutter mutter.



I glad wrap so this is an interesting discussion, how does this go with the commercial brewers who open ferment ?


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## pk.sax (18/6/12)

Lid without a hole you mean, I hope.

Gladwrap is simply easier to look through and needs no cleaning, just throw it away after use and put on a fresh clean (some say sterile) piece on for the next batch. That's where it beats the old lid, no screw threads and rubber oring for the nasties to hide that need cleaning.

Airlocks are just silly in lids. In a rubber bung on a carboy, I get it. In a grommet on a fermenter lid... Stupid even.


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## Greg.L (18/6/12)

DJR said:


> Yes, ethanol oxidation will cause acetaldehyde but poor yeast health may do the same. Acetaldehyde is an intermediate in the yeast metabolic pathway on the road to ethanol, if the yeast is stressed or in poor health it may not convert all the acetaldehyde into ethanol and your beer may taste like cloudy apple juice.
> 
> What MHB was getting at was if it was from oxidation there would be plenty more wrong (like sherry/wet cardboard)



Acetaldehyde IS the sherry flavour. This intermediate in the metabolic pathway stuff is true but is just distracting you. If ethanol is exposed to air it will produce acetaldehyde, full stop. It happens very quick, and is pretty much irreversible. This is how you get acetaldehyde, not from the yeast. But don't believe me, I only have years in the wine industry, just keep using your gladwrap.


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## Greg.L (18/6/12)

mxd said:


> I glad wrap so this is an interesting discussion, how does this go with the commercial brewers who open ferment ?



Open ferments only work while the fermentation is producing lots of protective CO2. A large batch produces a lot of CO2, so you get more protection.

I don't know what is wrong with a grommet and airlock, that's what I do with no problems. I don't need to watch my ferment, it should go without problems if your yeast is healthy, just check the sg every few days. You need to keep air away from your beer once the initial ferment slows, that's the basic technique of all fermenting. You can clean your o-ring and lid with hot water, no risk. The gladwrap thing is totally crazy, why would you do that? It gives no protection at all. Put a lid on it and stop looking all the time, it will be fine.


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## dr K (18/6/12)

Greg.L said:


> Acetaldehyde IS the sherry flavour. This intermediate in the metabolic pathway stuff is true but is just distracting you. If ethanol is exposed to air it will produce acetaldehyde, full stop. It happens very quick, and is pretty much irreversible. This is how you get acetaldehyde, not from the yeast. But don't believe me, I only have years in the wine industry, just keep using your gladwrap.



Perhaps the fermentation of wine sugars to ethanol takes a different path to the fermentation of beer sugars?
Sherry gets its flavour, and the sherry flavour is due to general oxidation, acetaldehyde is what is generally described as "green-apple" or "granny-smith" in beer terms I guess this is the problem that we beer worts have with assuming that fermentation is similar in beer and wine, seems it may not be ..maybe?
As to distractions, if I were to kill my ferment early my beer would reek, it may be a distraction to you, its a CF to me..

K


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## np1962 (18/6/12)

Greg.L said:


> Open ferments only work while the fermentation is producing lots of protective CO2. A large batch produces a lot of CO2, so you get more protection.
> 
> I don't know what is wrong with a grommet and airlock, that's what I do with no problems. I don't need to watch my ferment, it should go without problems if your yeast is healthy, just check the sg every few days. You need to keep air away from your beer once the initial ferment slows, that's the basic technique of all fermenting. You can clean your o-ring and lid with hot water, no risk. The gladwrap thing is totally crazy, why would you do that? It gives no protection at all. Put a lid on it and stop looking all the time, it will be fine.


I don't know what is wrong with Gladwrap, that's what I do with no problems.  
I'm not sure if you realise it but Gladwrap doesn't actually let air in to your fermenter. It does the same job as a lid. With some advantages. One of which is space saved by not having an airlock protruding from the top of your fermenter. The main reason I do it.
And as far as Acetaldehyde is concerned, far more likely in a homebrew situation that it is a byproduct of a poor fermentation than oxidation of the finished beer.


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## Greg.L (18/6/12)

dr K said:


> Perhaps the fermentation of wine sugars to ethanol takes a different path to the fermentation of beer sugars?
> Sherry gets its flavour, and the sherry flavour is due to general oxidation, acetaldehyde is what is generally described as "green-apple" or "granny-smith" in beer terms I guess this is the problem that we beer worts have with assuming that fermentation is similar in beer and wine, seems it may not be ..maybe?
> As to distractions, if I were to kill my ferment early my beer would reek, it may be a distraction to you, its a CF to me..
> 
> K



The main flavour of sherry is due to acetaldehyde, from oxidation. Get a sample of acetaldehyde and sniff it next to sherry, you will see what I mean. The ethanol in wine is the same as the ethanol in beer, they will both oxidise to acetaldehyde. I grow lots of apples, the green apple thing isn't really a good description, I have smelled a sample of acetaldehyde and I have had acetaldehyde problems due to too much air getting in. Just keep the air out of your beer and all will be fine.


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## /// (18/6/12)

Ok, at beer camp this year I have kinda learnt a bit about this cycle. Important is to reflect that like wort production, the process of sugar coming into yeast cells and its next steps are enzymic.

Yeasts primary reason is not to make alcohol. Yeasts primary job is to grow, breed and die. To do this it must follow the cycle of glycolosis. This involves the process of various sugars into the cell via one of the 4 transport methods.

This process unfortunately causes an unbalanced redox reaction. To balance this reaction the yeast must follow the break down of those sugars through to fermentation.

So the various sugars (sucrose, glucose, fructose, maltose and maltotriose) are transported into the cell and and broken down to glucose.The various reactions happen sequentially. The glucose once generated in the cell via enzymes are then broken down to pyruvate. 

An enzyme comes in and attacks some of the pyravate to make alpha-acetoactolate. This is released outside the cell and is absorbed into the cell at the end of the ferment. This compound is important as in the presence of free oxygen, the a-acetoactolate will spontaneously convert to diacetyl. Both these compounds will be absorbed back into the cell once the ferment is done.

Following the convert to pyruvate, an enzyme comes in and decarboxalates (removes CO2) the compound, while another enzyme comes in and converts the pyruvate to acetaldehyde. 

Acetaldehyde is then then converted via an enzyme to ethanol, thus the redox reaction is then balanced. At this time some of the acetaldehyde is released outside the cell. It is then absorbed back into the cell ater on ....

But, the thing to note, the time taken to release a-acetoactolate, reduction to diacetyl and absorbtion into the cell, as well as the release and absorbtion of acetadehyde takes twice as long as the original reactions to release the compound into the cell. Hence, they take longer to mop up than be produced.

