(Sponsored content) In the world of craft brewing, where tradition often collides with innovation, decoction mashing stands out as a time-honored technique that bridges centuries of craft with modern artistry. Originating from storied German and Czech brewing practices, decoction mashing involves boiling a portion of the mash and then reincorporating it to achieve optimal enzymatic activity and flavor complexity.

This labor-intensive process, which once defined the character of classic European lagers, has both its ardent advocates and skeptics. While proponents celebrate decoction mashing’s ability to produce rich, nuanced brews with enhanced malt profiles, critics point to the process’s time-consuming nature and lack of necessity due to today’s well-modified malts.

Yet, in an era where craft brewers seek to connect with history while pushing boundaries, decoction mashing endures as a testament to the art of brewing, offering a link to the past and a unique signature to contemporary creations.

“It’s definitely more of a labor of love style of brewing. But I’m a hardcore brewer in terms of process. Older styles of brewing and techniques, that’s just kind of what I’m drawn to.” – Andy Ruhland, Bad Weather Brewing Co.

What is Decoction Mashing?

In its simplest form, decoction mashing is multi-step mashing. In step mashing, the mash temperature is increased to various stages of rest, where varying beneficial reactions take place. Decoction mashing is step mashing in which a decoction is used to increase the temperature of the mash to a specific rest point.

A decoction is removing a portion of the main mash (typically from the thickest portion of the mash), boiling it, and then returning it to the main mash. This raises the temperature of the main mash to its next desired rest threshold. Modern decoction mashing can take the form of a limited number of rest steps combined with a single decoction to a complex combination of multiple rest steps and multiple decoctions.

Decoction Mashing History

Though the origin of decoction mashing is somewhat muddled, it became notable because of its use by German and Czech brewers in the late 1700s. It is widely believed that the process was born out of practicality more so than for the flavors and aromas it fostered.

Brewers of the late 18th and early 19th centuries employed decoctions to reliably raise the temperature of the mash to achieve desired results, whether or not they fully understood the exact reactions that were taking place in the mash.

With experience, brewers discovered which steps achieved the best results for what they were brewing. These steps and rests might be different for lighter ales and darker ales, for instance, as brewers uncovered the nuances of steps and decoctions. These various steps led to such discoveries as improved efficiency, increased extract volume, greater attenuation, and depth of character from malts that were less modified and less consistent than those produced by modern day malting practices.

As brewing equipment advanced, malting practices honed more highly modified malts, and large scale beer production became commonplace, the use of decoction mashing diminished. Even in Germany, often credited as decoction mashing’s birthplace, it has been widely replaced by the more economically advantageous direct-heat step infusion mashing or even single infusion mashing.

There are a number of breweries that still employ decoction mashing, swearing by the results, insisting that the end character of the beer can’t be matched by other methods. It is still common in southern Germany and Czechia.

Triple decoction mashing was so popular in the Bavarian region of southern Germany that it was often called the Bavarian Method of brewing. And in Czechia, the European Union has issued a legal seal of quality called a PGI (protected geographical indication) for Czech beer – “České pivo” – that can only be obtained by employing decoction mashing, amongst other qualifications.

Pilsner Urquell, the world’s first pale lager or Pilsner, is still brewed at mass scale using decoction mashing. There are also many renowned craft breweries in the United States and elsewhere that believe decoction mashing is necessary to achieve the finest results for many of their beers.

The benefits [of decoction] that we’ve noticed with our sensory [analysis] is just a more malty beer, but without using some specialty malt. And it has more of a depth of flavor than you would get from a step mash.” – Bradley Zimmerman, Badger Hill Brewing Co.

How to do a decoction mash

There are different ways to perform a decoction mash, but they share a couple of common goals. One is to boil a portion of the mash to break down cell walls to allow for more complete conversion of starch to sugar. The other is to raise the temperature of the mash to a specified rest temperature to favor specific enzymatic activity.

