Maturation rest for lagers

[Andy Brosius]

I brewed my first Munich Dunkel last Saturday, and it's been fermenting nicely at 50 F since then. I'm planning to increase the temperature today for the maturation phase (following Palmer's instructions in How to Brew), but I'm not exactly certain which temperature I should increase to.

In one paragraph, he states that on day 4 of fermentation you should increase the temp by 9 F for a diacetyl rest. But in a table on the same page, it says the temperature for lagers should be raised by 14-18 F.

Which is it? What do you guys typically do?

Thanks!

 

[cubalz]

Call it simple but what I have always done is just to pull the fermenter out of the chamber and let it sit out at room temperature within my brew room (around 70f) for 3-4 days for my diacetyl rest. That has always worked for me and my beers have never had any trace of diacetyl.

 

[Andy Brosius]

Is that the only rest that you do? That's basically the upper end of Palmer's recommended range, but he does suggest a minimum of six days.

Temps at my house can get a bit higher than 70, so I'm sticking with the old chest freezer for now.

 

[brownni5]

I think you'll find there's more than one way to skin this cat. Ask this question of 10 brewers, you're likely to get 13 answers. Some even primary ferment at ale temps - gasp!

Up to 60-ish in your case should be fine, especially if there are a few gravity points to go.

 

[Jag75]

Agree with ^^^^^

I start ramping up temp when its 75% done . I go up a few degrees a day . Once it's 66 or 67 I leave for 3 days then start dropping temp a few degrees a day until its 38f. Then keg .. there I skinned a cat lol

 

[monkeymath]

A lager fermentation is not nearly done on day four. I don't really get why you'd have to rush things, unless you're brewing commercially. Diacetyl cleans up perfectly fine on its own, also at fermentation temperature. Just let it sit for five days instead of two, what's the big deal? I don't really see the need for a diacetyl rest... Moreover, if you plan to coldcrash afterwards, all the ramping-up and ramping-down is not only cumbersome, but potentially stressful for the yeast and a vector for oxygen ingress (through suckback) unless you're careful.

 

[Andy Brosius]

Thanks, all. There's some very good info here, and it's clear that as brownni5 says there are many ways to approach this. As a fairly new home brewer (around 1 year in) I'm still doing almost everything according to The Book (Palmer). This is only my second lager, so I'm being particularly careful.

monkeymath: I thought it seemed early too, but this is what Palmer calls for. It's more than a diacetyl rest, as he claims it's necessary to clean up acetaldehyde and other aldehydes. Your concern about potential oxygenation is well taken - how would you avoid it when cold-crashing? I'm fermenting in a glass carboy with a blow-off tube attached.

 

[Jag75]

You should be set up to cold crash . As the beer drops in temp it will cause suckback . Some fill balloons with co2 and connect to the fermenter. Some put positive pressure on the FV . Search cold crashing and you will find good procedures

 

[Andy Brosius]

Now there's a new rabbit hole for me. I've been routinely cold-crashing my ales without any thought for potential oxygenation. With my current setup a balloon would probably work best.

 

[Jayjay1976]

I've been using a cold crash guardian for a while now, it's been working really well for me.
https://www.brewhardware.com/ProductDetails.asp?ProductCode=CCguardianV3

 

[Andy Brosius]

That looks excellent. Thanks for the recommendation.

 

[TheMadKing]

Thanks, all. There's some very good info here, and it's clear that as brownni5 says there are many ways to approach this. As a fairly new home brewer (around 1 year in) I'm still doing almost everything according to The Book (Palmer). This is only my second lager, so I'm being particularly careful.

monkeymath: I thought it seemed early too, but this is what Palmer calls for. It's more than a diacetyl rest, as he claims it's necessary to clean up acetaldehyde and other aldehydes. Your concern about potential oxygenation is well taken - how would you avoid it when cold-crashing? I'm fermenting in a glass carboy with a blow-off tube attached.

So what's really happening here is that yeast (all yeast) is more active at warmer temperatures. Lager yeast CAN ferment at cooler temperatures but they still prefer around 70F.

What you're doing by warming the beer is to keep the yeast just a little bit happier so they will process all those difficult-to-digest compounds (acetaldehyde, diacetyl, etc) without any additional stress from temperatures.

I do a very similar process to what JAG outlined above for my lagers but with some additional steps to reduce oxidation.

