THE BREWING PROCESS

The brewing process is typically divided into 7 steps: mashing, lautering, boiling, fermenting, conditioning, filtering, and filling.

Today, many simplified brewing systems exist which can be used at home or in restaurants. These homebrewing systems are often employed for ease of use, although some people still prefer to do the entire brewing process themselves.

Mashing
Mashing is the process of combining a mix of milled grain, known as the grist (typically malted barley with supplementary grains as maize, sorghum, rye or wheat; in a ratio of 90-10 up to 50-50), with water, and heating this mixture up which rests at certain temperatures (notably 45°C, 62°C and 73°C [3][4]) to allow enzymes in the malt to break down the starch in the grain into sugars, typically maltose.

Wort Separation
Wort separation is the separation of the wort containing the sugar extracted during mashing from the spent grain. It can be carried out in a mash tun outfitted with a false bottom, a lauter tun, a special-purpose wide vessel with a false bottom and rotating cutters to facilitate flow, a mash filter, a plate-and-frame filter designed for this kind of separation, or in a Strainmaster. Most separation processes have two stages: first wort run-off, during which the extract is separated in an undiluted state from the spent grains, and Sparging, in which extract which remains with the grains is rinsed off with hot water.

Boiling
Boiling the malt extracts, called wort, ensures its sterility, and thus prevents a lot of infections. During the boil hops are added, which contribute bitterness, flavour, and aroma compounds to the beer, and, along with the heat of the boil, causes proteins in the wort to coagulate and the pH of the wort to fall. Finally, the vapours produced during the boil volatilise off flavours, including dimethyl sulfide precursors.

The boil must be conducted so that it is even and intense. The boil lasts between 50 and 120 minutes, depending on its intensity, the hop addition schedule, and volume of wort the brewer expects to evaporate.

Fermenting
After the wort is cooled and aerated — usually with sterile air — yeast is added to it, and it begins to ferment. It is during this stage that sugars won from the malt are metabolized into alcohol and carbon dioxide, and the product can be called beer for the first time. Fermentation happens in tanks which come in all sorts of forms, from enormous tanks which can look like storage silos, to five gallon glass carboys in a homebrewer's closet.

Most breweries today use cylindro-conical vessels, or CCVs, have a conical bottom and a cylindrical top. The cone's aperture is typically around 60°, an angle that will allow the yeast to flow towards the cones apex, but is not so steep as to take up too much vertical space. CCVs can handle both fermenting and conditioning in the same tank. At the end of fermentation, the yeast and other solids which have fallen to the cones apex can be simply flushed out a port at the apex.

Kraeusen in an English brewery's fermentation tankOpen fermentation vessels are also used, often for show in brewpubs, and in Europe in wheat beer fermentation. These vessels have no tops, which makes harvesting top fermenting yeasts very easy. The open tops of the vessels make the risk of infection greater, but with proper cleaning procedures and careful protocol about who enters fermentation chambers, the risk can be well controlled.

Fermentation tanks are typically made of stainless steel. If they are simple cylindrical tanks with beveled ends, they are arranged vertically, as opposed to conditioning tanks which are usually laid out horizontally. Only a very few breweries still use wooden vats for fermentation as wood is difficult to keep clean and infection-free and must be repitched more or less yearly.

After high kraeusen a bung device (German: Spundapparat) is often put on the tanks to allow the CO2 produced by the yeast to naturally carbonate the beer. This bung device can be set to a given pressure to match the type of beer being produced. The more pressure the bung holds back, the more carbonated the beer becomes.

Conditioning
When the sugars in the fermenting beer have been almost completely digested, the fermentation slows down and the yeast starts to settle to the bottom of the tank. At this stage, the beer is cooled to around freezing, which encourages settling of the yeast, and causes proteins to coagulate and settle out with the yeast. If a separate conditioning tank is to be used, it is at this stage that the beer will be transferred into one. Unpleasant flavors such as phenolic compounds become insoluble in the cold beer, and the beer's flavor becomes smoother. During this time pressure is maintained on the tanks to prevent the beer from going flat.

A similar technique is used in home brewing, wherein the beer is simply siphoned into another vessel (usually a carboy), leaving the now-dormant yeast and other sediment behind. The batch is then sometimes refrigerated for the aforementioned benefits.

Conditioning can take from 2 to 4 weeks, sometimes longer, depending on the type of beer. Additionally lagers, at this point, are aged at near freezing temperatures for 1-6 months depending on style. This cold aging serves to reduce sulfur compounds produced by the bottom-fermenting yeast and to produce a cleaner tasting final product with fewer esters.

If the fermentation tanks have cooling jackets on them, as opposed to the whole fermentation cellar being cooled, conditioning can take place in the same tank as fermentation. Otherwise separate tanks (in a separate cellar) must be employed. This is where aging occurs.

Filtering

Filtering the beer stabilizes the flavour, and gives beer its polished shine and brilliance. Not all beer is filtered. When tax determination is required by local laws, it is typically done at this stage in a calibrated tank.

Filters come in many types. Many use pre-made filtration media such as sheets or candles, while others use a fine powder made of, for example, diatomaceous earth, also called kieselguhr, which is introduced into the beer and recirculated past screens to form a filtration bed.

Filters range from rough filters that remove much of the yeast and any solids (e.g. hops, grain particles) left in the beer, to filters tight enough to strain color and body from the beer. Normally used filtration ratings are divided into rough, fine and sterile. Rough filtration leaves some cloudiness in the beer, but it is noticeably clearer than unfiltered beer. Fine filtration gives a glass of beer that you could read a newspaper through, with no noticeable cloudiness. Finally, as its name implies, sterile filtration is fine enough that almost all microorganisms in the beer are removed during the filtration process.

Packaging
Packaging is putting the beer into the containers in which it will leave the brewery. Typically this means in bottles, aluminium cans and kegs, but it might include bulk tanks for high-volume customers.