# Diacetyl Rest



## reviled (25/11/08)

Hey guys

I have a Pilsner brewing at the moment, SG has come down from 1055 to about 1016-1017 at the mo... Its still fermenting, but im wondering, when should I do a Diacetyl rest? 

Is it better to do it just before fermentation stops? Or when it has definately stopped? And do I just take the fermenting cube out of the fridge and let it come up to room temp, then how long do I leave it at room temp before lagering?

Im using Wyeast 2000 Budvar lager (if this makes any difference?) Recipe was mainly just Pils malt with a tad carapils... 

Lagers are hard, this must be why I allways brew ales


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## therook (25/11/08)

reviled said:


> Hey guys
> 
> I have a Pilsner brewing at the moment, SG has come down from 1055 to about 1016-1017 at the mo... Its still fermenting, but im wondering, when should I do a Diacetyl rest?
> 
> ...




Do it now, bring the temp up to 18 - 20c for a couple of days

Rook


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## newguy (25/11/08)

therook said:


> Do it now, bring the temp up to 18 - 20c for a couple of days
> 
> Rook



+1

I've read that the "proper" time to do the diacetyl rest is when you're 2/3rds of the way done. In reality, it doesn't really matter so long as the beer is nearly done fermenting, just as long as you haven't racked it off the yeast in the meantime. I do my diacetyl rest just before I rack to secondary and begin the long lagering period.


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## reviled (25/11/08)

newguy said:


> +1
> 
> I've read that the "proper" time to do the diacetyl rest is when you're 2/3rds of the way done. In reality, it doesn't really matter so long as the beer is nearly done fermenting, just as long as you haven't racked it off the yeast in the meantime. I do my diacetyl rest just before I rack to secondary and begin the long lagering period.



:unsure: Woops... It is sitting in the 2ndary, but in saying that, there is still a nice yeast cake cos I racked it at 1020, wish I knew to do the diacetyl rest then, but hopefully it should be cool... Would anything adverse come of this?

So it seems the plan is to take it up to 16-18*, leave it for 2 days, then lager it for 2 weeks or so, keg, carb, drink :icon_cheers: 

Sound good?


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## therook (25/11/08)

reviled said:


> :unsure: Woops... It is sitting in the 2ndary, but in saying that, there is still a nice yeast cake cos I racked it at 1020, wish I knew to do the diacetyl rest then, but hopefully it should be cool... Would anything adverse come of this?
> 
> So it seems the plan is to take it up to 16-18*, leave it for 2 days, then lager it for 2 weeks or so, keg, carb, drink :icon_cheers:
> 
> Sound good?




There is a ton of info on this rev, stop celebrating the Kiwi's win in the Rugby and do a search  

Rook


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## reviled (25/11/08)

therook said:


> There is a ton of info on this rev, stop celebrating the Kiwi's win in the Rugby and do a search
> 
> Rook



lol, I did a search and it only came up with about 4 threads, and only one of em had info... Ill try again

I hate searching <_<


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## newguy (25/11/08)

You should be okay. Diacetyl is produced by the yeast (all yeast) early on in fermentation, but it is normally reabsorbed later on. Raising the temperature promotes this reabsorption, provided you haven't racked the beer off of the yeast. If there is a good yeast cake, you should be fine. If in 2 days it still has a slickness/buttery character, rouse the yeast and give it one more day.

Diacetyl can also be caused by bacteria (pediococcus damnosus), but this usually isn't an issue if your sanitation is fine. If you have a batch that develops diacetyl over time and then starts to sour, it's because of pediococcus. I don't wish this bacteria on anyone - it was named damnosus because it's extremely difficult to get rid of.


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## kabooby (25/11/08)

I always taste my beer during fermentation. If you don't detect any diacetyl then there is no need for a diacetyl rest.

If you are getting diacetyl in your beer try pitching more healthy yeast, pitch cold, and make sure your wort is well aerated.

Kabooby


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## drsmurto (25/11/08)

browndog said:


> Don't get pissed during the process until you know it backwards.
> Don't freak out about sanitation before the kettle, be freaked out after it.
> Make sure your gas bottle is full.
> Keep this in mind, it's pretty hard to bugger up an AG.
> ...



The great Jamil doesnt do diacetyl rests........


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## mika (25/11/08)

The great Jamil pitches cold.
And never Rack's. Why would you rack a Lager at 1020 ?


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## warrenlw63 (25/11/08)

I've found it to be conducive to yeast strain and pitching temps. Some strains seem to produce more than others. 

I generally pitch cool (between 9-15 degrees). I've rarely experienced any diacetyl. If you pitch warm and fail to cool the ferment quickly enough then yes, it can be one of the problems you'll encounter.

