Diacetyl Test and Diacetyl Rest Length

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ayoungrad

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I have my first lager (a 1.065 Pilsner) in the fermenter. It got down to 1.014-1.017 at one week, so I rasied the temp to 65 (from 52) for a diacetyl rest.

After 2 days at 65, I pulled a sample last night to recheck gravity and to do a diacetyl test. The gravity was 1.009 and the krausen had fallen.

For the test I put one half the sample in the frig. I heated the other half to 140 for about 30 minutes (intending to heat for 60 minutes). Then I read somewhere that a covered sample at 160 for 10-20 minutes was better, so I increased the temp and kept it covered with aluminum foil during the 10 minute heating.

There was no hint of butter in the cooled sample. There was horrible buttery aroma in the heated sample. Great... diacetyl.

So, last night I agitated the fermenter and increased the temp to 68 and I'm planning to retest tommorow night.

Is there anything else I can do? (I do not have krausen available.)

Also, does the diacetyl test detect ANY diacetyl or only that which will be noticeable in the final product? The smell was so in your face that I'm just concerned it will never completely go away.
 
The smell was so in your face that I'm just concerned it will never completely go away.

Its not going to go away on its own. I have done 5 lagers this year already and 4 of them had diacetyl after fermentation and lagering :D regardless of pitching temps, the only beer that did not had diacetyl is the one I pitched on a cake from previous batch. But don't worry. If you keg, I suggest to make small batch of beer about 1.5 quarts (1.040) and pitch in keg at high krausen just as it starts fermenting. Newly started fermentation will scrub any diacetyl as result. After week or so, chill beer down to 32F or lower to drop yeast out of suspension. I fixed all of my beers this way. It works so good that in fact I will do this for all my lagers in future, 1.5 qt starter will also carbonate your beer to about 2 volumes of CO2 so you killing to birds at same time.
 
Its not going to go away on its own. I have done 5 lagers this year already and 4 of them had diacetyl after fermentation and lagering :D regardless of pitching temps, the only beer that did not had diacetyl is the one I pitched on a cake from previous batch. But don't worry. If you keg, I suggest to make small batch of beer about 1.5 quarts (1.040) and pitch in keg at high krausen just as it starts fermenting. Newly started fermentation will scrub any diacetyl as result. I fixed all of my beers this way.

So, in your opinion, a diacetyl rest does not work at all?
 
So, in your opinion, a diacetyl rest does not work at all?

from my experience - not really. I tried everything. I waited till fermentation was down to 1.025-1.020 (75%) and then move fermentor to room temp - diacetyl. I tried wait out till fermentation completely over than move it to room temp - diacetyl. Note that I always pitch cool (50F) so I think the problem is stressed out yeast or starters not big enough in first place.
 
Interesting. I pitched a little warm at 58 degrees. I used Saflager 34/70 so I didn't use a starter but I pitched 3 rehydrated packs and aerated with oxygen for a little over a minute.

So, stressed yeast shouldn't be the issue but I suppose you never know.

I do not keg, so while I suppose I could try a small batch and pitch it into the ferementer I'm not really psyched about it. But if I were to go this route, what do you reccommend for yeast? I would imagine something clean like US05?
 
Interesting. I pitched a little warm at 58 degrees. I used Saflager 34/70 so I didn't use a starter but I pitched 3 rehydrated packs and aerated with oxygen for a little over a minute.

So, stressed yeast shouldn't be the issue but I suppose you never know.

I do not keg, so while I suppose I could try a small batch and pitch it into the ferementer I'm not really psyched about it. But if I were to go this route, what do you reccommend for yeast? I would imagine something clean like US05?

For small beer I used some W34/70 I had laying around. If you bottle, your diacetyl might be scrubbed up in the bottle by the yeast when they will chew on your priming sugar but I don't know for sure
 
How long have you extended your diacetyl rest in the past?

I'm trying to avoid a starter beer addition for several reasons. But I'm also surprised that some people feel a rest doesn't work when it is all over this site and is discussed in "Yeast".
 
