American Handy-book of the Brewing, Malting and Auxiliary Trades (1902)
– Robert Wahl, Max Henius
Limited Decoction. — This process seeks to combine the German decoction process with the English infusion method. The mash is carried out as usual, the mash-tun being, however, provided with a steam coil. After running off the first wort to the amount of half a barrel per quarter (1 U. S. barrel to 500 pounds of malt) into a separate vessel until required, steam is turned on, and the temperature of the mash raised to 212o F. (80° R.) where it is kept for about 15 minutes, when the temperature is reduced to about 160° F. (57o R.) by sparging with cold water while stirring. Then, the wort which was held in reserve is returned, and the temperature brought to 160o F. (57° R.). The mash is left to rest for 20 to 30 minutes, and taps are set, and operations continued as usual.
When unmalted cereals in the form of grits are employed they may be treated according to methods familiar to American brewers. In England, it would seem, the maize cannot be sufficiently gelatinized by employing the methods there in vogue, the unmalted cereals not being subjected to high enough temperatures, nor sufficiently long. The raw cereal mash when considered properly gelatinized, is cooled to the usual striking temperatures of the water, and the malt is run in to get the ordinary initial temperature, and operations are continued as usual.