Hope this helps ...

Scotty


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## MHB (18/6/12)

Greg sorry but somewhere along the line you have got the wrong end of the stick. Yes there are a couple of ways to make Acetaldehyde but when we find it in beer it is usually produced by yeast as a normal part of the process that takes glucose and turns it into alcohol. All be it under unfavourable conditions that have prevented complete metabolism.



Or if you want to get the Piled higher and Deeper version try this Sugar Metabolism in Yeasts View attachment 55315
see you in a couple of weeks when you come up for air.
Mark

Going same place Scotty was only slower
M


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## np1962 (18/6/12)

Greg.L said:


> Just keep the air out of your beer and all will be fine.


This statement is pretty misleading.
Greg is not totally wrong though in saying oxidation of ethanol is a cause of Acetaldehyde.
This LINK gives an easy to understand rundown of how Acetaldehiyde is formed, cleaned up and then can reform due to oxidation after yeast has been removed.


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## Greg.L (18/6/12)

The guy already admitted he uses glad wrap, glad wrap lets in air, air turns ethanol to acetaldehyde. I have done a degree in viticulture, I know about the transient production of acetaldehyde as part of the fermentation process, and how acetaldehyde binds to so2 (also produced by yeast). I have been making beer (from grain) for 15 years without a hint of acetaldehyde, it is not part of what you would expect with beer unless you let in air. I have never tasted acetaldehyde in beer, but often in wine because red wine is partly an oxidative process, beer is reductive. If you have sampled pure acetaldehyde then come back to me, if not you need more experience.


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## /// (18/6/12)

Greg.L said:


> The guy already admitted he uses glad wrap, glad wrap lets in air, air turns ethanol to acetaldehyde. I have done a degree in viticulture, I know about the transient production of acetaldehyde as part of the fermentation process, and how acetaldehyde binds to so2 (also produced by yeast). I have been making beer (from grain) for 15 years without a hint of acetaldehyde, it is not part of what you would expect with beer unless you let in air. I have never tasted acetaldehyde in beer, but often in wine because red wine is partly an oxidative process, beer is reductive. If you have sampled pure acetaldehyde then come back to me, if not you need more experience.



My only challenge would be that open fermentation is good, and the air absorbtion near to zero if not minimal. If it is due to air (well more succinctly free oxygen in solution), the dissolution of o2 once the fv is up and running or finished would be hard due to the constant release of co2, any oxidation would be from dissolved o2. Even at the end of the ferment approx 1 volume of co2 is in solution, so I cant see how an open fermenter is bad.


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## DJR (18/6/12)

Greg.L said:


> The guy already admitted he uses glad wrap, glad wrap lets in air, air turns ethanol to acetaldehyde.



Sorry glad wrap does not let in air, or if it does, too tiny an amount to cause the problems described (see open fermenters...). The way that people use glad wrap is to put some over the fermenter where the lid would go, and then put an o-ring over the wrap. How that lets in air when the beer is producing CO2 i don't know. I've done the glad wrap thing once, and I didn't get an oxidised beer with any sherry or green apple character. I did however get a beer with massive green apple character once from underpitching a cold fermented lager with a yeast pretty prone to it AFAIK (Budvar/WLP802).

Perhaps wine yeasts when treated well clean up the acetaldehyde quicker due to higher fermentation temperatures, the presence of yeast nutrient or not making poor yeast management decisions like pitching 5% then 8% then 9% onto the same yeast like the OP did, but there is more than one way to get there

anyway back to the problem raised in today's new post, try not gladwrapping instead to rule it out but 3 beers in a row with acetaldehyde sounds a bit much... maybe you're not leaving them in the fermenter long enough?


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## Greg.L (18/6/12)

/// said:


> My only challenge would be that open fermentation is good, and the air absorbtion near to zero if not minimal. If it is due to air (well more succinctly free oxygen in solution), the dissolution of o2 once the fv is up and running or finished would be hard due to the constant release of co2, any oxidation would be from dissolved o2. Even at the end of the ferment approx 1 volume of co2 is in solution, so I cant see how an open fermenter is bad.



The fact is that even a tiny bit of oxygen is bad. O2 is a very strong oxidiser, that's how the name came. You may think that a beer saturated in co2 is safe, but there is such a thing as partial pressures, it doesn't matter how saturated the beer is with co2 it can still dissolve oxygen. The only protection is the rapid movement of co2 out of the container, as soon as that slows o2 starts to enter. I use an open fermenter for cider because I can't afford a big closed fermenter. A basic rule for all alcoholic beverage production is to keep air out, there are a few special exceptions but beer isn't one.

If you think that glad wrap is sufficient protection for keeping air out then go for it, just don't complain when you get oxidation or infection. Most infections I see on AHB are aerobic in nature, caused by letting air in. If you keep air out of your beer the chances of getting a problem range from slim to zero. 

Now just don't get me started on leaving your wort in no-chill cubes.


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## manticle (18/6/12)

You have obvious experience of many things Greg but I'm presuming you have no personal experience of either glad wrapping or no-chill - only theory on which you are basing your claims.

When multiple people report a certain result (eg no-chill works, glad wrap works for actively fermenting beer* it questions at the very least an interpretation of a theory, if not the theory itself.

Science is always evolving - it is not stagnant.

Don't diss methods with which you are not personally familiar when there is much evidence (anecdotal/experiential 'evidence' perhaps but enough that it's at least worth testing).

Loads of people use glad wrap without getting noticeable acetaldhyde so to point the finger and say 'culprit there' is a bit simplistic. Possible culprit maybe. Definite - neither you, nor I can say that.

* For aging beer, I wouldn't recommend it.

Having said the above, I would consider oxidation as a very real possibility in why the acetaldehyde is appearing. That or unfinished beer - 14 days is irrelevant if the yeast hasn't finished and been given a chance to clean up. If you can taste acetaldehyde in the conditioning beer, it needs more conditioning in my experience.


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## Sprungmonkey (18/6/12)

Acetaldehyde is also from oxygenation after ferment - you can purge it out with CO2 in the keg. may take a while if it is strong though


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## Greg.L (18/6/12)

I actually did try glad wrap once, never again (I got lazy). My point is if you have a lid, why use gladwrap? It just doesn't make sense.


