Decoction Mash: Your Pro Guide

by Dane Wilson | Last Updated: August 18, 2022

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Most homebrewers dream of beers with glistening clarity, head retention, and a balance of malt and bitterness. Now that you have developed some understanding of how brewing beer at home works, you can start branching out and learning other techniques. That brings you to the decoction mash, an ancient and often misunderstood technique that can take your beers to the next level.

In all-grain brewing, mashing is one of the most essential steps. Most people opt for the single infusion mash route, and their beers come out great. But if you want to add a sparkle of something more to your homebrews, decoction mashing may be for you.

Table of Contents

• A Glossary of Mashing
  • All-Grain Brewing
  • Mashing
  • Single Infusion Mashing
  • Step Infusion Mashing
  • Resting
  • Wort
• What is Decoction Mashing?
  • Benefits
  • Drawbacks
• Why Use a Decoction Mash
  • Tannins
  • Melanoidins
• Which Beer Styles Benefit from Decoction Mashing?
• How to Do a Single Decoction Mash
  • Equipment For Decoction Mashing
  • Step 1: Mash In
  • Step 2: Perform Saccharification Rest
  • Step 3: Decoction Pull
  • Step 4: Boiling
  • Step 5: Add the Decoction Back to the Mash
  • Step 6: Sparge and Proceed as Normal
• How to Do a Double Decoction Mash
  • Step 1: Mash In
  • Step 2: Protein Rest
  • Step 3: First Decoction Pull
  • Step 4: Boiling
  • Step 5: Adding Decoction Back into Mash
  • Step 6: Second Decoction Pull
  • Step 7: Sparge
• How to Do a Triple Decoction Mash
  • Step 1: Mash In
  • Step 2: First Decoction Pull
    • Two Rest Options
  • Step 3: Boiling Your Decoction
  • Step 4: Adding Your Decoction Back Into the Mash Tun
  • Step 5: Second Decoction Pull & Saccharification
  • Step 6: Final Pull & Mashing Out
• Decoction, a Smashing Idea
• Decoction Mash FAQ

A Glossary of Mashing

Before getting into this chat about decoction mashing, what it is, and why you should give it a try, let’s briefly run through the whole mashing process. A grasp on all the brewhead terminology is a must for this one!

All-Grain Brewing

The brewing process where sugars from the malt are extracted through a mashing process. The grains are crushed, added to water, and then transformed into wort through a process with multiple steps. Prior to fermentation, hops are added to the wort for flavoring and aroma. Check out the Sound Brewery guide to all-grain brewing for more information.

Mashing

In all-grain brewing, mashing is when you soak crushed malts—your chosen grains—in hot water. The starches in the malt are turned into sugars. Specialized enzymes are required to carry this out.

Single Infusion Mashing

A form of mashing that requires a combination of heated water and crushed grains. The mixture is kept at a temperature of 148°F and 162°F (64°C and 72°C) for about an hour. Then you sparge (rinse) the mash with liquid from the mixture and fresh water, creating wort.

Step Infusion Mashing

Unlike single infusion mashing, you will rest the mash at two different temperatures. This is most often done by adding in heated adjuncts to the resting mash or by increasing the heat after a set amount of time.

Resting

When talking about rest, it means the period of time when the mash is left alone to develop. There are a couple rests, such as a protein rest, which breaks down the proteins that may cause cloudiness in beer. A saccharification rest gives starches the time to break down, creating sugars to sweeten your beer.

The video below discusses what rests do and the different effects rests have on your beer:

Wort

The all-important wort is what you extract from the mash through sparging. Wort is full of the sugars needed by the yeast to make alcohol and carbon dioxide. You cannot have beer without first making wort.

What is Decoction Mashing?

Now that you know the difference between step mashes and infusion mashes, it is time to introduce decoction mashing. As mentioned earlier, decoction mashing is a very ancient technique. To do it, you first perform a step mash. During the process, you remove a portion of the grain, boil it, and then add it back to the mash tun to increase the resting temperature of the rest of the mash.

The oldest version of decoction mash is called the triple decoction, but there is also a single and double decoction, too. In the triple decoction, you boil three separate portions of grain. Because there is so much added effort, decoction is rarely used in modern times. However, it does have some benefits. After all, Pilsner Urquell, one of the best beers you will ever have, is brewed using the decoction method.

Benefits

• Increases the amount of melanoidins and tannins in the beer, contributing to a maltier flavor and better mouthfeel
• Greater sugar extraction from the malt
• Enhanced clarity
• Richer beer color

Drawbacks

• Takes a long time to accomplish. Expect an extra 3 hours added to your day of brewing.
• Modern malts have been modified so much that they no longer need decoction mashes to get out all the flavors and to convert sugars. In this case, decoction mashing can be detrimental, because it may oxidize the malt or increase proteins, ruining head retention.