How long have you extended your diacetyl rest in the past?

I'm trying to avoid a starter beer addition for several reasons. But I'm also surprised that some people feel a rest doesn't work when it is all over this site and is discussed in "Yeast".

I had beer sitting for up to a week at room temp for diacetyl rest, most suggest 48 hours but it takes about 24 hours just to warm up to room temperature. I've read most, if not all on diacetyl rest on this forum as well, but as you probably experienced for yourself its not always work the way others describe. There is just too many variables between batches, yeast, brewers, equipment, techniques etc. I think I gained the most valuable info about diacetyl from this article: Diacetyl: Formation, Reduction, and Control
Hope this helps to understand it a little more.
 
If the yeast need sugar to clean up the diacetyl, why not add a few ounces of corn sugar to the fermenter when doing the diacetyl rest? The amount used to bottle prime isn't supposed to change the flavor or the ABV.
 
I'm trying to avoid a starter beer addition for several reasons.

"starter beer" addition called krausening (do a search on that) and it might be your only solution if you don't want to dump a batch. Germans used this technique to carbonate their beer since priming sugar was not allowed due to 1516 purity law. I naturally carbonate my kegs of lager this way, addition of krausening beer not only cleans up diacetyl but also carbonates my keg within week or two.
 
If the yeast need sugar to clean up the diacetyl, why not add a few ounces of corn sugar to the fermenter when doing the diacetyl rest? The amount used to bottle prime isn't supposed to change the flavor or the ABV.

The problem is, your yeast is already exausted. Most likely it will take up priming sugars very slowly and ignore diacetyl altogether. This is why you need to introduce fresh, ready to charge yeast during krausening
 
I have my first lager (a 1.065 Pilsner) in the fermenter. It got down to 1.014-1.017 at one week, so I rasied the temp to 65 (from 52) for a diacetyl rest.

After 2 days at 65, I pulled a sample last night to recheck gravity and to do a diacetyl test. The gravity was 1.009 and the krausen had fallen.

For the test I put one half the sample in the frig. I heated the other half to 140 for about 30 minutes (intending to heat for 60 minutes). Then I read somewhere that a covered sample at 160 for 10-20 minutes was better, so I increased the temp and kept it covered with aluminum foil during the 10 minute heating.

There was no hint of butter in the cooled sample. There was horrible buttery aroma in the heated sample. Great... diacetyl.

So, last night I agitated the fermenter and increased the temp to 68 and I'm planning to retest tommorow night.

Is there anything else I can do? (I do not have krausen available.)

Also, does the diacetyl test detect ANY diacetyl or only that which will be noticeable in the final product? The smell was so in your face that I'm just concerned it will never completely go away.

Putting aside the results of your diacetyl "test", did you detect it at all in your beer before the "test"? My one major bad experience with diacetyl was easily noticeable without a test. I fixed it by krausening as described in this thread: https://www.homebrewtalk.com/f14/will-work-205761/

Spoke to a person this past weekend in my beer club who said he only had diacetyl once and remedied it by putting dextrose into his secondary. With 3 packs of W 34/70 (I love that yeast) rehydrated you certainly didn't underpitch, which is what makes me wonder whether you really have diacetyl.
 
I definitely would not state that a diacetyl rest doesn't work at all. It absolutely can.

If you have diacetyl in your lager, then there's a problem with your fermentation profile, pitching rate or sanitation. If you have a crazy pedio infection going on, it's going to keep pumping out diacetyl, although that's a longshot.

I ferment my lagers at 52F, pitch at 50F. I soon as I notice the krausen dropping back, I start raising it 2 degrees a day until it's around 68F or so. Never noticed any diacetyl, never needed a rest.
 
I have done 5 lagers this year already and 4 of them had diacetyl after fermentation and lagering regardless of pitching temps, the only beer that did not had diacetyl is the one I pitched on a cake from previous batch.

So have you drawn the conclusion that you underpitched four batches out of five? How much yeast are you pitching?
 
