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A 16th-century brewery


Brewing is the production of alcoholic beverages and alcohol fuel through fermentation. The term is used for the production of beer, although the word "brewing" is also used to describe the fermentation process used to create wine and mead. It can also refer to the process of producing sake and soy sauce. "Brewing" is also sometimes used to refer to any chemical mixing process.

Brewing specifically refers to the process of steeping, such as with tea and water, and extraction, usually through heat. Wine and cider technically aren't brewed, rather vinted, as the entire fruit is pressed, and then the liquid extracted. Mead isn't technically brewed, as heating often isn't used in the mixing process, and the honey is used entirely, as opposed to being heated with water, and then discarded, as are hops and barley in beer, and or tea leaves for tea, and coffee beans for coffee. Spices could technically be brewed into a mead though.

Brewing has a very long history, and archeological evidence suggests that this technique was used in ancient Egypt. Descriptions of various beer recipes can be found in Sumerian writings, some of the oldest known writing of any sort.

The brewing industry is part of most western economies.

Brewing beer

All beers are brewed using a process based on a simple formula. Key to the process is malted grain—depending on the region, traditionally barley, wheat or sometimes rye. (When malting rye, due care must be taken to prevent ergot poisoning (ergotism), as rye is particularly prone to be infected by this toxic fungus.)

Malt is made by allowing a grain to germinate, after which it is then dried in a kiln and sometimes roasted. The germination process creates a number of enzymes, notably α-amylase and β-amylase, which convert the starch in the grain into sugar. Depending on the amount of roasting, the malt will take on a dark colour and strongly influence the colour and flavour of the beer.

The malt is crushed to break apart the grain kernels, expose the cotyledon which contains the majority of the carbohydrates and sugars, increase their surface area, and separate the smaller pieces from the husks. The resulting grist is mixed with heated water in a vat called a "mash tun" for a process known as "mashing". During this process, natural enzymes within the malt break down much of the starch into sugars which play a vital part in the fermentation process. Mashing usually takes 1 to 2 hours, and during this time various temperature rests (waiting periods) activate different enzymes depending upon the type of malt being used, its modification level, and the desires of the brewmaster. The activity of these enzymes convert the starches of the grains to dextrins and then to fermentable sugars such as maltose. In smaller breweries, the mash tun generally contains a slotted "false bottom" or other form of manifold which acts as a strainer allowing for the separation of the liquid from the grain.

A mash rest from activates various proteases, which break down proteins that might otherwise cause the beer to be hazy. But care is of the essence since the head on beer is also composed primarily of proteins, so too aggressive a protein rest can result in a beer that cannot hold a head. This rest is generally used only with undermodified (i.e. undermalted) malts which are decreasingly popular in Germanymarker and the Czech Republicmarker, or non-malted grains such as corn and rice, which are widely used in North American beers. A mash rest at activates β-glucanase, which breaks down gummy β-glucans in the mash, making the sugars flow out more freely later in the process. In the modern mashing process, commercial fungal based β-glucanase may be added as a supplement. Finally, a mash rest temperature of is used to convert the starches in the malt to sugar, which is then usable by the yeast laterin the brewing process. Doing the latter rest at the lower end of the range favors β-amylase enzymes, producing more low-order sugars like maltotriose, maltose, and glucose which are more fermentable by the yeast. This in turn creates a beer lower in body and higher in alcohol. A rest closer to the higher end of the range favors α-amylase enzymes, creating more higher-order sugars and dextrins which are less fermentable by the yeast, so a fuller-bodied beer with less alcohol is the result. Duration and pH variances also affect the sugar composition of the resulting wort.

After the mashing, the resulting liquid is strained from the grains in a process known as lautering. Prior to lautering, the mash temperature may be raised to about 75 °C (165-170 °F) (known as a mashout) to deactivate enzymes. Additional water may be sprinkled on the grains to extract additional sugars (a process known as sparging).

At this point the liquid is known as wort. The wort is moved into a large tank known as a "copper" or kettle where it is boiled with hops and sometimes other ingredients such as herbs or sugars. The boiling process serves to terminate enzymatic processes, precipitate proteins, isomerize hop resins, concentrate and sterilize the wort. Hops add flavour, aroma and bitterness to the beer. At the end of the boil, the hopped wort settles to clarify it in a vessel called a "whirl-pool" and the clarified wort is then cooled.