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## kevin_smevin (18/6/12)

Greg.L said:


> The fact is that even a tiny bit of oxygen is bad. O2 is a very strong oxidiser, that's how the name came. You may think that a beer saturated in co2 is safe, but there is such a thing as partial pressures, it doesn't matter how saturated the beer is with co2 it can still dissolve oxygen. The only protection is the rapid movement of co2 out of the container, as soon as that slows o2 starts to enter. I use an open fermenter for cider because I can't afford a big closed fermenter. A basic rule for all alcoholic beverage production is to keep air out, there are a few special exceptions but beer isn't one.
> 
> If you think that glad wrap is sufficient protection for keeping air out then go for it, just don't complain when you get oxidation or infection. Most infections I see on AHB are aerobic in nature, caused by letting air in. If you keep air out of your beer the chances of getting a problem range from slim to zero.
> 
> Now just don't get me started on leaving your wort in no-chill cubes.



Plenty of people use glad wrap in place of a lid on their fermenter and dont seem to have any problems. I use a lid so i cant say i have any personel experience. 

The common effect of oxygen in beer is wet cardboard and papery type flavours. Sherry like flavours do occur but seem to take a back seat to the afore mentioned. It would be rare to get sherry like flavours without the wet cardboard side of things. It is common in young beer to get the green apple type acetaldehyde flavours in the absence of typical oxidation flavours- if your yeast is healthy enough, it usually cleans these up in a few days.

If your beer is showing typical oxidation flavours such as paper, carboard/wet cardboard or sherry i would look at reducing exposure to air. If these green apple flavours are present in their absence i would suggest the problem is likely due to poor yeast health or possibly a contamination issue.


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## Greg.L (18/6/12)

Sprungmonkey said:


> Acetaldehyde is also from oxygenation after ferment - you can purge it out with CO2 in the keg. may take a while if it is strong though



Once the acetaldehyde is bad enough, which is most cases, there is no cure. The cost of the co2 for a cure that probably won't work would be a real waste. Just tip it out and use a lid next time.


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## Greg.L (18/6/12)

yum yum yum said:


> If your beer is showing typical oxidation flavours such as paper, carboard/wet cardboard or sherry i would look at reducing exposure to air.



See this is where people get things arse-about. You should be always trying to reduce exposure to air, not because you have a problem. Keep the air out and you won't get the problem, don't let the air in and wait for the problem.


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## MaestroMatt (18/6/12)

I brew in a vacuum chamber so I don't have any problems with oxygen. Of course, I can't breathe when I brew, and I eventually lose consciousness and die.....so that part sucks

but the important thing is that my Gladwrap lid seems fine.


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## daemon (18/6/12)

Have we got a contender for the the_new_new_darren Darren?

Greg.L: You seem to be a self confessed expert who hasn't really offered anything useful to the discussion and in contrast to what professional brewers have posted here. You've even disagreed with the "green apples" description, which means you'd be disagreeing with thousands of professional brewers around the world with far more experience than you. Seeing a trend here?

Please let us know how many PPM of oxygen that the glad wrap will allow to permeate through, especially considering the positive pressure of the co2. I have no doubt that glad wrap isn't as effective as the HDPE lid, but over a two week window (less for many) is it really that great of an issue? I haven't seen any evidence that positively concludes it is.

You've been doing it for 15 years without issue and that's great, but it doesn't mean that your methods or understanding is the only correct one.


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## stakka82 (18/6/12)

This has been a remarkably informative thread, despite, or perhaps because of, the 'vigorous' discussion.

I tried a pale ale of mine, all willamette, that had been in the bottle for only 7 days on the weekend. It was only half carbed but i couldn't wait to try it. Nice, but definite green apple character. Faint but noticable.

I wasnt sure if it was just the hops (never used willamette before this, and i had to put about 100 grams in a 22 litre batch to get a decent level of bittering) but reading here suggests it's an acetaldehyde issue. I'm going to try the batch again this weekend when its finished carbing, then cold condition all the bottles till I finish the batch.

Seems like I may have caught the conditioning yeast before they had cleaned up in the bottle? Does that sound correct? This thread also suggests that the conditioning time should fix the issue. Hoping it does.


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## bullsneck (18/6/12)

MaestroMatt said:


> I brew in a vacuum chamber so I don't have any problems with oxygen. Of course, I can't breathe when I brew, and I eventually lose consciousness and die.....so that part sucks
> 
> but the important thing is that my Gladwrap lid seems fine.



If you die from lack of Oxygen, I can't imagine how a kitten in an airlock would fare.


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## kevin_smevin (18/6/12)

Greg.L said:


> See this is where people get things arse-about. You should be always trying to reduce exposure to air, not because you have a problem. Keep the air out and you won't get the problem, don't let the air in and wait for the problem.



It's not ass about. You keep ignoring the fact that green apple from acetaldehyde is a normal part of beer fermentation. We're trying to understand the cause here. It could be oxygen exposure but it may have nothing to do with oxygen exposure. You are right, all brewers should avoid oxygen exposure post fermentation but in this instance it is not the only potential cause of the problem.


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## manticle (18/6/12)

Greg.L said:


> I actually did try glad wrap once, never again (I got lazy). My point is if you have a lid, why use gladwrap? It just doesn't make sense.



I think one big reason is to learn not to rely on an airlock as a sign of fermentation. That's where it starts.

Mostly convenience otherwise - clean one vessel and no accessories. It does make sense even if it's not your preferred method: However it doesn't make sense to condition beer that way for very long. Active fermentation only. I wouldn't be conditioning for ages with an HDPE lid either but some people do and report no issue. Long term beer gets racked to glass, short term stays in cube, tight lid, in fridge.

I mainly use a cube with a lid backed off during active fermentation so during conditioning I tighten the lid to reduce exposure to oxygen (I also no chill and ferment directly in the cube so you may faint over that one but I can tell you it works and it works very well: theoretically and practically).

I do agree with you that open fermentation will work best when it's active, not passive/conditioning and glad should be treated the same way. I don't agree that you can automatically point and say there's your issue because, in my experience, 14 days in primary with a glad lid will not automatically generate discernible acetaldehyde (which in beer often tastes like granny smiths or that toffee apple confecionery product you used to be able to buy around the place) and if loads of people do x and don't get y, it's not definite that x causes y.


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## browndog (18/6/12)

Greg L. I'm not convinced about your oxygen-gladwrap-use a lid arguement. Many moons ago I threw away all the seals in my fermenter lids and just screw them on without the seal, I'm sure this would provide an oxygen superhighway compared to a well fitting grladwrap seal. Guess what, no issues with acetaldehyde here. Very interesting banter going on though.