I definitely would not state that a diacetyl rest doesn't work at all. It absolutely can.

If you have diacetyl in your lager, then there's a problem with your fermentation profile, pitching rate or sanitation. If you have a crazy pedio infection going on, it's going to keep pumping out diacetyl, although that's a longshot.

I ferment my lagers at 52F, pitch at 50F. I soon as I notice the krausen dropping back, I start raising it 2 degrees a day until it's around 68F or so. Never noticed any diacetyl, never needed a rest.

Never needed a rest? Isn't a d-rest exactly what you're doing by raising the temp to 68 degrees?
 
All of this makes me wonder...

Has anyone ever had a positive diacetyl test CORRECT to a negative diacetyl test after a diacetyl rest?
 
I definitely would not state that a diacetyl rest doesn't work at all. It absolutely can.

I never said diacetyl rest is a myth :D I just said it didn't work for me on numerous occasions and under different conditions. One batch didn't had any diacetyl after fermentation, but it showed up after lagering. Lots of folks report good results after DR, but OP is in a same boat as me, the fact is diacetyl is still in beer
 
So have you drawn the conclusion that you underpitched four batches out of five? How much yeast are you pitching?

I been pitching around 2 qts in previous batches (1.050 beers). It could be amount of yeast and it can be infection since I wash/reuse my yeast. To help narrow down the cause for diacetyl I need to get some fresh smack packs and brew more lagers, to soon to jump to conclusions
 
Putting aside the results of your diacetyl "test", did you detect it at all in your beer before the "test"?

Sorry, missed this earlier.

No, I did not detect it. I tasted it when it was at 1.017 and when it was at 1.009 and the unheated samples tasted really good.

I also did not taste it initially or smell it initially in the heated sample. But I left the heated and cooled samples on the counter last night. I came back about 20 minutes later and smelled the heated (and now slightly cooled) sample. It was unmistakable movie popcorn butter. I had even started thinking that maybe I just did not know what it was supposed to smell like. But after smelling that sample, I have no doubt it was buttery.
 
I been pitching around 2 qts in previous batches (1.050 beers). It could be amount of yeast and it can be infection since I wash/reuse my yeast. To help narrow down the cause for diacetyl I need to get some fresh smack packs and brew more lagers, to soon to jump to conclusions

My first two or three lagers were total failures; I was not pitching enough yeast. People who are used to brewing ales, like I was, sometimes just don't get how important yeast count is for fermenting at or under 50 degrees. Based on my limited experience with lagers now (total of something like 10 under my belt) I would say there are three ways to be sure you pitch enough yeast:

(1) use dry yeast, two packs rehydrated for five gallons. I love W 34/70 but have used S-23 as well.

(2) with liquid yeast, MAKE A VERY BIG STARTER based on the pitching rate calculations at www.mrmalty.com What sucks is that not everyone has a big enough flask/stir plate to do this. My last lager starter was 4.5 litres. Obviously nobody wants to pitch 4.5 litres so you pretty well have to let it ferment out completely (I do it at pitching temperatures but I don't think you have to if you are going to decant), chill then decant and pitch.

(3) use slurry. My last lager was pitched on two cups of the cake from the lager before it and it took off very well.
 
Sorry, missed this earlier.

No, I did not detect it. I tasted it when it was at 1.017 and when it was at 1.009 and the unheated samples tasted really good.

I also did not taste it initially or smell it initially in the heated sample. But I left the heated and cooled samples on the counter last night. I came back about 20 minutes later and smelled the heated (and now slightly cooled) sample. It was unmistakable movie popcorn butter. I had even started thinking that maybe I just did not know what it was supposed to smell like. But after smelling that sample, I have no doubt it was buttery.

Man, I really don't know whether I'd worry about it or not if you can't taste it in the beer. Probably somewhere on the site there's a post about it; maybe you can find it. I can tell you for sure I have done quite a few lagers in the last six months and never bothered to test for diacetyl if I couldn't taste it in a sample.
 