Warren -


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## reviled (25/11/08)

To be honest, I dont know what diacetyl tastes like, so I wouldnt know, I just know its not sposed to be in a Lager so I want to do everything right...

Also, I pitched at 26 and waited for fermentation to happen, 48 hours, then I brought it down to 10, so if pitching warm is what makes diacetyl, id say that I definately have some in there...


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## drsmurto (25/11/08)

mika said:


> The great Jamil pitches cold.
> And never Rack's. Why would you rack a Lager at 1020 ?



I pitch cold (and big) but do rack and lager for several weeks but only after the yeast has spent 3-4 weeks on the yeast cake cleaning up its mess.

Always wondered why people rack before FG. Surely you still end up with a whole heap of yeast in your secondary vessel?

Was listening to Jamil on the way to work this morning and he mentioned he leaves the beer for minimum 4 weeks after which time he kegs. Sounds too simple to be true, am sure he glossed over a few points (finings/filter?).

Diacetyl is supposed to taste like butterscotch. I have never detected it but in the pilsner i entered into SABSOSA that was judged to contain diacetyl, i got a slick mouthfeel that is another way to detecting diacetyl?


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## newguy (25/11/08)

DrSmurto said:


> Diacetyl is supposed to taste like butterscotch. I have never detected it but in the pilsner i entered into SABSOSA that was judged to contain diacetyl, i got a slick mouthfeel that is another way to detecting diacetyl?



Slickness is definitely a sign of diacetyl. It reminds me of the chocolates that feel cold when you eat them. I think they're called icy squares. There's also a chocolate bar called zero that does the same thing. Slickness is my way of determining if diacetyl is present because I'm quite blind to it. It has to be over the top strong for me to detect it.

Butterscotch is one of the descriptors, but to me it's closer to microwave popcorn. :icon_vomit: My wife loves the stuff but to me it smells like boiled piss. And yes, I do happen to know what boiled piss smells like. Don't ask.


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## Effect (25/11/08)

newguy said:


> Slickness is definitely a sign of diacetyl. It reminds me of the chocolates that feel cold when you eat them. I think they're called icy squares. There's also a chocolate bar called zero that does the same thing. Slickness is my way of determining if diacetyl is present because I'm quite blind to it. It has to be over the top strong for me to detect it.
> 
> Butterscotch is one of the descriptors, but to me it's closer to microwave popcorn. :icon_vomit: My wife loves the stuff but to me it smells like boiled piss. And yes, I do happen to know what boiled piss smells like. Don't ask.




I know what boilled piss smells like. Some wankers pissed all over the hot rocks in the sauna in the hotel I work at...stinks out nearly a whole floor...


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## reviled (25/11/08)

Well when I tasted the sample at 1019 it definately had a slickness and I guess now that I think about it a slightly sweetish butterscotch flavour which I just thought was due to the extra sugar still in the beer, but now I know... 

Went home for lunch and took the cube out of the fridge, ill leave it 3 days then crash it down to 0 and lager for a few weeks, and then keg :icon_cheers: 

Man, I just wanna drink it, I cant remember waiting so long for a beer <_< But I guess the keg of Altbier will have to do for now...


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## kabooby (25/11/08)

reviled said:


> Went home for lunch and took the cube out of the fridge, ill leave it 3 days then crash it down to 0 and lager for a few weeks, and then keg :icon_cheers:



Raise the temp up, wait for it to finnish completely and then leave it for a few more days. Have a taste. If it taste clean then chill it, rack it, carb it, drink it.

Kabooby


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## dr K (25/11/08)

Diacetyl seeems to have the largest flavour threshold variance of any of the common beer by-products.
In my case diacetyl has to be fairly high to be noticeable, in fact at what I consider low levels I find it (in ales) to be a positive flavour component. High levels in any beer is unacceptable.
Diacetyl is both formed and reduced during fermentation so if you want to be rid of it you have to create conditions that will lower your chances of formation and increase your chances of reduction.
Low gravity beers are more likely produce diacetyl as will will high adjunct beers.
If you rack your beer (unless under CO2) you will introduce O2 and greatly increase the chance of diacetyl production.
Take two samples of your almost finished beer, hold one at at say 10C and warm the other to about 50C, if the warm one smells like popcorn, give the beer a rest at around 20C for a day or two. If the cold one smells like popcorn....rest and test again !!

K


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## 3G (26/11/08)

I normally pitch at 9 degrees and ferment at 10. Havent needed a rest yet  Generally 3 weeks in fermenter then keg and wait 4 weeks .