Why Use a Decoction Mash

You may be wondering why you should ever cast aside extract brewing or single infusion mashing for a decoction mash. In order to understand why a decoction mash is worthwhile, we need to go back in time for a moment.

Beer has been around since about 3,500 BCE, which is pretty much the whole of human history. However, our ancestors had no idea how to utilize enzymes. In fact, they didn’t even know there were microscopic organisms hard at work in the beer. Because of this, many brewers way back there were using grains that were not ideal for brewing beer.

Decoction mashing was designed with these undermodified grains in mind. Separating a bit of mash and heating it meant extracting as much sugar as possible. Brewers also did not have modern tools, like thermometers, to tell them if they were maintaining the correct temperature. Heating portions separately and returning them to the mash tun encouraged a more uniform heating and coaxed the grains to release more sugar.

You also get more tannins and melanoidins, too.

Tannins

More commonly referred to as polyphenols, tannins are found organically in a lot of things, including tea and beer. In your brew, tannins can make it cloudy and add an astringent taste. Decoction mashing naturally reduces the amount of tannins produced, due to lower pH levels. Whatever tannins are added to the final product usually add something to the flavor profile of the beer.

Melanoidins

Melanoidins are amino acids found in beer that interact with the sugars through Maillard reactions. The whole thing is a little complex, so we won’t go into depth here. However, when sugars and melanoidins react, they add color and flavor to your beer. If you ever wanted caramel or coffee notes in your beer, you are looking for melanoidins.

Decoction mashing encourages more melanoidins to develop throughout the process. In doing so, the complexity of your beer is increased. Furthermore, your dark beer styles get a rich color.

Which Beer Styles Benefit from Decoction Mashing?

One of the best beer styles to try this method with is a European lager. In other words, you can whip up traditional pilsners, bocks, helles, and dunkels easily when utilizing the decoction mash method. You will get more maltiness, breadiness, and even a touch of grains in the finished product. If you want to enhance the flavors of Hefeweizen or Kolsch beers, you can use a single decoction mash.

How to Do a Single Decoction Mash

Are you ready for a great undertaking? If you do not want to dive directly into decoction mashing, a good baby step is a single decoction mash. You can use single decoction mashes to add a touch of complexity to the malt in your brew. Additionally, you can use it to give some color or body to a Hefeweizen or Pilsner.

Check out this video which details how to make a maibock using a single decoction mash:

Equipment For Decoction Mashing

Before beginning, make sure you have the right equipment:

• Your grains
• Water
• Digital thermometer
• Brew kettle
• Separate kettle for your decoctions
• Slotted spoon or mash paddle
• Calcium chloride or gypsum (for triple decoction brewing, seen far below)

Once your brew lab is ready to go, follow these steps:

Step 1: Mash In

Begin your brew day as any other. Heat the strike water in preparation for the saccharification rest. The temperature is usually between 145-155°F (62.7-68.3°C), depending on the style of beer you are making.

Step 2: Perform Saccharification Rest

Rest the mash for about 30 to 45 minutes.

Step 3: Decoction Pull

You will need to pull enough grains to raise the mash temperature to 170°F (76.7°C). You can use an online decoction calculator to help you figure out decoction volume.

Remove the thickest section of the mash, where there is more grain than liquid. The decoction should be thick but not so thick that you cannot give it a stir. Bring the decoction portion to a boil slowly. Keep stirring it to keep it from getting scorched.

Step 4: Boiling

Boil the decoction for 5 to 30 minutes. The duration of the boil will increase melanoidins. 30 minutes, for example, gives you more color and flavor.

Step 5: Add the Decoction Back to the Mash

Turn off the decoction kettle’s heat. Start transferring the decoction back to the mash tun, about 1-2 quarts at a time. Be careful during this transfer, as the decoction will still be close to boiling temperature.

In the mash tun, stir the mash regularly and monitor the temperature with a thermometer. Once the temperature of 170°F (76.7°C) is reached, you must hold the temperature for about 10 minutes. Chill any leftover decoction to 170°F before adding it back to the mash tun.

Step 6: Sparge and Proceed as Normal

Whichever sparging method you choose, this is the time to do it. Collect all the wort you can and add it to your boiling kettle. From here on out, you would follow your brewing process as you normally would. Continue boiling the wort, add in any hops, chill, and then pitch that yeast.

How to Do a Double Decoction Mash

Plan on brewing up a German bock any time soon? You can use a double decoction mash to make it taste phenomenal. Plus, a double decoction can speed up the whole brewing method. Much of the process is the same as your single decoction mash, except you will do both a protein rest and a saccharification rest.

Here are the steps:

Step 1: Mash In

Bring your strike water to about 122°F (50°C).

Step 2: Protein Rest

Allow the mash to rest for 10 to 15 minutes at 122°F (50°C).