Never needed a rest? Isn't a d-rest exactly what you're doing by raising the temp to 68 degrees?

I guess you could call it that. My point is that I'm not specifically calling it a "diacetyl rest", it's just part of my fermentation regimen. I don't have to worry about it, because conducting the fermentation in that manner has never produced diacetyl.
 
I guess you could call it that. My point is that I'm not specifically calling it a "diacetyl rest", it's just part of my fermentation regimen. I don't have to worry about it, because conducting the fermentation in that manner has never produced diacetyl.

You don't have to call it a diacetyl rest for it to be a diacetyl rest.:tank:

Either way, your process works and that makes for some great lagers! I frickin' love brewing them! :mug:
 
Man, I really don't know whether I'd worry about it or not if you can't taste it in the beer. Probably somewhere on the site there's a post about it; maybe you can find it. I can tell you for sure I have done quite a few lagers in the last six months and never bothered to test for diacetyl if I couldn't taste it in a sample.

I have read (I think on here) that it is possible to detect no diacetyl in the sample and then have butter beer after lagering. My guess has been that the yeast hides the off-flavor.

But this is why I'm wondering if the diacetyl test everyone uses is actually too sensitive. Beers will have SOME diacetyl but usually below detectable taste thesholds.

So does the diacetyl test detect minute amounts?

This is why I'm also wondering if anyone has successfully reversed the test results.
 
Krauezening is a fabulous technique for lager brewing. It can fix so many of the problems unique to lagers. I strongly recommend it for anyone who wants to make better lagers. I also strongly recommend pitching your entire starter when it's at high krauezen, I have had much better results with much smaller starters (1/2 gallon) doing it that way then letting it ferment out, crashing the yeast, then decanting, then pitching the yeast cake.

I did just try 34/70 for my last lager. Still waiting to see the results of that experiment, finished exactly where I expected though, that's a good sign.
 
You don't have to call it a diacetyl rest for it to be a diacetyl rest.:tank:

Either way, your process works and that makes for some great lagers! I frickin' love brewing them! :mug:

Semantics. :cross:

What's funny is when I started brewing, I wasn't crazy about lagers. At all. I think learning how to brew them has made me appreciate them much more. There really is something magical about noble hops and pilsner malt, so good...
 
Krauezening is a fabulous technique for lager brewing. It can fix so many of the problems unique to lagers. I strongly recommend it for anyone who wants to make better lagers. I also strongly recommend pitching your entire starter when it's at high krauezen, I have had much better results with much smaller starters (1/2 gallon) doing it that way then letting it ferment out, crashing the yeast, then decanting, then pitching the yeast cake.

I did just try 34/70 for my last lager. Still waiting to see the results of that experiment, finished exactly where I expected though, that's a good sign.

I'll have to try your smaller starter at high krausen suggestion.

The krausening thing is intriguing. How/why does this work so well for lagers?
 
I just saw this opinion/experience on a different thread:

"I've done that test many times actually but I've learned it really isn't necessary. If there is any appreciatable amount of diacetyl in there, you can tell if the beer is even slightly warm. In other words, the diacetyl might only be slightly noticeable when the beer comes out of the fridge at 35 degrees, but as the beer warms up to 50 it slowly becomes stronger and at room temperature there is no question. Actually heating the beer makes the diacetyl unbearable if there is any diacetyl in it at all. Its a useful test if you don't know what diacetyl smells like or you aren't particularly sensitive to it but once you know what you are looking for it's not necessary."

This may answer my question. And it makes me feel a little better. I thought the other samples I tried actually tasted pretty good.

Maybe the diacetyl test actually detects trace diacetyl. And, honestly, who cares about trace diacetyl?

I think I'll taste test again tommorrow and if it tastes good I may just start to lower temps down for lagering.
 
