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Brewing is the production of
beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...
by
steeping Steeping is the soaking of an organic solid, such as leaves, in a liquid (usually water) to extract flavours or to soften it. The specific process of teas being prepared for drinking by leaving the leaves in heated water to release the flavour a ...
a
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
source (commonly
cereal A cereal is any Poaceae, grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, Cereal germ, germ, and bran. Cereal Grain, grain crops are grown in greater quantit ...
grains, the most popular of which is
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
) in water and
fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
the resulting sweet liquid with
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...
. It may be done in a
brewery A brewery or brewing company is a business that makes and sells beer. The place at which beer is commercially made is either called a brewery or a beerhouse, where distinct sets of brewing equipment are called plant. The commercial brewing of be ...
by a commercial brewer, at home by a
homebrewer Homebrewing is the brewing of beer or other alcoholic beverages on a small scale for personal, non-commercial purposes. Supplies, such as kits and fermentation tanks, can be purchased locally at specialty stores or online. Beer was brewed dom ...
, or communally. Brewing has taken place since around the 6th millennium BC, and archaeological evidence suggests that emerging civilizations, including ancient Egypt and
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...
, brewed beer. Since the nineteenth century the
brewing industry Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and Fermentation (food), fermentation of starches, mainl ...
has been part of most western economies. The basic ingredients of beer are water and a fermentable starch source such as
malted barley Malt is germinated cereal grain that has been dried in a process known as "malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, whis ...
. Most beer is fermented with a
brewer's yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitu ...
and flavoured with
hops Hops are the flowers (also called seed cones or strobiles) of the hop plant ''Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to whi ...
. Less widely used starch sources include
millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets al ...
,
sorghum ''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many othe ...
and
cassava ''Manihot esculenta'', common name, commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively ...
. Secondary sources (
adjuncts In brewing, adjuncts are unmalted grains (such as corn, rice, rye, oats, barley, and wheat) or grain products used in brewing beer which supplement the main mash ingredient (such as malted barley). This is often done with the intention of cut ...
), such as maize (corn), rice, or sugar, may also be used, sometimes to reduce cost, or to add a feature, such as adding wheat to aid in retaining the foamy head of the beer. The most common starch source is ground cereal or "grist" - the proportion of the starch or cereal ingredients in a beer recipe may be called grist, grain bill, or simply
mash ingredients Mash ingredients, mash bill, mashbill, or grain bill are the materials that brewers use to produce the wort that they then ferment into alcohol. Mashing is the act of creating and extracting fermentable and non-fermentable sugars and flavor co ...
. Steps in the brewing process include
malting Malting is the process of steeping, germinating and drying grain to convert it into malt. The malt is mainly used for brewing or whisky making, but can also be used to make malt vinegar or malt extract. Various grains are used for malting, most ...
, milling,
mashing In brewing and distilling, mashing is the process of combining a mix of ground grains – typically malted barley with supplementary grains such as corn, sorghum, rye, or wheat – known as the "grain bill" with water and then heating the mixtu ...
,
lautering Lautering () is the beer brewing process that separates the mash into clear liquid wort and residual grain. Lautering usually consists of three steps: mashout, recirculation, and sparging. Mashout Mashout is the term for raising the temperature ...
,
boiling Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. Th ...
,
fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
,
conditioning Conditioning may refer to: Science, computing, and technology * Air conditioning, the removal of heat from indoor air for thermal comfort ** Automobile air conditioning, air conditioning in a vehicle ** Ice storage air conditioning, air condition ...
,
filtering Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
, and
packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a co ...
. There are three main fermentation methods: warm,
cool Cool commonly refers to: * Cool, a moderately low temperature * Cool (aesthetic), an aesthetic of attitude, behavior, and style Cool or COOL may also refer to: Economics * Country of origin labelling * mCOOL - US consumer legislation to enforc ...
and
spontaneous Spontaneous may refer to: * Spontaneous abortion * Spontaneous bacterial peritonitis * Spontaneous combustion * Spontaneous declaration * Spontaneous emission * Spontaneous fission * Spontaneous generation * Spontaneous human combustion * Spontan ...
. Fermentation may take place in an open or closed fermenting vessel; a secondary fermentation may also occur in the
cask A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, u ...
or
bottle A bottle is a narrow-necked container made of an impermeable material (such as glass, plastic or aluminium) in various shapes and sizes that stores and transports liquids. Its mouth, at the bottling line, can be sealed with an internal stopp ...
. There are several additional
brewing methods Beer is produced through steeping a sugar source (commonly Malted cereal grains) in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BC, and archeological evidence suggests that this technique was ...
, such as
Burtonisation Beer is produced through steeping a sugar source (commonly Malted cereal grains) in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BC, and archeological evidence suggests that this technique was ...
, double dropping, and
Yorkshire Square Beer is produced through steeping a sugar source (commonly Malted cereal grains) in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BC, and archeological evidence suggests that this technique was ...
, as well as post-fermentation treatment such as
filtering Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
, and barrel-ageing.


