Decoction is a method of mashing developed by Bavarian brewmasters before the invention of the thermometer. The idea was to take out a measured portion of the mash in ratio to the full mash, boil it, and add it back in to raise the temperature in consistent increments. The brewmasters didn’t know the complex chemistry that was taking place when they did this, but they did know that they were getting better extract from the same amount of grain along with richer, maltier beers.
Decoction works on two levels to affect the composition of the unfermented beer. First, it explodes the starch molecules allowing the enzymes in the mash to more easily convert them to sugars giving higher extracts from the (then) under modified malt. Second, the boiling induces sugar and amino acid reactions, called Maillard reactions, that produce compounds called melanoidins.
Today we have the thermometer to exactly measure temperature changes and highly modified malts for brewing that do not require the extra help with sugar extraction. However, the Maillard reactions remain unique to the decoction process in brewing. The melanoidins produced add a distinct richness to malt-forward beers. Look for subtle notes of honey and toffee in beers mashed with the decoction process.
Rally King is one of just a handful of breweries in the U.S. that uses decoction. Come in and try our Small Hours dark lager and 360º light lager and taste the difference.