But aren't you by asking this question just rehashing the stupid debate..there's literally 10,000 threads or more asking this same question including those asking if there's scientific validity...so how is this thread any different?
Can you read what's already been said, and try for yourself, and choose which works for you?
I'm not gonna get into this stupid debate- (it's been done to death no matter what the OP thinks) anymore but there are some things out there about long primaries, and I've posted it repeatedly..
One of them deals quite clearly with extended yeast contact and "yeast cleaning up after itself." And that deals with cleaning up diacetyl.
"THE ROLE OF DIACETYL IN BEER
By Moritz Kallmeyer"
The Abstract begins...
Diacetyl as a product of fermentation is more characteristic of ales than lagers. Diacetyl is produced early in the fermentation, and then most of it is reabsorbed by the yeast and reduced to flavourless compounds later on. Yeast strains differ markedly in their diacetyl reduction ability. Some ales and a few lagers (such as the famous Pilsner Urquell) contain perceptible amounts of diacetyl, but as a rule modern brewers consider it as a fault. This is because certain bacterial infections and other errors in brewing technique will increase diacetyl levels resulting in unacceptable beer aroma and flavour profile. This parameter thus serves as a quality check. However, it is important to remember that diacetyl flavour is a natural by-product of yeast fermentation, and in some beer styles it is an optional or even required flavour component in low amounts.
From here....
Drayman's Brewery and Distillery
There's two methods of rests listed in the Kallmeyer article...one for ales and warmer beers....interesting.
Maturation of beer flavour requires the presence of yeast as a catalyst. There are many methods of finishing that have the sole objective of prolonging the contact of beer with yeast after primary fermentation is completed. I want to emphasize that a diacetyl rest with most of the yeast lying at the bottom of the tank and not enough in suspension is of no use. Most lager breweries, especially those that use Weinhenstephan 308 or similar “diacetyl producing yeast’s” employ a long diacetyl rest, in order to minimize diacetyl in the finished beer.
Method 1
If a very cold primary fermentation was used it involves allowing the beer temperature to rise from the controlled primary fermentation temperature of about 10°C to 15-18°C when the primary fermentation is coming to an end. Normally, the time is determined by the attenuation of the beer. If, for example the wort starting gravity was 1050 and the expected terminal gravity is 1010, then the diacetyl rest would be commenced when the beer has attenuated to about SG 1023 when two-thirds of the total fermentable material in the wort has been consumed. The diacetyl rest normally lasts for 48-72 hours, until primary fermentation is over and secondary fermentation is under way. At this time the temperature is lowered when the more traditional method is followed, probably 1°C per day until the lagering temperature of 0-1°C is reached.
Method 2
If a warmer primary fermentation temperature was used for ale or lager the diacetyl rest involves either lowering the beer temperature 2 or 3°C at the end of primary fermentation or keeping it constant for up to 6 days. In lager yeast strains with low diacetyl production it is common practise nowadays to employ a short diacetyl rest followed by centrifuging to remove excess yeast and then crash cooling to 0°C. When brewing ales, that should have very low diacetyl levels especially German Ales like Alt and Kölsch, the implications are to not use highly flocculent yeast and to allow an extended primary fermentation, albeit at cooler temperatures until sufficiently low diacetyl levels are reached. Yeast that settles in the cone is still removed on a daily basis.
And someone referenced THIS article last week...
Beer Flavors #1: Diacetyl
Modern brewing practice dictates that beer be aged on live yeast until the vast majority of AAL is converted into diacetyl. Brewer’s yeast, while unable to metabolize AAL, will readily absorb and break down diacetyl into relatively flavorless compounds. By giving the beer enough contact time with the active yeast, the brewer can eliminate the diacetyl. It generally takes only about two weeks of aging an ale to assure that it will have no buttery flavors
Secondly people demanding scientific papers backing this stuff up have to realize something important about this....This long primary discussion has only in the last year or so, since Basic Brewing/BYO decided to tackle it, been beyond here. WE experimented/fought/argued/debated for about 4 years or more in relative obscurity until our arguments got brought out to the larger brewing community, and with such a lot of dicussions that folks started to listen an wonder.
Because prior to that the rest brewing community just assumed autolysis was inevitable, repeated the rote chestnuts of Papazian, and then Palmer, and kept repeating it...But noone gave it any thought, no one bothered to write about it or experiment,
except maybe us.
AND THEN PALMER admitted that he did the same thing. He just regurgitated the same old belief, not really researching it or anything,
just repeating what he heard.
John Palmer said:
My recommendation was based on the premise that (20 years ago) larger (higher gravity) beers took longer to ferment completely, and that getting the beer off the yeast reduced the risk of yeast autolysis (ie., meaty or rubbery off-flavors) and it allowed more time for flocculation and clarification, reducing the amount of yeast and trub carryover to the bottle. Twenty years ago, a homebrewed beer typically had better flavor, or perhaps less risk of off-flavors, if it was racked off the trub and clarified before bottling. Today that is not the case.
Just because the papers aren't written YET doesn't mean there's no "scientific validity" to this....
the papers are being written now.
And a lot of it, just happenning simple by people trying things out and deciding for themselves if it's valid or not.
When people aren't open minded about something, or don't think deeper and just look the old arguments without thinking...then noone bother's researching or caring.
Thing is, once BYO/Basic Brewing picked up on what we were doing, folks outside of here started to look deeper....Palmer is a good example....And once he did it, the culture shifted, and people ARE researching it. Hopefully more thoroughly than the basic brewing guys.
But I predict you'll be seeing plenty of "scientific papers" coming out on this topic.
You know there's no point in quoting a paper form 10, or 20, or 30 years ago,
we're not brewing with the same yeast or the same quality of yeast we were back then. Even if the strains are the same, they're produced better, and they're in our hands fresher, than anything available to homebrewers than ever before...heck there's even more yeast strains available than before....So maybe Fixe's Book, or Papzizain's or Palmer's or even a brewing science article from the 70's, that we want to bandy about as "proof" isn't exactly going to be the best source- maybe we're writing the new articles now, or just making the discoveries by our own experiences.
This thread is no different than the 10,000s of other threads on here about this....plenty of "scientific" stuff has been brought it in other threads, for or against. This is just another beating of the dead horse....it's no different than all the other ones.
I'm not gonna engage or debate in here, I just wanted to bring up a couple of points, but they've been posted in many of the other threads asking for "scientific validity."
And to give some food for thought for those demanding "scientific proof" about this...it's hard to have science done about it if no one took it serious enough to look into it, or just repeated the old info. There had to be a shift in the brewing culture, which there has been largely because of us on here, before it was in a position where people will start to do the research further.
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