Lager ferm temp & diacetyl rest

[beerisyummy]

Greetings, Zymurgists.

I have embarked on my second-ever lager brew and I'm sending up this trial balloon for any thoughts you may be inclined to generously bestow upon me.

My first lager was supposed to be a Maibock and it wasn't great. It was "beer" but didn't hit many of the right targets for the style. So, a few months later, I'm trying another Maibock.

Here are the specifics. I'm basing my recipe & technique on this article: https://beerandbrewing.com/make-your-best-maibock/
I have had good luck in the past with the "Make Your Best" series.

So I had a grain bill of 30% Munich, 30% Belgian Pllsner and 40% Maris Otter at OG=1.068.
My yeast is WY2206. I made a 3L starter, cold-crashed and decanted before pitching. My fermentation chamber is a chest-freezer with a Ranco temperature controller.

I followed the article's suggestion of beginning the fermentation at 50° and slow-rising the temp beginning on the third day (I waited until the fourth). I'm not taking the temperature of the beer directly, but assuming that the temp of the liquid simply lags behind the ambient temp by a degree or two as I raise the temp.

I don't like to open the beer to take gravity readings. (Besides the infection risk, each time wastes a couple mouthfuls of beer!!!) So I just count the airlock bubbles per minute to track fermentation activity until such time as a gravity reading may be indispensable. The beer has been bubbling happily and the activity has been increasing steadily. I am about to be at day 9 and 60°.

NOW TO MY QUESTION(S). It is, basically, where do I go from here? Is 60° good enough for a diacetyl rest? I have anecdotal evidence that a local brewery does this successfully with their lagers. Do I keep increasing 2° per day until I hit the more traditional d.r. range of 65-68 degrees? Or do I just zoom up there at this point? If the airlock bubbling starts to slow, how should I factor this into my temp. decisions?

Grateful for any thoughts you may have.

 

[Franktalk]

First, let me say that I LOVE me some Maibock!

This is what I go by for fermenting my lagers, and it works wonderfully: http://brulosophy.com/methods/lager-method/

The other thing I wanted to comment on is that Maris Otter seems out of place in the style. My Maibock, which is a perennial favorite in my taproom, is 66% Weyermann pilsner and 33% Weyermann light Munich, with the remaining 1% Weyermann acidulated. All German. The only thing in the recipe that is not German is S-189 yeast which is awesome and easy to use.

I ferment at 55 F (the beer is measured with a thermowell) and begin ramping up a few degrees a day after the 6th day, finally keeping the beer at 68 F for at least two days, but sometimes four or five. This has never failed me.

 

[beerisyummy]

First, let me say that I LOVE me some Maibock!

This is what I go by for fermenting my lagers, and it works wonderfully: http://brulosophy.com/methods/lager-method/

The other thing I wanted to comment on is that Maris Otter seems out of place in the style. My Maibock, which is a perennial favorite in my taproom, is 66% Weyermann pilsner and 33% Weyermann light Munich, with the remaining 1% Weyermann acidulated. All German. The only thing in the recipe that is not German is S-189 yeast which is awesome and easy to use.

I ferment at 55 F (the beer is measured with a thermowell) and begin ramping up a few degrees a day after the 6th day, finally keeping the beer at 68 F for at least two days, but sometimes four or five. This has never failed me.

Thanks for that. Ya, you would think that Maris Otter would be "out of place," but Mr. Weikert does make a rather passionate recommendation: "Starting with the grain bill, I do use Munich malt here, but nowhere near half. For base grains, I use 40 percent Pilsner, 20 percent Munich, and 40 percent Maris Otter. That’s right—British pale malt. The reasoning behind it is that I find it contributes a nice doughy, bready note without being heavy. Going with more Munich or Vienna malt runs the risk of bogging down your flavor profile, whereas this blend is throttled to prevent it and make it nearly impossible."

So we'll see! Next time maybe I'll try your grain bill and see if I like it better!

 

[Franktalk]

He does explain it well. The only way you'll know is to try it and see.

 

[McKnuckle]

I max out my lagers at 60°F. Unless you have mistreated the yeast or underpitched, you probably don’t have diacetyl anyway.