The wort is then moved into a "fermentation vessel" where yeast is added or "pitched" with it. The yeast converts the sugars from the malt into alcohol, carbon dioxide and other components through a process called fermentation. After one to three weeks, the fresh (or "green") beer is run off into conditioning tanks. After conditioning for a week to several months, the beer is often filtered to remove yeast and particulates. The "bright beer" is then ready for serving or packaging.

There are four main families of beer styles determined by the variety of yeast used in their brewing.

Ale (top-fermenting yeasts)

Ale yeasts ferment at warmer temperatures between , and occasionally as high as . Pure ale yeasts form a foam on the surface of the fermenting beer, because of this they are often referred to as top-fermenting yeast—though there are some British ale yeast strains that settle at the bottom. Ales are generally ready to drink within three weeks after the beginning of fermentation, however, some styles benefit from additional aging for several months or years. Ales range in colour from very pale to an opaque black. England is best known for its variety of ales. Ale yeasts can be harvested from the primary fermenter, and stored in the refrigerator or freezer.

Lager (bottom-fermenting yeasts)

While the nature of yeast was not fully understood until Emil Hansen of the Carlsberg brewery in Denmarkmarker isolated a single yeast cell in the 1800s, brewers in Bavariamarker had for centuries been selecting these cold-fermenting lager yeasts by storing (lagern) their beers in cold alpine caves. The process of natural selection meant that the wild yeasts that were most cold tolerant would be the ones that would remain actively fermenting in the beer that was stored in the caves. Some of these Bavarian yeasts were brought back to the Carlsberg brewery around the time that Hansen did his famous work.

Traditionally, ales and lagers have been differentiated as being either a top fermentor or bottom fermentor, respectively. But, as the years go by homebrewers and microbrewers alike keep pushing the envelope of the craft these distinctions are beginning to blur. The main difference between the two is lager yeast's ability to process raffinose. Raffinose is a trisaccharide composed of galactose, fructose, and glucose.

Lager yeast tends to collect at the bottom of the fermenter and is often referred to as bottom-fermenting yeast. Lager is fermented at much lower temperatures, around , compared to typical ale fermentation temperatures of . It is then stored for 30 days or longer close to freezing point. During storage, the beer mellows and flavours become smoother. Sulfur components developed during fermentation dissipate. The popularity of lager was a major factor that led to the rapid introduction of refrigeration in the early 1900s.

Today, lagers represent the vast majority of beers produced, the most famous being a light lager called Pilsner which originated in Pilsenmarker, Czech Republicmarker (Plzeň in Czech). It is a common misconception that all lagers are light in color—lagers can range from very light to deep black, just like ales.

Beers of Spontaneous Fermentation (wild yeasts)

These beers are nowadays primarily only brewed around Brussels, Belgium. They are fermented by means of wild yeast strains that live in a part of the Zenne river which flows through Brussels. These beers are also called Lambic beers. However, with the advent of yeast banks and the National Collection of Yeast Cultures, brewing these beers, although not through spontaneous fermentation, is possible anywhere.

Beers of mixed origin

These beers are blends of spontaneous fermentation or they are ales/lagers which are also fermented by wild yeasts.

Ingredients

The basic ingredients of beer are water; a starch source, such as malted barley, able to be fermented (converted into alcohol); a brewer's yeast to produce the fermentation; and a flavouring such as hops. A mixture of starch sources may be used, with a secondary starch source, such as maize (corn), rice or sugar, often being termed an adjunct, especially when used as a lower-cost substitute for malted barley. Less widely used starch sources include millet, sorghum and cassava root in Africa, potato in Brazil, and agave in Mexico, among others. The amount of each starch source in a beer recipe is collectively called the grain bill.

Water

Beer is composed mostly of water. Regions have water with different mineral components; as a result, different regions were originally better suited to making certain types of beer, thus giving them a regional character. For example, Dublinmarker has hard water well suited to making stout, such as Guinness; while Pilzenmarker has soft water well suited to making pale lager, such as Pilsner Urquell. The waters of Burton in England contain gypsum, which benefits making pale ale to such a degree that brewers of pale ales will add gypsum to the local water in a process known as Burtonisation.