History

Brewing has taken place since around the 6th millennium BC, and archaeological evidence suggests emerging civilizations including ancient Egypt and
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...
brewed beer. Descriptions of various beer recipes can be found in
cuneiform Cuneiform is a logo-syllabic script that was used to write several languages of the Ancient Middle East. The script was in active use from the early Bronze Age until the beginning of the Common Era. It is named for the characteristic wedge-sha ...
(the oldest known writing) from ancient
Mesopotamia Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...
. In Mesopotamia the brewer's craft was the only profession which derived social sanction and divine protection from female deities/goddesses, specifically:
Ninkasi Ninkasi was the Mesopotamian goddess of beer and brewing. It is possible that in the first millennium BCE she was known under the variant name Kurunnītu, derived from a term referring to a type of high quality beer. She was associated with both ...
, who covered the production of beer,
Siris Siris may refer to: Geography *Siris (Magna Graecia), an ancient city in southern Italy *Serres, a city in Macedonia called Siris by the Ancient Greek historian Herodotus * Siris, Sardinia, an Italian commune *Sinni (river) (Siris in Latin), Italy ...
, who was used in a metonymic way to refer to beer, and
Siduri Siduri, or more accurately Šiduri (Shiduri), is a character in the ''Epic of Gilgamesh''. She is described as an alewife. The oldest preserved version of the composition to contain the episode involving her leaves her nameless, and in the later s ...
, who covered the enjoyment of beer. In pre-industrial times, and in developing countries, women are frequently the main brewers. As almost any cereal containing certain sugars can undergo
spontaneous fermentation Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley) in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer, ...
due to wild yeasts in the air, it is possible that beer-like beverages were independently developed throughout the world soon after a tribe or culture had domesticated cereal. Chemical tests of ancient pottery jars reveal that beer was produced as far back as about 7,000 years ago in what is today Iran. This discovery reveals one of the earliest known uses of fermentation and is the earliest evidence of brewing to date. In Mesopotamia, the oldest evidence of beer is believed to be a 6,000-year-old Sumerian tablet depicting people drinking a beverage through reed straws from a
communal bowl A bowl is a typically round dish or container generally used for preparing, serving, or consuming food. The interior of a bowl is characteristically shaped like a spherical cap, with the edges and the bottom forming a seamless curve. This makes ...
. A 3900-year-old Sumerian poem honouring Ninkasi, the patron goddess of brewing, contains the oldest surviving beer recipe, describing the production of
beer Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from ce ...
from barley via bread. The invention of bread and beer has been argued to be responsible for humanity's ability to develop technology and build civilization. The earliest chemically confirmed barley beer to date was discovered at
Godin Tepe Godin Tepe is an archaeological site in western Iran, located in the valley of Kangavar in Kermanshah Province. Discovered in 1961, the site was excavated from 1965 to 1973 by a Canadian expedition headed by T. Cuyler Young Jr. and sponsored by ...
in the central
Zagros Mountains The Zagros Mountains ( ar, جبال زاغروس, translit=Jibal Zaghrus; fa, کوه‌های زاگرس, Kuh hā-ye Zāgros; ku, چیاکانی زاگرۆس, translit=Çiyakani Zagros; Turkish: ''Zagros Dağları''; Luri: ''Kuh hā-ye Zāgro ...
of Iran, where fragments of a jug, at least 5,000 years old was found to be coated with
beerstone Calcium oxalate (in archaic terminology, oxalate of lime) is a calcium salt of oxalic acid with the chemical formula . It forms hydrates , where ''n'' varies from 1 to 3. Anhydrous and all hydrated forms are colorless or white. The monohydrate ...
, a by-product of the brewing process. Beer may have been known in
Neolithic Europe The European Neolithic is the period when Neolithic (New Stone Age) technology was present in Europe, roughly between 7000 BCE (the approximate time of the first farming societies in Greece) and c.2000–1700 BCE (the beginning of the Bronze Age ...
as far back as 5,000 years ago, and was mainly brewed on a domestic scale. Ale produced before the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
continued to be made and sold on a domestic scale, although by the 7th century AD beer was also being produced and sold by European
monasteries A monastery is a building or complex of buildings comprising the domestic quarters and workplaces of monastics, monks or nuns, whether living in communities or alone (hermits). A monastery generally includes a place reserved for prayer which ...
. During the Industrial Revolution, the production of beer moved from
artisan An artisan (from french: artisan, it, artigiano) is a skilled craft worker who makes or creates material objects partly or entirely by hand. These objects may be functional or strictly decorative, for example furniture, decorative art ...
al manufacture to industrial manufacture, and domestic manufacture ceased to be significant by the end of the 19th century. The development of
hydrometer A hydrometer or lactometer is an instrument used for measuring density or relative density of liquids based on the concept of buoyancy. They are typically calibrated and graduated with one or more scales such as specific gravity. A hydrometer ...
s and
thermometer A thermometer is a device that temperature measurement, measures temperature or a temperature gradient (the degree of hotness or coldness of an object). A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb of a merc ...
s changed brewing by allowing the brewer more control of the process, and greater knowledge of the results. Today, the brewing industry is a global business, consisting of several dominant
multinational companies A multinational company (MNC), also referred to as a multinational enterprise (MNE), a transnational enterprise (TNE), a transnational corporation (TNC), an international corporation or a stateless corporation with subtle but contrasting senses, i ...
and many thousands of smaller producers ranging from
brewpub Craft beer is a beer that has been made by craft breweries. They produce smaller amounts of beer, typically less than large breweries, and are often independently owned. Such breweries are generally perceived and marketed as having an emphasis o ...
s to regional breweries. More than 133 billion litres (35 billion gallons) are sold per year—producing total global revenues of $294.5 billion (£147.7 billion) in 2006.