-Browndog

edit:clumbsy fingers


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## Greg.L (18/6/12)

browndog said:


> Greg L. I'm not convinced about your oxygen-gladwrap-use a lid arguement. Many moons ago I threw away all the seals in my fermenter lids and just screw them on without the seal, I'm sure this would provide an oxygen superhighway compared to a well fitting grladwrap seal. Guess what, no issues with acetaldehyde here. Very interesting banter going on though.
> 
> -Browndog
> 
> edit:clumbsy fingers



Browndog, keeping out air is just a basic technique of brewing. You wouldn't brag about driving drunk, but you would probably get away with it. It's just not safe. Put the seals back on, show us you can do the right thing.

Glad to keep you entertained.


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## WitWonder (18/6/12)

Perhaps here in all the banter I missed the answer to the question about open fermentations and why that practise still goes on today if it was the mother-of-all green apples? Also, the fact Greg has studied wine making which, coupled with "15 years" of homebrewing, has made him an expert on brewing is to my mind like suggesting an ear nose and throat surgeon should start treating cancer patients


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## np1962 (18/6/12)

I didn't know Viticulture was Winemaking B)


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## Greg.L (18/6/12)

I doubt if anyone on this thread has actually tried a sample of acetaldehyde (myself excepted). Just because you think you have noticed "green apples" doesn't mean you know what acetaldehyde smells like, and it is a smell more than a taste. And yes, the viticulture degree does include winemaking.


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## manticle (18/6/12)

Actually there's a few people (myself included) who have sampled acetaldehyde in the form of fault tasting kits etc. I'll be tasting it again week after this.

I don't think the 'sink the boot into greg because he's in the wine industry, not the beer industry' attitude is justified but neither is you suggesting that no-one here (and there are professional brewers who've posted in this thread) has tasted acetaldehyde samples.


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## pk.sax (18/6/12)

How pissed are you tonight Greg?


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## kario (19/6/12)

stakka82 said:


> This has been a remarkably informative thread, despite, or perhaps because of, the 'vigorous' discussion.
> 
> I tried a pale ale of mine, all willamette, that had been in the bottle for only 7 days on the weekend. It was only half carbed but i couldn't wait to try it. Nice, but definite green apple character. Faint but noticable.
> 
> ...



Sure will....crack a bottle each month and test it. I had a batch that took 5mths to come good....and GOOD it was!


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## Screwtop (19/6/12)

Gregs statements may have sound scientific validity, however my kinesthetic learning style prevents me from agreeing :blink: 

Screwy


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## WitWonder (19/6/12)

My post was somewhat tongue in cheek, but the question was serious - why is the practise of open fermenting still continued to this day if it is highly likely (certain?) to introduce acetaldehyde in the final product?


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## Greg.L (19/6/12)

WitWonder said:


> My post was somewhat tongue in cheek, but the question was serious - why is the practise of open fermenting still continued to this day if it is highly likely (certain?) to introduce acetaldehyde in the final product?



I don't know enough about industrial brewing to know how common open fermenting is, but the principle is quite different on a large scale. The relative surface area is much smaller so the risk from air contact is smaller. Anything of 100L or less is generally at an extreme risk of oxidation, but if you keep the air out it doesn't matter. Keeping air excluded has the added benefit of protecting against infection, most infections need air to grow.


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## glenwal (19/6/12)

An airlock will actually let in more oxygen (any nasties that are in the air) than glad wrap as the glad wrap is flexable and can expand and contract. During fermentation, the oxygen inside the fermenter is consumed, and CO2 is produced. With glad wrap the end result is a positive pressure inside (ie. excess quantity) of CO2, with an air lock the pressure equalises.

When a sample is drawn through the tap with glad wrap, the sample reduces the pressure inside and helps it to equalise with the external pressure, meaning no air is drawin into the fermenter. And even if more liquid is taken out than there is excess CO2 inside, the glad wrap lid will "deform" to displace the volume instead of sucking in outside air. With an air lock, drawing off a sample will reduce the pressure inside, which will suck air in through the airlock resulting in air inside the fermenter.


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## MastersBrewery (19/6/12)

informative and amusing ... that how I like my threads h34r:


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## mattyra (19/6/12)

WitWonder said:


> My post was somewhat tongue in cheek, but the question was serious - why is the practise of open fermenting still continued to this day if it is highly likely (certain?) to introduce acetaldehyde in the final product?



Have you tasted VB. Obviously the best flavour is not the main goal when these people make beer :lol: 

To add something to the discussion. I have only been brewing for a couple of years but have tried both methods and trying to make my brewing better. I didn't really notice any differance when using the lid or the glad wrap. I just come to the conclusion that if you are just fermenting your beer it won't really make much of a differance as long as you give a decent attempt at trying to keep the oxygen out (CO2 is heavier the O2 therefore sitting low in the fermenter and not letting the O2 in).


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## Greg.L (19/6/12)

According to wikipedia the permeability of polythene wrap is 2000 cm3 μm m-2 d-1 kPa-1. Thats a pretty high figure for such a thin film. Holding it down with an o-ring won't help, if the co2 can flow out then the o2 can get in, remember the concentration gradient from out to in is pretty steep.


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## glenwal (19/6/12)

Greg.L said:


> According to wikipedia the permeability of polythene wrap is 2000 cm3 μm m-2 d-1 kPa-1. Thats a pretty high figure for such a thin film. Holding it down with an o-ring won't help, if the co2 can flow out then the o2 can get in, remember the concentration gradient from out to in is pretty steep.



Except the CO2 is heavier than air and the CO2 is lower so there isn't going to be an exchange of gases (not to mention the positive pressure from fermentation that will also prevent oxygen from flowing inwards)


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## Greg.L (19/6/12)

Glen W said:


> Except the CO2 is heavier than air and the CO2 is lower so there isn't going to be an exchange of gases (not to mention the positive pressure from fermentation that will also prevent oxygen from flowing inwards)



Here's Dalton's law for you.

"The partial pressure of an ideal gas in a mixture is equal to the pressure it would exert if it occupied the same volume alone at the same temperature. This is because ideal gas molecules are so far apart that they don't interfere with each other at all. Actual real-world gases come very close to this ideal."

The o2 and co2 can both reach saturation irrespective of each individual concentration. Having co2 in there won't keep the o2 out at all, being heavier only helps keep the co2 in.


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## kymba (19/6/12)

aww, Greg...please do not speak ill of our gas layers - Long live the thick, creamy, impervious blanket of CO2 that is Our Saviour & benevolent protector of our open fermentation vessels!


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## OneEye (19/6/12)

For anyone that comes here for the original point of the thread... I found this on HomeBrewTalk.com which some may find useful... at least worth a shot I think.

"Either way, I barely noticed this when transfering to the keg and thought it was mild and would lager-out. 3 weeks later, I took a sample and definitely decided I couldnt drink a keg of the stuff. So I started doing some research. It turns out that acetylaldehyde is very volatile, and the fact that the keg was already carbed could be a huge benefit, as the escaping CO2 at warmer temps would bring the acetylaldehyde right with it.