I just saw this opinion/experience on a different thread:

"I've done that test many times actually but I've learned it really isn't necessary. If there is any appreciatable amount of diacetyl in there, you can tell if the beer is even slightly warm. In other words, the diacetyl might only be slightly noticeable when the beer comes out of the fridge at 35 degrees, but as the beer warms up to 50 it slowly becomes stronger and at room temperature there is no question. Actually heating the beer makes the diacetyl unbearable if there is any diacetyl in it at all. Its a useful test if you don't know what diacetyl smells like or you aren't particularly sensitive to it but once you know what you are looking for it's not necessary."

This may answer my question. And it makes me feel a little better. I thought the other samples I tried actually tasted pretty good.

Maybe the diacetyl test actually detects trace diacetyl. And, honestly, who cares about trace diacetyl?

I think I'll taste test again tommorrow and if it tastes good I may just start to lower temps down for lagering.

Yeah, I really think you are safe. Good job!

This thread got me thinking about diacetyl so I just tasted my Czech pil that has been lagering for a couple of weeks...very very pleased with how it's coming along and it will be totally clear soon. Can't wait for this one to be carbed up!
 
Sorry, missed this earlier.

No, I did not detect it. I tasted it when it was at 1.017 and when it was at 1.009 and the unheated samples tasted really good.

I also did not taste it initially or smell it initially in the heated sample. But I left the heated and cooled samples on the counter last night. I came back about 20 minutes later and smelled the heated (and now slightly cooled) sample. It was unmistakable movie popcorn butter. I had even started thinking that maybe I just did not know what it was supposed to smell like. But after smelling that sample, I have no doubt it was buttery.

If you dont detect it at your lagering temp around 50º I wouldnt worry about doing a diacetyl rest (granted it wouldnt hurt).

I just brewed two lagers in the past month and Oktoberfest and a session lager I call Munich Lite, but the Oktober had no hints of diacetyl so I went from primary to lager. Now the session I tried a sample was a butter bomb, so at 1.020 I moved to room temp for 4 days, tried a smaple and it cleared itself up, zero diacetyl. Just a little more info on the brews, both used wlp833 yeast, both had a starter, 2L for the Oktober (1.060og) made at lager temps 50º, while the Munich Lite (1.044og) was made with a 1200mL starter at room temp, 68º. Now I dont know why the Munich Lite was a butter bomb, maybe do to the smaller starter or starter at room temp (which I doubt after talking to White Labs). But both were pitched at around 58º (coolest I could get the wort w/ my IC, also both took of in about 10-12 hours while taking both about 10 days to finish fermenting.


Quick question why did you heat the one to 140º? Seems like you more than likely pasteurized the beer, which would kill of any yeast, which wouldnt allow them to clean up after themself.
 
Quick question why did you heat the one to 140º? Seems like you more than likely pasteurized the beer, which would kill of any yeast, which wouldnt allow them to clean up after themself.

Apparently that's the way you do a quick d-test on a small sample of beer (if you do a forum search for diacetyl test it should turn up). I've never done it myself but some do. Not like he heated a whole batch to that temp!
 
Quick question why did you heat the one to 140º? Seems like you more than likely pasteurized the beer, which would kill of any yeast, which wouldnt allow them to clean up after themself.

Thanks for the info. Sounds like a diacetyl rest can work.

I heated one sample (about 4 oz) and cooled the second (also 4 oz) because that is how I have read to do a test for diacetyl. They were just samples, the rest of the beer is in the fermenter.
 
Apparently that's the way you do a quick d-test on a small sample of beer (if you do a forum search for diacetyl test it should turn up). I've never done it myself but some do. Not like he heated a whole batch to that temp!

Thanks for the info. Sounds like a diacetyl rest can work.

I heated one sample (about 4 oz) and cooled the second (also 4 oz) because that is how I have read to do a test for diacetyl. They were just samples, the rest of the beer is in the fermenter.