Starch source

The starch source in a beer provides the fermentable material and is a key determinant of the strength and flavour of the beer. The most common starch source used in beer is malted grain. Grain is malted by soaking it in water, allowing it to begin germination, and then drying the partially germinated grain in a kiln. Malting grain produces enzymes that convert starches in the grain into fermentable sugars. Different roasting times and temperatures are used to produce different colours of malt from the same grain. Darker malts will produce darker beers.

Nearly all beer includes barley malt as the majority of the starch. This is because of its fibrous husk, which is not only important in the sparging stage of brewing (in which water is washed over the mashed barley grains to form the wort), but also as a rich source of amylase, a digestive enzyme which facilitates conversion of starch into sugars. Other malted and unmalted grains (including wheat, rice, oats, and rye, and less frequently, corn and sorghum) may be used. In recent years, a few brewers have produced gluten-free beer made with sorghum with no barley malt for those who cannot consume gluten-containing grains like wheat, barley, and rye.

Hops

Flavouring beer is the sole major commercial use of hops. The flower of the hop bine (yes, that's bine, not vine) is used as a flavouring and preservative agent in nearly all beer made today. The flowers themselves are often called "hops".
Hops were used by monastery breweries, such as Corvey in Westphalia, Germany, from 822 AD, though the date normally given for widespread cultivation of hops for use in beer is the thirteenth century. Before the thirteenth century, and until the sixteenth century, during which hops took over as the dominant flavouring, beer was flavoured with other plants; for instance, Glechoma hederacea. Combinations of various aromatic herbs, berries, and even ingredients like wormwood would be combined into a mixture known as gruit and used as hops are now used. Some beers today, such as Fraoch' by the Scottish Heather Ales company and Cervoise Lancelot by the French Brasserie-Lancelot company, use plants other than hops for flavouring.

Hops contain several characteristics that brewers desire in beer. Hops contribute a bitterness that balances the sweetness of the malt; the bitterness of beers is measured on the International Bitterness Units scale. Hops contribute floral, citrus, and herbal aromas and flavours to beer. Hops have an antibiotic effect that favours the activity of brewer's yeast over less desirable microorganisms, and hops aids in "head retention", the length of time that a foamy head created by carbonation will last. The acidity of hops is a preservative.

Yeast

Yeast is the microorganism that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces alcohol and carbon dioxide, and thereby turns wort into beer. In addition to fermenting the beer, yeast influences the character and flavour.The dominant types of yeast used to make beer are ale yeast (Saccharomyces cerevisiae) and lager yeast (Saccharomyces uvarum); their use distinguishes ale and lager. Brettanomyces ferments lambics, and Torulaspora delbrueckii ferments Bavarian weissbier.Before the role of yeast in fermentation was understood, fermentation involved wild or airborne yeasts. A few styles such as lambics rely on this method today, but most modern fermentation adds pure yeast cultures.

Clarifying agent

Some brewers add one or more clarifying agents to beer, which typically precipitate (collect as a solid) out of the beer along with protein solids and are found only in trace amounts in the finished product. This process makes the beer appear bright and clean, rather than the cloudy appearance of ethnic and older styles of beer such as wheat beers.

Examples of clarifying agents include isinglass, obtained from swimbladders of fish; Irish moss, a seaweed; kappa carrageenan, from the seaweed Kappaphycus cottonii; Polyclar (artificial); and gelatin. If a beer is marked "suitable for Vegans", it was clarified either with seaweed or with artificial agents.

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 with rests at certain temperatures (notably 45°C, 62°C and 73°C) 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.

Lauter tun

A lauter tun is a special container used in all-grain brewing for separating the sweet wort from the spent grains (malted barley etc.). In essence it is a tank with holes in the bottom small enough to hold back the large bits of grist and hulls. The bed of grist that settles on it is the actual filter. It can be as simple as a plastic bucket with holes in the bottom. Commercial lauter tuns have provision for rotating rakes or knives to cut into the bed of grist to maintain good flow. The knives can be turned so they push the grain, a feature used to drive the spent grain out of the vessel.

