Diacetyl rest

Brewing processes and methods. How to brew using extract, partial or all-grain. Tips and tricks.

Moderator: slothrob

Diacetyl rest

Postby Dr Strangebrew » Sun Aug 24, 2003 5:15 pm

I am attempting my first lager and would like to know how to perform a diacetyl rest for a lager. The yeast is White Labs WLP830 German Lager yeast. I have kept fermentation at 50 degrees F. 33% of the grist was wheat malt- I'm not sure if that will make a difference. I would like to know-

1) Do I need to raise the temp, if so to what temp?

2) When do I perform the 'diacetyl rest'?

3) For ales I just let the beer sit on the yeast a little longer, is this all that is required for lagers too?

Thank you
Cheers
Nate
Dr Strangebrew
Pale Ale
Pale Ale
 
Posts: 77
Joined: Tue May 13, 2003 7:01 pm
Location: Lincoln, NE, US

Diacetyl Rest Instructions...

Postby Mesa Maltworks » Sun Aug 24, 2003 7:22 pm

Once the beer is fermented to it's intended final gravity, allow the beer to raise to 60 deg. F. and hold for 24 hours. Then rack the beer to a secondary and cool to as close to 32 degrees as possible to begin lagering.

With ales such a rest is unneccesary due to the fermentation temperature which keeps the yeast very active and reducing diacetyl as they are flocculating out.

As long as you don't have too short of a fermentation or prematurely crash cool the beer, residual diacetyl should not be a concern.

With ales, always rack them immediately to a secondary when they hit the intended final gravity. This is necessary because yeast autolysis is greatly accelerated at ale fermentation temperatures and to preclude beer spoiling bacteria from gaining a foothold via the trub.

Ideally, to avoid trub derived problems completely, you should rack the wort off the trub after you see the first signs of a head forming in the primary. Worry not... any of the yeast you would leave behind are the least viable of the population. There will be more than enough left in suspension to do the job. This technique is a real good idea if you intend to repitch the secondary yeast slurry (NEVER pitch with a primarys' trub!) or reculture it.

Eric
User avatar
Mesa Maltworks
Strong Ale
Strong Ale
 
Posts: 474
Joined: Tue Sep 11, 2001 11:16 pm
Location: Georgetown, Grand Cayman Island

What about adding oxygen?

Postby Lobby » Tue Aug 26, 2003 3:21 am

If you rack off the trub when there is a foam head are you not allowing extra oxygen intake?

Is this still during the aerobic phase so there is no harm?

What is the major problem with repitching with trub? I have read that when making a starter the trub is necessary for oxygen take up.

Thanks for your imput.
Dee
Lobby
 
Posts: 2
Joined: Fri Mar 22, 2002 9:24 am
Location: London, On, CA

No O2 !....

Postby Mesa Maltworks » Tue Aug 26, 2003 4:48 am

Research (and my lab work) has shown that almost all of the oxygen uptake by yeast occurs within 6 hours of pitching. If there are signs of fermentation... ie CO2 bubbles, the yeast are in their anaerobic phase and the utmost care must be taken NOT to allow anymore oxygen to be solubilized. If there is a krausen (foam head) evident, the yeast are at their most active stage of fermentation and this is the best time for the first racking to occur.

The problems associated with pitching trub are that:

1) The trub is composed mostly of proteins and vegetal matter. Assuming you had a good fermentation with little contaminants present, the majority of the bacteria will be entrained in the trub. When primary fermentation is complete, the yeast flocs out into this trub and goes dormant. But... some bacteria are able to switch to consuming the dextrins in the trub and begin to grow, potentially contaminating the batch if left too long on the trub.

2) The yeast that settles in the primary are the least viable among the population and will be the most likely to cause fermentation problems after repitch down the line, the most common is flavor profile drift. Repitching yeast should be harvested from the secondary where it is trub free and contains the healtiest yeast.

Regarding: "I have read that when making a starter the trub is necessary for oxygen take up."

The only thing yeast need in the first 6 hours of being pitched is oxygen. They metabolize nothing else (including sugars) during this phase. An exception to this is with dry yeast which is best if hydrated before pitching. Dry yeast is kicked out of it's dormancy by hydration. This is best done before pitching by placing the yeast in 90 degree sterile water and allowed to soak for 20 minutes. Then add the solution to a pitching temperature wort.