Ingredients

The basic ingredients of beer are water; a starch source, such as
malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, wh ...
ed
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
, able to be fermented (converted into alcohol); a
brewer's yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitu ...
to produce the fermentation; and a flavouring, such as
hops Hops are the flowers (also called seed cones or strobiles) of the hop plant ''Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to whi ...
,alabev.com
''The Ingredients of Beer''. Retrieved 29 September 2008
to offset the sweetness of the malt. A mixture of starch sources may be used, with a secondary saccharide, such as maize (corn), rice, or sugar, these often being termed
adjuncts In brewing, adjuncts are unmalted grains (such as corn, rice, rye, oats, barley, and wheat) or grain products used in brewing beer which supplement the main mash ingredient (such as malted barley). This is often done with the intention of cut ...
, especially when used as a lower-cost substitute for malted barley.beer-brewing.com
Ted Goldammer, ''The Brewers Handbook'', Chapter 6 – Beer Adjuncts, Apex Pub (1 January 2000), . Retrieved 29 September 2008
Less widely used starch sources include
millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets al ...
,
sorghum ''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many othe ...
, and
cassava ''Manihot esculenta'', common name, commonly called cassava (), manioc, or yuca (among numerous regional names), is a woody shrub of the spurge family, Euphorbiaceae, native to South America. Although a perennial plant, cassava is extensively ...
root in Africa, potato in Brazil, and
agave ''Agave'' (; ; ) is a genus of monocots native to the hot and arid regions of the Americas and the Caribbean, although some ''Agave'' species are also native to tropical areas of North America, such as Mexico. The genus is primarily known for ...
in Mexico, among others. The most common starch source is ground cereal or "grist" - the proportion of the starch or cereal ingredients in a beer recipe may be called grist, grain bill, or simply
mash ingredients Mash ingredients, mash bill, mashbill, or grain bill are the materials that brewers use to produce the wort that they then ferment into alcohol. Mashing is the act of creating and extracting fermentable and non-fermentable sugars and flavor co ...
. ;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,
Dublin Dublin (; , or ) is the capital and largest city of Republic of Ireland, Ireland. On a bay at the mouth of the River Liffey, it is in the Provinces of Ireland, province of Leinster, bordered on the south by the Dublin Mountains, a part of th ...
has
hard water Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, bicarbo ...
well suited to making
stout Stout is a dark, top-fermented beer with a number of variations, including dry stout, oatmeal stout, milk stout, and imperial stout. The first known use of the word ''stout'' for beer, in a document dated 1677 found in the Egerton Manuscript ...
, such as
Guinness Guinness () is an Irish dry stout that originated in the brewery of Arthur Guinness at St. James's Gate, Dublin, Ireland, in 1759. It is one of the most successful alcohol brands worldwide, brewed in almost 50 countries, and available in ove ...
; while Pilsen has soft water well suited to making
pale lager Pale lager is a very pale-to-golden-colored lager beer with a well- attenuated body and a varying degree of noble hop bitterness. The brewing process for this beer developed in the mid-19th century, when Gabriel Sedlmayr took pale ale brewing ...
, such as
Pilsner Urquell Pilsner Urquell (; cs, Plzeňský prazdroj ) is a lager beer brewed by the Pilsner Urquell Brewery in Plzeň (German name: Pilsen), Czech Republic. Pilsner Urquell was the world's first pale lager, and its popularity meant it was much copied, ...
. The waters of Burton in England contain
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...
, which benefits making
pale ale Pale ale is a golden to amber coloured beer style brewed with pale malt. The term first appeared around 1703 for beers made from malts dried with high-carbon coke, which resulted in a lighter colour than other beers popular at that time. Diff ...
to such a degree that brewers of pale ales will add gypsum to the local water in a process known as
Burtonisation Beer is produced through steeping a sugar source (commonly Malted cereal grains) in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BC, and archeological evidence suggests that this technique was ...
. ;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 Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...
, and then drying the partially germinated grain in a kiln. Malting grain produces enzymes that will allow conversion from starches in the grain into fermentable sugars during the mash process. 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 important not only in the sparging stage of brewing (in which water is washed over the
mashed Mashed may refer to: * Mashed, that created from mash ingredients * Mashed, the result of a mashing * Mashed, the result of a mashup (music) * ''Mashed'' (album), a 2007 mashup album * ''Mashed'' (video game), a vehicular combat video game * ...
barley grains to form the
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...
) but also as a rich source of
amylase An amylase () is an enzyme that catalyses the hydrolysis of starch (Latin ') into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of ...
, a digestive
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
that facilitates conversion of starch into sugars. Other malted and unmalted grains (including wheat, rice, oats, and rye, and, less frequently, maize (corn) and sorghum) may be used. In recent years, a few brewers have produced
gluten-free beer Gluten-free beer is beer made from ingredients that do not contain gluten such as millet, rice, sorghum, buckwheat or corn (maize). People who have gluten intolerance (including celiac disease and dermatitis herpetiformis sufferers) have a reaction ...
made with sorghum with no barley malt for people who cannot digest
gluten Gluten is a structural protein naturally found in certain cereal grains. Although "gluten" often only refers to wheat proteins, in medical literature it refers to the combination of prolamin and glutelin proteins naturally occurring in all grain ...
-containing grains like wheat, barley, and rye. ;Hops Hops are the female flower clusters or seed cones of the hop vine ''
Humulus lupulus ''Humulus lupulus'', the common hop or hops, is a species of flowering plant in the hemp family Cannabinaceae, native to Europe, western Asia and North America. It is a perennial, herbaceous climbing plant which sends up new shoots in early spr ...
'', which are used as a flavouring and preservative agent in nearly all beer made today. Hops had been used for medicinal and food flavouring purposes since Roman times; by the 7th century in
Carolingian The Carolingian dynasty (; known variously as the Carlovingians, Carolingus, Carolings, Karolinger or Karlings) was a Frankish noble family named after Charlemagne, grandson of mayor Charles Martel and a descendant of the Arnulfing and Pippin ...
monasteries in what is now Germany, beer was being made with hops, though it isn't until the thirteenth century that widespread cultivation of hops for use in beer is recorded. Before the thirteenth century, beer was flavoured with plants such as
yarrow ''Achillea millefolium'', commonly known as yarrow () or common yarrow, is a flowering plant in the family Asteraceae. Other common names include old man's pepper, devil's nettle, sanguinary, milfoil, soldier's woundwort, and thousand seal. The ...
,
wild rosemary Wild rosemary is a common name for several plants and may refer to: *Wild growing forms of the cultivated rosemary *''Andromeda polifolia'' (Bog rosemary) is known as wild rosemary, found in North America and Eurasia *Wild relatives of cultivated ...
, and
bog myrtle ''Myrica gale'' is a species of flowering plant in the family Myricaceae, native to parts of Japan, North Korea, Russia, mainland Europe, the British Isles and parts of northern North America, in Canada and the United States. Common names include ...
, and other ingredients such as