Regardless, mine have all come out clean so far. I typically rest at that temp for 2-3 days then start dropping back down. I’m usually kegged by day 14, 45°F, and I then lager in my keezer at 40°F which is serving temp. I’ll wait 2-3 weeks from there before drinking.

 

[dmtaylor]

First, let me say that I LOVE me some Maibock!

This is what I go by for fermenting my lagers, and it works wonderfully: http://brulosophy.com/methods/lager-method/

The other thing I wanted to comment on is that Maris Otter seems out of place in the style. My Maibock, which is a perennial favorite in my taproom, is 66% Weyermann pilsner and 33% Weyermann light Munich, with the remaining 1% Weyermann acidulated. All German. The only thing in the recipe that is not German is S-189 yeast which is awesome and easy to use.

I ferment at 55 F (the beer is measured with a thermowell) and begin ramping up a few degrees a day after the 6th day, finally keeping the beer at 68 F for at least two days, but sometimes four or five. This has never failed me.

I agree with this response completely. I too love maibock, one of my favorite beer styles.

I'll add that if you're already at 60 F, I truly don't think it will matter whether or not you continue to raise temp for the D rest. I think 60 F is good enough. If it were my own beer, I might bring to room temperature for a couple days, but I would be equally likely to just leave it alone. Honestly not sure which way is "better" if any. Experiment and find out!

 

[cactusgarrett]

Really, you're just looking for a temp to help the yeast along over the last hump of fermentation. With a traditional d-rest, that just means increasing the temp 5°F or so from the current temp. Realistically, one temp is as good as the next (or even NO rest at all), though, provided the yeast finish up properly. I know this is really a non-answer answer, but that's how I sees it.

 

[Jag75]

I haven't done a ton of Lagers but this is what I follow . Ferment at 50-53 until about 75% completion . Then up the temp a few degrees a day until it reaches 66 degrees . Hold at 66 for 3 days then drop temp down 4 degrees a day until it hits mid 30's . Transfer to keg then Lager.

 

[beerisyummy]

dmtaylor Love your tag line btw!

 

[couchsending]

Pitch at 44 ferment at 48. Step down and hold at 40 for a week then continue to 30 for a month. Pitch enough healthy yeast, aerate well and you’ll never get diacetyl.

 

[camonick]

So I just count the airlock bubbles per minute to track fermentation activity until such time as a gravity reading may be indispensable.

I myself have just a few lagers under my belt and am by no means an expert, but I believe by reading many threads on here that airlock activity is generally not a good indicator of fermentation completion... a fair gauge yes, but hydrometer readings are the only way to know for sure. Also, (somebody with more experience can correct me if I’m wrong) as temperatures are increased, CO2 begins to come out of solution which will create more airlock activity while the beer may not actually be fermenting more vigorously and give a false impression of “renewed” or continued fermentation.
I’ve personally fermented 34/70 @ 55° until about 80% complete then let free rise to room temperature for 3+ days before cold crashing (when hydrometer verifies complete fermentation) then transferring to keg. I’ve also read this may not be necessary for 34/70 yeast, but other strains may certainly require different handling.

 

[cactusgarrett]

I’ve personally fermented 34/70 @ 55° until about 80% complete then let free rise to room temperature for 3+ days before cold crashing

This guy gets it! Just don't cold crash too fast - a decrease of 3-5°F/day is advised.

 

[Franktalk]

After the diacetyl rest, I keg (carefully leaving yeast behind to the extent that I can) and then cold crash (in the keg) and lager. That way I get no oxygen suck-back during the cold crash.

 

[cactusgarrett]

But that's the trick, especially if lagering: if cold crashing too fast, you essentially inactivate the yeast due to thermal shock, and they won't do their assigned job in cleaning up the beer during aging/lagering. That's why i mentioned a 3-5°F drop per day earlier.

 

[beerisyummy]

I believe by reading many threads on here that airlock activity is generally not a good indicator of fermentation completion... a fair gauge yes, but hydrometer readings are the only way to know for sure.