I took the keg out of the kegerator, and burped the pressure relief valve every day or so for 5 days now. Additionally, I took some yeast cake, added about 8oz of wort to it, let it start fermenting for about 24h and pitched that.

The combination seems to have completely cleared up the problem after only a few days. It delays the whole process though, as I really need to re-lager the beer now, but at least I will have a (at this point it is promising) very good tasting Munich Helles."


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## glenwal (19/6/12)

Greg.L said:


> Here's Dalton's law for you.
> 
> "The partial pressure of an ideal gas in a mixture is equal to the pressure it would exert if it occupied the same volume alone at the same temperature. This is because ideal gas molecules are so far apart that they don't interfere with each other at all. Actual real-world gases come very close to this ideal."
> 
> The o2 and co2 can both reach saturation irrespective of each individual concentration. Having co2 in there won't keep the o2 out at all, being heavier only helps keep the co2 in.


Except there is a layer of solid in between in this case, and permeability of a solid does not follow Daltons law. The positive partial pressure of the CO2 inside the fermenter will reduce the total permeability of the sold (in this case - glad wrap)


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## drsmurto (19/6/12)

A lot of brewers and winemakers (pros and amateurs) think they know a lot about O2 and it's impact on beer and wine but the fact people like myself are paid to research the impact of oxygen before, during and after fermentation should make it clear that neither industry has stopped trying to understand it, nore are they anywhere near really understanding it. We did a large scale trial during vintage this year looking at O2 during winemaking and are following it through monitoring the development, acetaldehyde production is one of hundreds of molecules we are tracking. In addition, i am currently writing a review on a closely related topic that should be published later this year, currently going through the peer review process.

As an FYI, the Journal of the Institute of Brewing is currently allowing free online access so I strongly suggest many of you make use of this unique opportunity (most research organisations including mine, both academic and private, pay $1000s per year per journal/publisher for access) to dispel many of the myths that circulate this forum. I can only dream.  

Whilst there is a large positive pressure of CO2, gladwrap will be ok, not ideal but ok. Once that pressure drops (ie the gladwrap is not stretched to breaking point) the pressure is no longer enough to prevent O2 getting in. Gladwrap is a bacterial barrier, it is not designed to, nor does it prevent gas transfer. O2 and CO2 are miscible and despite the apparent difference in densities, environments at or close to atmospheric pressure will result in mixing of these 2 gases. I have spent and continue to spend a lot of time and effort removing and keeping O2 out of my experiments in the lab and am measuring the content down to 1 ppb. Even inside the standard corny keg (which i use as an inert gas chamber) there is a minimum pressure required to prevent O2 from getting back in. So if O2 can get into a sealed keg, with a slight positive pressure, then what hope does gladwrap have.

My 2 c, not intended as a lecture but seems to have come across that way.
Cheers
DrSmurto

p.s I have smelt pure acetaldehyde on numerous occasions, we use it to train up sensory panellists and I recently went through a rigorous training regime on faults and taints in wine, acetaldehyde was one of them and i rarely picked it as green apples. At varying concentrations, in different media the perception changes. When mixed with other volatile compunds this is further complicated due to a synergistic effect that may have positive or negative results. Sensory science is far from simple.


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## gunbrew (19/6/12)

Interesting thread.
I went to a brew pub and saw 800 litre open fermentation vessels.
One was full, see photo.
The bar tender sent me into the brewery to have a look.
At the time I was in shock that they let a customer walk in there and I was thinking that people walking in there had to be an infection risk to the beer.
The place only made 2 beers a dark and a light, no idea what yeast.
Brewer was not there to quiz.
I asked the bar tender numerous questions for what ever that was worth, he said:
Open fermenting was only whilst there was a vigourous ferment, they had 2 large open fermenters.
Then they moved the beer to a large closed fermenter for the remainser of the ferment, visible at back of photo.
Then they moved the beer to closed conditioning tanks in a cool room.


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## Greg.L (19/6/12)

gunbrew said:


> Interesting thread.
> I went to a brew pub and saw 800 litre open fermentation vessels.
> One was full, see photo.
> The bar tender sent me into the brewery to have a look.
> ...



That makes sense, brief open fermentation then into sealed SS fermentation vessels. I have no problem with that.

Thanks for your input Dr Smurto. It is a very complex area with lots of complications.


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## OneEye (19/6/12)

Thanks for all the input guys, especially Greg.L and Dr.S. I'll persist with trying to 'fix' this beer but future brews (at least the next couple at least) I'll try and throw a lid on.... I'll just have to try and find a relatively low profile airlock (maybe a small 3-piece?) so it will fit in my ferm chamber!


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## [email protected] (19/6/12)

DrSmurto said:


> My 2 c, not intended as a lecture but seems to have come across that way.
> Cheers
> DrSmurto




I guess that just depends on your POV eh? I found it to be quite informative along with many other great contributions in this thread. 
So :icon_cheers:


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## mattyra (19/6/12)

Thanks Dr What a read. Not meaning to spark anything up again but wouldn't the lid on the fermenting vessel be in the same position as the glad wrap. If the keg wasn't able to keep all of the O2 out then what hope does a plastic lid (that has a hole and airlock in it)?


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## daemon (19/6/12)

Greg.L I'm curious that if you think Glad Wrap during fermentation is such a bad idea, what method do you use to transfer the beer into kegs / bottles that guarantees that there is no oxgen left in the keg / bottle? 

The risk of oxidisation when transferring post-fermentation are far, far greater (IMHO) than during fermentation yet I don't know of any way to purge 100% of the oxygen from my kegs.


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## Greg.L (19/6/12)

Daemon said:


> Greg.L I'm curious that if you think Glad Wrap during fermentation is such a bad idea, what method do you use to transfer the beer into kegs / bottles that guarantees that there is no oxgen left in the keg / bottle?
> 
> The risk of oxidisation when transferring post-fermentation are far, far greater (IMHO) than during fermentation yet I don't know of any way to purge 100% of the oxygen from my kegs.



I bottle condition, the yeast soak up the little bit of o2 in the bottles. I handle my beer/wine/cider as little as possible. The fact that some contact with air is inevitable when handling makes it more important to reduce air contact at other times, the effect tends to be cumulative.

As for lids v film, the lids are thicker hdpe rather than thin ldpe used for film, so the permeability is much lower. SS or glass are even better. The seals on a screw thread lid with an o-ring are much better, only a small amount of o2 can get past.


