A decoction is a method of extraction by boiling of dissolved chemicals, or herbal or plant material, which may include stems, roots, bark and rhizomes. Some 'teas' are decoctions. Likewise, the term is used colloquially in South India to refer to black coffee prepared by the traditional method. Decoctions, however, differ from most teas, infusions, or tisanes, in that decoctions are usually boiled.
Use in breweries
Decoction mashing is the traditional method used in many breweries. It was used out of necessity before the invention of thermometers allowed simpler step mashing. But the practice continues for many traditional beers because of the unique malty flavor it lends to the beer; boiling part of the grain results in Maillard reactions leading to malty flavors. The first wort hops method (FWH) involving addition of hops to the boiler at the first step of sparging lends a bitter and complex aroma to beers .
Use in herbalism
In herbalism, decoctions are usually made to extract fluids from hard plant materials such as roots and bark. To achieve this, the plant material is usually boiled for 8–10 minutes in water. It is then strained.