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Delayed Diacetyl Appearance In Lager

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Goose

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Gents, I don't mean this to be yet another diacetly thread, but having repeated issues with what appears to be a delayed formation of diacetyl in the last two lagers I have done.

What happens is that there appears to be no trace of diacetly right up to the racking stage, and it appears only after I have carbonated up the beer. My fermentation process has been 3 weeks at a steady 10 deg C using a fresh Wyeast 2042 Danish Lager made up to a 4 litre starter. Beer tastes fantastic, clean, clear and fresh prior to racking and I can detect no diacetly at all. Then, I rack, chill to 2 deg C and slow force carbonate over 10 days at 12 psi. I regularly taste and can detect no off taste, but afer a few days I can detect a hint , and it gradually gets stronger with time. After full carbonation, its positively gross. So now, no choice but to try and get it reabsorbed by raising the temperature to 18 deg c for a few days. if that fails I fear it will become fertiliser.

At first I thought the diacetyl was being created from residual yeast that get affected by the force carbonation pressure which I usually do, ie 2 days at around 25 psi. Seems even the low pressure carbonation has the same end result.

So a tad puzzled by this, I'd always assumed a diacetyly rest was necessary only if diacetyl was present and detectable, and raising the temperature would cause the yeast to consume and metabolise it. However its creation post racking / chilling / carbonation is really p*ssing me off...

any experienced lager brewers out there that can shed some light ?
 

gava

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I've got the same issue with my lager the other day, I'd be interetsed in your findings.
 

mxd

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I always get my D through fermentation, and always do a D-Rest whether I taste it or not.

Your starter was a good size, temp looks good, what temp did you pith at ?

Are you sure it's diacetly your tasting ?

All (with the exception of the first and the last) of my Boh pills are popcorn city, the last one I did an acid rest, added appropriate salts etc.. so I'm working on (it helps me sleep) no matter what I did through fermentation I would always have a fault as the brewing was where the issue is caused.
 

sean_0

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Could it be an infection? Beer line infections from Lactobacillus and Pediococcus bacteria can produce diacetyl too. I thought this would only be a problem with really long lines like in a pub, but maybe it's a factor here too. Just a thought.
 

Goose

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I always get my D through fermentation, and always do a D-Rest whether I taste it or not.

Your starter was a good size, temp looks good, what temp did you pith at ?

Are you sure it's diacetly your tasting ?

All (with the exception of the first and the last) of my Boh pills are popcorn city, the last one I did an acid rest, added appropriate salts etc.. so I'm working on (it helps me sleep) no matter what I did through fermentation I would always have a fault as the brewing was where the issue is caused.
hey mxd

pitch 12 deg C

oh yeah mate, I can detect diacetyl at a thousand paces...



Could it be an infection? Beer line infections from Lactobacillus and Pediococcus bacteria can produce diacetyl too. I thought this would only be a problem with really long lines like in a pub, but maybe it's a factor here too. Just a thought.
txs for that sean.... thats possible of course.... but its confined to lagers, I would expect the same in my ales of my lines were infected, and I dont get it in ales....
 

Fourstar

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Point 1.

Diacetyl rests are your friend with lagers and i'd say you need to incorporate them. Eeven if you are steady after 3 weeks at 10 degrees. When you are a couple of point from hitting expected FG/attenuation, kill the temp control to the fridge and let it naturally raise to finish off fermentation for 2 days. You WILL NOT cause off flavours in your beer. Esters are formed predominately during the growth phase which you have controlled.


Point 2.

Diacetyl formed by 'oxidation'. Look it up.
http://www.brewingtechniques.com/library/b...sue1.2/fix.html. a starting point. "acetolactate"

I had big issues with this from filtering and not puprging enough. Always when racking ensure you purge receiving kegs with C02 as much as possible otherwise 2 days after hitting the keg. Diacetyl town.

I also circumvented this by filling kegs from the tap on the fermenter via a craftbrewer JG fitting and silicone hose to fit the fermenter tap. Connect this to beer line and a beer in post and you're on your way. This way way you are filling from the dip tube in a bottom-up approach. In short, perform point 1 and you are unlikely to have to worry about point 2 as much. However it is good practice to reduce oxidation of your beer at all steps in your process so i would strongly suggest looking into the above point.
 