Eric
User avatar
Mesa Maltworks
Strong Ale
Strong Ale
 
Posts: 474
Joined: Tue Sep 11, 2001 11:16 pm
Location: Georgetown, Grand Cayman Island

Is secondary yeast "tired"?

Postby Push Eject » Tue Aug 26, 2003 3:04 pm

:::Repitching yeast should be harvested from the secondary where it is trub free and contains the healtiest yeast.

Eric,

I read, I think in this month's Zymurgy, the primary vs. secondary yeast-reusage question.

Your point seems sound, but the author mentions "tired" yeast that aren't as "fresh" coming out of secondary.

Is that mallarky or what? And how do you spell mallarky anyway?

Cheers,
Charlie
User avatar
Push Eject
Double IPA
Double IPA
 
Posts: 233
Joined: Wed Mar 21, 2001 2:01 pm
Location: Lancaster, CA, US

"Tired" Yeast?....

Postby Mesa Maltworks » Wed Aug 27, 2003 1:58 pm

I don't get Zymurgy any longer, so I can't comment on the author's intent when calling yeast "tired". But... tired yeast to me means yeast of either low vitality and viability or being dead altogether. The author may be using this to refer to yeast that have gone into or are preparing for dormancy which is a natural protective mechanism that yeast have developed as they evolved to survive environmental stress such as the lack of food. In preparation for dormancy, they produce stores of glycogen that will sustain them for a while until oxygen and sugars become available.

If this is not what the author referred to, I can't agree that after a healthy fermentation that the yeast in the secondary are somehow suffering from compromised viability or vitality. On the contrary.... if yeast is in suspension actively fermenting a wort rather than flocced out at the bottom of a vessel, how could they be "tired". Sounds more like they are "hungry"!

Once this population, rather than the flocced one, has been transferred to the secondary it will finish out the fermentation and floc. This will be best to harvest and repitch.

In a perfect world, it would be best to harvest only the last band of settling yeast, but it is impossible to get a pitchable quantity in this way. This is, however, a great way to get the "pick of the litter" if you are cell culturing.

If you can implement this regimen, below is the optimum of handling to produce ultra clean beer as well as ensure the best in re-pitchable slurry:

1) 1st Racking: When a krausen first forms on the wort leaving ALL trub behind. This signals the beginning of logarithmic fermentation where the most viable and vital yeast are already in suspension working their magic. This occurs, hopefully, within 12~16 hours of pitching. You want to rack before super vigorous action is taking place because otherwise, part of the trub will be stirred into suspension by yeast action.

2) 2nd Racking: When the specific gravity of the beer is within ~3 degrees plato of the intended final gravity. This is where you are selecting the best performing yeast for later settling.

3) 3rd. Racking: When the beer has reached it's intended final gravity and has dropped bright or is ready to filter. In most cases, this will be either a transfer to a priming tank or a keg of some sort. The yeast at the bottom of this vessel is what you want to harvest.

Harvest Instructions:

1) Sanitize (preferably, sterilize) a wide mouth mason jar, lid and band.

2) After racking the beer, wipe the neck, lip and inside of the lip of the carboy with isopropyl alcohol and flame the wiped areas to burn off the alcohol. Don't heat the carboy directly as it might crack.

3) Swirl the contents of the carboy to suspend the yeast slurry and carefully pour into the jar. Immediately seal the jar and refrigerate it.

This harvested slurry will maintain 95+ percent of it's viability for up to 2 weeks and after being allowed to warm up, can be pitched directly into new wort, but is still best to produce a starter. I have seen yeast do fine after this point, but you are taking unnecessary risks in doing so such as increased fermentation lag which may allow the meanies to gain a foothold.

To make a starter, prepare a 5~6 degree plato wort and cool 2 days prior to brewing. Pour the refrigerated slurry into this wort (and swirl it vigorouly to aerate) in a sanitized (better=sterilized) container with an airlock. By pitching time, this yeast should have gone through respiration and reproduction phases and be ready to ferment when pitched into the new wort. There will be a 5~8 hour lag while they further reproduce, but the inital signs of vigorous fermentation should be visible within 12 hours or so.