For our purposes, we’ll explain a few mash schedules to give an idea of the basic process. There are, however, numerous areas in which to alter these schedules to achieve various outcomes depending on the type of beer being made and the specific ingredients being used.

Most decoction mashes typically start with a higher liquid to grist ratio than a single infusion mash. A common ratio is 1.9 to 2.2 quarts of strike water per pound of grain (4 to 4.6 liters per kilogram). This is to account for evaporation when bringing the decoction to a boil.

The volume of the decoction is typically a quarter to a third of the total volume of the mash but can be calculated with the following basic formula:

decoction volume = total mash volume × (target temp – start temp) / (boil temp – start temp)

(NOTE: Total mash volume includes liquid and grain. Target temp is the rest temperature being targeted. Start temp is the temperature of the mash prior to achieving the target temp. Boil temp is the temperature for boiling adjusted to whatever elevation brewing is taking place (i.e. 212°F [100°C] at sea level, but 203°F [95°C] at 5,000 feet [1,524 meters] of elevation).

There are more specific decoction volume formulas available via software calculators and books, such as A Handbook of Basic Brewing Calculations published by Master Brewers Association of the Americas.

Also note that it is important to heat the decoction gradually, so as not to scald the mash or denature the enzymes too quickly. The temperature should be raised at a rate of about 2-4°F (or 1-2°C) per minute.

Courtesy MaltEurop Malting Co.
Sample Triple Decoction mash Schedule. Courtesy MaltEurop Malting Co.

The basis for all other decoction mash procedures is the grand-daddy of them all, the traditional triple decoction mash. This procedure begins with mashing in at a fairly low temperature that also serves as an acid rest, a decoction that then steps up to a protein rest, another decoction that steps up to a saccharification rest, and a final decoction that steps up to mash-out temperature.

Triple Decoction Mash Schedule

Mash-in / Acid Rest: 95°F (35°C) to 113°F (45°C) for +/-20 minutes

Decoction #1: thick mash,boiling for 10 to 40 minutes

Protein Rest: 113°F (45°C) to 131°F (55°C) for 10 to 30 minutes

Decoction #2: thick mash, boiling for 10 to 40 minutes

Saccharification Rest: 149°F (65°C) to 160°F (71°C) for +/-20 minutes

Decoction #3: thin mash, boiling for 10 to 40 minutes

Mash-out: 167°F (75°C) to 172°F (78°C) for 10 minutes

Decoction Mash Details and Explanations

Acid Rest: The acid rest is used to adjust pH level, but also aids beta-glucan breakdown which can benefit lautering. The time can span whatever is necessary to achieve the desired pH level (generally within the 5.4 to 5.8 range, though this can vary depending upon style). Most modern brewing utilizes other pH adjusting methods and foregoes the acid rest.

Decoction #1 and #2: The first two decoctions are pulled from the starch saturated thicker portion of the mash, leaving behind the thinner portion of the mash which is loaded with the enzymes necessary for conversion. When the thick mash is boiled, the starches are made more readily accessible for conversion when the decoction is returned to the main mash. It is important in these two decoctions to allow them to rest between 149°F (65°C) and 160°F (71°C) for about 15 to 20 minutes to allow for saccharification before bringing them to a boil. Slowly add the boiled mash back into the main mash a little bit at a time to make sure you don’t overshoot your next rest temperature. Any excess mash should be cooled to the rest temperature before being added back into the main mash.

Protein Rest: The protein rest should be kept closer to the low end of the range for 15 to 20 minutes for less modified malts or grains such as wheat, which has a greater amount of proteins than barley. This allows for free amino nitrogen production necessary for yeast nutrition and the reduction of beta-glucans which aids lautering. If the malt is well-modified and has an appropriate amount of FAN, the protein rest should be held at the upper end of the range for only 5 to 10 minutes, as this helps retain the medium chain proteins that aid body and head retention. Holding a protein rest too long for a well-modified malt can be detrimental, as it can break down the proteins necessary for maintaining the body, resulting in a beer that is thin and watery.