MaestroMatt

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Have you experimented with ramping up the temp in your primary towards the end of your fermentation period?

With the majority of yeast still in the vessel, a raise in temp might give them a bit of a kick needed to absorb the majority of the diacetyl. The rest of it might then just need the lagering period to settle out.

Just a thought at this stage :)


EDIT: Fourstar beat me to it :)
 

argon

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I agree with fourstar. I’d be focussing in on your racking procedure and oxygen pickup.

Do you rack from primary to packaging or are your moving to a secondary vessel prior to packaging?

Typically there are 3 ways diacetyl is produced;
1. Through fermentation
It seems as you’re pitching plenty of viable yeast and fermenting low and cool. Do you start low and cool, or lower once pitched? Ie pitch at ambient and allow temp control to lower
2. Infection
Are you confident... if no other signs of infection then you’re most probably ok
3. Oxidation
With the first 2 causes most common and easily identified and rectified, focus here in my opinion. Diacetyl production occurs via oxygen pickup, often over time (as you’ve described) and occurs in a similar way to the processes that create diacetyl during fermentation... that is, the non-enzymatic oxidation of alpha-acetolactate. This occurs now even without yeast present since the yeast have excreted the alpha-acetolactate during fermentation.

Also have a read of this link

Particularly do these things;
How to limit diacetyl production
So how can the small-scale brewer or homebrewer use this information to limit diacetyl in their own products?

- Use high quality malt (high nitrogen)
- Use healthy yeast at a good pitching rate (10^6 cells/ml/Plato), with good oxygenation/aeration after cooling
“Diacetyl rest” at the end of fermentation (possibly including rise in temperature, especially for lagers)
- Good sanitation practices to prohibit infection
- Limited oxygen in packaging and minimized mechanical agitation
And check out these cool graphs;
 

MaestroMatt

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Interesting graph there Argon.

The most interesting point for me from that is that it seems that there will ALWAYS be some diacetyl in beer by its nature. Could someone with extremely sensitive tastebuds pick up those levels as per the control (looks like 15ppb)?
 

Goose

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I agree with fourstar. Id be focussing in on your racking procedure and oxygen pickup.

Do you rack from primary to packaging or are your moving to a secondary vessel prior to packaging?
straight from fermenter to dispenser. I find that lager yeasts settle well, and i don't like the risks and loss associated with going to secondary prio to dispensing keg.

Typically there are 3 ways diacetyl is produced;
1. Through fermentation
It seems as youre pitching plenty of viable yeast and fermenting low and cool. Do you start low and cool, or lower once pitched? Ie pitch at ambient and allow temp control to lower
pitch at 12 deg c, ferment at 10...

2. Infection
Are you confident... if no other signs of infection then youre most probably ok
3. Oxidation
With the first 2 causes most common and easily identified and rectified, focus here in my opinion.
diacetyl production occurs via oxygen pickup, often over time (as youve described) and happens is similar to the processes that create diacetyl during fermentation that is, the non-enzymatic oxidation of alpha-acetolactate. This occurs now even without yeast present since the yeast have excreted the alpha-acetolactate during fermentation.


Also have a read of this link

Particularly do these things;
How to limit diacetyl production

So how can the small-scale brewer or homebrewer use this information to limit diacetyl in their own products?

Use high quality malt (high nitrogen)
Use healthy yeast at a good pitching rate (10^6 cells/ml/Plato), with good oxygenation/aeration after cooling
Diacetyl rest at the end of fermentation (possibly including rise in temperature, especially for lagers)
Good sanitation practices to prohibit infection
Limited oxygen in packaging and minimized mechanical agitation
And check out these cool graphs;

thanks.

this and the post from fourstar suggests I need to focus on post fermentation care with a decent rest and elimination of oxygen. Sounds like I need to try and get my fermenter to keg otransfer operation as closed system as possible. I have always purged my kegs with co2 before siphoning in, but of course there has been that gap in the top where some air could ingress. This last lager was racked into a sanke, but I didnt have the correct coupler to allo wme to fill through the beer out valve. Most sanke couplers have aa check valve which allows one way flow only, so I am going to order the modded one today.

i don't think its my beer lines, but no harm in extra care there as well.
 

kevin_smevin

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Hi.

lots of good info in there and i'll add something (hopefully i'm not just repeating everything that's already been said. Sorry if I am).