juniper berries A juniper berry is the female seed cone produced by the various species of junipers. It is not a true berry, but a cone with unusually fleshy and merged scales, which gives it a berry-like appearance. The cones from a handful of species, especial ...
,
aniseed Anise (; '), also called aniseed or rarely anix is a flowering plant in the family Apiaceae native to Eurasia. The flavor and aroma of its seeds have similarities with some other spices and herbs, such as star anise, fennel, licorice, and tar ...
and
ginger Ginger (''Zingiber officinale'') is a flowering plant whose rhizome, ginger root or ginger, is widely used as a spice A spice is a seed, fruit, root, bark, or other plant substance primarily used for flavoring or coloring food. Spices ...
, which would be combined into a mixture known as
gruit Gruit (alternately grut or gruyt) is a herb mixture used for bittering and flavouring beer, popular before the extensive use of hops. The terms gruit and grut ale may also refer to the beverage produced using gruit. Historically, gruit is the te ...
and used as hops are now used; between the thirteenth and the sixteenth century, during which hops took over as the dominant flavouring, beer flavoured with gruit was known as ale, while beer flavoured with hops was known as beer. 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: they contribute a bitterness that balances the sweetness of the malt; they provide floral, citrus, and herbal aromas and flavours; they have an
antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...
effect that favours the activity of
brewer's yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitu ...
over less desirable microorganisms; and they aid in "head retention", the length of time that the foam on top of the beer (the
beer head Beer is a village and civil parish in the East Devon district of Devon, England. The village faces Lyme Bay and is a little over west of the town of Seaton. It is situated on the Jurassic Coast World Heritage Site and its picturesque cliffs, ...
) will last. The preservative in hops comes from the lupulin glands which contain soft resins with alpha and beta acids. Though much studied, the preservative nature of the soft resins is not yet fully understood, though it has been observed that unless stored at a cool temperature, the preservative nature will decrease. Brewing is the sole major commercial use of hops. ;Yeast Yeast is the
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
that is responsible for fermentation in beer. Yeast metabolises the sugars extracted from grains, which produces
alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...
and
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
, and thereby turns
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. 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 ''
Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been o ...
'', known as ale yeast, and ''
Saccharomyces pastorianus ''Saccharomyces pastorianus'' is a yeast used industrially for the production of lager beer, and was named in honour of Louis Pasteur by the German Max Reess in 1870. This yeast's complicated genome appears to be the result of hybridisation bet ...
'', known as lager yeast; ''
Brettanomyces ''Brettanomyces'' is a non-spore forming genus of yeast in the family Saccharomycetaceae, and is often colloquially referred to as "Brett". The genus name ''Dekkera'' is used interchangeably with ''Brettanomyces'', as it describes the teleomorph ...
'' ferments
lambic Lambic () is a type of beer brewed in the Pajottenland region of Belgium southwest of Brussels and in Brussels itself since the 13th century. Types of lambic beers include gueuze, kriek lambic and framboise. Lambic differs from most other beers ...
s, and ''
Torulaspora delbrueckii ''Torulaspora delbrueckii'' is a ubiquitous yeast species with both wild and anthropic habitats. The type strain of ''T. delbrueckii'' is CBS 1146T, equivalent to CLIB 230 or ATCC 10662etc. The type strain of ''T. delbrueckii'' CBS 1146 T was seq ...
'' ferments Bavarian
weissbier Wheat beer is a top-fermented beer which is brewed with a large proportion of wheat relative to the amount of malted barley. The two main varieties are German ''Weizenbier'' and Belgian ''witbier''; other types include Lambic (made with wild ye ...
. Before the role of yeast in fermentation was understood, fermentation involved wild or airborne yeasts, and a few styles such as
lambic Lambic () is a type of beer brewed in the Pajottenland region of Belgium southwest of Brussels and in Brussels itself since the 13th century. Types of lambic beers include gueuze, kriek lambic and framboise. Lambic differs from most other beers ...
s still use this method today.
Emil Christian Hansen Emil Christian Hansen (8 May 1842 – 27 August 1909) was a Danish mycologist and fermentation physiologist. Born in Ribe, he financed his education by writing novels. He was awarded a gold medal in 1876 for an essay on fungi, titled ''De dans ...
, a Danish biochemist employed by the
Carlsberg Laboratory The Carlsberg Research Laboratory is a private scientific research center in Copenhagen, Denmark under the Carlsberg Group. It was founded in 1875 by J. C. Jacobsen, the founder of the Carlsberg brewery, with the purpose of advancing biochemica ...
, developed pure yeast
cultures Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups.Tyl ...
which were introduced into the Carlsberg brewery in 1883, and pure yeast strains are now the main fermenting source used worldwide. ;Clarifying agent Some brewers add one or more
clarifying agent Clarifying agents are used to remove suspended solids from liquids by inducing flocculation, causing the solids to form larger aggregates that can be easily removed after they either float to the surface or sink to the bottom of the containment vess ...
s to beer, which typically
precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
(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 Bright may refer to: Common meanings *Bright, an adjective meaning giving off or reflecting illumination; see Brightness *Bright, an adjective meaning someone with intelligence People * Bright (surname) * Bright (given name) *Bright, the stage na ...
and clean, rather than the cloudy appearance of ethnic and older styles of beer such as
wheat beer Wheat beer is a top-fermented beer which is brewed with a large proportion of wheat relative to the amount of malted barley. The two main varieties are German ''Weizenbier'' and Belgian ''witbier''; other types include Lambic (made with wild ye ...
s. Examples of clarifying agents include
isinglass Isinglass () is a substance obtained from the dried swim bladders of fish. It is a form of collagen used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes. The E ...
, obtained from
swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled Organ (anatomy), organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their curren ...
s of fish; Irish moss, a seaweed; kappa
carrageenan Carrageenans or carrageenins ( ; ) are a family of natural linear sulfated polysaccharides that are extracted from red edible seaweeds. Carrageenans are widely used in the food industry, for their gelling, thickening, and stabilizing properties. T ...
, from the seaweed ''
kappaphycus ''Kappaphycus'' is a genus of red algae. Species are distributed in the waters of East Africa, Indonesia, Malaysia, Hainan Island, the Philippines, and Micronesia.Guiry, M. D. In: Guiry, M. D. & G. M. Guiry. 2013''Kappaphycus''.AlgaeBase. Nationa ...
'';
polyclar Polyvinylpolypyrrolidone (polyvinyl polypyrrolidone, PVPP, crospovidone, crospolividone, or E1202) is a highly cross-linked modification of polyvinylpyrrolidone (PVP). The cross-linked form of PVP is used as a disintegrant (see also excipients) in ...
(a commercial brand of clarifier); and
gelatin Gelatin or gelatine (from la, gelatus meaning "stiff" or "frozen") is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also ...
. If a beer is marked "suitable for Vegans", it was generally clarified either with seaweed or with artificial agents, although the "Fast Cask" method invented by
Marston's Marston's plc is a British pub and hotel operator. Founded by John Marston in 1834, it is listed on the London Stock Exchange. Marston's disposed of its brewing operations in 2020, selling the assets to a newly formed joint venture with the Ca ...
in 2009 may provide another method.