My bad, I missed the "they were samples part" :drunk:

But, yes it can work and work excellent, if you wouldve taste the hydro sample you would have never thought yeast could clean that butter popcorn taste up, and it did just that. :mug:
 
My bad, I missed the "they were samples part" :drunk:

But, yes it can work and work excellent, if you wouldve taste the hydro sample you would have never thought yeast could clean that butter popcorn taste up, and it did just that. :mug:

And if you don't taste diacetyl in the sample but there IS some present, the beer will get much worse. Sometimes there is no hint of diacetyl in a sample but when it's been lagered for a beer, the beer is movie-theatre-butter-style beer. In other words, it gets worse, not better!

Diacetyl is buttery in large quantities but in very small quantities it's more of an "oily" feel on the tongue or teeth, or a slickness in the mouthfeel. I bet if you try an unheated sample again, you may have a slight hint of an oily feel.

In any case, keep doing the diacetyl rest.
 
Yooper would you say to always do a d-rest for every lager, no matter what? Seems to make sense to me but I was talking to a fellow lager brewer last weekend do doesn't do them routinely b/c he thinks the temp increase affects the flavour of lagers. I had really convinced myself to just do one for every lager at 1.020 since the flavour profile should have been determined by that point.

What say you?
 
I do what you could call a D-rest for all my beer, ales and lagers. It's just part of my normal fermentation profile whereby I let the temperature free-rise after about three or four days of fermentation. I do this mostly to improve attenuation, but reducing diacetyl is a nice side-effect (although I don't usually have much diacetyl in my beers to begin with).
 
I do what you could call a D-rest for all my beer, ales and lagers. It's just part of my normal fermentation profile whereby I let the temperature free-rise after about three or four days of fermentation. I do this mostly to improve attenuation, but reducing diacetyl is a nice side-effect (although I don't usually have much diacetyl in my beers to begin with).

Yes, this is just a normal part of many people's process. Jamil Z recommends it for every beer also.

I don't always do one, but usually I do. For lagers, some of them may not be strictly needed but it's a "can't hurt, might help" step.
 
Sorry ayoungrad, can't read the whole thread now, but there was any consensus on when the D-rest should be done. I hear all types of different versions even in the famous books... I always do it before fermentation is done, in the last quarter, but then my last Pilsners all had more than adequate diacetyl on them, so I don't know...
 
This is a very good post - Lots of questions on my part:

1) OK to Krauezen (add fermenting beer) after lagering?

2) What temp should "Krauezen beer" ferment at (before added to the original beer)?

3) What yeat should "Krauezen beer" use? (same lager strain as original beer, neutral lager strain, ale strain)?

4) After adding "Krauezen beer", what temp to ferment at, and for how long?

5) Related to #4, simply cold crash after the "Krauezen beer" has done its job and carbonate/serve?

6) Should the "Krauezen beer" mimic that of the original beer (e.g., same malts) or could one simply used DME?

I ask all of this because my first lager attempt (Marzen brewed 8 weeks ago) had zero diacetyl taste until I tasted a sample during lagering. I raised temp to ~68F for about a week and most of the diacetyl was cleaned up (I was lagering on the yeast cake - a mistake??) but some diacetyl is still discernible.
 
This is a very good post - Lots of questions on my part:

1) OK to Krauezen (add fermenting beer) after lagering?

2) What temp should "Krauezen beer" ferment at (before added to the original beer)?

3) What yeat should "Krauezen beer" use? (same lager strain as original beer, neutral lager strain, ale strain)?

4) After adding "Krauezen beer", what temp to ferment at, and for how long?

5) Related to #4, simply cold crash after the "Krauezen beer" has done its job and carbonate/serve?

6) Should the "Krauezen beer" mimic that of the original beer (e.g., same malts) or could one simply used DME?

I ask all of this because my first lager attempt (Marzen brewed 8 weeks ago) had zero diacetyl taste until I tasted a sample during lagering. I raised temp to ~68F for about a week and most of the diacetyl was cleaned up (I was lagering on the yeast cake - a mistake??) but some diacetyl is still discernible.
I would love to know the answers to these questions as well from the people who have Krausend their beer. It is something I would love to do now that I keg my homebrew
:mug:
 
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