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Sanity check - timing of diacetyl rest

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jimyoung

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Hi everyone.. Sanity check please - only my second Lager, and first in about 4 years.

I'm making a lager, Wyeast #2308. Used a large (2.5L) starter for a 19L batch, decanted. Pitched at 18c, it fell to target 12c within 10 hours.

Air lock was bubbling by morning, and it was a very active fermentation. Activity slowed down, so on day 7 (today) I took a sample and did a gravity check.

OG 1.046
Today's FG 1.013, target 1.012.

So, despite the recipe calling for a 2 week ferment, my thinking is to try and start the diacetyl rest now before the yeast completely floc out. Maybe even give them a rousing.

Am I missing something obvious? I'd rather go by the gravity than the timing...

Thanks!
 

day_trippr

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I agree with your thinking - I try to bump up with a couple more fermentation points left - so I wouldn't wait any longer to ramp...

Cheers!
 
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jimyoung

jimyoung

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I agree with your thinking - I try to bump up with a couple more fermentation points left - so I wouldn't wait any longer to ramp...

Cheers!
Thanks!! you're right, I should have checked earlier. Another indicator I use for fermentation is to watch the temps in my beer fridge. When fermentation is vigorous, the fridge is always well below the beer. As it slows down, the fridge cools less as there is less heat generated:

1594178319653.png
 

Bohern

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That is one of the methods I have used in the cooler months of the year, when the beer quits heating the chamber I know it is time to start the warm up. A little harder to gauge in the summer but getting good at it.
 
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jimyoung

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He pitched at 18°C so I think the answer is "Hell yeah". ;)
I drank the sample I took to test the gravity... so yeah, "Hell yeah".

I thought the fridge would cool the wort faster than it did. Next time, I'll put both the starter and beer in the fridge and let them both fall before pitching.
 

jclark248

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Hi everyone.. Sanity check please - only my second Lager, and first in about 4 years.

I'm making a lager, Wyeast #2308. Used a large (2.5L) starter for a 19L batch, decanted. Pitched at 18c, it fell to target 12c within 10 hours.

Air lock was bubbling by morning, and it was a very active fermentation. Activity slowed down, so on day 7 (today) I took a sample and did a gravity check.

OG 1.046
Today's FG 1.013, target 1.012.

So, despite the recipe calling for a 2 week ferment, my thinking is to try and start the diacetyl rest now before the yeast completely floc out. Maybe even give them a rousing.

Am I missing something obvious? I'd rather go by the gravity than the timing...

Thanks!
In the future you may want to look into yeast profiles. I’ve been brewing for years and lately had a chance to update my equipment and added a chiller and two fermentors. Now I have full control of my brewing in that I can control the temp and keep it in optimum range. A diacetyl
 

jclark248

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In the future you may want to look into yeast profiles. I’ve been brewing for years and lately had a chance to update my equipment and added a chiller and two fermentors. Now I have full control of my brewing in that I can control the temp and keep it in optimum range. A diacetyl rest occurs when you bump up the temp, something you have little control over with basic equipment. You can cold crash your brew before bottling if you have a spare fridge or even a cool basement or crawl space for 3-7 days, this will help immensel.
 

day_trippr

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Well, the OP is clearly running BrewPi on his fermentation fridge, so control was not the issue here...

Cheers!
 

day_trippr

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Well, heck. I merely pointed out the OP has an adequate control system. Would never have considered that a trigger...
 
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jimyoung

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In the future you may want to look into yeast profiles. I’ve been brewing for years and lately had a chance to update my equipment and added a chiller and two fermentors. Now I have full control of my brewing in that I can control the temp and keep it in optimum range. A diacetyl rest occurs when you bump up the temp, something you have little control over with basic equipment. You can cold crash your brew before bottling if you have a spare fridge or even a cool basement or crawl space for 3-7 days, this will help immensel.
Hm. Would you mind giving a little more info? I'm curious. Wyeast posts a very small information page on the strain (Munich Lager | Wyeast Laboratories), but not much else. It also suggests a "thorough diacetyl rest" which is why I made this one a little longer than I did last time. What do you mean by yeast profiles, e.g., is there somewhere else I can look?
 

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In order to determine if you need to do a diacetyl rest, you should first smell and taste the beer. If you get a movie popcorn or butterscotch aroma and/or flavor, then yes, by all measns do a d-rest.

Different yeast strains produce different levels of diacetyl which is what jclark248 is talking about. Raising the temperature to room temp for 24-48 hours will allow the yeast to re-absorb the diacetyl. But with some strains, if you don't smell or taste it, you are probably would be OK.
 

VikeMan

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In order to determine if you need to do a diacetyl rest, you should first smell and taste the beer. If you get a movie popcorn or butterscotch aroma and/or flavor, then yes, by all measns do a d-rest.
I agree that if you smell/taste diacetyl, a diacetyl rest is in order. But I would add that even if you can't smell/taste it, a diacetyl rest might still be a good idea, particularly when using strains known for production of diacetyl (or, more accurately, its precursor alpha-acetolactate).

The thing about diacetyl is that even when you think you don't have it (like when tasting before packaging), it can still be made. At the same time that the yeast are cleaning up diacetyl that was already made, any precursor left over in the beer can still be converted to diacetyl. If you've ever seen a notional diacetyl concentration time line curve, it can be misleading, because they show net diacetyl in the beer, and the natural interpretation would be to think that diacetyl is produced until it peaks and then is cleaned up until it's gone, which isn't how it works. The only way to really be sure that your beer is no longer at risk is to take a sample and do a diacetyl force test. Most people don't do this. I don't.
 

Vale71

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I drank the sample I took to test the gravity... so yeah, "Hell yeah".

I thought the fridge would cool the wort faster than it did. Next time, I'll put both the starter and beer in the fridge and let them both fall before pitching.
If you can already taste strong diacetyl then you are probably in big trouble...
Being already at or almost at FG is also a bit late to do a proper diacetyl rest, which requires active yeast to perform. You can still bump up the temperature and hope that the yeast will manage to reduce it below its threshold level but you should mentally prepare for the worst.
In the future you should try and pitch at or slightly below fermentation temperature. Pitching warm is really the N.1 cause for diacetyl issues.
 
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jimyoung

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If you can already taste strong diacetyl then you are probably in big trouble...
Being already at or almost at FG is also a bit late to do a proper diacetyl rest, which requires active yeast to perform. You can still bump up the temperature and hope that the yeast will manage to reduce it below its threshold level but you should mentally prepare for the worst.
In the future you should try and pitch at or slightly below fermentation temperature. Pitching warm is really the N.1 cause for diacetyl issues.
Thanks. I assumed the lag phase would have been fine, and thought it'd drop to temp in 1-2 hours - I was wrong. It still dropped to 12c before the main fermentation hit so I hope it'll be OK.

The beer tasted fine, but certainly smelled buttery. I'm in the middle of the rest now (after a near fire - but that's in a different thread), and I roused the yeast. I also gave them a talking to and asked them nicely to wake up and do some work for me. Since fermentation is done I'll do a slightly longer d-rest and hope for the best.
 
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