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## mattyra (19/6/12)

Greg.L said:


> As for lids v film, the lids are thicker hdpe rather than thin ldpe used for film, so the permeability is much lower. SS or glass are even better. The seals on a screw thread lid with an o-ring are much better, only a small amount of o2 can get past.



Makes sense. I would love to be able to get glass equipment to brew in but money is the issue there. I always add priming sugar to my kegs as well. Not sure why, I have just had better success in doing so.

You brew AG don't you Greg?


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## MaltyHops (19/6/12)

Mattyra said:


> ... I always add priming sugar to my kegs as well. Not sure why,
> I have just had better success in doing so. ...


Gives the yeast in the kegged beer something to chew on and
use up O2 in the keg along the way.


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## Greg.L (19/6/12)

Mattyra said:


> Makes sense. I would love to be able to get glass equipment to brew in but money is the issue there. I always add priming sugar to my kegs as well. Not sure why, I have just had better success in doing so.
> 
> You brew AG don't you Greg?



Yes I do brew AG, though a bit more basic than most of the brewers on AHB. I think hdpe is fine for brewing if you bottle or keg within a month (or 2). For wine or cider at home you need glass or ss, because you store it longer. I mainly do wine and cider now because I can grow my own grapes and apples, growing barley is a bit harder at my place.


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## MHB (19/6/12)

Given that a lot of what Greg.L has said about the permeability of plastics films, containers and lids is right (even the bullet dodged on nochill cubes) his comments still lead to the wrong conclusion.
You can get Acetaldehyde in a beer brewed in a stainless steel uni tank (CCV) where from the time the yeast is pitched to the time the beer is ready to serve there is going to be overpressure and no measurable oxygen ingress.
I think this shows conclusively that taste able amounts of Acetaldehyde can and I would argue are generally caused by poor brewing rather than oxygen uptake and the chemical conversion of alcohol to Acetaldehyde.
I personally doubt you can get enough Oxidisation of Alcohol to Acetaldehyde without a lot of other related faults being very obvious. True O2 uptake after the yeast is pitched is something you want to minimise but for the average home brewer its going to be far more important to make sure you have a big and healthy enough yeast pitch going into a well made wort and that the temperature of the ferment is well managed.
If you are using gladwrap I wouldnt stop, there are lots of more important issues that would need to be addressed before I worried about that. The trace amounts of O2 that can (and do) get into the wort will be quickly consumed by the yeast
Wine makers often have different points of view to brewers I think largely because they throw SO2 at everything with a wide mouthed shovel, something we as brewers just dont have the luxury of doing.
Mark


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## Greg.L (19/6/12)

It may be possible to get residual acetaldehyde from the fermentation process, but it's not something I have experienced, and I doubt that it is common. It is very easy for ethanol to oxidise to acetaldehyde after fermentation has finished, something i have seen very often with wine and cider. You don't usually get other faults, though it is quite possible because o2 causes infections as well as oxidation.

If you are happy using gladwrap, then by all means continue. Personally I like to eliminate the chance of problems before they happen, rather than after, and that means a lid with a good solid seal.

brewers don't add so2 but yeast produce their own so2 naturally.


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## drsmurto (19/6/12)

Greg.L said:


> It may be possible to get residual acetaldehyde from the fermentation process, but it's not something I have experienced, and I doubt that it is common. It is very easy for ethanol to oxidise to acetaldehyde after fermentation has finished, something i have seen very often with wine and cider. You don't usually get other faults, though it is quite possible because o2 causes infections as well as oxidation.
> 
> If you are happy using gladwrap, then by all means continue. Personally I like to eliminate the chance of problems before they happen, rather than after, and that means a lid with a good solid seal.
> 
> brewers don't add so2 but yeast produce their own so2 naturally.



You get vastly more acetaldehyde in wine due to a set of complex redox cycles in which the polyphenols play a central role (along with transition metals such as Fe and Cu). The levels of polyphenols in wine, as far i my research tells me, is much, much higher than in beer. Without these redox cycles oxygen does nothing as molecular oxygen cannot react with organic compounds.


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## pk.sax (19/6/12)

I've had had a beer brewed with gladwrap develop a slight film, this was at the end of a 4ish week ferment. The problem is that for the average time a homebrewer keeps it under gladwrap, there is a decent amount of CO2 coming out and then after that it takes time for enough oxygen to seep through the wrap (observational) to cause anything noticeable. with an HDPE lid, this will be a longer time but most home brewers don't keep it like that for so long anyway. Hence the common experience here of using gladwrap.
I personally ditched the wrap and use a blowoff tube now because of the bother the wrap creates with handling (I tears too easily) and moving fermenters.

Then again, some people have heaps of space in their sheds and don't need to move their fermenters ever so they don't have to care. Horses for golf courses.


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## Greg.L (19/6/12)

The problem with all threads about taints and faults is you can't taste beer over the internet (or is there an app for that?). Descriptions are subjective and you really need to taste the beer and see the process to diagnose a fault. I have never tasted acetaldehyde in beer, and it's not a taint I would associate with beer. My advice is only general, how to improve your process to reduce the general chance of faults. I think that if you are getting acetaldehyde in beer you must be doing something very wrong, and since the poster was using gladwrap it seems like a good place to start. The general principal of excluding air whenever possible can't really be challenged (IMO).


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## daemon (19/6/12)

Greg.L said:


> I bottle condition, the yeast soak up the little bit of o2 in the bottles. I handle my beer/wine/cider as little as possible. The fact that some contact with air is inevitable when handling makes it more important to reduce air contact at other times, the effect tends to be cumulative.


So what would be the difference between o2 permeating the glad wrap vs o2 contained within bottles and kegs? I would have thought there'd be an order of magnitude in o2 concentration in a keg / bottle vs what can possibly enter a glad wrap barrier (especially since a fermenter has positive co2 production). I'm still fairly certain you're chasing the wrong cause here, especially since many experienced brewers use glad wrap without any Acetaldehyde problems.



Greg.L said:


> The problem with all threads about taints and faults is you can't taste beer over the internet (or is there an app for that?). Descriptions are subjective and you really need to taste the beer and see the process to diagnose a fault. I have never tasted acetaldehyde in beer, and it's not a taint I would associate with beer. My advice is only general, how to improve your process to reduce the general chance of faults. I think that if you are getting acetaldehyde in beer you must be doing something very wrong, and since the poster was using gladwrap it seems like a good place to start. The general principal of excluding air whenever possible can't really be challenged (IMO).


Actually, many of us are in clubs that meet monthly to taste and judge beer, as well as general AHB meetups / case swaps. Faults (if they exist) are identified and generally then discussed with the brewer afterwards to help determine the cause and/or eliminate it in future brews. This is with experienced and professional brewers too, not just a few neighbours meeting to try the latest kit + sugar.