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## gibbocore (26/11/08)

i've been getting diacetyl on the nose in my english ales of late, using wyeast esb, now i'm fermenting at 20 degrees, so its a bit hard to raise the temp for a rest?


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## newguy (26/11/08)

gibbocore said:


> i've been getting diacetyl on the nose in my english ales of late, using wyeast esb, now i'm fermenting at 20 degrees, so its a bit hard to raise the temp for a rest?



Some strains are just natural producers. If you use the wyeast or white labs Scottish strain, look out! Give it a bit of extra time on the yeast - maybe a week once it drops out and it should be reduced. Maybe not gone, but reduced. If you want it completely gone, there's not much danger in raising the temp beyond 20C once fermentation is over.

Edit: Could be you have a natural sensitivity to diacetyl too. Most people I know are pretty blind to it, as am I.


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## gibbocore (26/11/08)

mate you could be right ie the natural sesnsitivity, cause i ask my brother about it and he reckons i'm going mad. I can also usually name all the fruits and spices in a bottle of red before i read the back of the bottle, damned pallet.


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## buttersd70 (26/11/08)

Diacetyl seems to me to be one of those funny flavours, where you're either very sensitive, or very blind to it, with very little middle ground.


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## matti (26/11/08)

Yep very true.

I seem to detect it as a slick flavour in bigger flavoured beer.
I firmly believe the rest should happen while the yeast is still relative active.
2/3rds of the the way in the fermentation cycle.

Matti


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## reviled (29/11/08)

Bump...

So the Pilsners been resting for three days now at 18-19*, the SG is down to 1012, but I think its still fermenting...

Question is, what do I do? Do I leave it at 18* till fermentation has finished and then lager? Or should I bring down to 12* for fermentation to finish before lagering? Or should I just stop fermentation myself and go ahead and lager it?


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## newguy (29/11/08)

Take it down 2C every 12 hours until you get to 2-3C and lager as normal. When it gets down to 2-3C you can transfer again if you like. Just let it lager for 4-8 weeks and bottle/keg. It will continue to slowly ferment and it will be finished when you bottle - no need to worry. You may require a fresh dose of yeast but I've never had problems with my bottles not carbonating even if the beer was crystal clear at bottling.


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## reviled (29/11/08)

newguy said:


> Take it down 2C every 12 hours until you get to 2-3C and lager as normal. When it gets down to 2-3C you can transfer again if you like. Just let it lager for 4-8 weeks and bottle/keg. It will continue to slowly ferment and it will be finished when you bottle - no need to worry. You may require a fresh dose of yeast but I've never had problems with my bottles not carbonating even if the beer was crystal clear at bottling.



Dont you love kegs just for that reason  

So will it still slowly ferment at say 2-3*?? Crazy, so I cant just make it crash out like an ale if I want fermentation to stop?


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## newguy (29/11/08)

If you drop the temperature very abruptly, it will stun the yeast. If that's what you want, drop the temp on your fridge to 2 or 3C now and it should pretty much stop fermenting. Or at least slow way down.


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## reviled (29/11/08)

newguy said:


> If you drop the temperature very abruptly, it will stun the yeast. If that's what you want, drop the temp on your fridge to 2 or 3C now and it should pretty much stop fermenting. Or at least slow way down.



After talking to Screwtop about the mash schedule I used, I dont know if I want to let the yeast run its course as it may end up drier than I wanted... 1012 is good for a Pilsner imo, not too dry for my tastes.. So I may do just that...

Cheers mate :icon_cheers:


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## jmnug2 (23/6/10)

If you are raising the temp for diacetyl rest before the beer has finished fermenting will the yeast not produce some off flavours (ester, etc....). I'm talking about a lager that's been fermented at 11 degrees for a week (OG 1037) now down to 1014, so if I bring it up to 17-18 for the remainder will it have any detrimental effect on the taste?


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## Phoney (23/6/10)

jmn said:


> If you are raising the temp for diacetyl rest before the beer has finished fermenting will the yeast not produce some off flavours (ester, etc....). I'm talking about a lager that's been fermented at 11 degrees for a week (OG 1037) now down to 1014, so if I bring it up to 17-18 for the remainder will it have any detrimental effect on the taste?



No. Given that you only bump up the temperature when most of the fermentation has completed there will be no esters released from the yeast. they generally only happen in the first few days during vigorous fermentation.


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## Thirsty Boy (24/6/10)

Diacetyl re-absorbtion is about exposure to active yeast... even very slightly active yeast.