As far as spelling "mallarky", I have know idea, I couldn't find it in my dictionary ! I have a feeling this may be yet another example of a !@#$ of a foreign language word that has made it into our lexicon!

Eric
User avatar
Mesa Maltworks
Strong Ale
Strong Ale
 
Posts: 474
Joined: Tue Sep 11, 2001 11:16 pm
Location: Georgetown, Grand Cayman Island

Thanks for the great info... here's a little more:

Postby Push Eject » Wed Aug 27, 2003 8:23 pm

ma
User avatar
Push Eject
Double IPA
Double IPA
 
Posts: 233
Joined: Wed Mar 21, 2001 2:01 pm
Location: Lancaster, CA, US

Amen, Eric

Postby fitz » Thu Aug 28, 2003 4:18 am

I haven't done all of the research that Eric has done in the micro organism field, but common sense tells you that these yeast cells have to be the strongest. Although I think Darwin only saw half of the picture, evolution does take place on some scale, but not to his extent.
Just from the info stated here, it sounded like the author believed the yeast in that vial, was the only yeast in the wort/beer. Does he know they reproduce. Sorry Jeff, hope this doesn't qualify as "sexual talk"
My son is 5 years old, and loves science. We do our own "testing" on some of the yeast after
I have transferred. He gets a kick out of seeing them multiply, It is pretty cool to watch if you aren't concerned about light reaching the mix.
Yeah, I'm a deviant, I watch yeast porn.
Watch them become active again, especially if you have a kid. They'll think it is really cool.
fitz
Strong Ale
Strong Ale
 
Posts: 442
Joined: Thu Dec 19, 2002 9:36 am

primary vs secondary

Postby brewforbeer » Mon Dec 15, 2008 4:50 pm

I am curious enough about this discussion to join this forum and ask if any one has done any tests (staining, cell counts, oxygen take up, ph drop, etc) in terms of vitality and viability on primary vs secondary yeast harvest.

At siebel I was instructed both ways... Graeme Walker, BSc, PHD, DSc, Professor of Zymology at the University of Abertay Dundee Scotland made a clever analogy of the first cells to be dropped in fermentation were typically young and drunk and corpses from previous slurries, full of petites, and that cells dropped late in fermentation were stressed old mothers and has beens hanging around for that last drink and also full of mutants. He recomended the common practice of harvesting the from middle layer of the primary fermentation...

However another instructor- a brewer from Doemens in Germany-- said that some German breweries were indeed harvesting the yeast cells late in the fermentation making a similar argument that they indeed the strongest and best because they were still working. Although I cannot remember the lecture completely I do remember him saying the yeast harvested from the late fermentation was done quickly, given a precise dose of oxygen, and then added in the correct pitching amounts to primary fermenters with fresh wort... The main benefit he claimed was no need to aerate the main fermenter, lower dissolved O2 levels, and improve shelf life of the product. They were also aiming to limit yeast growth and increase fermentation--- It's a waste of barley for brewers to produce yeast when they sell beer...

My comment to him, other then stating that another instructor contrasted his opinion on the vitality of secondary yeast, was that using natural as guidelines to presume what yeast is most healthy is certainly a two way street... Darwinism may suggest the yeast still eating late in fermentation is the healthiest because of that fact but that it does not [i]prove[/i] that it is...

The strongest lions at a kill eat first-- and weak, sick, and sub-ordinate lions of the pack eat the scraps last...

Logic to me --- dictates that in a closed envrionment made up of increasing amounts of your waste--- The strongest would eat the best food first...

BUT neither logic nor Darwin really have anything to do with it.... Yeast often acts illogical in my mind and Darwin was a hack and racist... I am wondering if anyone has actually test results that point in one direction or another-- rather then analogies and opinion...

It would be really cool if someone did...
brewforbeer
 
Posts: 4
Joined: Mon Dec 15, 2008 4:14 pm


Return to Techniques, Methods, Tips & How To

Who is online

Users browsing this forum: No registered users and 0 guests