Brewing process

There are several steps in the brewing process, which may include malting, mashing, lautering,
boiling Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. Th ...
,
fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
,
conditioning Conditioning may refer to: Science, computing, and technology * Air conditioning, the removal of heat from indoor air for thermal comfort ** Automobile air conditioning, air conditioning in a vehicle ** Ice storage air conditioning, air condition ...
,
filtering Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...
, and
packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a co ...
. The brewing equipment needed to make beer has grown more sophisticated over time, and now covers most aspects of the brewing process.
Malting Malting is the process of steeping, germinating and drying grain to convert it into malt. The malt is mainly used for brewing or whisky making, but can also be used to make malt vinegar or malt extract. Various grains are used for malting, most ...
is the process where barley grain is made ready for brewing. Malting is broken down into three steps in order to help to release the starches in the barley. First, during steeping, the grain is added to a vat with water and allowed to soak for approximately 40 hours. During
germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, fer ...
, the grain is spread out on the floor of the germination room for around 5 days. The final part of malting is kilning when the malt goes through a very high temperature drying in a kiln; with gradual temperature increase over several hours. When kilning is complete, the grains are now termed
malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, wh ...
, and they will be milled or crushed to break apart the kernels and expose the
cotyledon A cotyledon (; ; ; , gen. (), ) is a significant part of the embryo within the seed of a plant, and is defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." The numb ...
, which contains the majority of the carbohydrates and sugars; this makes it easier to extract the sugars during mashing.
Mashing In brewing and distilling, mashing is the process of combining a mix of ground grains – typically malted barley with supplementary grains such as corn, sorghum, rye, or wheat – known as the "grain bill" with water and then heating the mixtu ...
converts the starches released during the malting stage into sugars that can be fermented. The milled grain is mixed with hot water in a large vessel known as a
mash tun In brewing and distilling, mashing is the process of combining a mix of ground grains – typically malted barley with supplementary grains such as corn, sorghum, rye, or wheat – known as the "grain bill" with water and then heating the ...
. In this vessel, the grain and water are mixed together to create a cereal mash. During the mash, naturally occurring enzymes present in the malt convert the starches (long chain carbohydrates) in the grain into smaller molecules or simple sugars (mono-, di-, and tri-saccharides). This "conversion" is called
saccharification In chemistry, saccharification is a term for denoting any chemical change wherein a monosaccharide molecule remains intact after becoming unbound from another saccharide. For example, when a carbohydrate is broken into its component sugar molecul ...
which occurs between the temperatures . The result of the mashing process is a sugar-rich liquid or "wort", which is then strained through the bottom of the mash tun in a process known as
lautering Lautering () is the beer brewing process that separates the mash into clear liquid wort and residual grain. Lautering usually consists of three steps: mashout, recirculation, and sparging. Mashout Mashout is the term for raising the temperature ...
. Prior to lautering, the mash temperature may be raised to about (known as a mashout) to free up more starch and reduce mash viscosity. Additional water may be sprinkled on the grains to extract additional sugars (a process known as sparging). The wort is moved into a large tank known as a "copper" or
kettle A kettle, sometimes called a tea kettle or teakettle, is a type of pot specialized for boiling water, commonly with a ''lid'', ''spout'', and ''handle'', or a small electric kitchen appliance of similar shape that functions in a self-contained ...
where it is boiled with
hops Hops are the flowers (also called seed cones or strobiles) of the hop plant ''Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to whi ...
and sometimes other ingredients such as herbs or sugars. This stage is where many chemical reactions take place, and where important decisions about the flavour, colour, and aroma of the beer are made. The boiling process serves to terminate enzymatic processes,
precipitate In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
proteins, isomerize hop
resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on natu ...
s, and concentrate and sterilize the wort. Hops add flavour,
aroma An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...
and bitterness to the beer. At the end of the boil, the hopped wort settles to clarify in a vessel called a "whirlpool", where the more solid particles in the wort are separated out. After the whirlpool, the wort is drawn away from the compacted hop trub, and rapidly cooled via a
heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
to a temperature where yeast can be added. A variety of heat exchanger designs are used in breweries, with the most common a plate-style. Water or glycol run in channels in the opposite direction of the wort, causing a rapid drop in temperature. It is very important to quickly cool the wort to a level where yeast can be added safely as yeast is unable to grow in very high temperatures, and will start to die in temperatures above . After the wort goes through the heat exchanger, the cooled wort goes into a fermentation tank. A type of yeast is selected and added, or "pitched", to the fermentation tank. When the yeast is added to the wort, the fermenting process begins, where the sugars turn into alcohol,
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
and other components. When the fermentation is complete the brewer may rack the beer into a new tank, called a conditioning tank. Conditioning of the beer is the process in which the beer ages, the flavour becomes smoother, and flavours that are unwanted dissipate. After conditioning for a week to several months, the beer may be
filtered Filtration is a physical separation process that separates solid matter and fluid from a mixture using a ''filter medium'' that has a complex structure through which only the fluid can pass. Solid particles that cannot pass through the filter m ...
and force carbonated for bottling, or fined in the
cask A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, u ...
.


