Decoction mashing is an often-misunderstood German brewing technique. I’m not going to dive into the history and tradition, but if you’d like to learn more, the most accurate and in-depth resource I have found is Braukaiser Decoction Mashing.
This will be a short walkthrough of a decoction brewday. I’m performing a Hochkurz decoction mash for a German Pilsner (see Braukaiser article for a description of different decoction schedules.) The basic outline is as follows:
63c/145f – 40 mins
-pull thick decoction at 10 mins, convert at 70c/158f, boil 10 mins, return decoction
70c/158f – 30 mins
-pull lauter (thin) decoction with 15 mins remaining, boil 10 mins, return
75c/167f – 10 mins
As you can see, the total mash time for this schedule is one hour and twenty minutes, not much more of a time commitment than a standard infusion mash, but with some of the added benefits of decoction mashing. There are some benefits to performing the more traditional, long decoction schedules, but this schedule is much less intimidating to the inexperienced decoction masher, and easier to manage, because everything is done within normal saccharification temperature range; basically, if you screw up the rests, the beer will still turn out fine.
The equipment necessary to decoct portions of the mash is simple:
-a heat source; I use a propane burner, I know others use induction burners or electric, but I like having the extra power of gas to quickly raise the temperature.
-a kettle about twice the size of the decoctions you will be pulling, for easier stirring without spills. Mine is 8 gals, to easily handle 5 or more gallon decoctions when I brew large batches.
-a ladle or strainer to remove the decoction from the mash tun. I use a large skimmer (for deep frying) like this.
-an accurate thermometer. Most decoctions require a short rest at saccharification temperature.
Well, let’s dive right in, step by step.
After 5 mins, I check the pH, and adjust if needed. At 10 mins, I pull the first decoction.
It is a fool’s errand to try and calculate a precise volume for each decoction. I just pull around 30% of the volume in the mash tun, including as much of the grain as I can skim out. This gives me more than enough decoction to move the temperature from saccharification to dextrinization; any extra is left to cool and added back slowly over the course of about 10 mins to maintain the rest mash temperature.
I like a gentle boil, just above a simmer, for light beers. The above photo was just after the hot break/foam up, so it looks a little more vigorous than normal.
Contrary to a lot of what you’ll hear in the American homebrewing community, decoction boiling doesn’t add much color to the wort, nor does it produce a substantial amount of maillard reaction products or melanoidins, UNLESS it is specifically handled with that goal in mind.
Because this was a Hochkurz schedule, I only pulled grain from the mash tun once. The next decoction was pulled 15 mins after establishing the second rest.
That’s all the pictures I have, my photographer got bored before the job was finished, but the rest is straightforward. The lauter decoction is added back to the MLT after the boil to hit the mashout rest of 75c/167f, then recirculating and sparging proceeds as normal.
Decoction mashing isn’t for everyone, it definitely takes some thought and effort, but it is a fairly straightforward process. I like it because it gives me something to do while the main mash is converting, and I notice a more distinct malt flavor and aroma in my decoction mashed beers, as well as clearer wort to the boil kettle, less hot break, better conversion efficiency, and greater control over the body and mouthfeel of the beer.
Plus, the smell wafting through my basement as the decoction comes to the boil is absolutely HEAVENLY… and no, boiling wort doesn’t come close to comparing to boiling mash!