Making Dunkel, decocting part of the grains

[Nebraskan]

I was reading that one of the reason German Dunkel beer has such a unique flavor profile is the method of decocting part of the grain. Part of the grain is boiled for a while and then returned to the mash tun. This can be repeated several times. My question is does anyone know a good percentage of the total grain bill that would be used for decocting? I am thinking at making 3 gallons of Dunkel and whatever pounds of barley I use for my mash, I would also add an extra amount used in only the boiling. My reasoning is that there would be killing of the enzymes during the boiling and Maillard reaction, and that means the OG would not be achieved if you did the decocting on the original volume of malt. Is this correct, or does some of the other active enzymes finish out the starches from the decocktion portion?

 

[thaefathan]

I made a 5 gal Iserweizen recently, its just a Hefeweizen, but at the saccharification temp I scooped out a gallon of thick mash and boiled it for about 15 min. The beer got a higher OG than expected, and it finished fine. I think the enzymes in the main part of the mash convert the starches in the boiled portion just fine.

 

[JimRausch]

One of the reasons for doing a decoction is the mysterious 'special flavor' that decoction gives you. This has been debunked by some, but I believe there's something there. Something that adding a couple oz. of Melanoidin malt doesn't get. Braukaiser has a good read on his website. Typically, you take about 1/3 of the mash at a time. But the main reason I do a decoction is to raise the temp in my 5G mashtun which is typically filled to the top. For my lagers and my altbiers, I mash in at 147. After 10 minutes I take 3 qt. of thick mash, raise that to 157 for 10 minutes, then boil for 10 minutes before adding it back to the main mash. This raises the main mash to 157, which I hold for 20 minutes before mashing out. Increases my total mash time by only an additional 10-15 minutes, and I do the decoction on a campstove next to my main BK. The boiling of the decoction does destroy the enzymes in the decoction, but the main amount of the enzymes are in the mash liquid back in the main mash. Boiling the decoction does also help increase your mash efficiency by breaking down and denaturing some of the 'hidden' starches in the decoction that would otherwise be unavailable to the enzymes. So decoction actually helps you increase your starch ->sugar conversion.

 

[Yooper]

I was reading that one of the reason German Dunkel beer has such a unique flavor profile is the method of decocting part of the grain. Part of the grain is boiled for a while and then returned to the mash tun. This can be repeated several times. My question is does anyone know a good percentage of the total grain bill that would be used for decocting? I am thinking at making 3 gallons of Dunkel and whatever pounds of barley I use for my mash, I would also add an extra amount used in only the boiling. My reasoning is that there would be killing of the enzymes during the boiling and Maillard reaction, and that means the OG would not be achieved if you did the decocting on the original volume of malt. Is this correct, or does some of the other active enzymes finish out the starches from the decocktion portion?

There are some calculations to do with volume and hitting the next temperature rest, but generally it's about 1/3 of the thick mash (not the liquid). You don't want to do a separate boil, as part of the reason that there is no extraction of tannins during the boiling of the decoction has to do with mash pH. Using the thick mash means using as little of the liquid as possible, just enough to boil and be able to stir without the mash burning. That ensures you don't denature the enzymes. Also, you bring the decoction to the next rest temperature and hold it there before boiling, to ensure that grain converts.

 

[Nebraskan]

 

[Lefou]

Yes, when doing a step mash with single decoction for lighter wheats, I've used about 1/3 of the mash to boil, then re-added. I keep amylase enzyme powder for this and use a thinner mash, too .... about 2qt water per pound of grain. It allows for absorption and boil-off to some degree.
I typically won't do a decoction until the mash is partially converted, waiting maybe a half-hour or so before extracting a portion. My mix is usually Pilsner, white or red wheat, and a smaller portion of either Vienna or Munich light or dark grains. A higher diastatic mash done with a saccharification rest near 145F-150F will usually give nicely attenuated wort with a slight bit of color and a great foam stand for a wheat-forward finished beer.
Never done a decoction for a dark ale yet, and probably won't as I'd be a bit paranoid about boiling the darker grains and getting a bitter result.

 

[fredthecat]

decoction adding a lot of good qualities is absolutely true despite debunking claims. if im doing a simple grist beer i likely will do a single decoction as it doesn't take that much extra time or effort.

 

[Lefou]

That "mysterious special flavor" results in part from base malt starch that is less modified. When doing a decoction with a Pilsner/wheat malt there should be plenty of diastatic enzyme power left to convert any unmodified starches returned via decoction after about 15-20 minutes. Sometimes I will extend my mash past 60 minutes, skip the decoction, and do the extended single infusion mash. It really depends on what malts I choose and how the beer is designed.
I tend to use Belgian Pilsner as a base malt. That grain will give me a slightly lower mash efficiency, so I've gotten around that by using a couple methods, depending on the style.