Diacetyl Rest In Ales

[RdeVjun]

Folks, I've had a squiz in the obvious places, but turned up not much.

Is there any reason that an ale's diacetyl rest for things like Wy1968 and 1187 can't be achieved in the bottle? Or must it take place in the fermenter so that decomposition products are left behind, gas liberated etc?

I'll often put freshly- bottled ales on top of the electric hot water system for a few days to kick start carbonation, in the cool conditions of late its been a godsend as its been nearly freezing in my laundry. So, would continuing to do this achive a dicetyl rest at the same time? Oh, I don't keg. Yet...

TIA.

 

[Bribie G]

They do clear up a bit in the bottle but it takes bloody ages, I made a nice butterscotchy Ale with Wyeast 1768 - that yeast always gives me diacetyl which I don't mind in a dark UK ale - but the two month old bottles are now losing the twang but only gradually.

 

[Happyrock]

For what its worth I did an ordinary bitter recently with wyeast 1968. Left it in the fermentor for 10 days at 20 degrees. I cant pick up any diacetyl character in it.

 

[Adamt]

From my understanding diacetyl is a ketone that is cleaned up by the yeast (i.e. not liberated and can be done in the bottle).

You will only get diacetyl in ales if you're fermenting real low (<17ish).

 

[Scruffy]

There's a couple of contributing factors that leave you with diacetyl; When brewing yeast turns sugar into ethanol one by product is an ester called α-acetolactate. The yeast cells can use some of this ester to produce valine, an amino acid. The rest of the α-acetolactate gets dumped into your beer. That wouldn't be much of a problem, except that in beer's lowish pH environment, α-acetolactate gets transformed into diacetyl. Oxygen helps that reaction along, as do elevated fermentation temperatures. If you separate the yeast from the beer, if there's still α-acetolactate, you're going to get diacetyl... Now, when the yeast is finished fermenting, it will reabsorb Diacetyl, and higher temperatures help that process. Once it's back in the cell, the diacetyl is converted into acetone and subsequently into 2,3-butanediol. A by-product of each of those conversions is a compound called NAD+, which helps the cell produce energy.
All you have to do is leave an ale a few more days in the fermenter, the yeast isn't going to produce any more Ale character, but will clean up behind itself... (I guess you would let a lager naturally warm up once the brew has dropped to half its OG - somebody that actually brews this Foreign Muck could possibly put me right here?)

The way I check is to pull a sample from the fermenter and split it into two covered jars. Stick one in the fridge and heat the other to 20C for an hour or so, then taste them both. If they taste the same, you're ready to rack your beer, if you can taste butter (popcorn) in the heated sample, your yeast is still at work, and you should give it another day or two.

 

[bconnery]

The way I check is to pull a sample from the fermenter and split it into two covered jars. Stick one in the fridge and heat the other to 20C for an hour or so, then taste them both. If they taste the same, you're ready to rack your beer, if you can taste butter (popcorn) in the heated sample, your yeast is still at work, and you should give it another day or two.

Assuming you are not one of the people who can't detect diacetyl of course...
Many people, approaching 40% is a number I've read, have a hard time detecting it, and something like 25% can't detect it at all other than at really really big levels...

 

[RdeVjun]

Thanks BribieG, that's interesting. BTW, the 'Landlord County' (i.e. your Ruddles County recipe X TTL hybrid, basically a TTL with a generous amount of BramlingX) is on the 1768PC, its what I have in mind for this possible diacetyl rest, but I will be using 1968 in the future and a thorough rest is recommended with it. A few others I've done on 1768PC haven't really needed a rest, perhaps its not as pronounced as 1968 (I'm guessing 1768PC has a similar diacetyl character to 1968, only because Wyeast say its similar) or I'm not that sensitive to diacetyl but other tasters, although largely naive as they were, haven't pipped it. I'll have to get a few samples over to you, if there's any left that is- stepson's wedding on the weekend just decimated my reserves.

Wow Scruffy, that's a really detailed explanation, many many thanks indeed. I generally leave them ferment for over a fortnight (often via secondary but not as a rule) and well past SG stability, so may be achieving the same end in doing so. I've learnt not to rush these things of exquisite beauty, plus I am a lazy bum anyway and my motto is 'why do today what can be put off until tomorrow?'. And I agree, if there's any errors, I'm sure the foreign muck brewers will no doubt be along pretty smartly to put the record straight!! :lol:

Also, while were at it, has anyone else found 1768PC a shade recalcitrant? I've had two out of six split smackpack starters, one fresh and bubbling the other refrigerated and gently roused, just completely fail. No signs of fermentation after almost three days (no don't- I use clingfilm and a hydrometer ), so I had to repitch from another starter/ reuse slurry. Is a very nice strain though, quite pleased with it and will be slanting some for future use if I can't get another pack.

Thanks heaps guys and, as usual, there's loads of information and many interesting and diverse views!

 

[discoloop]

Assuming you are not one of the people who can't detect diacetyl of course...
Many people, approaching 40% is a number I've read, have a hard time detecting it, and something like 25% can't detect it at all other than at really really big levels...

Very interesting. I've always wondered whether the reason I've never tasted Diacetyl is because I've always managed to avoid it or because I couldn't pick it up....