Mash filter

A mash filter is a plate-and-frame filter. The empty frames contain the mash, including the spent grains, and have a capacity of around one hectoliter. The plates contain a support structure for the filter cloth. The plates, frames, and filter cloths are arranged in a carrier frame like so: frame, cloth, plate, cloth, with plates at each end of the structure. Newer mash filters have bladders that can press the liquid out of the grains between spargings. The grain does not act like a filtration medium in a mash filter.

Strainmaster

A Strainmaster is a device invented at Anheuser Buschmarker. It separates the wort by allowing it to flow into horizontal slotted tubes. As with a lauter tun, the actual filtration is carried out by the spent grain.

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.

Boiling equipment

The simplest boil kettles are direct-fired, with a burner underneath. These can produce a vigorous and favourable boil, but are also apt to scorch the wort where the flame touches the kettle, causing caramelization and making clean up difficult.

Most breweries use a steam-fired kettle, which uses steam jackets in the kettle to boil the wort. The steam is delivered under pressure by an external boiler.

State-of-the-art breweries today use many interesting boiling methods, all of which achieve a more intense boiling and a more complete realisation of the goals of boiling.

Many breweries have a boiling unit outside of the kettle, sometimes called a calandria, through which wort is pumped. The unit is usually a tall, thin cylinder, with many tubes upwards through it. These tubes provide an enormous surface area on which vapor bubbles can nucleate, and thus provides for excellent volitization. The total volume of wort is circulated seven to twelve times an hour through this external boiler, ensuring that the wort is evenly boiled by the end of the boil. The wort is then boiled in the kettle at atmospheric pressure, and through careful control the inlets and outlets on the external boiler, an overpressure can be achieved in the external boiler, raising the boiling point by a few Celsius degrees. Upon return to the boil kettle, a vigorous vaporization occurs. The higher temperature due to increased vaporization can reduce boil times up to 30%. External boilers were originally designed to improve performance of kettles which did not provide adequate boiling effect, but havesince been adopted by the industry as a sole means of boiling wort.

Modern brewhouses can also be equipped with internal calandria, which requires no pump. It works on basically the same principle as external units, but relies on convection to move wort through the boiler. This can prevent overboiling, as a deflector above the boiler reduces foaming, and also reduces evaporation. Internal calandria are generally difficult to clean.

Whirlpooling

At the end of the boil, the wort is set into a whirlpool. The so-called teacup effect forces the denser solids (coagulated proteins, vegetable matter from hops) into a cone in the center of the whirlpool tank.

In most large breweries, there is a separate tank for whirlpooling. These tanks have a large diameter to encourage settling, a flat bottom, a tangential inlet near the bottom of the whirlpool, and an outlet on the bottom near the outer edge of the whirlpool. A whirlpool should have no internal protrusions that might slow down the rotation of the liquid. The bottom of the whirlpool is often slightly sloped towards the outlet. Newer whirlpools often have "Denk rings" suspended in the middle of the whirlpool. These rings are aligned horizontally and have about 75% of the diameter of the whirlpool. The Denk rings prevent the formation of secondary eddies in the whirlpool, encouraging the formation of a cohesive trub cone in the middle of the whirlpool.Smaller breweries often use the brewkettle as a whirlpool.In the United Kingdom, it is common practice to use a device known as a hopback to clear the green wort (green wort is wort to which yeast has not yet been added). This device has the same effect as, but operates in a completely different manner than, a whirlpool. The two devices are often confused but are in function, quite different. While a whirlpool functions through the use of centrifugal forces, a hopback uses a layer of fresh hop flowers in a confined space to act as a filter bed to remove trub (pronounced tr-oo-b, tr-uh-b in the UK). Furthermore, while a whirlpool is only useful for the removal of pelleted hops (as flowers don't tend to separate as easily), hopbacks are generally used only for the removal of whole flower hops (as the particles left by pellets tend to make it through the hopback.)

In homebrewing, where a brewer has the power to lift the entire stock and manipulate it by hand; the process of trub removal (the process addressed by the whirlpool and hopback) is generally accomplished by simply allowing the trub to settle to the bottom of the brew kettle and slowly decanting the wort from the top so as not to disturb the thin layer of trub. Siphoning may also be employed but this is rare.