I agree. I'll take a hydrometer reading when the bubbling "looks" like it might be finished (probably tomorrow). I just don't want to do it frequently, like ... okay yesterday I'm at 50% completion .... and today 60% .... ya know?

 

[Dland]

You do not want to wait until it is finished bubbling to start D rest, just beginning to slow. You need the yeast to still be active to clean things up.

If you do want to open beer up for hydrometer reading, I'd go with airlock slowing down, as stopped is might be too late.

 

[beerisyummy]

You do not want to wait until it is finished bubbling to start D rest, just beginning to slow. You need the yeast to still be active to clean things up.

If you do want to open beer up for hydrometer reading, I'd go with airlock slowing down, as stopped is might be too late.

Agreed on both counts. By "finished" I actually meant "slow but still bubbling."

 

[SpeedYellow]

... I followed the article's suggestion of beginning the fermentation at 50° and slow-rising the temp beginning on the third day (I waited until the fourth).
...

That's bad advice. If you didn't pitch enough healthy yeast, then you'd be raising the temp far too early. Standard advice is to raise the temp for the d-rest after 50%-80% done. Granted, some yeast are more tolerant to warmer ferm temps, so your process won't necessarily be a problem. Nor is there any reason to slow-rise.

... So I just count the airlock bubbles per minute to track fermentation activity until such time as a gravity reading may be indispensable. The beer has been bubbling happily and the activity has been increasing steadily. I am about to be at day 9 and 60°...

Lager fermentation should be done in 7-10 days, so it sounds like you didn't pitch enough healthy yeast. Counting bubbles is perfectly fine -- no need to ever use a hydrometer fermenting lagers. A common practice is to just wait until airlock activity starts to slow (like 4-6 days) then raise the temp to 64-68F for your 3-5 day d-rest.

But that's the trick, especially if lagering: if cold crashing too fast, you essentially inactivate the yeast due to thermal shock, and they won't do their assigned job in cleaning up the beer during aging/lagering. That's why i mentioned a 3-5°F drop per day earlier.

That's an interesting hypothesis, but I've never seen support for it. Indeed some (most?) commercial breweries do this 3-5F per day drop, but we don't know why -- does the beer flavor improve, or does it simply create the same beer in less time? I suspect very few homebrewers do this slow-drop method since there's no widely-accepted reason. But I'm intrigued if it might reduce total lagering time, since I loathe the 4-6 week lager period.

 

[Bassman2003]

I think with the advent of quick and warm fermented lagers, when discussing lager brewing one needs to decide if you are in the traditional or new camp. Traditional lager brewing pitches a TON of yeast at keeps the temps low. The beer is spunded which needs the yeast to stay active all the way through to create the carbonation - hence the need to slow lower temps. If a traditional brewery would do a D-rest it would only get to the low to mid 50's.

Modern warmer fermentation lets the brewer use far less yeast but this increases the risk of off flavors. Cold crashing speed in my view depends upon when you are doing it and if you are spunding or not. If you raise the temps to the 60's and let the beer finish, then the beer is finished. No need to care about saving the yeast on the way down as they are out of the picture. So a true cold crash is more about dropping out the "stuff" than yeast cleaning up.

My practice is to make a 2L starter, decant, add 2 more liters, decant, pitch at 46F, ferment at 48F and ramp up to 58-60F for the last 20% of fermentation. If one is spunding you can just transfer at 60F and keep it as long as you want in the keg, get your CO2 then cold crash for lager/serving.

Some strains work well at warmer temps but the traditional folks do not want their lager yeasts seeing much of anything above 55F. But it has been shown there are many ways to get to the finish line!

 

[cactusgarrett]

If you raise the temps to the 60's and let the beer finish, then the beer is finished.

Just because it's done fermenting doesn't necessarily mean the yeast aren't done cleaning up after themselves. To me, that's like saying a sour is done once it hits its terminal gravity.

 

[SpeedYellow]

But that's the trick, especially if lagering: if cold crashing too fast, you essentially inactivate the yeast due to thermal shock, and they won't do their assigned job in cleaning up the beer during aging/lagering. That's why i mentioned a 3-5°F drop per day earlier.

