Decoction Mash
decoction mash. (dee-kak'-shen mae'-sh)
One of the three mashing methods that is often used for bottom-fermentation beers. The process requires three vessels: a mash tun for mash mixing, a mash kettle (or copper or mash copper) for boiling, and a lauter tun ( or clarifying tun) for straining. Mashing is carried out in a mash tun, and starts at a low temperature while portions of the mash are taken out and boiled in the mash kettle and later returned to the mash tun, thus gradually raising the temperature of the entire mash. The process is usually repeated two or three times, taking five to six hours. The mash temperature may start as low as 95°F (35 °C) but more often at 113-122 °F (45-50 °C) to reach 158-169 °f (70-76 °C). The mash is then filtered in a separate vessel known as a luter tun. Syn: decoction brewing method. See also: infusion mashing; mashing.
COMMENTS
Decoction is generally a step that can be skipped when using malted grains. The purpose of decoction is to allow starches to be broken down into sugars, which is also the purpose of malting. Using malted grain renders this step superfluous and produces the same quality of beer from a single temperature boil. (see Protein Rest)
The description misses the intermediate rests for the decocted portion. It is NOT just pulled and boiled but rather is taken through the remaining temperature steps on the way to the boil.