Saccharification Rest: The saccharification rest is where beta-amylase and alpha-amylase break down starches into simpler sugars. At the lower end of the temperature range, beta-amylase creates more easily fermentable sugars, allowing for a lower final gravity. At higher temperatures, alpha-amylase continues to break down longer chain sugars into simpler form, but also maintains some unfermentable dextrins that help achieve a higher gravity and fuller body. Beta-amylase and alpha-amylase are working at both extremes of the saccharification temperature range, but the efficiency of each is emphasized by rest temperature selection.

Decoction #3: The final decoction is pulled from the most liquid portion of the mash (the thin mash), as enzymatic conversion should be complete at this point. It no longer needs to rest, simply to be brought to a boil and added back into the main mash. This raises the main mash to your mash-out temperature, where it rests for about 10 minutes to thin the mash for lautering and to denature enzymatic activity, essentially locking in the wort profile.

Decoction Boil Time: The duration of the decoction boil is typically adjusted per beer style. Decoctions for lighter beers are generally boiled for less time, while darker, more robustly flavored beers are boiled longer. Shorter boil times keep the color lighter and the flavor notes softer, such as crackery or bread crust-like. The longer boil time allows for increased maillard reactions, which darkens the color and increases flavor notes such as caramel, toffee, and roast.

Courtesy MaltEurop Malting Co.
Sample Double Decoction Mash Schedule. Courtesy MaltEurop Malting Co.

With easier ways to adjust for pH, most modern day decoction mashing is single or double decoction, again depending upon beer style and desired results. Though highly modified malts also negate the necessity for the protein rest in double decoction mashing techniques, there are still benefits to utilizing a protein rest for certain styles.

Instead of mashing in at the lower acid-rest temperature of a triple decoction mash, a double decoction mash usually mashes in at the protein rest temperature. As in the protein rest of a triple decoction mash, the specific temperature at which double decoction mash-in occurs is largely dependent upon the malt or other grains being used. Unmalted wheat, for instance, would necessitate mashing in at a lower temperature and for longer than a well-modified malted barley.

Double Decoction Mash Schedule

Mash-in / Protein Rest: 113°F (45°C) to 131°F (55°C) for 5 to 30 minutes

Decoction #1: thick mash,boiling for 10 to 40 minutes

Saccharification Rest: 149°F (65°C) to 160°F (71°C) for +/-20 minutes

Decoction #2: thin mash, boiling for 10 to 40 minutes

Mash-out: 167°F (75°C) to 172°F (78°C) for 10 minutes

Common Single Decoction Mash

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Sample Single Decoction Mash Schedule. Courtesy MaltEurop Malting Co.

In a single decoction mash, as the name suggests, there is only one decoction performed. Most commonly, it is used in conjunction with a simple temperature step. Mash in at a protein rest temperature around 131°F (55°C), add boiling water to reach the saccharification rest temperature, then a decoction is pulled, boiled, and used to reach mash-out temperature.

This allows for optimal protein hydrolysis of modern highly modified malts, increasing attenuation while maintaining foam stability. The decoction puts emphasis on increased depth of color and malt character.

Because there is an infusion of water after the mash-in/protein rest, the initial strike water volume is typically around 1.2 quarts per pound (2.5 liters per kilogram), which results in a thicker starting mash than the other decoction schedules. After the water infusion, the mash consistency should be closer to 1.7 to 2 quarts of water per pound of grain (3.5 to 4.2 liters per kilogram), which accounts for evaporative loss in the boil and aids lautering.

A single decoction mash is most commonly used with lighter colored European lagers, which are subtler but still benefit from the emphasis on malt character and a drier finish.

