Decoction
Decoction is a way to raise mash temperature by removing a portion of the mash, heating it,and returning it to the mash vessel.
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This is a technique developed by old style European brewers for brewing lager beers. Mostly used on undermodified malts that can't fully convert the starches to sugars. Boiling the grains for a short time, 10 mins. will reduce the size and complexity of malt starch and protein molecules and make them more convertable into sugars for the yeast to eat, and make a clearer beer. It will also raise your effiency. It will give the beer slightly more color, and a deeper malt flavor, creating a compound called melonoidin. Think of searing a steak on a grill. With highly modified malts such as those in the U.S., only a protein rest and a single decoction 33-40% of the thick mash, with a raise to saccarification rest may be sufficient. After your protein rest pull the decoction amount and bring the malt up to boiling gently by stiring and 50% of your heat output to avoid scorching. You can use a strainer to pull out the thick malt, with only enough liquid to cover it. Note your data in the decoction box in BTP.