Mashing

Mashing is the process of combining a mix of milled grain (typically
malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, wh ...
ed
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia as early as 10,000 years ago. Globally 70% of barley pr ...
with supplementary grains such as
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
,
sorghum ''Sorghum'' () is a genus of about 25 species of flowering plants in the grass family (Poaceae). Some of these species are grown as cereals for human consumption and some in pastures for animals. One species is grown for grain, while many othe ...
, rye or wheat), known as the "grist" or "grain bill", and water, known as "liquor", and heating this mixture in a vessel called a "mash tun". Mashing is a form of steeping, and defines the act of brewing, such as with making tea,
sake Sake, also spelled saké ( ; also referred to as Japanese rice wine), is an alcoholic beverage of Japanese origin made by fermenting rice that has been polished to remove the bran. Despite the name ''Japanese rice wine'', sake, and indee ...
, and
soy sauce Soy sauce (also called simply soy in American English and soya sauce in British English) is a liquid condiment of Chinese origin, traditionally made from a fermented paste of soybeans, roasted grain, brine, and '' Aspergillus oryzae'' or ''Asp ...
. Technically, wine,
cider Cider ( ) is an alcoholic beverage made from the fermented juice of apples. Cider is widely available in the United Kingdom (particularly in the West Country) and the Republic of Ireland. The UK has the world's highest per capita consumption, ...
and
mead Mead () is an alcoholic beverage made by fermenting honey mixed with water, and sometimes with added ingredients such as fruits, spices, grains, or hops. The alcoholic content ranges from about 3.5% ABV to more than 20%. The defining character ...
are not brewed but rather
vinified The process of fermentation in winemaking turns grape juice into an alcoholic beverage. During fermentation, yeasts transform sugars present in the juice into ethanol and carbon dioxide (as a by-product). In winemaking, the temperature and spe ...
, as there is no steeping process involving solids. Mashing allows the
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
s in the malt to break down the
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...
in the grain into sugars, typically
maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...
to create a malty liquid called
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...
. There are two main methods –
infusion Infusion is the process of extracting chemical compounds or flavors from plant material in a solvent such as water, oil or alcohol, by allowing the material to remain suspended in the solvent over time (a process often called steeping). An inf ...
mashing, in which the grains are heated in one vessel; and
decoction Decoction is a method of extraction by boiling herbal or plant material (which may include stems, roots, bark and rhizomes) to dissolve the chemicals of the material. It is the most common preparation method in various herbal-medicine systems. De ...
mashing, in which a proportion of the grains are boiled and then returned to the mash, raising the temperature. Mashing involves pauses at certain temperatures (notably ), and takes place in a "mash tun" – an insulated brewing vessel with a
false bottom A false bottom (or false back) is an internal partition in a container, typically at the bottom of a drawer, suitcase or similar item, enabling the concealment of objects from a cursory examination of the item's contents. A false bottom may be pr ...
."Abdijbieren. Geestrijk erfgoed" by Jef Van den Steen The end product of mashing is called a "mash". Mashing usually takes 1 to 2 hours, and during this time the various temperature rests activate different enzymes depending upon the type of malt being used, its modification level, and the intention of the brewer. The activity of these enzymes convert the starches of the grains to
dextrin Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch and glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic bonds. Dextrins can be produced from ...
s and then to fermentable sugars such as
maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...
. A mash rest from activates various
protease A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes (increases reaction rate or "speeds up") proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the ...
s, which break down proteins that might otherwise cause the beer to be hazy. This rest is generally used only with undermodified (i.e. undermalted) malts which are decreasingly popular in Germany and the Czech Republic, or non-malted grains such as
corn Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. Th ...
and rice, which are widely used in North American beers. A mash rest at activates β-
glucanase Glucanases are enzymes that break down large polysaccharides via hydrolysis. The product of the hydrolysis reaction is called a glucan, a linear polysaccharide made of up to 1200 glucose monomers, held together with glycosidic bonds. Glucans are a ...
, 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 later in the brewing process. Doing the latter rest at the lower end of the range favours β-amylase enzymes, producing more low-order sugars like
maltotriose Maltotriose is a trisaccharide (three-part sugar) consisting of three glucose molecules linked with α-1,4 glycosidic bonds. It is most commonly produced by the digestive enzyme alpha-amylase (a common enzyme in human saliva) on amylose in starc ...
,
maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...
, and
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
which are more fermentable by the
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...
. This in turn creates a beer lower in body and higher in alcohol. A rest closer to the higher end of the range favours
α-amylase α-Amylase is an enzyme (EC 3.2.1.1; systematic name 4-α-D-glucan glucanohydrolase) that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose: :Endohyd ...
enzymes, creating more higher-order sugars and
dextrin Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch and glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic bonds. Dextrins can be produced from ...
s 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.


Lautering

Lautering is the separation of the
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...
(the liquid containing the sugar extracted during mashing) from the grains. This is done either in a mash tun outfitted with a false bottom, in a lauter tun, or in a mash filter. 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. The lauter tun is a tank with holes in the bottom small enough to hold back the large bits of grist and hulls (the ground or milled cereal). The bed of grist that settles on it is the actual filter. Some 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. The 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.


Boiling

After mashing, the beer
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...
is boiled with
hops Hops are the flowers (also called seed cones or strobiles) of the hop plant ''Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to whi ...
(and other flavourings if used) in a large tank known as a "copper" or brew kettle – though historically the mash vessel was used and is still in some small breweries. The boiling process is where chemical reactions take place, including sterilization of the wort to remove unwanted bacteria, releasing of hop flavours, bitterness and aroma compounds through
isomerization In chemistry, isomerization or isomerisation is the process in which a molecule, polyatomic ion or molecular fragment is transformed into an isomer with a different chemical structure. Enolization is an example of isomerization, as is tautomeriz ...
, stopping of enzymatic processes,
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
of proteins, and concentration of the wort. Finally, the vapours produced during the boil volatilise off-flavours, including
dimethyl sulfide Dimethyl sulfide (DMS) or methylthiomethane is an organosulfur compound with the formula (CH3)2S. Dimethyl sulfide is a flammable liquid that boils at and has a characteristic disagreeable odor. It is a component of the smell produced from cook ...
precursors. The boil is conducted so that it is even and intense – a continuous "rolling boil". The boil on average lasts between 45 and 90 minutes, depending on its intensity, the hop addition schedule, and volume of water the brewer expects to evaporate. At the end of the boil, solid particles in the hopped wort are separated out, usually in a vessel called a "whirlpool".


Brew kettle or copper

Copper is the traditional material for the boiling vessel for two main reasons: firstly because copper transfers heat quickly and evenly; secondly because the bubbles produced during boiling, which could act as an insulator against the heat, do not cling to the surface of copper, so the wort is heated in a consistent manner. 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 caramelisation and making cleanup difficult. Most breweries use a steam-fired kettle, which uses steam jackets in the kettle to boil the wort. Breweries usually have a boiling unit either inside or outside of the kettle, usually a tall, thin cylinder with vertical tubes, called a calandria, through which wort is pumped.


Whirlpool

At the end of the boil, solid particles in the hopped wort are separated out, usually in a vessel called a "whirlpool" or "settling tank". The whirlpool was devised by Henry Ranulph Hudston while working for the
Molson Brewery The Molson Brewery is a Canadian based brewery company based in Montreal which was established in 1786 by the Molson family. In 2005, Molson merged with the Adolph Coors Company to become Molson Coors. Molson Coors maintains some of its Can ...
in 1960 to utilise the so-called
tea leaf paradox The tea leaf paradox is a phenomenon where tea leaves in a cup of tea migrate to the center and bottom of the cup after being stirred rather than being forced to the edges of the cup, as would be expected in a spiral centrifuge. The correct p ...
to force the denser solids known as "trub" (coagulated proteins, vegetable matter from hops) into a cone in the centre of the whirlpool tank. Whirlpool systems vary: smaller breweries tend to use the brew kettle, larger breweries use a separate tank, and design will differ, with tank floors either flat, sloped, conical or with a cup in the centre. The principle in all is that by swirling the wort the
centripetal force A centripetal force (from Latin ''centrum'', "center" and ''petere'', "to seek") is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous c ...
will push the trub into a cone at the centre of the bottom of the tank, where it can be easily removed.


