Who – Mainly all Continental lagers are/were produced using a “Decoction” style mashing method. Even back in 1842 when Pilsner Urquell was first brewed, the tradition was well formed. One theory guessed that the tradition was established as thermometers were not either invented or widely known about when decoction brewing started. The style of brewing allowed them to brew fairly consistently without the aid thermometers, as weight and volume were easy to calculate. Other issues like not needing heat under the mash may also have played into this style being so popular.
What - Decoction mashing is a temperature controlled mashing method, it is similar to step infusion mashing, its difference is in the way that the heat is added.
The main difference is that in decoction mashing part of the mash is boiled in a separate kettle. The boiled part is added back to the mash to achieve the required temperature raise. The boiling of the mash can have a major effect on the final flavor of the beer.
Why – Flavor! The reactions that occur produce malt flavors that seem to be unreachable by any other style of mashing. Boiling the mash helps to break down the protein that surrounds the starch, this makes the starch more accessible to enzymes, so with under modified malts are best converted using the decoction style mast. Multi-stage decoctions also help adjust the mash pH, as well as providing natural agents that aid clarification of the wort.
How – Ah the hard part.
The Basics:
Thick portions of the mash are drawn off at three different times. Each portion, or decoction, is heated to saccharification temperature, then boiled briefly, and finally returned to the main mash vessel to step up the main mash's temperature.
The mash begins with cold water stirred into the grains (about 1qt to 1lb); hot water is added to bring the temperature to 95 °F for an acid rest(about 1.1qts to 1lb) . The first decoction raises the temperature to around 127 °F to break down the larger proteins; the second addition raises the mash temperature to 143 °F for starch conversion; and the third brings the temperature to about 163 °F for mash-out .
The Details:
While there is many types of decoction mash schedules, this is for the ever so fun triple decoction as it is probably the most popular in Bavaria and surrounding areas.
Step 1: Hydrate the grains – mix 1qt per pound of grain and let stand for 15 minutes.
Step 2: Add 150F degree water at 1.1 qts per pound of grain to get to 95F let sit 15 minutes, this is your “Acid Rest.”
Step 3: remove 1/3 of the thick part of the mash, heat to 126. F and let sit for 15 minutes, heat to 144F over 10 minutes stirring continuously during the raise, let sit 15 minutes. Heat to 167F over 10 minutes stirring continuously during the raise, let sit 10 minutes. Bring to a boil over 15 minutes, stirring continuously during the raise, and hold at the boil for 30 minutes.
Step 4: Add the 1/3 section back to the main mash and stir well, this should achieve around 122-140F, adjust if need be and let sit 15 minutes, this is the “Protein Rest.”
Step 5: Remove 1/3 of the thick part of the mash, heat to 167F over 20 minutes stirring continuously during the raise, let sit for 10 minutes. Bring to boil over the next 15 minutes stirring continuously during the raise, hold the boil for 30 minutes.
Step 6: Add the 1/3 section back to the main mash and stir well, this should achieve around 149-160F, adjust if need be and then hold for 10 minutes, this is the “Saccharification Rest.”
Step 7: Remove 1/3 of the thin part of the mash, heat to 167F over 20 minutes stirring continuously during the raise, let sit for 10 minutes. Bring to boil over the next 10 minutes stirring continuously during the raise, hold the boil for 20 minutes.
Step 8: Return the 1/3 section to the main mash and stir well, this should achieve around 163-168F, this is your “Mash out”