Single Decoction Mash Schedule

Mash-in / Protein Rest: 131°F (55°C) for 10 minutes

Boiling Water Addition: enough to reach desired saccharification temperature

Saccharification Rest: 149°F (65°C) to 160°F (71°C) for +/-45 minutes

Decoction: thin mash, boiling for 10 to 40 minutes

Mash-out: 167°F (75°C) to 172°F (78°C) for 10 minutes

Decoction mashing sample schedule diagrams courtesy of Braukaiser.com under a Creative Commons License CC BY-NC 3.0.

Decoction mashing is both art and science

Like most brewing techniques, decoction mashing is an elegant interplay between art and science. As such, there are many ways to adjust a decoction mashing schedule to coax desired results. The triple, double, and single decoction methods we described are simply ground zero. All the variables can be changed to fit the style of beer being brewed, the ingredients being used, and the finished beer that you crave.

Decoction Mashing Benefits

There are many arguments for the use of decoction mashing. Chiefly, brewers argue that a decoction mashing technique achieves superior character, largely from melanoidin development due to Maillard reaction, that can’t be matched even by modern day processes and techniques.

The main decoction mashing benefits cited by modern decoction brewers are:

  • Increased malt efficiency
  • Improved yield
  • Greater attenuation
  • Naturally clearer final product
  • Greater depth of malt character
  • Drier, crisper, more drinkable finished beer

Melanoidin development is a critical element to decoction mashing

A key benefit to decoction mashing is the development of melanoidins through the Maillard reaction. Reducing sugars and amino acids go through multiple reactions to form rich amber and red colors, as well as flavor active compounds that contribute flavors to the wort ranging from caramel, toast, toffee, and even bitter and burnt.

While there are malt varieties that can contribute these colors and flavors to wort, such as Melanoidin malt, decoction loyalists argue that these aren’t exactly the same in flavor as the compounds that are created through Maillard reactions that occur in decoction mashing.

“There’s a certain flavor you get, a depth of malt,” says Andy Ruhland, Head Brewer at Bad Weather Brewing Co. in St. Paul, Minnesota. “Chris Lohring from Notch Brewing says it best. They talk about layered malt flavor when they talk about decoctions, which I think is a perfect way to describe it. I don’t think you can get that from a Melanoidin Malt. There’s something you can’t really mimic. You can smell it during the decoction. They just don’t get that with any type of specialty malt.”

Decoction Mashing Disadvantages

Decoction mash brewers are typically insistent upon the superior results they achieve with this specialized mashing technique. Its detractors, while generally not as ardently against its use as its supporters are for it, mostly decry this brewing technique as antiquated and unnecessary because of highly modified modern malts.

The key arguments against employing decoction mashing are:

  • Time consuming
  • Labor intensive
  • Energy intensive
  • Unnecessarily complex
  • Can require additional equipment
  • Unnecessary for highly modified malts
  • End results not readily distinguishable by many consumers

Excess energy usage is a primary argument against decoction mashing

Using too much energy versus what can measurably be gained from decoction mashing is probably the most common argument against its usage in an age of highly modified malts. According to Siebel Institute of Technology, home to one of the world’s leading brewing education programs, a single-decoction mash uses more than 130-percent of the energy of a single-infusion mash. That figure jumps to more than 160-percent for a double-decoction mash versus a single-infusion mash.

“It’s not energy efficient, it’s time consuming, and there’s a lot of drawbacks. It’s definitely more of a labor of love style of brewing,” Ruhland admitted.

“It’s a fun way to make beer, but it’s very labor intensive,” added Bradley Zimmerman, Head Brewer at Badger Hill Brewing Co. in Shakopee, Minnesota. “But I think the juice is worth the squeeze if you’re going to devote your time to a lager program.”

PLEASE NOTE: This article is for educational and informational purposes only.

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About Malteurop Malting Company (MMC)

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RESOURCES:

Decoction mashing sample schedule diagrams are courtesy of Braukaiser.com under Creative Commons License CC BY-NC 3.0.)