Decoction Mashing: Benefits and Cons

Paulaner Dunkel

Dunkel Bier. A darker german lager that will benefit from a decoction style mash.

I have asked myself this very question…. In fact, everytime I decide to use this intensive and traditional process known as “decoction mashing“, I always ask myself, is it really worth the extra work? I say yes and no.

  •  benefits of the step mash associated with decoction
  1. Allows the different enzymes to work on the complex sugars associated with all barley malt wort.
  2. The typical protein rest at around 122 degrees F can help lautering (rinsing) the mash because this rest breaks down high protein malts such as wheat and rye. Stuck sparges are very typical when using these ingredients.
  • benefits of boiling of the mash
  1. Darker color beer. More kettle caramelzation , usually a flavor associated with darker german beers Ex. Bock, Dunkel, Helles (even though Helles is a lighter colored beer, it is traditionally brewed with decocotions).
  2. Allows for a better extract because of the breaking down of the malt due to the boil.
  3. Leaves more of the protein behind in the mash when recirculating, resulting in a clearer wort and ultimately a clearer beer.
  • Cons: Brew session time is doubled.
  1.  bringing the mash up to boil can take time, every time.
  2. Allowing a conversion rest when pulling a decoction can add extra time but can contribute to a better overall conversion.
  3. Conversion MUST be checked with the iodine test to ensure completion.
  4. It is said decoction mash schedule can add about 2hrs to your brewday.
  •  A third boiling vessel must be used.
  1. After all, you will need to pull your decoction and boil it in a pot. However, if you get innovative, you may be able to use your HLT (hot liquor tank, ie: hot water tank) or even you boil kettle. So I’ll say the third vessel is optional , but when you choose to decoct your mash you don’t want to make your day anymore difficult than it needs to be.
  • Tips for decoction mashing and hitting correct temps:
  1. Mash in thick. Usually 1.25 quarts to 1 pound of grain or thicker. Also when its time to add the pull back to the main mash, have some extra boiling water on hand to raise up your temps if you under shoot you intended temps.
  2. When adding the decoction pull back to the main mash tun to raise the temps, keep a close eye on the temp of the main mash. You don’t want to over shoot the intended mash temp. In that case, ice is you best friend!
  3. It’s not necessary but it does help if you already have a direct-fired mash tun. Consider that when the bulk of the thick mash is pulled, you are decreasing the thermal mass in the mash tun and  the tun will lose heat from the pull. Here is where the direct fire mash tun will come in handy. Adding back lost heat to the tun is as simple as turning on the flame. Just remember to watch the mash tun temps and keep stirring to avoid scorching and denaturing the enzymes left in the tun.
  4. Remember the decoction mash rule of thumb: for every step, pull 1 quart of thick mash per pound of grist in the recipe. So in other words, if your recipe has 12 pounds of grain, then try to pull 12 quarts of thick mash. That ratio should give you an idea of how much decoction should be pulled. If you can’t manage this exact ratio, just try to get it close as you can,it does not need to be exact.
  5. Try not to decoct too thick. You should have some liquid mixed in also. If the mash gets too thick, 1). you could scorch the grain easily. 2). It will be difficult to get an even mash temp due to the thickness of the mash. Just remember to keep stirring the decoction as it heats.

In summary – pros: while decoction mashing will not benefit every beer made, it can add more malt flavor and authenticity to some beers. It can also break down the gummy glutens that cause stuck sparges when a protein rest is used. It will increase your brewhouse efficiency and you can also say goodbye to those troublesome “dough balls” when mashing in. This is because you will mash in at a lower temp than 150 degrees , (which is the temp that barley malt becomes glutenous and sticky). So in retrospect the grist will mix better at the lower mash in temps. You will also have a clearer wort due to the intensive boiling and this encourages to free protein to stay in the mash and not in the boiler with proper re-circulation. (see article on Achieving Clarity in Your Beer).

cons: Decoction mashing is labor intensive. You’d better have extra propane, time, and patience because it will take all three! Decoction is definitely not an exact science when it comes to temps as you must watch out for over and under shooting your intended temps. There is no “set it and forget it” when it come to this style of brewing and this is where the “time and patience” part come in. Mash conversion must be checked before the mash is complete.

If you are an all grain brewer, there is no reason in the world you shouldn’t try decoction. It is a good process to learn to do. If you ever need to up your mash temps (example: missing temps in the mash process), decoction is a skill that is used to do this. This is also the way brewing was traditionaly done before there was thermometers. So for extra authenticity in that Oktoberfest, Double Bock, or Pilsner, try it and decide for yourself!


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