• I will ferment at 50-52F for the first 4 days or so, and then start ramping my temp up to about 60F
• I will keg it (we're talking 5-7 days in), no cold crash, and under pressure so that it's an oxygen free transfer
• hit it with 30PSI of CO2
• l attach a spunding valve set to 27PSI and allow that keg to sit at 70F, and under pressure for about 2 weeks.
• Then I will put it directly into my keezer and let it lager for about 1-2 months before calling it done.

 

[Andy Brosius]

Interesting. So you only keep it at 60 F for 1 day or 2, and then keg and bring to 70 F? Or it stays at 60 F for 5-7 days, then you keg?

I was under the impression that it was best to lager on the yeast cake, as it helps to absorb residual sulfur. I may need to reconsider.

 

[Jayjay1976]

Interesting. So you only keep it at 60 F for 1 day or 2, and then keg and bring to 70 F? Or it stays at 60 F for 5-7 days, then you keg?

I was under the impression that it was best to lager on the yeast cake, as it helps to absorb residual sulfur. I may need to reconsider.

I could be wrong, but my understanding is that the sulfur dissipates or drops out rather than being reabsorbed by the yeast. I think I read somewhere that sulfur can be 'scrubbed' from the beer by forcing CO2 through it from the dip tube, then purge it out via the PRV. Sounds like fun to me!

Right now I'm sipping on a dampfbier that has a bit of diacetyl that luckily seems to be fading. I kegged it maybe two weeks ago, last weekend when my wife took a sip and said 'what's that buttered popcorn flavor?' I groaned loudly. I think it'll age out though I wish it was a quick fix.

 

[monkeymath]

monkeymath: I thought it seemed early too, but this is what Palmer calls for. It's more than a diacetyl rest, as he claims it's necessary to clean up acetaldehyde and other aldehydes. Your concern about potential oxygenation is well taken - how would you avoid it when cold-crashing? I'm fermenting in a glass carboy with a blow-off tube attached.

All these processes are part of the yeast's metabolism. You do not have to raise the temperature or sing to it in order to have the yeast do its thing. You'd have to take drastic measures in order for the yeast to not finish its dinner (unless you start with off with unhealthy yeast or exceed its alcohol limit).
It's like the countless threads on here of people worrying their beer will not finish fermentation, only to be followed some time later by "oh yeah, it's doing its thing now": it is basically impossible for the yeast notto finish. Because that's just what it does to survive.

I bottle all my beers and I'd love to know of a way to trap diacetyl in a Czech lager. At bottling day, it might be a buttery delight, but that is all gone when the bottles are carbonated.

The longer I brew, the more I feel that many things that homebrewers obsess about are mostly there to give a sensation of control and technical progression. And yes, of course, your beer tastes so much better once you put all this effort into it.

 

[Jayjay1976]

...You'd have to take drastic measures in order for the yeast to not finish its dinner (unless you start with off with unhealthy yeast or exceed its alcohol limit).

Haha! If/when I exceed my alcohol limit I'll reliably finish my meal and then some.

 

[TheMadKing]

Interesting. So you only keep it at 60 F for 1 day or 2, and then keg and bring to 70 F? Or it stays at 60 F for 5-7 days, then you keg?

I was under the impression that it was best to lager on the yeast cake, as it helps to absorb residual sulfur. I may need to reconsider.

I typically take 3 days or so to ramp the temp up and then keg it on the day it hits 60.

Once it's under pressure, ester production is suppressed by the pressure fermentation so I just let it free rise to ~70 (room temp).


I've not encountered an issue with sulfer doing in this way but I have never taken measures to specifically eliminate it

It may be escaping through the spunding valve during carbonation, or it may be mostly gone by the time I keg.

The strains of lager yeast I prefer may also just not produce much sulfer so I've been lucky.

I typically use WLP833 and Fermentis 34/70

 

[Jayjay1976]

I like 2308; ferments moderate gravity wort in just 3-4 days at 52, then I ramp it up to ~66 for a few days and then keg it.

 

[Vale71]

I bottle all my beers and I'd love to know of a way to trap diacetyl in a Czech lager. At bottling day, it might be a buttery delight, but that is all gone when the bottles are carbonated.

Paseurization. Sterile filtration will also work but it's too difficult to do in a homebrew setup. I'm probably going to try it in the FV the next time I do a Czech lager. I'm hypersensitive to diacetyl but also find it yummy (in the proper beer style) and I too hate that it keeps fading away after it has reached just the right level of yummyness.

 

[Andy Brosius]

Thanks, everyone. Some excellent advice here.

