double decoction

    • Glucanase rest: Temp = 95 F hold for 20’ (will lower pH of mash; this can really be skipped with today’s well modified malts)
    • Protein rest: Raise to 127 F (122-127); hold 30‘
    • Decoction 1: Remove 40% of thickest part of mash into second kettle
      • Raise second kettle to 158 F (158-162); hold saccharification for 20’
      • Keep rest mash 122 F (122-127)
      • Bring second kettle to boil; boil 15-30’
    • Beta amylase rest: Recombine with rest mash; raise temp to 148 F (145- 153F) & hold for 15-30’
    • Decoction 2: Remove 1/4 mash into second kettle, slowly raise to boil for 15’
    • Alpha amylase Rest: Recombine with rest mash; raise temp to 158-162F; hold for 1 hour
    • Mash out: Raise to 170 F (168-171) and hold for 10’

For drier beers (pilsners), stay on the lower end of the temp range during the rests. For sweeter beers (bocks), stay on the higher end of the temp range during rests.

Don’t let the boiled mash burn; keep stirring.

Editor’s note- I posted this page for my reference 9 years ago. I’ve learned a lot since then and my brewing continues to evolve. I typically now only do a protein rest when I have a healthy percentage of high protein grains, like wheat and rye. If my grain bill is 80% or more barley, I don’t do a protein rest.

Recently I’ve experimented with doing a protein rest on only the wheat and rye grains, mashing the wheat and rye separately from the barley, and then combining the two at the first sugar rest at 148F.

Here’s a link to Keith Thomas’s post on Protein Rest from Beer & Brewing that kinda defines where I’m at with the protein rest.

I’m also noting that I really only do decoction brewing with the German style beers, which means lagers, which means for me that I’m doing them in the winter, which means the outside air temps are always cold, and that always makes it difficult to maintain the higher temps in the mash tun. We always seem to hit 158-162F, but I can’t remember the last time we bumped to mash out temperatures. Despite not mashing out, we have still been making decent lagers.

Huck, March 19, 2021


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