Beer (both lager and ale) is made in a brew house. A brew house consists of a grist mill, mash tun, copper, fermenter, fermenting tanks, conditioning tanks and, usually, a kegging or bottling line. In the case of a brew pub there is no bottling or kegging so the beer is drawn to the tap directly from the conditioning tanks.
The traditional brewery (building containing a brew house) was built on at least three levels. This was done to allow gravity to do much of the work of moving the grain, grist, mash, wort and spent grains. It was also important that the fermenting and conditioning tanks be in cellars where the temperature was optimum for the fermenting and conditioning the beer.
Ale can be fermented and conditioned at higher temperature than Lager, but both need cool stable temperatures to produce the best product.
The first step is to crush the grain into grist. The grain is rolled between metal rollers that are set a specific distance apart so that the crushing is done without turning the grain into flour. The grain should be just crushed to allow for optimum extraction of the fermentable sugars from the grain when hot water”liquor” is added to create the “mash.” The crushing also leaves the husk of the grain intact so that it can form a “bed” at the bottom of the large kettle where the mash is allowed to convert the starch in the grain into sugars and fermentable substances. This large metal container (often copper clad to efficiently distribute heat to the mash) is called the mash tun. When the mash is done, as much of the starch has been converted to sugars and fermentable substances, the liquid in the mash tun is drained through the bed of husks and spent grain in the bottom of the mash tun. This sweet liquid is now called “wort.”
Now hot water/liquor is sprayed on the grains that are left in the mash tun after the wort has been drained. This is done to extract as much fermentables as possible. This process is called “sparging”.
The crushed grain (grist) is shoveled into the mash tun where hot liquor (water), heated to approximately 175F, is added. This is the striking temperature and is a few degrees higher than the optimum mash temperature of about 150-152F. However, this is the best temperature for the enzymes found naturally in the grain to turn the starches, that make up most of the grain, into maltose (malt sugar) that is fermented by the yeast later in the process.
The temperature range of the mash creates the optimum environment for the enzyme diastase to convert the starch in the malted barley into sugar and other non-fermentable products. Lower temperatures usually produce more non-fermentables; higher temperatures mean less non-fermentable products. These non-fermentables give the finished beer “body”, or “mouth-feel”.
The following photograph is a look in a Mash Tun.:
At this point the sweet liquor, now called “wort”, is piped into a kettle where it is boiled, with the hops, until the proteins are extracted from the wort and the essential oils are extracted from the hops. The hopped wort is then quickly chilled to around 60F and piped into fermenting tanks.
The following photograph is a look at a Brew Kettle:
The fermenting tanks (traditionally open in a clean room) are filled with the cool wort and then, either top fermenting or bottom fermenting yeast is “pitched” (added) and fermentation takes place. Basically, this is when the yeast metabolizes the sugar in the wort and the resulting products are ethyl alcohol and carbon dioxide.
When almost all the fermentable sugar has been changed into ethyl alcohol and CO2 the brew is filtered and piped into special “finishing tanks”, where the yeast is allowed to finishing fermenting. These fermentation tanks are designed to withstand the pressure created as the yeast produced the CO2 necessary for effervescence in the beer.
In some commercial mass production breweries this step is bypassed and the fermented brew is injected with CO2. This process is much faster than “natural” conditioning.
The brew is then bottled, kegged, or, in the case of pub-breweries, drawn by taps in the bar, and served to customers.