Diacetyl is formed via a non-enzymatic oxidation of a precursor molecule. The precursor will be in all beers so it's no point trying to eliminate that. Towards the end of fermentation, your yeast will begin to reduce the diacetyl to non-offensive compounds. Like everyone else said, a diacetyl rest will help this alot.

One of the most important things to note is that if you do not add enough oxygen prior to pitching your yeast, then not all of the diacetyl precursor will be converted to diacetyl. While this may not seem like it will be a problem, it actually can be. You can do diacetyl rests which will clean up any diacetyl present but it doesn't affect the level of diacetyl precursor which is still present (but is not detectable). When you keg, filter or bottle your lager, you are undoubtedly going to introduce oxygen. No matter how careful you are, some oxygen will still get in. This oxygen then goes and converts the leftover diacetyl precursor (which has no flavour or aroma) to diacetyl. Because your yeast is mostly all gone and any remaining will be pretty knackered, it wont get cleaned up. You get left with permanent diacetyl.

If you want to check if your beer has "potential" diacetyl from unconverted precursor, you simply take a sample of your beer post fermentation. Split the same in two. I'm pretty sure the next step involved shaking one of them and giving it a little heat. If there is any diacetyl precursor present, it will be converted to diacetyl. You then simply compare the sample that has been shaken and heated to the one that hasn't. The Chris White and Jamil Yeast book gives more precise details about how this is done. If the test shows that your beer still has potential diacetyl, i'm not sure what can be done. The book will tell you. It's a really good book.

In short, good oxygenation of wort, very healthy yeast and a diacetyl rest should eliminate your problem. If you yeast isn't healthy, it may not be able to clean it up by the end of fermentation.

Hope this helps.

Cheers
 

Goose

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Hi.

lots of good info in there and i'll add something (hopefully i'm not just repeating everything that's already been said. Sorry if I am).

Diacetyl is formed via a non-enzymatic oxidation of a precursor molecule. The precursor will be in all beers so it's no point trying to eliminate that. Towards the end of fermentation, your yeast will begin to reduce the diacetyl to non-offensive compounds. Like everyone else said, a diacetyl rest will help this alot.

One of the most important things to note is that if you do not add enough oxygen prior to pitching your yeast, then not all of the diacetyl precursor will be converted to diacetyl. While this may not seem like it will be a problem, it actually can be. You can do diacetyl rests which will clean up any diacetyl present but it doesn't affect the level of diacetyl precursor which is still present (but is not detectable). When you keg, filter or bottle your lager, you are undoubtedly going to introduce oxygen. No matter how careful you are, some oxygen will still get in. This oxygen then goes and converts the leftover diacetyl precursor (which has no flavour or aroma) to diacetyl. Because your yeast is mostly all gone and any remaining will be pretty knackered, it wont get cleaned up. You get left with permanent diacetyl.

If you want to check if your beer has "potential" diacetyl from unconverted precursor, you simply take a sample of your beer post fermentation. Split the same in two. I'm pretty sure the next step involved shaking one of them and giving it a little heat. If there is any diacetyl precursor present, it will be converted to diacetyl. You then simply compare the sample that has been shaken and heated to the one that hasn't. The Chris White and Jamil Yeast book gives more precise details about how this is done. If the test shows that your beer still has potential diacetyl, i'm not sure what can be done. The book will tell you. It's a really good book.

In short, good oxygenation of wort, very healthy yeast and a diacetyl rest should eliminate your problem. If you yeast isn't healthy, it may not be able to clean it up by the end of fermentation.

Hope this helps.

Cheers

hey yums,

actually I feel I am meticulous on wort oxygenation, in fact I use medical grade o2, and push it through an airstone in my plate heat exchanger as I rundown to the fermenter. I will read up on potential diacetyl, but in my case there is no doubt its forming post racking.

so next batch I will do a 2 day rise for a diacetyl rest, as well as a closed system transfer, and see how I go.

appreciate all the suggestions lads, thanks.
 