That 3-5F slow temp drop method seems to be purely a diacetyl-management issue. See Kunze "Technology Brewing and Malting," 4th ed., pp. 503-505. The slow-drop method is only done for short cold fermentations. If you do long cold, or short warm, or short cold followed by a few day d-rest, then you crash cool down near freezing. 1-2 weeks later (day 20) the beer is officially done regardless of method.

Just because it's done fermenting doesn't necessarily mean the yeast aren't done cleaning up after themselves. To me, that's like saying a sour is done once it hits its terminal gravity.

As I write in this post, Kunze would seem to disagree with you, with respect to commercial production. Again, perhaps your idea would help decrease lagering time but I'm not seeing any support.

 

[dmtaylor]

Some do not worship Kunze. Perhaps we should...?

 

[Bassman2003]

Just because it's done fermenting doesn't necessarily mean the yeast aren't done cleaning up after themselves. To me, that's like saying a sour is done once it hits its terminal gravity.

I think this is a topic of disagreement or even confusion for homebrewers. If the yeast do clean up after finishing fermentation, then how long does it take for them to finish cleaning up? I am being serious. 12 hours? A day? A week? etc...

 

[Franktalk]

I think this is a topic of disagreement or even confusion for homebrewers. If the yeast do clean up after finishing fermentation, then how long does it take for them to finish cleaning up? I am being serious. 12 hours? A day? A week? etc...

We don't really know, and that's why we err on the side of caution, giving it a "few days."

 

[beerisyummy]

I think this is a topic of disagreement or even confusion for homebrewers. If the yeast do clean up after finishing fermentation, then how long does it take for them to finish cleaning up? I am being serious. 12 hours? A day? A week? etc...

As I mentioned at the start of the thread, this is only my second lager. However, inspired by other discussions in this forum, I started some time ago letting my ales sit in the primary for four weeks, no racking to secondary, and then bottling. The idea advanced int he discussions was that it gave the yeastie beasties time to "clean up after themselves." Now, I haven't conducted any experiments, with splitting a batch in two and trading one half in this way and racking the other before bottling. I can't give you any numbers on it. All I can say is the beer is DAMN good. I'm not in a hurry to drink my beer. I give it four weeks in the bottle too. So with lager I'm fine with the slow drop. Because I'm not in a hurry, and maybe the yeast does "clean up" better.

Thoughts?

 

[beerisyummy]

Having said that ^^
I am wondering about one aspect of lagering. Keeping in mind that I don't keg, I bottle, I'll be going for that long lagering period in the carboy in my chest freezer. Should I be concerned about leaving the beer on the cake for lotsa weeks?

 

[Vale71]

As I mentioned at the start of the thread, this is only my second lager. However, inspired by other discussions in this forum, I started some time ago letting my ales sit in the primary for four weeks, no racking to secondary, and then bottling. The idea advanced int he discussions was that it gave the yeastie beasties time to "clean up after themselves." Now, I haven't conducted any experiments, with splitting a batch in two and trading one half in this way and racking the other before bottling. I can't give you any numbers on it. All I can say is the beer is DAMN good. I'm not in a hurry to drink my beer. I give it four weeks in the bottle too. So with lager I'm fine with the slow drop. Because I'm not in a hurry, and maybe the yeast does "clean up" better.

Thoughts?

This is unfortunately yet another HB myth that will be hard or possibly impossible to kill. Yeast that has dropped and is laying at the bottom of the bucket has zero contact with the beer and hence plays no role whatsoever in maturation. Even if you rack the beer to a secondary vessel without filtration your beer will have millions of yeast cells per milliliter swimming around in it ready to do all the clean-up work. Even if you were to do your split batch experiment you would have zero difference between the two, provided you keep temperature and times the same. When one finds mention in the literature of "leaving the beer on the yeast" this means simply, in a commercial setting, not to filter and/or pasterurize to soon. Without that your beer will still be "on the yeast" for a year after fermentation is finished.

 

[beerisyummy]

When one finds mention in the literature of "leaving the beer on the yeast" this means simply, in a commercial setting, not to filter and/or pasterurize to soon. Without that your beer will still be "on the yeast" for a year after fermentation is finished.