 

[Scruffy]

Hey, look, I have enough trouble at BABBS detecting any subtle nuances like raspberries or wasps or soot in the beer judging and in that respect I'm still learning (but I think I know a good beer from fudge)- but if we were presented with a beer at (say 25C ) and it reeked of popcorn... you'd know wouldn't you? Contrary to what the BJCP Style Guidelines might imply, i reckon beers WITHOUT ACTUAL diacetyl, taste a lot better than beers with detectable diacetyl. At low levels, granted, it gives beer a slick mouthfeel; at higher levels, the flavour becomes buttery they make artificial butter out of diacetyl after all then like butterscotch, and eventually rancid - I'm guessing the OP has beer that has an uninvited flavour and wants to know if he can rid (he mentioned it after all)...
I hadn't touched on bacterial infections, or the merits (or notoriety) of Pediococcus and Lactobacillus strains. Just an unwanted taste and how to fettle it...

 

[A3k]

Very interesting. I've always wondered whether the reason I've never tasted Diacetyl is because I've always managed to avoid it or because I couldn't pick it up....

Yeah, i'm in the same boat. Can't say i've ever tasted it.
Hopefully my mates aren't bagging my butter beer without me having a clue.

 

[Bribie G]

I took a bottle of that butterscotch ale to the BABBs meeting before last and on our table some could taste it, some couldn't and a couple of tasters actually said 'I like the caramel flavour in this'. Actually I gave a bottle to Scruffy at the end of the meeting if he can still remember it.

 

[RdeVjun]

Hey, look, I have enough trouble at BABBS detecting any subtle nuances like raspberries or wasps or soot in the beer judging and in that respect I'm still learning (but I think I know a good beer from fudge)- but if we were presented with a beer at (say 25C ) and it reeked of popcorn... you'd know wouldn't you? Contrary to what the BJCP Style Guidelines might imply, i reckon beers WITHOUT ACTUAL diacetyl, taste a lot better than beers with detectable diacetyl. At low levels, granted, it gives beer a slick mouthfeel; at higher levels, the flavour becomes buttery they make artificial butter out of diacetyl after all then like butterscotch, and eventually rancid - I'm guessing the OP has beer that has an uninvited flavour and wants to know if he can rid (he mentioned it after all)...
I hadn't touched on bacterial infections, or the merits (or notoriety) of Pediococcus and Lactobacillus strains. Just an unwanted taste and how to fettle it...

Yep, actually I was hoping to avoid a potential diacetyl problem in some upcoming brews with 1968, a rest is recommended, but now that you mention the slick mouthfeel, I have noted it and its in a couple of my TTLs with 1768 and definitely don't like it either. I didn't realise the mouthfeel was perhaps diacetyl, I thought maybe it was the Munich II in Dr S' recipe and was going to drop it, but I think now that I'm quite mistaken. Am hoping and praying its not infection, its been present and persistent in a few, so I am inclined to think not.

Righto- I'm going to do a few experiments! I have some 1768 and Ringwood ales underway and will test for butter with Scruffy's method, particularly now that the temps have been a bit lower. It could be that I'm not sensitive to its taste, but if the slick mouthfeel can be eliminated with a diacetyl rest then that's even better- it'll be gone as well as any buttery flavour. Great!

I am one for not sticking to the guidelines/rules too, to me guidelines are just guidelines, like recipes for cookery, and I'm not a competition brewer anyway so I don't feel the need to follow something that I may or may not agree with. If I think something is missing or shouldn't be there, I'll take action rather than just carry on wondering.

Again, many thanks Scruffy and also everyone else, this has been a really useful discussion and I appreciate it!

 

[Scruffy]

I took a bottle of that butterscotch ale to the BABBs meeting before last and on our table some could taste it, some couldn't and a couple of tasters actually said 'I like the caramel flavour in this'. Actually I gave a bottle to Scruffy at the end of the meeting if he can still remember it.

Do you want it back?

:icon_cheers:

 

[Bribie G]

Do you want it back?

:icon_cheers:

:lol:

 

[going down a hill]

Re-opening an old thread.

My Ringwood yeast ale has dropped to 1.010 and I'm going to give a diacetyl rest as suggested by Wyeast, my problem is they dont offer any suggestions on an ideal diacetyl rest temperature. What temperature do I raise the beer to? It has been brewing at 18c and I have just brought it up to 23c. Is that enough for ale?

Any suggestions would be appreciated
Cheers

 

[RdeVjun]

23C sounds fine to me, a day or two like that and you should be home and hosed as far as diacetyl goes. I now park mine on top of the electric hot water system for a few days, in mid winter they sit around 20C and are so stable that I'm tempted to put an ale straight on to it instead of in the fridge.

 

[going down a hill]

Thanks for that, I didn't want to cook it, just rest it.

 

[RdeVjun]

No sweat at all. So long as most of the action is over as far as the ferment goes, then the beer becomes reasonably hardy, a few days at 23C should trouble it nought.

Interesting to see how my own perceptions have changed over a couple of years, today I'm convinced that I'm quite naive to diacetyl (and a few other things), whereas I think I was just naive in the past. :icon_cheers: