do i have to do a DAR

[fluketamer]

hi i have 2.25 gallons of lager fermenting in a 2.6cu ft fridge at 52 degrees. about day 10. i am using cellarscience baja. i usually rest my lagers at 68-72 degrees for a few days before bottling. i would like to just cold crash it in the fridge now instead of taking it out , warming it up for DAR then moving it back to the fridge to cold crash. is DAR always necessary. i remember there was a DAR test you can do. if i dont detect diacetyl can i just cold crash and bottle. do you guys always rest your lagers?

thanks

 

[lumpher]

I always dr my lagers, but Bobby may be able to provide more input on this, since he sells some lager yeast that doesn't need a d rest.

 

[Bobby_M]

Its just a good insurance policy especially if you underpitched.

 

[VikeMan]

is DAR always necessary. i remember there was a DAR test you can do. if i dont detect diacetyl can i just cold crash and bottle.

The test you are referring to is called a Forced Diacetyl Test. If you perform it and the beer passes, you can be sure that there won't detectable* levels of diacetyl in the finished beer (barring infection).

If you don't do a test, but do a diacetyl rest, you can be "pretty sure" the beer will be ok. The longer/warmer the rest, the more confidence.

Or you can just roll the dice and do neither. Consider the yeast strain's propensity for making lots (or not) of diacetyl precursor and the temperature and length of the fermentation as factors in making that choice. Nutrient (specifically Valine) deficiency can also drive higher diacetyl levels.

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*Detectable by you (or whoever performed the test). Every beer contains diacetyl, and people have different taste thresholds.

 

[DuncB]

Adding ALDC enzyme at the start of ferment might avoid need for D rest.

 

[Dland]

A D rest is not necessary if you can't taste it.

However, I always do one as I'm believe yeast cleans up the beer for a while after most visible and active fermentation is over, even if no detectable diacetyl.

Since I spund in kegs, my procedure would be of little interest to you. But since you are bottling and if you are going to prime to carbonate, if you raise temp for carbonation, D rest will probably be achieved.

 

[VikeMan]

A D rest is not necessary if you can't taste it.

Sometimes/usually. But Diacetyl levels in beer can be reduced to levels below taste threshold while there is still some unconverted diacetyl precursor (α-acetolactate) in the beer. At that point, nothing would be tasted. Remaining precursor will subsequently oxidize to diacetyl and (potentially) bring the diacetyl back above threshold. This is the reason for forced diacetyl tests. When the beer is heated to very high temps it accelerates the oxidation (conversion from precursor to diacetyl) reactions, so we can find out pretty quickly if there was significant precursor left.

 

[AlexKay]

Also, not much point in forcing diacetyl if you are diacetyl-blind. If you are, the rest is always a good idea, unless you’re awfully sure your yeast strain won’t cause problems for you.

 

[Dland]

Sometimes/usually. But Diacetyl levels in beer can be reduced to levels below taste threshold while there is still some unconverted diacetyl precursor (α-acetolactate) in the beer. At that point, nothing would be tasted. Remaining precursor will subsequently oxidize to diacetyl and (potentially) bring the diacetyl back above threshold. This is the reason for forced diacetyl tests. When the beer is heated to very high temps it accelerates the oxidation (conversion from precursor to diacetyl) reactions, so we can find out pretty quickly if there was significant precursor left.

Interesting, how about the notion that diacetyl would likely be also be worked out during carbonation, assuming OP primes and and brings up temp for carbonation after bottling? Last time I bottle carbonated my beer was before anyone in homebrewing talked about diacetyl, but am curious if this might be a solution for OP's process.

 

[VikeMan]

Interesting, how about the notion that diacetyl would likely be also be worked out during carbonation, assuming OP primes and and brings up temp for carbonation after bottling?

IMO that could be a double edged sword, because you're adding more fermentables (priming sugar), which could cause more α-acetolactate (and thus diacetyl) to be made. In heavily dryhopped beers, people have certainly experienced added diacetyl along with hop creep, because of the extra fermentables introduced. It's not exactly the same thing as bottle carbonating, but similar.

 

[Dland]

IMO that could be a double edged sword, because you're adding more fermentables (priming sugar), which could cause more α-acetolactate (and thus diacetyl) to be made. In heavily dryhopped beers, people have certainly experienced added diacetyl along with hop creep, because of the extra fermentables introduced. It's not exactly the same thing as bottle carbonating, but similar.

In normal priming situation, dry hops aside, would not the yeast working out the priming sugar to carbonate also work out any diacetyl? Assuming bottles were in something like room temp.