Diacetyl, rest vs. no rest

I recently did ten gallons of my house bitter.
I used:
20# 2-row
2# honey malt
1# crystal 20
1 qt of yeast starter made from washed 1968 (london ESB)
1 oz citra

I have noticed when tasted side by side the bottle conditioned 5 gal tastes much cleaner than the 5 gal that went into the corny and straight into the kegerator. I had been planning on doing something like this for a while with this yeast.
I think they both taste good. The kegged half has the expected malt/hops profile just like the bottle. The keg though, has that butterscotch nose and the bottle doesn't. My investigation points to the very obvious difference in temperature while finishing the secondary process. The bottles were left to do their thing in the bath tub about 73F and as previously stated the keg went into the 34F temp zone(I have a temp controller). I read a lot about the usefulness/necessity of the diacetyl rest and thought this could shed some light on it for those with the same curiosity.

My experience and understanding is that most of the english yeasts have a habit of floculating in the medium to high range. What also happens is during fermentation it's not actually diacetyl but the precursor chemical that is then oxidized into diacetyl ((see "Home Brewer's Answer Book" by Ashton Lewis) a great toilet read by the way). Most brewers use a warmer fermentation or one of increased length to give the yeast time to clean up diacetyl in the beer. The yeasts that have a high floculation property settle to the bottom of the fermenter before having a chance to clean this flavor chemical up. I think Wyeast says 1968 is medium low but I like it anyway.

My theory is the secondary fermentation that occurred at room temperature and the subsequent rest enabled the yeast to produce a "cleaner" product in terms of diacetyl while the batch that went into the kegerator was essentially cold crashed and left with noticable diacetyl.

Yes I know it's not traditional. Let's try not to get hung up on the little things and focus on the fact that I'm providing this information as a way to side step the people that feel it necessary to provide info irrelevant to the topic being specifically posted or to hijack the thread. This recipe does however comply with the guidelines set forth by the AHA. As with all my beers I brew them to these so I have a reasonable starting point.

Your "theory" is completely correct. Some beers have flavours that disappear if you wait too long. I usually bottle my bitters as soon as possible (4-7 days after pitching) and start drinking them as soon as they are carbonated.

The whole "leave it in primary for at least 3-4 weeks" is only a rule of thumb, and many beers benefit from not waiting.

I like this explanation given here

theredben said:

Your "theory" is completely correct. Some beers have flavours that disappear if you wait too long. I usually bottle my bitters as soon as possible (4-7 days after pitching) and start drinking them as soon as they are carbonated.

The whole "leave it in primary for at least 3-4 weeks" is only a rule of thumb, and many beers benefit from not waiting.

Click to expand...

I am impatient like you, but I notice an outrageous improvement to the quality of any ale I make at the 6 week mark.

I can get anything with a shaken keg, drinkable in 3 weeks, but the taste at 6 weeks is so much better.

Question for you. How do you carobonate your kegs? I presume you force carb like most people since you said you just threw the keg straight into your 34 degree kegorator.

I think sure, part of it is that the bottle conditioning cleaned up some of the diacetyl in there, but you also sent your yeast into another fermentation cycle. of COURSE that is going to taste different than your force carbonated beer. This guy in my brew club actually naturally carbs his kegged beer. His bottled stuff at meetings is always drawn off his keg, and he's easily one of the best brewers in our club. You could try carbing your keg naturally next time to kind of even the playing field between your kegged beer and your bottled ones. Just an idea I had.

You're missing some pretty vital information here:

a) What temperature did you ferment at, and what method do you use to control temperature?
b) Did you use a single 10gal fermentor, or two 5gal's?
c) How long was it in the primary for?
d) Did you use a secondary fermentor, and if so, how long did you leave the beer in there?

When fermenting a typical bitter with typical English yeast, diacetyl cleanup should happen as much as it's going to fairly early on, as long as you do everything properly. One big reason I think the extended warm aging would be of any benefit in this case is if you racked or kegged it too early. But it'd have to be pretty darn early.

Diacetyl rests are usually for lagers, as well as ales fermented at cooler temperatures, although they are alsi used in special circumstances for ales fermented at more typical temps. The lethargic pace and activity of colder ferments doesn't give it much of a chance to clean it up. And in fact, it's considered important to do the diacetyl rest before fermentation is even completely finished, as dormant and settled yeast are pretty useless for this.

There are many other factors involved in diacetyl production (and reduction), but I don't want to get too ahead of myself before getting more information, especially on the questions I asked above.