DKS

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Could Diacytle come through as a honey flavour? The above posts seem extremely familiar with the last two lagers Ive done. Same brew 2 cubes. One dry hopped. The dry hopped one took an extra month or so to give honey notes. I had this honey once before in an Ordinary bitter. Could it be the same dramas as OP I wonder?
Daz
 

dougsbrew

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hey yums,

actually I feel I am meticulous on wort oxygenation, in fact I use medical grade o2, and push it through an airstone in my plate heat exchanger as I rundown to the fermenter.

really, thats cool, got a pic of that setup of yours. how much o2 you pushing into a brew (at the cool end of the exchanger i take it?)
 

Goose

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really, thats cool, got a pic of that setup of yours. how much o2 you pushing into a brew (at the cool end of the exchanger i take it?)
sure thing dougsbrew

I shipped in one of these beasties from Sabco (cheap US$ has its advantages these days):



I just attach an O2 source to the airstone inlet and as I pump wort through the chiller I just bleed in enough O2 at a round 1 psi so that I can see bubbles/froth emerge at the wort out side. The wort is pumped into the bottom of the fermenter and the undissolved excess O2 bubbles through the fermenter vessel and exits a valve at its top. The O2 also has the advantage of blowing the transfer hose clean of wort at the end of the transfer directly into the fermenter.

yes it goes in at the cool end.
 

Goose

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Could Diacytle come through as a honey flavour? The above posts seem extremely familiar with the last two lagers Ive done. Same brew 2 cubes. One dry hopped. The dry hopped one took an extra month or so to give honey notes. I had this honey once before in an Ordinary bitter. Could it be the same dramas as OP I wonder?
Daz

Oh yes, thats the old 2-3 Pentadione . Related to diacetyl and also been there, done that....

Diacetyl and 2,3-Pentanedione
Diacetyl and 2,3-pentanedione, which are classified as ketones, are important contributions to beer flavor and aroma. Often these two ketones are grouped and reported as the vicinal diketone (VDK) content of beer, which is the primary flavor in differentiating aged beer from green beer. Of the two, diacetyl is more significant because it is produced in larger amounts and has a higher flavor impact than 2,3-pentanedione. A "buttery" or "butterscotch" flavor usually indicates the presence of diacetyl, while 2,3-pentanedione has more of a "honey" flavor.
from http://www.beer-brewing.com/beer-brewing/b..._byproducts.htm
 

kevin_smevin

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In that case, i'm buggered if i know.

If the diacetyl rest doesn't work you could try more oxygen, it's possible you're not getting enough. I use 50kPa for 2 minutes through a sanitary filter and airstone. I'd say your getting as much or more dissolved O2 then i am considering it is added in-line but it's worth a shot. Alternatively it could be a yeast health or microbial contamination issue. How much yeast are you adding - are you re-pitching or is it fresh? Do you do starters? If so, how?

I'd go ahead and do the potential diacetyl (which the yeast book calls Diacetyl force test) test on your next brew - that will at least tell you if it is due to insufficient diacetyl precursor oxidation. I've just grabbed my yeast book. What you will need is:
- 2 glasses
- aluminium foil
- hot water bath
- ice water bath
- thermometer.

Heat water bath to 60-71 deg C. Collect a sample of beer in each glass and cover with foil - place 1 in the water bath and keep the other at room temp.
after 10-20 minutes remove the beer from the hot bath and cool to the same temp as the other sample. Remove al foil and smell/taste each sample.

If both samples are negative for diacetyl - there is no precursor left and your beer is ready for kegging etc.

If both samples are positive, the beer has a lot of precursor or could be contaminated. If it isn't contaminated, it needs more time on the yeast.

If the room temp sample is negative while the heated sample is positive, there is precursor present and the beer needs more time on the yeast. That said, if your yeast isn't happy, it will not be able to perform the task very well.

Other listed causes for diacetyl in case some have been missed out are listed (in the yeast book) as:
- FAN/amino acid deficiency. This would only occur if you are using high levels of adjunct (sugar) and not enough yeast nutrient
- contamination or wild yeast
- underpitching
- incorrect fermentation temp
- vacillating fermentation temperature
- reused yeast collected too early
- incomplete mixing of fermentor - usually would only happen with a very sluggish ferment
- yeast mutation - would only be an issue if you are reusing you yeast over a number of generations
- dehydration of yeast??
- poor yeast health - low viability/vitality

Another thing is not to crash chill your beer too early. I always leave my beer at diacetyl rest temp for a couple of days after fermentation has completely stopped - no harm in doing this unless there is lots of oxygen exposure.