Hmmm interesting. Although it sounds more like "leaving yeast in beer" than "leaving beer on yeast."

What about autolysis? From what I've read concerns about autolysis are probably exaggerated; but why wouldn't yeast in suspension be as likely to suffer from autolysis as yeast in the cake? What am I missing?

 

[Vale71]

Hmmm interesting. Although it sounds more like "leaving yeast in beer" than "leaving beer on yeast."

What about autolysis? From what I've read concerns about autolysis are probably exaggerated; but why wouldn't yeast in suspension be as likely to suffer from autolysis as yeast in the cake? What am I missing?

As long as yeast is "alive" autolysis is not a concern. Autolysis is a natural decomposition process akin to the decomposition of a corpse. Cavities in the cell (vacuoles) hold enzymes whose sole role is to destroy proteins, basically waste management facilities. As long as the cell is active these cavities will remain intact and the enzymes will not "run loose" in the cell. Once the cell "dies" vacuoles burst and the cell structure will be destroyed by the enzymes. Yeast that has dropped has ceased all activity and will be more likely to undergo this form of cell "death". But of course even yeast in suspension can be affected although not as much, which is why filtered beer is more stable and has a longer shelf life than unfiltered.

 

[beerisyummy]

I think with the advent of quick and warm fermented lagers, when discussing lager brewing one needs to decide if you are in the traditional or new camp. Traditional lager brewing pitches a TON of yeast at keeps the temps low. The beer is spunded which needs the yeast to stay active all the way through to create the carbonation - hence the need to slow lower temps. If a traditional brewery would do a D-rest it would only get to the low to mid 50's.

Modern warmer fermentation lets the brewer use far less yeast but this increases the risk of off flavors. Cold crashing speed in my view depends upon when you are doing it and if you are spunding or not. If you raise the temps to the 60's and let the beer finish, then the beer is finished. No need to care about saving the yeast on the way down as they are out of the picture. So a true cold crash is more about dropping out the "stuff" than yeast cleaning up.

My practice is to make a 2L starter, decant, add 2 more liters, decant, pitch at 46F, ferment at 48F and ramp up to 58-60F for the last 20% of fermentation. If one is spunding you can just transfer at 60F and keep it as long as you want in the keg, get your CO2 then cold crash for lager/serving.

Some strains work well at warmer temps but the traditional folks do not want their lager yeasts seeing much of anything above 55F. But it has been shown there are many ways to get to the finish line!

Not familiar with the term "spunding," can you define please?

Would you mind giving more details on your starter? Looks like you are doing a stepped starter. Are you letting it ferment out all the way before you step/pitch? Cold crash before decant?

 

[Bassman2003]

#1 - Vale71 is right on target here, letting the yeast clean up after itself is a homebrew myth in my opinion. There are reasons for keeping yeast alive and around which are related to fermentation and carbonation. The main point being dead or dormant yeast cells do not do anything. So once the fermentable food runs out in your beer the yeast literally drop out of the picture. Whatever cleanup they do, they do as they are eating and active. So leaving beer in the primary for a month does not accomplish much other than more time for everything to drop out.

It is such a simple concept that it gets overlooked. The most important thing about aging is gravity causing all of the "stuff" to drop out of the beer. Seriously. That's pretty much what lagering is - colder temps speed up the dropping out of "stuff" to the bottom of the vessel which gets left behind.

I have always noticed when I drink a beer young and it is not totally clear that the flavor is kind of muddy. Once it drops bright the flavors are more defined and the beer tastes a lot better. Very simple and not magic from the yeast.

#2 - Spunding. This is where you transfer fermenting beer with about 1 Plato left in fermentation to capture the CO2. This is a way to naturally carbonate your beer. The spunding valve is a device that lets you set what pressure to hold and everything above that gets released. So when I spund I transfer from my primary into a keg, put the spunding valve on and let the beer finish in the keg. When I go to serve or lager the beer it gets put in the fridge and is ready to go with carbonation.

This is where the slow cold crash comes into effect as you do not want to put your yeast to sleep if you still want them to ferment and create CO2 for carbonation.