I'm going slightly off the topic of the original post, but the talk about oxidation through suck back has me a bit concerned about how to cool to the lagering temperature. I don't have the right equipment to implement any of the solutions I've seen, and I wouldn't be able to get it in time for this beer.

I'm planning to naturally carbonate this beer with leftover wort, so here's what I was thinking about doing. Any feedback would be appreciated!

• Leave at 60 F for a total of 6 days to complete the maturation rest
• Rack to keg and add leftover wort
• Increase temperature to 70 F, and allow to naturally carbonate for 2 weeks (this should absorb any residual O2)
• Lager for 4+ weeks in the keg

Is there any reason why naturally carbonating first might interfere with the lagering?

 

[TheMadKing]

Thanks, everyone. Some excellent advice here.

I'm going slightly off the topic of the original post, but the talk about oxidation through suck back has me a bit concerned about how to cool to the lagering temperature. I don't have the right equipment to implement any of the solutions I've seen, and I wouldn't be able to get it in time for this beer.

I'm planning to naturally carbonate this beer with leftover wort, so here's what I was thinking about doing. Any feedback would be appreciated!

• Leave at 60 F for a total of 6 days to complete the maturation rest
• Rack to keg and add leftover wort
• Increase temperature to 70 F, and allow to naturally carbonate for 2 weeks (this should absorb any residual O2)
• Lager for 4+ weeks in the keg

Is there any reason why naturally carbonating first might interfere with the lagering?

How long will you be fermenting at 50-52? That is important from pitch until ~50% attenuation because the low temperature is what suppresses ester formation and keeps your lager very clean.

The majority of esters are produced during the lag phase when yeast is consuming sugar in the presence of oxygen and converting it into biomass (more yeast). Once all the oxygen is gone, fermentation starts and biomass still increases more slowly for a few days until the yeast cell density is at the maximum level that the competition for food supply can support. Esters can be produced during this time as well.

So it's important to keep the temperature low long enough for the maximum cell density to be reached. Typically this is around high Krausen, so to add a safety factor you should wait for a day or two after peak Krausen is reached before increasing the temperature.

Incidentally this is also when to cold crash a yeast starter. In the smaller volume and at warmer temps, these steps happen in hours rather than days, so once your max cell density is reached (high Krausen), there's no reason to let it continue to ferment because the yeast only reproduce to replace dead cells and the total count won't change much. Plus you are stressing your yeast starter by allowing it to form alcohol, so it's best not to let it ferment out.

 

[Andy Brosius]

I pitched at 50 F and kept it there for four days. I then set the freezer to 59 F, which took about 12 hours to warm up.

 

[monkeymath]

Incidentally this is also when to cold crash a yeast starter. In the smaller volume and at warmer temps, these steps happen in hours rather than days, so once your max cell density is reached (high Krausen), there's no reason to let it continue to ferment because the yeast only reproduce to replace dead cells and the total count won't change much. Plus you are stressing your yeast starter by allowing it to form alcohol, so it's best not to let it ferment out.

I know that most people perform this step (and often use the opportunity to 'decant' the starter liquid), but I'll be the black sheep once more and make a case against this practice.
The yeast starter's purpose is not solely - perhaps not even primarily, in some cases - the increase in cell count, but an increase in yeast health and vitality. I always try to pitch at high kräusen - I often fail, as it is hard to estimate the yeast vitality beforehand and so the starter is either not yet fully rolling or already cooling down.
Anyways, I advise against actively slowing down your yeast's metabolism before pitching. It just counteracts the benefit of making a starter in the first place. Yes, alcohol does stress yeast, but so do drops in temperature. Also, I would not "decant" the starter and flush the most active cells - those which have not yet dropped out - down the drain, just to pitch the dormant cells instead.

I know this is a rather unpopular opinion on here. I'm not saying I'm right and everyone else is wrong; this is just my stance based on advice from Ulrich Preise, head of the Weihenstephan yeast bank. I trust he knows a thing or two about yeast.

 

[TheMadKing]

I know that most people perform this step (and often use the opportunity to 'decant' the starter liquid), but I'll be the black sheep once more and make a case against this practice.
The yeast starter's purpose is not solely - perhaps not even primarily, in some cases - the increase in cell count, but an increase in yeast health and vitality. I always try to pitch at high kräusen - I often fail, as it is hard to estimate the yeast vitality beforehand and so the starter is either not yet fully rolling or already cooling down.
Anyways, I advise against actively slowing down your yeast's metabolism before pitching. It just counteracts the benefit of making a starter in the first place. Yes, alcohol does stress yeast, but so do drops in temperature. Also, I would not "decant" the starter and flush the most active cells - those which have not yet dropped out - down the drain, just to pitch the dormant cells instead.

I know this is a rather unpopular opinion on here. I'm not saying I'm right and everyone else is wrong; this is just my stance based on advice from Ulrich Preise, head of the Weihenstephan yeast bank. I trust he knows a thing or two about yeast.

Not trying to start an argument, but I would guarantee the Ulrich stores yeast by chilling it at some stage, and then warming it prior to pitching. If this didn't work, white labs and Wyeast would not be in business. I fully agree that so-called "vitality" is important, but not as important as cell count (as proven by the successful use of dry yeast). But it's also important for cells to have strong glycogen stores when they are pitched, which is all you're doing with a "vitality starter". They maintain that condition (strong glycogen stores) even when cold crashed, so the "speed of their metabolism" isn't a real thing as far as I know. If there are enough cells, they are healthy and have good thick cell walls, they will reproduce and eat sugar and make good beer.

Yeast metabolisms are pretty flexible, and cold crashing just makes them go dormant in whatever state they were in when the temperature dropped suddenly. It doesn't have negative effects on yeast health.

My argument against pitching a starter at high krausen is based entirely on the fact that the starter wort contains oxidized compounds that I don't want in my beers (and can definitely taste, as I have tried this method). I 100% agree that it's effective and will result in a good fermentation, but it might not result in the best beer.

 

[Jayjay1976]

I know this is a rather unpopular opinion on here. I'm not saying I'm right and everyone else is wrong; this is just my stance based on advice from Ulrich Preise, head of the Weihenstephan yeast bank. I trust he knows a thing or two about yeast.

I'm interested in reading what Preise has to say on the subject, can you link to an article?

 

[VikeMan]

The majority of esters are produced during the lag phase when yeast is consuming sugar in the presence of oxygen and converting it into biomass (more yeast).

I think you mean "log" (not "lag") phase here, as in logarithmic/exponential growth phase? Very little (if any) esters are produced in the "lag" phase, because the yeast have to first make alcohols before they can convert the alcohols into esters. Also, oxygen is normally depleted by the time log/exponential starts.

 

[monkeymath]

I'm interested in reading what Preise has to say on the subject, can you link to an article?

Sure, but it's entirely in German, I'm afraid.

Der ideale Starter

When I get around to it, I can try and compile a brief summary.

EDIT: here's my attempt at a transcription of the article

 

[TheMadKing]

I think you mean "log" (not "lag") phase here, as in logarithmic/exponential growth phase? Very little (if any) esters are produced in the "lag" phase, because the yeast have to first make alcohols before they can convert the alcohols into esters. Also, oxygen is normally depleted by the time log/exponential starts.

Yes sorry, I did mistype, and was referring to the exponential growth phase, but there's some issues with what you've said. Do you have any references for this?

The exponential growth phase is not triggered by lack of oxygen in anything that I can find. It appears to be pretty much dependent on the sterol/glycogen levels in the yeast. The exponential growth phase begins as soon as the yeast are used to their new environment and have sufficient sterols and glycogen to begin budding.

Yeast are also capable of producing esters directly while in the presence of oxygen and the majority are produced due to cell growth during the exponential growth phase (not during fermentation/stationary phase), and they do not all come from conversion alcohols (thought some do).

 

[VikeMan]

Do you have any references for this? It directly contradicts my understanding of microbiology.

My understanding is that the lag phase IS the exponential growth phase.

Here's one, written by Dr. Chris White, Biochemist and founder/president of White Labs, author of the book "Yeast"...
Fermentation Timeline - Brew Your Own
It agrees closely with every article/paper/text I've seen on the matter.

Oxygen is depleted when fermentation starts, but not when exponential growth starts.

O2 is depleted very quickly, during the lag phase. Here's a datapoint...
Study # 1 - Low Oxygen Brewing
Note the dissolved O2 levels as this progressed.

 

[TheMadKing]

Here's one, written by Dr. Chris White, Biochemist and founder/president of White Labs, author of the book "Yeast"...
Fermentation Timeline - Brew Your Own
It agrees closely with every article/paper/text I've seen on the matter.



O2 is depleted very quickly, during the lag phase. Here's a datapoint...
Study # 1 - Low Oxygen Brewing
Note the dissolved O2 levels as this progressed.

The second link is indeed striking - thank you for posting.

At this point we are just discussing semantics and it has no real impact on process at all. I posted in Monkey's other thread, and I believe there is a false premise in the article he kindly translated for us.