Step 3: First Decoction Pull

Figure out the decoction volume so you can raise the mash temperature to 145-155°F (62.7-68.3°C) for saccharification. Similar to the single decoction mash, you want to take the thickest part of the mash and add it to your decoction kettle. Heat the portion you pulled over medium high heat and stir gently.

Once the mash has reached 150°F (65.5°C), let it sit for about 20 minutes. This will allow the starches to begin converting into sugars. After sitting for 20 minutes, continue heating and stirring.

Step 4: Boiling

Boil for at least 5 minutes. If you want a dark beer with more caramel notes, boil for as long as 30 minutes.

Step 5: Adding Decoction Back into Mash

Take the decoction kettle off the heat. Begin transferring the decoction portion back into the mash tun, about 1-2 quarts at a time. Be very careful.

Stir your mash regularly and use a thermometer to check the temperature. It should reach 150°F and stay there. If you have any leftover decoction, let it sit and chill to 150°F before adding it back into the mash tun. Maintain the temperature for about 45 minutes.

Step 6: Second Decoction Pull

This time, you are repeating the pulling process but will bring the portion up to 170°F (76.7°C). You do not need a rest this round.

Step 7: Sparge

Sparge using whichever method you would like and then continue out your brewing process as usual.

How to Do a Triple Decoction Mash

Having learned the process for both single and double decoction mashing, you might be thinking that it does not seem like too big a challenge. Well, prepare to be taken aback. The holy grail of traditional brewing, also known as triple decoction mashing, is not for the faint of heart. You will need to procure undermodified grains, not a modified one. If you do, everything from resting to boiling will have to be shortened, which can open up a greater window of error.

In short, you are going to need to talk to your friendly neighborhood maltser.

Secondly, you will need help. Triple decoction mashing is time-consuming and arduous. Another pair of eyes can assist with monitoring the mash tun and decoction kettle.

Lastly, triple decoction can take up to 6 hours. Be prepared for that before you begin.

When you are prepped, having everything cleaned and sanitized, and your grains gathered, follow these steps:

Step 1: Mash In

Grab your brew kettle and combine grain and water. You want your water to reach 99°F (37°C). If you plan on making a pale beer, you need 2.3 to 2.6 quarts of water per pound of grain. For a darker brew, use 1.4 to 1.9 quarts per pound.

Step 2: First Decoction Pull

After 15 minutes of letting the grain and water sit in 99°F (37°C) water, it is time to pull your first decoction. Since you are doing this three times, you can divide the mash up into thirds. Take the thickest part, put it into a decoction kettle, and then heat to 150°F (66°C). Once the target temperature is achieved, the decoction needs to sit for about 20 minutes.

If you are using a modified malt, cut back the time. Otherwise, all the starches are going to convert during this step.

For each of the pulls, you will need to continuously stir the decoction while it heats. Add a small dash of calcium chloride or gypsum to the pot to keep your mash from getting scorched.

Two Rest Options

You have a couple of resting options to consider. First, you can leave the two-thirds of mash in the mash tun to sit for several hours at a temperature of 99°F (37°C). Doing so will encourage an enzyme called phytase to release the phytic acid from the grains. This is called an acid rest, and it was once used to acidify water that was too pure.

Another option is called the modified ferulic acid rest. This requires a maintained temperature of 104-122°F (40-50°C). Your beer will take on a unique flavor. Weissbier, for example, requires ferulic acid for its distinctive taste and color.

Step 3: Boiling Your Decoction

After the decoction has rested, begin to heat it. Pale beers need about 15 minutes. Darker beers should go no longer than 40 minutes.

Step 4: Adding Your Decoction Back Into the Mash Tun

Once the timer goes off, remove the decoction kettle from the heat and start returning the mash to the two-thirds left in the mash tun. The temperature should be around 125°F (52°C). Hold the mash at this temperature for about 15-30 minutes for a protein rest. For modified malts, you will need to skip this step. Go right to the second pull instead.

Step 5: Second Decoction Pull & Saccharification

Next, take the second most thick section of the mash to use for your pull. Boil it for 15-30 minutes in the decoction kettle then put it right back into the mash tun. Adjust the temperature to around 149°F (65°C). Maintain this temperature for 60 minutes, allowing for saccharification to occur. Modified malts need only 30 minutes.

Step 6: Final Pull & Mashing Out

With the saccharification rest complete, you will do one final pull. Again, you boil it for 15-30 minutes then put it back into the main mash. Now you can mash out. The temperature should be around 170°F (77°C) before continuing. From here on out, you can recirculate the wort, sparge, lauter, and continue on with your brewing process.

Decoction, a Smashing Idea

Decoction mashing is a wonderful idea to add a bit of complexity to your next homebrew, particularly if you want to make a more historically accurate beer. Despite the time and effort, trying a decoction mash is a fun way to switch up tactics. You may also find that you create something incredibly delicious. Although this process does add another day to the whole homebrewing process, there is no doubt that it is worth it in the end.

Decoction Mash FAQ