#3 - Starters. I pressure can 1.070 wort in mason jars. When I make a starter I add a bottled water amount to make a 2 liter starter. For ales I will make the night before and pitch the entire thing at high krausen. For lagers I let it ferment out, put in the fridge, siphon off and then add another 2L of wort and repeat the siphon routine. The best case scenario is to double the size of the second starter (4L) but I do not think I can put 4L in my starter container. Anyway, this is with one yeast pack to begin with. After all of this, I am still under the best case scenario for lager pitch rates. But I do not want to buy multiple packs so my ferment goes a bit longer.

Hope this helps!

 

[Vale71]

#1 - Vale71 is right on target here, letting the yeast clean up after itself is a homebrew myth in my opinion. There are reasons for keeping yeast alive and around which are related to fermentation and carbonation. The main point being dead or dormant yeast cells do not do anything. So once the fermentable food runs out in your beer the yeast literally drop out of the picture. Whatever cleanup they do, they do as they are eating and active. So leaving beer in the primary for a month does not accomplish much other than more time for everything to drop out.

It is such a simple concept that it gets overlooked. The most important thing about aging is gravity causing all of the "stuff" to drop out of the beer. Seriously. That's pretty much what lagering is - colder temps speed up the dropping out of "stuff" to the bottom of the vessel which gets left behind.

I have always noticed when I drink a beer young and it is not totally clear that the flavor is kind of muddy. Once it drops bright the flavors are more defined and the beer tastes a lot better. Very simple and not magic from the yeast.

I'm sorry but I never said that and you're just projecting your (mostly) wrong assumptions on others (me). Yeast that is still in suspension has residual metabolic activity long after all fermentables have been exhausted by primary fermentation. Yeast has energy reserves that allow it to keep going even without primary nourishment (much like we don't drop dead the minute we stop eating) and will absorb and metabolize lots of substances from wort besides simple sugars in an attempt to postpone cell death as long as possible. This residual (primarily reducing) metabolism plays a very important role in beer maturation, both in a homebrew setting as well as in an industrial setting. The only difference is that the industry relies on very expensive and sophisticated lab measurements to drive the process whereas a homebrewer relies on trial and error and experience.

 

[cactusgarrett]

letting the yeast clean up after itself is a homebrew myth in my opinion. There are reasons for keeping yeast alive and around which are related to fermentation and carbonation. The main point being dead or dormant yeast cells do not do anything. So once the fermentable food runs out in your beer the yeast literally drop out of the picture. Whatever cleanup they do, they do as they are eating and active. So leaving beer in the primary for a month does not accomplish much other than more time for everything to drop out.

Respectfully, I couldn't disagree with this more. What's the point of aging a beer (especially big beers) then? What is the rationale behind beers improving with aging, post-fermentation, then?

 

[Bassman2003]

No worries. I am sorry if I mis-interpreted what you said. I have heard and read stuff on this topic all over the map. When one looks at commercial operations they have much shorter times for most processes which leaves no time for the extended activity homebrewer's are expecting see. I listened to a Beersmith podcast with Charlie Bamforth who had the position that the positive effects of aging are achieved in a shorter time than traditionally thought. Overall it seems to me that extended beer aging is in the category as needing a strong boil.

Look, I am not saying to avoid aging beer nor to dump the primary within a short time of saying "it's done!" What I am saying is that more and more evidence is appearing that a lot of homebrew practices are being called in question.

But, Vale71, a few posts ago you just wrote that "Yeast that has dropped and is laying at the bottom of the bucket has zero contact with the beer and hence plays no role whatsoever in maturation." Well my opinion is that by the time of the usual homebrew 'wait three days to have the same gravity reading then it's done' the active yeasts in suspension have enough time to clean up. The rest have fallen and apply to your quote. How is that different from what you know?

I asked the question that nobody answered - If the yeast do perform this cleanup, how long does it take? If a primary fermentation can be finished in as little as three days, surely the cleanup would not take as long?

Not being an ass here but this stuff is in a huge gray area and I think it is good to discuss it.

 

[cactusgarrett]

What I am saying is that more and more evidence is appearing that a lot of homebrew practices are being called in question.

