diacetyl rest too early

Know The Implications of Diacetyl Rest Too Early!

Yes, diacetyl rest is quite essential for yeast fermentation. With the diacetyl rest you can produce lagers, ales and all good brews!

The diacetyl rest even has tremendous impact on british ale-

Diacetyl is a chemical compound, one of 500, that is created when yeast is fermented. Diacetyl is known for making a rich yet buttery flavor. 

Lager brewing is where diacetyl rest is more frequently utilized. As diacetyl is only reabsorbed by yeast at higher temperatures. 

Knowing if diacetyl rest is too early or not depends on knowing the diacetyl level. The rest can be done for all beers. 12oz and 16oz beers can be differentiated, but not in this case.

3 Steps For Testing Diacetyl Levels

How do you tell if you finished the diacetyl rest too early? Well, you test the diacetyl levels in your beer of course. 

Testing whether diacetyl is truly gone or not is pretty easy. 

Step 1: Collecting Samples

In order to test the beer, we must have samples. One sample will not be enough. Get two 100 ml samples.

Collecting Samples
Source: Brulosophy.com

After getting the beer samples, seal them inside jars. Label the jars as well. 

Label the jars in any way you want. Name the jars 1 and 2, or A and B. Just ensure that you can differentiate them. 

Step 2: Working With the Samples

Now we put the two samples in different heat levels. Put one of the samples inside a refrigerator. Put the other sample inside an oven. 

Set the oven’s temperature at 140ºF–150ºF (60ºC–66ºC). Now heat the other sample in the oven for 20 or so minutes. 

After the second sample has been heated, remove it from the oven. Then put the second sample in the refrigerator as well. Let it cool down. 

Wait until the two samples have reached equal temperature. 

Step 3: Testing the Samples

Time to bring the two jars out of the fridge. Give both of them a good swirl. Then proceed to taste individually. 

The diacetyl rest has been completed if the sample tastes the way you want. But if any of the samples have a hint of buttery taste, the rest is incomplete. 

Buttery or any diary-like taste means the beer was taken out of diacetyl rest too early. 

How to Do Forced Diacetyl Test

This is another method of testing the diacetyl levels. Knowing the level will tell you if your diacetyl rest is still early or not.

Forced Diacetyl Test
Source: berkeleyyeast.com

A forced diacetyl test helps identify diacetyl levels. Heating up a sample will tell you whether there are still diacetyl forming precursors present.

The forced diacetyl test is pretty simple. The steps go like this: 

Step 1: Collecting Sample

For the force test, you have to begin by taking one sample. Just take one 100 ml sample out of the fermenter.

Step 2: Warming Sample

Now you have to warm up the sample. You will need to heat the test sample to 140ºF–145ºF (60ºC–63ºC). 

You can heat the sample in an oven. But in that case, make sure the sample was taken in a microwave-proof container. 

However, if you don’t want to use ovens, fermentation heaters can be your thing. There are plenty of affordable heaters you can choose-

Heat the sample for around 15 minutes. Afterward, proceed to cool the sample down to room temperature. 

Step 3: Comparing Samples

After the first sample has cooled down, take another sample. This sample will also be of 100 ml and taken from the fermenter. 

Now it is time for comparing the samples. You will compare both the taste and the flavor of the samples. 

If neither samples smell or taste buttery or like dairy, the diacetyl rest is complete. The beer can be packaged. 

But if only the first sample (the warmed sample) tastes or smells like butter. If the fermented does not, then the diacetyl rest is still at an early stage. The rest needs to continue for a few days more. 

If both samples taste like butter, the problem is not with diacetyl rest. In such cases, the batch might be contaminated. 

How Early Diacetyl Rest Feels

Diacetyl affects the flavor greatly. If you bring out the lager too early, the flavor becomes kind of undesirable. The flavor becomes like that of Steam Beer.

The taste is hard to describe precisely. But it is somewhat similar to a “rough” flavor. And you may even get a hint of fruity esters too. 

But, the beer may already have started fermenting at the correct temperature and you see bubbles. In this case, the beer has been warmed up a little early. And the above-mentioned flavor will be at a minimum.

How to Do a Diacetyl Rest Properly In 4 Simple Steps

Beginning the process of diacetyl rest properly is very important. That way you probably will not have to worry about finishing too early.

Diacetyl Resting steps
Source: oculyze.ne

Here is how you properly do a diacetyl rest: 

Step 1: Specifying Wort’s Gravity

First you have to specify the wort’s gravity. You can begin when the wort’s specific gravity is around 2 to 5 points of its terminal gravity. The gravity can be that of the final gravity of the finished lager. 

Step 2: Planning

At this point the primary fermentation is nearing its end. So you have to start planning a two-day or longer diacetyl rest. 

Around two days is how long to diacetyl rest.  But it might take even more time in certain situations.

Step 3: Raising the Wort’s Temperature 

During the last 48 hours of fermentation, increase the temp of the wort. Raise it to around 65°and 69°F. This temperature is best suited for yeasts to function. 

The amount of yeast needed for a gallon of mead is different from the amount needed for beer. So be careful about that.

Increasing yeast activity helps in remove diacetyl beer. Removing diacetyl is what we are aiming for, so this is the most important step. 

The temperature can be raised by relocating the wort to a warmer location. That will raise the temperature on its own 

Temperature can also be raised with the help of a warm-water bath. A carboy warming jacket or carboy heater can also be used. 

Step 4: Testing 

After 48 hours, take two samples for testing. The testing methods have been noted above. 

If the test results in the flavor you want, you can stop the diacetyl rest. Then proceed to bottle or rack the beer to lager in cold storage. 

Frequently Asked Questions (FAQs)

When should I start taking diacetyl rest?

Diacetyl rest begins when the beer is nearing terminal gravity. Specifically when the fermented beer is two to five specific gravity points away from your target terminal gravity. This is the ideal time to fix the diacetyl levels.

How do you fix diacetyl?

The diacetyl level in a batch can be fixed by adding more yeast. The process is known as diacetyl rest. The process is done when the beer is nearing the end of fermentation. More specifically it is done when the beer is two to five specific gravity points away from your target terminal gravity.

How do you check for diacetyl?

There are two methods of testing diacetyl levels. The forced diacetyl test is done by taking one sample and heating it up to 140ºF. Then cool it down and compare it with another fresh sample. The presence of a buttery taste will tell you the diacetyl levels. 


Now we know how to know whether diacetyl rest too early or not. There are two ways to test the diacetyl level. And the presence of diacetyl tells you if the rest is early. 

Follow our instructions properly. Doing the diacetyl rest properly is a big help in the process as well. 

That’s all!

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