Here’s a picture of me mashing my decoction (note the two pots).  There are certain types of beer that are very conducive to the various mashing regiments.  I’ve mentioned in previous posts which types of beers tend to fit into which categories.  We’ve covered single infusion and step-mashing to this point, but what about decoction mashing?

The word decoction refers to reducing/concentrating/boiling down a solution.  It also refers to extracting the essence of something.  In the context of beer, it refers to boiling the thickest part of the mash, which, in turn, allows further water penetration and starch conversion.  Also, various elements that are essential to stylistic flavor profiles are produced.

Decoction mashing is the traditional method for beers like Doppelbock, Lambic, and several styles that can also be step mashed.  Some of the benefits of decoction mashing are debated among beer geeks, but it does offer a pretty thorough conversion of starches to sugars and adds some tannin qualities, which are desirable for some styles.  In addition, Melanoidin (formed from Amino acids and sugars), which is accomplished through the so-called Mailard reaction, is said to happen during the boiling portions of the decoction.  This yields some of the deeper flavors of Bocks, for instance.

The basic method for decoction mashing entails separating 25% of the mash and bringing it up to temps that are conducive to starch conversion.  Often times, the remaining 75% of the mash is left at 122° (F) for a protein rest.  After about 30 minutes of conversion occurs in the 25% separated mash, it is brought to a boil for a short amount of time, creating some tannin qualities and character in final beer. The boiling mash is then added back to the 75% mash and brings it up to conversion range.  The increased viscosity and sugar content in the re-addition are said to “jump start” conversion in the larger mash.  At any rate, the beer is allowed to convert at the new temperature range.  That is, unless…

Sometimes double, and even triple, decoction mashes are performed to add even more character to the beer.  Double and Triple are used earlier in the process, achieving various temp ranges that are known to accomplish various by-products in the beer.  Let me say it in a less abstract manner.  Say you have a beer that is supposed to be mashed and rested at 95º.  You added your water to the grains to achieve the mash temp.  It also calls for a protein rest at 122º (the protein rest is known to break down various proteins and promote others that create good head retention).  What do you do?  Some recipes call on the brewer to pull 1/4 of the mash, perform a sachrification rest at 158º, raise to boiling, and re-add to the mash.  This grain that is re-added to the mash will have converted sugars, tannin qualities, and get the temperature to the proper range.  That’s one decoction.  A second one might be called for to achieve the conversion range for the entire mash.  So, 1/4 of the mash is pulled out, heated to 158º, rested for 30 minutes, made to boil and added back to the remaining mash.  A third one might be performed at any point along the way.

I know this is uncharted to many of us, so maybe a short diagramish thingy will help.

Grains+Water= Mash (let’s assume the initial temperature of the mash is 95º)

Whole mash—>1/4 taken out, heated to 158º, rested for 30 min, boiled (this is decoction)

1/4 boiled mash—>Added back to 3/4 mash

All the mash now=122º—>1/4 taken out, heated to 158º, rested for 30 min, boiled (this is decoction number 2)

1/4 boiled mash—>Added back to 3/4 mash

All mash now 148-158º (depending on targets temps and calculations).

That’s the long and short of decoction mashing.  Perhaps saying what is happening is harder than actually doing it, so I encourage you to try it some time.