Hopback

A hopback is a traditional additional chamber that acts as a sieve or filter by using whole
hops Hops are the flowers (also called seed cones or strobiles) of the hop plant ''Humulus lupulus'', a member of the Cannabaceae family of flowering plants. They are used primarily as a bittering, flavouring, and stability agent in beer, to whi ...
to clear debris (or "
trub Trub is one of the largest municipalities of Switzerland (62 km²) in size, but not in population. It is located in the Emmental region of the canton of Bern in the administrative district of Emmental. History Trub is first mentioned in ...
") from the unfermented (or "green")
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...
, as the whirlpool does, and also to increase hop aroma in the finished beer. It is a chamber between the brewing kettle and wort chiller. Hops are added to the chamber, the hot wort from the kettle is run through it, and then immediately cooled in the wort chiller before entering the fermentation chamber. Hopbacks utilizing a sealed chamber facilitate maximum retention of volatile hop aroma compounds that would normally be driven off when the hops contact the hot wort. While a hopback has a similar filtering effect as a whirlpool, it operates differently: a whirlpool uses centrifugal forces, a hopback uses a layer of whole hops to act as a filter bed. Furthermore, while a whirlpool is useful only for the removal of pelleted hops (as flowers do not tend to separate as easily), in general hopbacks are used only for the removal of whole flower hops (as the particles left by pellets tend to make it through the hopback). The hopback has mainly been substituted in modern breweries by the whirlpool.


Wort cooling

After the whirlpool, the wort must be brought down to fermentation temperatures before yeast is added. In modern breweries this is achieved through a plate
heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...
. 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 wort to while warming the cooling medium from about to . The last few plates often use a cooling medium which can be cooled to below the
freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
, which allows a finer control over the wort-out temperature, and also enables cooling to around . After cooling, oxygen is often dissolved into the wort to revitalize the yeast and aid its reproduction. Some of the craft brewery, particularly those wanting to create
steam beer Steam beer is a highly effervescent beer made by fermenting lager yeasts at warmer ale yeast fermentation temperatures. It has two distinct but related meanings: *Historic steam beer produced in California, and in the East at the James River St ...
, utilize
coolship A coolship (Anglicized version of the Dutch/Flemish koelschip) is a type of brewing vessel traditionally used in the production of beer. It is a broad, open-top, flat vessel in which wort cools. The high surface-to-mass ratio allows for more effici ...
instead. 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

Fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...
takes place in fermentation vessels which come in various forms, from enormous cylindroconical vessels, through open stone vessels, to wooden vats. After the wort is cooled and
aerated Aeration (also called aerification or aeriation) is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration processes create additional surface area in ...
– usually with
sterile Sterile or sterility may refer to: *Asepsis, a state of being free from biological contaminants * Sterile (archaeology), a sediment deposit which contains no evidence of human activity *Sterilization (microbiology), any process that eliminates or ...
air – yeast is added to it, and it begins to ferment. It is during this stage that sugars won from the
malt Malt is germinated cereal grain that has been dried in a process known as " malting". The grain is made to germinate by soaking in water and is then halted from germinating further by drying with hot air. Malted grain is used to make beer, wh ...
are converted into alcohol and
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
, and the product can be called beer for the first time. Most breweries today use cylindroconical vessels, or CCVs, which have a conical bottom and a cylindrical top. The cone's angle is typically around 60°, an angle that will allow the yeast to flow towards the cone's 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 cone's apex can be simply flushed out of a port at the apex. 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.


Fermentation methods

There are three main fermentation methods, warm,
cool Cool commonly refers to: * Cool, a moderately low temperature * Cool (aesthetic), an aesthetic of attitude, behavior, and style Cool or COOL may also refer to: Economics * Country of origin labelling * mCOOL - US consumer legislation to enforc ...
, and wild or spontaneous. Fermentation may take place in open or closed vessels. There may be a secondary fermentation which can take place in the brewery, in the
cask A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, u ...
or in the
bottle A bottle is a narrow-necked container made of an impermeable material (such as glass, plastic or aluminium) in various shapes and sizes that stores and transports liquids. Its mouth, at the bottling line, can be sealed with an internal stopp ...
. Brewing yeasts are traditionally classed as "top-cropping" (or "top-fermenting") and "bottom-cropping" (or "bottom-fermenting"); the yeasts classed as top-fermenting are generally used in warm fermentations, where they ferment quickly, and the yeasts classed as bottom-fermenting are used in cooler fermentations where they ferment more slowly. Yeast were termed top or bottom cropping, because the yeast was collected from the top or bottom of the fermenting wort to be reused for the next brew. This terminology is somewhat inappropriate in the modern era; after the widespread application of brewing mycology it was discovered that the two separate collecting methods involved two different yeast species that favoured different temperature regimes, namely ''Saccharomyces cerevisiae'' in top-cropping at warmer temperatures and ''Saccharomyces pastorianus'' in bottom-cropping at cooler temperatures. As brewing methods changed in the 20th century, cylindro-conical fermenting vessels became the norm and the collection of yeast for both ''Saccharomyces'' species is done from the bottom of the fermenter. Thus the method of collection no longer implies a species association. There are a few remaining breweries who collect yeast in the top-cropping method, such as Samuel Smiths brewery in Yorkshire, Marstons in Staffordshire and several German hefeweizen producers. For both types, yeast is fully distributed through the beer while it is fermenting, and both equally
flocculate Flocculation, in the field of chemistry, is a process by which colloidal particles come out of suspension to sediment under the form of floc or flake, either spontaneously or due to the addition of a clarifying agent. The action differs from pre ...
(clump together and precipitate to the bottom of the vessel) when fermentation is finished. By no means do all top-cropping yeasts demonstrate this behaviour, but it features strongly in many English yeasts that may also exhibit chain forming (the failure of budded cells to break from the mother cell), which is in the technical sense different from true flocculation. The most common top-cropping brewer's yeast, ''Saccharomyces cerevisiae'', is the same species as the common baking yeast. However, baking and brewing yeasts typically belong to different strains, cultivated to favour different characteristics: baking yeast strains are more aggressive, in order to carbonate
dough Dough is a thick, malleable, sometimes elastic paste made from grains or from leguminous or chestnut crops. Dough is typically made by mixing flour with a small amount of water or other liquid and sometimes includes yeast or other leavening ag ...
in the shortest amount of time; brewing yeast strains act slower, but tend to tolerate higher alcohol concentrations (normally 12–15%
abv Alcohol by volume (abbreviated as ABV, abv, or alc/vol) is a standard measure of how much alcohol (ethanol) is contained in a given volume of an alcoholic beverage (expressed as a volume percent). It is defined as the number of millilitres (mL) o ...
is the maximum, though under special treatment some ethanol-tolerant strains can be coaxed up to around 20%). Modern quantitative genomics has revealed the complexity of ''Saccharomyces'' species to the extent that yeasts involved in beer and wine production commonly involve hybrids of so-called pure species. As such, the yeasts involved in what has been typically called top-cropping or top-fermenting ale may be both ''Saccharomyces cerevisiae'' and complex hybrids of ''Saccharomyces cerevisiae'' and ''Saccharomyces kudriavzevii''. Three notable ales,
Chimay Chimay (, wa, Chimai) is a city and Municipalities of Belgium, municipality of Wallonia located in the Hainaut Province, province of Hainaut, Belgium. In 2006, Chimay had a population of 9,774. The area is 197.10 km2 which gives a populatio ...
, Orval and
Westmalle Westmalle is a village in the Belgian province of Antwerp which is part of the municipality of Malle. History See history of Malle. Tourism Westmalle is primarily known for the Trappist Abbey of Westmalle of the Order of Cistercians of the Stric ...
, are fermented with these hybrid strains, which are identical to wine yeasts from Switzerland.