Increased temps for D rests are not necessary, they just make things happen faster. The D is both produced (from its pre-cursors) and re-absorbed more quickly. The reason you get higher levels of D with some english yeast strains, is that they are so flocculent that they drop out and go dormant when there is still D to absorb. In the case of an ale, you would be trying to "extend" the active phase of the yeast, rather than simply bump the temp. Lager yeasts will do the trick all the way down to nearly zero degrees... and thats one of the reason why lagers are "lagered" for long periods. If you are going to raise the temp at the end of fermentation, then there is no need for an _extensive_ lagering period - this is exactly why the technique of an slightly higher D rest was developed, to shortcut the time.

There are so many different techniques of lagering, aging, conditioning; of reducing Diacetyl, acetylaldehyde etc - but at the end of the day they all boil down to giving the yeast a chance to do its job. Either for a shorter time at a higher temperature, or for a longer time at a lower temperature.


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## Mikedub (21/5/11)

G'day brewers
I've got an ale at 1.005 and have diacetyl, I'm blaming the long lag time (30hrs) due to what now seems to be poor a reculture of Coopers PA, its been in primary for 11 days, I'm thinking that the yeast have finished their work and wont be able to reduce it now, is this the case do you think?, 
unsure to raise temp, add some yeast to clean it up, leave it another week, or do neither, have a beer and re-read about yeast farming techniques


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## RdeVjun (21/5/11)

Mikedub, I'd elevate the temperature for a few days- AFAIK it won't hurt anything. So long as there's enough yeast that haven't flocced out, in which case a very gentle rouse might fix the problem.
I'm using my electric hot water system in the laundry for D- rests, gently bumps it up to around 22C for a few days with a jumper and a coat insulating the fermenter, seems to work quite well but I would understand that not everyone has that 'luxury'.


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## Mikedub (21/5/11)

thanks RdeVjun, shall give it a crack


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## RdeVjun (21/5/11)

No sweat Mikedub. 
It shits me doing D-rests as I suspect I'm one of the unlucky ones (that depends on your POV of course) who are unable to detect the stuff (yet to be confirmed). However I got pinged badly for it last year at the Nats, so I run through this rigmarole as a rule nowadays, particularly in winter.


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## Bribie G (21/5/11)

I like Diacetyl in its place, but of course you can't go handing out foaming jugs of Butterscotch Lager - According to the new Yeast book if you pitch a wee bit high (normally to counter a rather meagre yeast count to start off with) then you should bring the beer up to that temperature for a few days at the end. Underpitching can be a problem with recultured Coopers yeasts - just did one now and it took forever to culture up so I've dragged it out of the fridge after a week in primary an it's sitting in the garage at 22 degrees (bit warmer here down the Hill than at RdeV's place B)) and there it will sit for a few days. 

I've often heard that when re-using yeast from a Coopers style clone, the subsequent brews are a fair bit different from the first one. I have a theory that - rather than the yeast "drifting off style" this is more likely a result of pitching at a good rate in the child brews, as opposed to the often dodgy initial pitch from the bottle culture. I'll certainly be reusing this batch as it took me two goes and around 9 tallies to get a good one going. Yes, had to force myself to drink all that Coopers Sparkling, oh the humanity. 

Eddit: Grammatik


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## a1149913 (25/5/11)

I was told that once fermentation is finished the chance for diacetyl rest is over.?

also slightly off topic, but do the coopers pale ale and coopers sparkling beers use the same yeast?

JT


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## bignath (25/5/11)

Jacob Thomas said:


> also slightly off topic, but do the coopers pale ale and coopers sparkling beers use the same yeast?




As far as i know JT, yep same yeast.

However, most brewers seem to prefer the lower ABV% of pale ale to higher % of the sparkling due to the yeast being in "better condition" or something like that....Not sure i completely believe this, however when reculturing Coopers yeast, i do tend to go for the pale ale, as it is a beer that i prefer over the sparkling.


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## manticle (25/5/11)

Jacob Thomas said:


> I was told that once fermentation is finished the chance for diacetyl rest is over.?
> 
> also slightly off topic, but do the coopers pale ale and coopers sparkling beers use the same yeast?
> 
> JT



Same yeast in all coopers ales.

Cleaning of diacetyl will continue while in contact with active yeast so bottle conditioning is included, left on yeast cake post primary is included.


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## haysie (25/5/11)

Jacob Thomas said:


> I was told that once fermentation is finished the chance for diacetyl rest is over.?
> 
> also slightly off topic, but do the coopers pale ale and coopers sparkling beers use the same yeast?
> 
> JT



same yeast,
Diacetyl rest is something I always do with this yeast, reckon 10 days at 16-20 it ranks of it, I bump it up to 22 for 24-36 hours, crash it, bottle/keg it and dont look it for a month. More important next time I brew it, pitch an active starter. you would like to shoot for the 1008 range.


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