Wort cooling

After the whirlpool, the wort must be brought down to fermentation temperatures (20-26°Celsius) before yeast is added. In modern breweries this is achieved through a plate heat exchanger. A plate heat exchanger has many ridged plates, which form two separate paths. The wort is pumped into the heat exchanger, and goes through every other gap between the plates. The cooling medium, usually water, goes through the other gaps. The ridges in the plates ensure turbulent flow. A good heat exchanger can drop 95 °C wort to 20 °C while warming the cooling medium from about 10 °C to 80 °C. The last few plates often use a cooling medium which can be cooled to below the freezing point, which allows a finer control over the wort-out temperature, and also enables cooling to around 10 °C. After cooling, oxygen is often dissolved into the wort to revitalize the yeast and aid its reproduction.

Energy Recovery

While boiling, it is useful to recover some of the energy used to boil the wort. On its way out of the brewery, the steam created during the boil is passed over a coil through which unheated water flows. By adjusting the rate of flow, the output temperature of the water can be controlled. This is also often done using a plate heat exchanger. The water is then stored for later use in the next mash, in equipment cleaning, or wherever necessary.

Another common method of energy recovery takes place during the wort cooling. When cold water is used to cool the wort in a heat exchanger, the water is significantly warmed. In an efficient brewery, cold water is passed through the heat exchanger at a rate set to maximize the water's temperature upon exiting. This now-hot water is then stored in a hot water tank.

Fermenting

Modern fermentation tanks


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, which 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.
Krausen in an English brewery's fermentation tank
Open 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 krausen 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. Thiscold 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.

Sheet (pad) filters

These filters use pre-made media and are relatively straightforward. The sheets are manufactured to allow only particles smaller than a given size through, and the brewer is free to choose how finely to filter the beer. The sheets are placed into the filtering frame, sterilized (with hot water, for example) and then used to filter the beer. The sheets can be flushed if the filter becomes blocked, and usually the sheets are disposable and are replaced between filtration sessions. Often the sheets contain powdered filtration media to aid in filtration.

It should be kept in mind that pre-made filters have two sides. One with loose holes, and the other with tight holes. Flow goes from the side with loose holes to the side with the tight holes, with the intent that large particles get stuck in the large holes while leaving enough room around the particles and filter medium for smaller particles to go through and get stuck in tighter holes.

Sheets are sold in nominal ratings, and typically 90% of particles larger than the nominal rating are caught by the sheet.

Kieselguhr filters

Filters that use a powder medium are considerably more complicated to operate, but can filter much more beer before needing to be regenerated. Common media include diatomaceous earth, or kieselguhr, and perlite.

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.

Secondary fermentation

Secondary fermentation is an additional fermentation after the first or primary fermentation. For the secondary fermentation, the beer is transferred to a second fermenter, so that it is no longer exposed to the dead yeast and other debris (also known as "trub") that have settled to the bottom of the primary fermenter. This prevents the formation of unwanted flavors and harmful compounds such as acetylaldehydes, which are commonly blamed for hangovers.

Among homebrewers, secondary fermentation is a common source of discussion and debate. Some believe that the majority of homebrewed beers can simply be fermented in a single fermenter for approximately two weeks and then bottled, making secondary fermentation unnecessary. However, secondary fermentation is a necessary step when brewing beers with long fermentation times, such as lagers. Many homebrewers use secondary fermentation as a way of Conditioning, to enhance both the flavor and appearance of the beer.

During secondary fermentation, most of the remaining yeast will settle to the bottom of the second fermenter, yielding a less hazy product. Some beers may have three fermentations, the third being the bottle fermentation.

Bottle fermentation
See Bottle conditioning.
Most homebrewed beers undergo a fermentation in the bottle, giving natural carbonation. This may be a second or third fermentation. They are bottled with a viable yeast population in suspension. If there is no residual fermentable sugar left, sugar may be added. The resulting fermentation generates CO2 which is trapped in the bottle, remaining in solution and providing natural carbonation.

Cask conditioning
See Cask ale.
Cask ale or cask-conditioned beer is the term for unfiltered and unpasteurised beer which is conditioned (including secondary fermentation) and served from a cask without additional nitrogen or carbon dioxide pressure.

See also



References

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  10. I. Hornsey, A History of Beer and Brewing (Rsc Paperbacks), Washington D.C.: Royal Society of Chemistry, 2004, Print.


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