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And, to bring up something only minimally related, I think you may have the wrong idea about just exactly what flocculation is. Many people are understandably mistaken when picking it up in conversation, and that only contributes to further misinformation - it is very likely the most misused term among English-speaking homebrewers by far. Flocculation is NOT the ability or speed with which a yeast strain falls out and settles (although it does influence this to some degree). Flocculation specifically refers to the ability of yeast to clump up, forming bigger yeast chunks. British ale yeasts are generally high flocculators, and they are also well-known for being some of the best top-cropping yeasts. The clumps that they form allow the convection and rising CO2 to push them to the top much more easily during fermentation, although they easily fall out afterwards.

Was the diacetyl present before you bottled/kegged? A quick taste should have revealed it's presence, letting you know whether you needed to do a rest and if the difference in storage temps cleaned up the flavor. Pediococcus can also cause diacetyl to form. Keg sanitation could be the culprit.

TheBeerist said:

Question for you. How do you carobonate your kegs? I presume you force carb like most people since you said you just threw the keg straight into your 34 degree kegorator.

I think sure, part of it is that the bottle conditioning cleaned up some of the diacetyl in there, but you also sent your yeast into another fermentation cycle. of COURSE that is going to taste different than your force carbonated beer. This guy in my brew club actually naturally carbs his kegged beer. His bottled stuff at meetings is always drawn off his keg, and he's easily one of the best brewers in our club. You could try carbing your keg naturally next time to kind of even the playing field between your kegged beer and your bottled ones. Just an idea I had.

Click to expand...

Yes I force carbonate. I've tried to naturally condition in my kegs. They don't hold low pressure very well. I have tried sealing the keg with Co2 then letting it go at room temp for the yeast to ferment the priming sugar. Came back a week later to flat beer.

emjay said:

You're missing some pretty vital information here:

a) What temperature did you ferment at, and what method do you use to control temperature?
b) Did you use a single 10gal fermentor, or two 5gal's?
c) How long was it in the primary for?
d) Did you use a secondary fermentor, and if so, how long did you leave the beer in there?

When fermenting a typical bitter with typical English yeast, diacetyl cleanup should happen as much as it's going to fairly early on, as long as you do everything properly. One big reason I think the extended warm aging would be of any benefit in this case is if you racked or kegged it too early. But it'd have to be pretty darn early.

Diacetyl rests are usually for lagers, as well as ales fermented at cooler temperatures, although they are alsi used in special circumstances for ales fermented at more typical temps. The lethargic pace and activity of colder ferments doesn't give it much of a chance to clean it up. And in fact, it's considered important to do the diacetyl rest before fermentation is even completely finished, as dormant and settled yeast are pretty useless for this.

There are many other factors involved in diacetyl production (and reduction), but I don't want to get too ahead of myself before getting more information, especially on the questions I asked above.

—————

And, to bring up something only minimally related, I think you may have the wrong idea about just exactly what flocculation is. Many people are understandably mistaken when picking it up in conversation, and that only contributes to further misinformation - it is very likely the most misused term among English-speaking homebrewers by far. Flocculation is NOT the ability or speed with which a yeast strain falls out and settles (although it does influence this to some degree). Flocculation specifically refers to the ability of yeast to clump up, forming bigger yeast chunks. British ale yeasts are generally high flocculators, and they are also well-known for being some of the best top-cropping yeasts. The clumps that they form allow the convection and rising CO2 to push them to the top much more easily during fermentation, although they easily fall out afterwards.

Click to expand...

a- 64F. A ranco ETC
b- 2 six gal fermenters.
c- 1 week.
d- yes two carboys. I blend the beer for consistency when I'm transferring and bottling. By this I mean I put half of each into each vessel when transferring from primary to secondary and when I go to the bottling bucket.1 week.

Just 1 week in the primary??! I think that may be what's giving you diacetyl issues. It would be more noticeable with certain yeasts and certain temperatures, so if 1 week is typical for you, it doesn't mean it would show up in all beers, but you really should keep the beer in contact with all that yeast for a bit longer if you can, especially when doing a cooler ale ferment like at 64°

Paul07293 said:

Was the diacetyl present before you bottled/kegged? A quick taste should have revealed it's presence, letting you know whether you needed to do a rest and if the difference in storage temps cleaned up the flavor. Pediococcus can also cause diacetyl to form. Keg sanitation could be the culprit.

Click to expand...

I soak them in B Brite so it's probably not the kegs. Then I sanitize with iodophor.

Yeah I was thinking I should ferment it warmer for the style. This is the only british yeast I use. American 2 from wyeast is my go to for everything else except belgians. And I use irish for my porter and winter warmer. Needless to say I make more IPAs and it's probably evident. I think it's a west coast thing.

I had a couple beers last night out of the keg. No diacetyl on the nose. I even waited for it to warm up. I do have another ten gallons in the fermenter right now and they've been in primary for two weeks so we'll see how much different it is in a couple days.