You think that's very wrong to get Acetaldehyde in a beer yet it's naturally produced by yeast but normally "cleaned up" by the yeast once fermentation has completed. If you're bottling then the time it takes for the secondary fermentation will be long enough to clean up most of the Acetaldehyde if it's been a healthy fermentation.

MHB has offered the best advice, check the health of your yeast, check the quantities you're pitching and ensure you manage the fermentation process well (time + temp). Also allow the beer to condition for longer on the original yeast to allow the yeast to cleanup the Acetaldehyde. Personally I ferment for 7 days, let it sit for an additional 3 days to allow the yeast to cleanup and then cold condition for up to 7 days before kegging. Many others have different timings (depending on style + personal preferences etc), so figure out what works for you.


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## OneEye (19/6/12)

Thanks again for all the replies guys. I could be wrong and what I've got here isn't acetaldehyde (although it is super green) at the same time it is sour too, and seems to be getting worse. Could be an infection of some kind? This will be the 3rd batch that's exhibited the same signs. The first was an extract porter recipe (15L pitched unhydrated US05), and on the same brew day I made a 15L CPA BIAB (cooled with my plate chiller and pitched a 1L starter of 1056 that I made the day before) The third batch was a DrSmurto Golden Ale, again 15L BIAB with a 1L starter of 1056. 
2 different fermenters in total. The extract never touched my urn or chiller. The only thing they all had in common was being in the same temp controlled fermentation space (an old bathroom vanity than I've insulated and installed a flood light into) all with glad wrap lids. 14 days each (give or take a few days)

I'm currently soaking the fermenters in PBW and I might pick up a FWK and try and ferment that into something drinkable to fill my little kegs up.

Edit: It's just weird that this is popping its head up after half a dozen successful brews so far, using pretty much the same equipment/process


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## /// (19/6/12)

Some of the best beer I've ever had, and the best brewery I have ever been too (and I go to alot of them) ... open fermentation and lots of air ... boyah Anchor Brewing.

Open air ferments have been done for hundreds of years, may the practice continue ....


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## daemon (19/6/12)

The fact that it's also got a sour taste isn't a good sign, normally this a bacterial infection. Did you notice any problems with the fermentation, eg a film over the top of the krausen? Have a look at the Infection Photo thread for examples: http://www.aussiehomebrewer.com/forum/inde...showtopic=51830

It could be acetic acid bacteria if oxygen has re-entered the beer, how careful are you when transferring to the keg?


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## manticle (20/6/12)

Greg.L said:


> The problem with all threads about taints and faults is you can't taste beer over the internet (or is there an app for that?). Descriptions are subjective and you really need to taste the beer and see the process to diagnose a fault. I have never tasted acetaldehyde in beer, and it's not a taint I would associate with beer. My advice is only general, how to improve your process to reduce the general chance of faults. I think that if you are getting acetaldehyde in beer you must be doing something very wrong, and since the poster was using gladwrap it seems like a good place to start. The general principal of excluding air whenever possible can't really be challenged (IMO).



All that's well and good Greg but you were very specific and assured about your reasoning for a fault you admit you can't taste over the net and admit you have never tasted in beer (doesn't mean it doesn't exist) and when questioned, suggested no-one else had ever tasted a sample of acetaldehyde.

I think you were off base with the way you approached this. You have a good knowledge base and good experience that can help people out but there's a lot of others with a very decent knowledge base and experience here too - many comparable to yours. Casting aspersions on their experience won't make people want to listen to you, even if and when you are correct.


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## kirem (20/6/12)

DrSmurto said:


> You get vastly more acetaldehyde in wine due to a set of complex redox cycles in which the polyphenols play a central role (along with transition metals such as Fe and Cu). The levels of polyphenols in wine, as far i my research tells me, is much, much higher than in beer. Without these redox cycles oxygen does nothing as molecular oxygen cannot react with organic compounds.



WINE NERD


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## Screwtop (20/6/12)

kirem said:


> WINE NERD




Yeah, bloody wine nerds :lol:

Screwy


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## Greg.L (20/6/12)

I've posted a bit on this thread because some people think glad wrap is a good barrier against oxygen getting in beer. The fact is that it's not. I understand the confusion because it seems counter-intuitive that oxygen can get in when it is full of co2, but it can and will. There isn't a good reason to use glad wrap, a tight lid with an airlock keeps oxygen out much better. 

I also think that because beer is so tolerant of rough treatment people get a bit relaxed about good brewery practise. Talk about open ferments and such encourages people to think it's ok to get a bit of air in there. If you keep a tight lid on and don't handle the beer too much the chances of having a problem are pretty remote.


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## drsmurto (20/6/12)

kirem said:


> WINE NERD



B)


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## Nick JD (20/6/12)

Why is kit beer often acetylaldehydey? Is it the sucrose?


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## drsmurto (20/6/12)

Breweries and wineries may open ferment but I doubt many fermenters remain open when the fermentation slows down/stops.


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## Acasta (13/9/12)

Well after sifting through the great debate in this thread, I'm wondering if we can get some good discussion on the topic of how to get rid of Acetaldehyde?
Granted that it may be caused by oxygenation or poor yeast conditions.

I'm not sure what has caused the Acetaldehyde in my brew. I pitched it onto the cake of a previous beer (so enough yeast cells) and left it there for 2 weeks at 18-20deg (which should have been long enough for yeast to finish and clean up?). I then chilled it, after 2 days added gelatine and 2 days after that kegged and force carbed.
The fresh fruit/green taste didn't really show up until recently (few days in the keg), I'm quite sure it wasn't there in the fermenter early on, but I didn't sample from after 1.5 weeks from pitching to after kegging.

What are some ways of getting it to clean up? It was chilled in the fridge, so I've taken the keg out and left it in the garage to warm up and hopefully help the flavours balance out a bit quicker.

As I was reading this thread I found this, which moosebeer had come accross. Anyone tried it? I'm thinking of attempting to burp it a bit for a few days if that might help.

I've also had a beer, a pils using S189 that never got rid of this flavour. 4 weeks in fermenter and 4 weeks in keg and still had that flavour.




moosebeer said:


> "Either way, I barely noticed this when transfering to the keg and thought it was mild and would lager-out. 3 weeks later, I took a sample and definitely decided I couldnt drink a keg of the stuff. So I started doing some research. It turns out that acetylaldehyde is very volatile, and the fact that the keg was already carbed could be a huge benefit, as the escaping CO2 at warmer temps would bring the acetylaldehyde right with it.
> 
> I took the keg out of the kegerator, and burped the pressure relief valve every day or so for 5 days now. Additionally, I took some yeast cake, added about 8oz of wort to it, let it start fermenting for about 24h and pitched that.


