Milling. Grains are normally received in breweries in bulk and transferred to silos. Malt needs to be crushed before it is used. This is done just before use. The aim in milling is to crush the endosperm of the barley, but leave the husk as intact as possible. These husks act as the filtration medium during later processing. A six-roller malt mill is shown in Figure 14.
Corn as received in a brewery does not need any treatment before use. It has already been crushed by a corn miller and separated pneumatically. The lighter germ of the corn is conveyed in a different airstream from the heavier, starchy endosperm. It is this latter fraction that is used by breweries.
Mashing. This step determines the ultimate structure of the finished beer. A typical mashing cycle requires the use of four vessels, a cooker, mash tub (tun in Europe), lauter tub, and kettle. Examples of some brewhouse control panels are shown in Figure 15.
The cooker is a simple vessel, with an agitator and some means of being heated. The lauter tub is a complex vessel with a specially perforated false bottom through which the mash is strained or filtered. It has variable speed rakes, with adjustable flights that can be raised and lowered. The husks of the malt serve as the filtration medium in the lauter tub. A cut-out diagram of a lauter tub is shown in Figure 16. The kettle is also complex. It is heated internally with steam passing through coils and a percolator, or directly with a flame; or externally in a steam boiler. Steam-heated kettles are shown in Figure 17
There are several systems of mashing, each with certain advantages and each setting the requirements for the brewhouse equipment. The most common system in the United States and most other countries is a double-mash system. The corn or rice is boiled in the cooker, with a small amount of malt to lower the viscosity. The main portion of malt is admitted to the mash tub, and, after a stand at about 50°C for proteolysis, the temperature is raised by
Figure 15. Brewhouse control panels. Source: Courtesy of Wittemann Hasselberg.
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