There are loads of references to diacetyl, their causes, how to prevent it etc in the yeast book by Chris White and Jamil Zainasheff. Doesn't cost that much, i highly recommend it.

Hopefully some of this might help.

Good luck!
hey yums,

actually I feel I am meticulous on wort oxygenation, in fact I use medical grade o2, and push it through an airstone in my plate heat exchanger as I rundown to the fermenter. I will read up on potential diacetyl, but in my case there is no doubt its forming post racking.

so next batch I will do a 2 day rise for a diacetyl rest, as well as a closed system transfer, and see how I go.

appreciate all the suggestions lads, thanks.
 

kevin_smevin

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Gents, I don't mean this to be yet another diacetly thread, but having repeated issues with what appears to be a delayed formation of diacetyl in the last two lagers I have done.

What happens is that there appears to be no trace of diacetly right up to the racking stage, and it appears only after I have carbonated up the beer. My fermentation process has been 3 weeks at a steady 10 deg C using a fresh Wyeast 2042 Danish Lager made up to a 4 litre starter. Beer tastes fantastic, clean, clear and fresh prior to racking and I can detect no diacetly at all. Then, I rack, chill to 2 deg C and slow force carbonate over 10 days at 12 psi. I regularly taste and can detect no off taste, but afer a few days I can detect a hint , and it gradually gets stronger with time. After full carbonation, its positively gross. So now, no choice but to try and get it reabsorbed by raising the temperature to 18 deg c for a few days. if that fails I fear it will become fertiliser.

At first I thought the diacetyl was being created from residual yeast that get affected by the force carbonation pressure which I usually do, ie 2 days at around 25 psi. Seems even the low pressure carbonation has the same end result.

So a tad puzzled by this, I'd always assumed a diacetyly rest was necessary only if diacetyl was present and detectable, and raising the temperature would cause the yeast to consume and metabolise it. However its creation post racking / chilling / carbonation is really p*ssing me off...

any experienced lager brewers out there that can shed some light ?

OK, I've just re-read the original post and something stood out. Is the 10 degrees for 3 weeks you fermentation time? If so, that is too long for good healthy yeast. Even though lagers ferment slower then ales, 3 weeks is way too long. If you pitch the correct amount of healthy yeast, a lager ferment should take 7-10 days (in my experience). I have just finished fermenting a baltic porter with an og of 1.083. It fermented at 10 degrees with a lager yeast down to 1.015 in 7 days.

A 4 litre starter might seem like enough but it's often hard to tell how much the yeast have actually replicated and if they are healthy. I'd really look into buying that yeast book (sounds like i have shares in it) - it will give you loads of info on everything you need to know.

Hope this isn't all too long winded and boring.
 

Goose

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Old thread sorry, but a bit further down the learning curve. I am still plagued by random occurrences of diacetyl weeks after racking though undetectable at the time fermentation is complete.

What I have learned from the reading of Mr George Fix is that the precursor to diacetyl, is alpha acetolactate or AAL, is tasteless but formed by the normal yeast metabolic processes. This precursor (unstable ?) converts to diacetyl but does not require yeast to make it happen but the speed of this reaction is a function of temperature. If there are active yeast still in suspension, the diacetyl is reabsorbed and broken down into tasteless compounds by the yeast. However if the AAL -> Diacetyl occurs after the yeast are rendered dormant by lagering temps there is no means by which it can be removed unless active yeast is re-introduced into suspension,

I think this explains (in my case) why it appears after racking and increased in concentration slowly.

So now I am in the process of religiously following the test described in this link to see if AAS is indeed my issue.

Which leads me to this idea... there is an enzyme available to the brewing industry that eliminates the diacetyl formation step completely. Branded "Exalase". Nice to give this a shot as it would seem to solve the need for a diacetyly rest, but have not heard of it being available anywhere.

Anybody head of this stuff ?
 

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