This i am TOTALLY on board with. I abhor, in life in general, when people fall back on "that's the way we've always done it."

I asked the question that nobody answered - If the yeast do perform this cleanup, how long does it take? If a primary fermentation can be finished in as little as three days, surely the cleanup would not take as long?

I don't think anyone answered it because it was too hypothetical. That's like asking "When's my beer done/ready?" What's the definition of "done?". Seems like there are two approaches:

• One could bust out the lab equipment and say "byproduct X is removed within Y days of formation, blah blah blah", or
• One could rely more on the qualitative aspect and say "cleanup is done when i no longer taste the byproduct/off-flavor." But then you get the whole 'taste is relative' issue. Talk about a gray area!

 

[beerisyummy]

As long as yeast is "alive" autolysis is not a concern. Autolysis is a natural decomposition process akin to the decomposition of a corpse. Cavities in the cell (vacuoles) hold enzymes whose sole role is to destroy proteins, basically waste management facilities. As long as the cell is active these cavities will remain intact and the enzymes will not "run loose" in the cell. Once the cell "dies" vacuoles burst and the cell structure will be destroyed by the enzymes. Yeast that has dropped has ceased all activity and will be more likely to undergo this form of cell "death". But of course even yeast in suspension can be affected although not as much, which is why filtered beer is more stable and has a longer shelf life than unfiltered.

Okay, yes that sounds right. So to get back to your earlier statement, it sounds like you are saying that any "clean-up" work done by yeast after fermentation proper is done by yeast in suspension rather than in the cake. Right?

 

[Vale71]

Okay, yes that sounds right. So to get back to your earlier statement, it sounds like you are saying that any "clean-up" work done by yeast after fermentation proper is done by yeast in suspension rather than in the cake. Right?

Actually, any work that is performed by yeast is performed by the cells that are in suspension. This includes primary fermentation too. Any yeast that collects on the bottom can be dumped (if technically capable) with no delay and no regrets.

 

[Vale71]

But, Vale71, a few posts ago you just wrote that "Yeast that has dropped and is laying at the bottom of the bucket has zero contact with the beer and hence plays no role whatsoever in maturation." Well my opinion is that by the time of the usual homebrew 'wait three days to have the same gravity reading then it's done' the active yeasts in suspension have enough time to clean up. The rest have fallen and apply to your quote. How is that different from what you know?

I asked the question that nobody answered - If the yeast do perform this cleanup, how long does it take? If a primary fermentation can be finished in as little as three days, surely the cleanup would not take as long?

Commercial breweries can only dream of three-days maturation times and believe me, they've expended a lot of effort in order to shorten processing times as much as possible. Your question is too generic to be answerable. There are so many variables starting with ale vs. lager, yeast strain, pitch rate, oxygenation, OG, size and shape of vessel(s), temperature profile that can make minimum maturation times swing between just a week (possible with very light British ales) to several months with Doppelbock-type lagers fermented traditionally (cold fermentation, cold maturation).

 

[beerisyummy]

I just checked my copy of White & Zainasheff Yeast. "Clean-up" is not in the index lol.

However the following passage is relevant to much of this discussion:

"Many people ask if they can crash the beer temperature, or should they lower it slowly? The concern comes over sending the yeast into a dormant state, thereby preventing them from continuing the uptake of compounds during the long cold-conditioning period. The reality is that very little happens once you take the yeast below 40° F ... If you want the yeast to be active and to carry on reduction of fermentation by-products, it happens much faster at higher temperatures. As far as yeast activity goes, crashing the temperature or lowering it slowly makes little flavor difference if you are dropping the beer below 40° F ... However, very rapid reduction in temperature (less than 6 hours) at the end of fermentation can cause the yeast to excrete more ester compounds instead of retaining them." [emphases mine]

This would seem to be an argument for a longer diacetyl rest, and maybe slow lowering of temp at least to 40° and then you could crash the rest of the way down to 32°

Opinions?

 

[Vale71]

When doing lagers I always maintain fermentation temperature for three days after FG has been reached and then lower it by exactly 0,8°C per day. Make of that what you will...