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## [email protected] (13/9/12)

Acasta said:


> Well after sifting through the great debate in this thread, I'm wondering if we can get some good discussion on the topic of how to get rid of Acetaldehyde?
> Granted that it may be caused by oxygenation or poor yeast conditions.
> 
> I'm not sure what has caused the Acetaldehyde in my brew. I pitched it onto the cake of a previous beer (so enough yeast cells) and left it there for 2 weeks at 18-20deg (which should have been long enough for yeast to finish and clean up?). I then chilled it, after 2 days added gelatine and 2 days after that kegged and force carbed.
> ...



Did we establish that you probably had aceto infection in other thread?

Granted you may be talking about different beers? If so it could be that your other beers have a less severe mild infection and that is what you are tasting? and not Acetaldehyde

Just a theory, maybe see if you can get an experienced taster to taste it?


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## Acasta (13/9/12)

Sadly, a different beer...

Different everything actually. Hops, yeast, malt, fermenter, time of brew. All different, but still 2 with Acetaldehyde and one with solvent taste (which we determined an infection).

1/4 kegs are drinkable but haha <_<

I've even started re-reading 'how to brew' chapter one to see wtf is going on. After fermenting for 2-3 weeks I have no idea what these beers are picking up these flavours.


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## [email protected] (13/9/12)

I would start by nuking everything with various chemicals and heat. Get new / fresh yeast and pitch lots of it.
Look into how much O2 you are introducing in your process after ferment.


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## drsmurto (13/9/12)

SO2 reacts with acetaldehyde so if you have any potassium metabisulphite i would start dosing that in - 20 ppm total at a time (use an online SO2 additions calculator).


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## MHB (13/9/12)

You might try carbing and venting the keg a couple of times, a lot of volatiles can be stripped out this way. Still not as good an answer as preventing it in the first place, but it might help.
Mark


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## Helles (13/9/12)

If the bad flavours are leaving the keg via venting so are the good ones


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## Acasta (13/9/12)

Beer4U said:


> I would start by nuking everything with various chemicals and heat. Get new / fresh yeast and pitch lots of it.
> Look into how much O2 you are introducing in your process after ferment.


Getting new fermenters and transfer lines and a stainless spoon, so thats everything cold side replaced. Will nuke the fridge and kegs too before filling them again.



DrSmurto said:


> SO2 reacts with acetaldehyde so if you have any potassium metabisulphite i would start dosing that in - 20 ppm total at a time (use an online SO2 additions calculator).


Unfortunately no, I'll see how it goes with some more age then maybe source some.



MHB said:


> You might try carbing and venting the keg a couple of times, a lot of volatiles can be stripped out this way. Still not as good an answer as preventing it in the first place, but it might help.
> Mark


Kegs are carbes and I have them warming up now so I'll vent a bit of carb over a few days and keep it topped with co2

Definitely looking to prevent it occurring again. As Beer4U mentioned, I'll be careful with yeast pitching rates, and watch for splashing during transfer.
I will also look at better aeration of the wort prior to pitching so help the yeast finish up in the fermenter.


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## mr_tyreman (14/9/12)

I had a run of Acetaldehyde beers recently, everything i read said yeast, sanitation and 02.....after trying all these i still had the issue, i finally figured out my issue, it turned out that i had not seled up my fermenters properly post fermentation. So as the C02 had stopped being created by the yeast, the air outside the fermenter had equalised inside the fermenter and oxidised the ethanol giving a Acetaldehyde type flavour.

So make sure (if you dont) that you seal up the fermenter to stop any transfer of air into the fermenter, use airlocks, rubber bung, glad wrap....anything to really get an air tight seal on the vessel.

not gospel, just my experience

cheers and good luck


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## Acasta (17/9/12)

mr_tyreman said:


> I had a run of Acetaldehyde beers recently, everything i read said yeast, sanitation and 02.....after trying all these i still had the issue, i finally figured out my issue, it turned out that i had not seled up my fermenters properly post fermentation. So as the C02 had stopped being created by the yeast, the air outside the fermenter had equalised inside the fermenter and oxidised the ethanol giving a Acetaldehyde type flavour.
> 
> So make sure (if you dont) that you seal up the fermenter to stop any transfer of air into the fermenter, use airlocks, rubber bung, glad wrap....anything to really get an air tight seal on the vessel.



This is something I had not considered yet. How long after fermentation do you recommend adding the lid? With an airlock still fitted or could it be without?
Thanks


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## MastersBrewery (17/9/12)

Having read through some of the comments regarding oxygen permeating all but preasurised vessels, leaves me wondering why so few have moved to ss preasure vessels to ferment in. Dont get me wrong I know connicals cost the earth, but a 50l keg is about the same shape as what most of us use now and a simple adjustable preasure relief valve could keep your ferment at say 4 or 5 psi. I note this was brought up on HBT a while back and some now have even used cornies to ferment in.


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## labels (17/9/12)

I recently kegged two and a half kegs from the same batch that were fermented in two fermenters (50L batch). The half keg had some from each fermenter in it.

Now, strange as it is, the half keg tastes like a granny smith orchard while the two full kegs have no acetaldehyde whatsoever!

I'm putting this down to an infection possibly. The other cause maybe is I soaked one keg in a bleach solution to rid a mouldy problem. Although I rinsed and rinsed and rinsed and finished off with a mild acid solution (phosphoric) to re-pacify the metal, it still could have caused a problem if that was the keg in question.

In any case, I am suggesting that (1) acetaldehyde could have more than one cause other than immature beer or beer taken off the yeast too soon and (2) the taste could be something else completely that's being put down to acetaldehyde when it is something quite different.


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## jc64 (17/9/12)

mr_tyreman said:


> I had a run of Acetaldehyde beers recently, everything i read said yeast, sanitation and 02.....after trying all these i still had the issue, i finally figured out my issue, it turned out that i had not seled up my fermenters properly post fermentation. So as the C02 had stopped being created by the yeast, the air outside the fermenter had equalised inside the fermenter and oxidised the ethanol giving a Acetaldehyde type flavour.
> 
> So make sure (if you dont) that you seal up the fermenter to stop any transfer of air into the fermenter, use airlocks, rubber bung, glad wrap....anything to really get an air tight seal on the vessel.
> 
> ...



You sure did, and apparently so did I. I've given up on my 'open ferment' experiment. My ABA will be just out of the FV by next club night so I'm going to try and carb a bottle for your critique, be gentle! :lol: :lol:


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