Warm fermentation

In general, yeasts such as ''
Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been o ...
'' are fermented at warm temperatures between , occasionally as high as , while the yeast used by
Brasserie Dupont Dupont Brewery (in French: ''Brasserie Dupont'') is a brewery in Tourpes (Leuze-en-Hainaut), in western Hainaut, Belgium. Founded in 1950, it is on a working farm which dates back to 1759 and has significant brewing history. In the 1990s, a bre ...
for
saison Saison ( French, "season," ) is a pale ale that is highly carbonated, fruity, spicy, and often bottle conditioned. It was historically brewed with low alcohol levels, but modern productions of the style have moderate to high levels of alcohol. ...
ferments even higher at . They generally form a foam on the surface of the fermenting beer, which is called
barm Barm is the foam or scum formed on the top of a fermenting liquid, such as beer, wine, or feedstock for spirits or industrial ethanol distillation. It is used to leaven bread, or set up fermentation in a new batch of liquor. Barm, as a leaven, has ...
, as during the fermentation process its
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...
surface causes the flocs to adhere to CO2 and rise; because of this, they are often referred to as "top-cropping" or "top-fermenting" – though this distinction is less clear in modern brewing with the use of cylindro-conical tanks. Generally, warm-fermented beers, which are usually termed
ale Ale is a Type of beer, type of beer brewed using a Warm fermentation, warm fermentation method, resulting in a sweet, full-bodied and fruity taste. Historically, the term referred to a drink brewed without hops. As with most beers, ale typicall ...
, are ready to drink within three weeks after the beginning of fermentation, although some brewers will condition or mature them for several months.


Cool fermentation

When a beer has been brewed using a cool fermentation of around , compared to typical warm fermentation temperatures of , then stored (or lagered) for typically several weeks (or months) at temperatures close to
freezing Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid o ...
point, it is termed a "
lager Lager () is beer which has been brewed and conditioned at low temperature. Lagers can be pale, amber, or dark. Pale lager is the most widely consumed and commercially available style of beer. The term "lager" comes from the German for "storage" ...
". During the lagering or storage phase several flavour components developed during fermentation dissipate, resulting in a "cleaner" flavour. Though it is the slow, cool fermentation and cold conditioning (or lagering) that defines the character of lager, the main technical difference is with the yeast generally used, which is ''
Saccharomyces pastorianus ''Saccharomyces pastorianus'' is a yeast used industrially for the production of lager beer, and was named in honour of Louis Pasteur by the German Max Reess in 1870. This yeast's complicated genome appears to be the result of hybridisation bet ...
''. Technical differences include the ability of lager yeast to metabolize
melibiose Melibiose is a reducing disaccharide formed by an α-1,6 linkage between galactose and glucose (D-Gal-α(1→6)-D-Glc). It differs from lactose in the chirality of the carbon where the galactose ring is closed and that the galactose is linked to a ...
, and the tendency to settle at the bottom of the fermenter (though ales yeasts can also become bottom settling by selection); though these technical differences are not considered by scientists to be influential in the character or flavour of the finished beer, brewers feel otherwise - sometimes cultivating their own yeast strains which may suit their brewing equipment or for a particular purpose, such as brewing beers with a high abv. Brewers in
Bavaria Bavaria ( ; ), officially the Free State of Bavaria (german: Freistaat Bayern, link=no ), is a state in the south-east of Germany. With an area of , Bavaria is the largest German state by land area, comprising roughly a fifth of the total lan ...
had for centuries been selecting cold-fermenting 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. A sample of these Bavarian yeasts was sent from the Spaten brewery in Munich to the Carlsberg brewery in Copenhagen in 1845 who began brewing with it. In 1883 Emile Hansen completed a study on pure yeast culture isolation and the pure strain obtained from Spaten went into industrial production in 1884 as Carlsberg yeast No 1. Another specialized pure yeast production plant was installed at the Heineken Brewery in Rotterdam the following year and together they began the supply of pure cultured yeast to brewers across Europe. This yeast strain was originally classified as ''Saccharomyces carlsbergensis'', a now defunct species name which has been superseded by the currently accepted taxonomic classification ''Saccharomyces pastorianus''.


Spontaneous fermentation

Lambic Lambic () is a type of beer brewed in the Pajottenland region of Belgium southwest of Brussels and in Brussels itself since the 13th century. Types of lambic beers include gueuze, kriek lambic and framboise. Lambic differs from most other beers ...
beers are historically brewed in
Brussels Brussels (french: Bruxelles or ; nl, Brussel ), officially the Brussels-Capital Region (All text and all but one graphic show the English name as Brussels-Capital Region.) (french: link=no, Région de Bruxelles-Capitale; nl, link=no, Bruss ...
and the nearby
Pajottenland The Pajottenland (in English occasionally Payottenland) is a distinct region within the Flemish Brabant province and the south-western part of the Brussels Region of Belgium. The region is located west-southwest of Brussels. The Pajottenland is pre ...
region of Belgium without any yeast inoculation. The wort is cooled in open vats (called "
coolship A coolship (Anglicized version of the Dutch/Flemish koelschip) is a type of brewing vessel traditionally used in the production of beer. It is a broad, open-top, flat vessel in which wort cools. The high surface-to-mass ratio allows for more effici ...
s"), where the yeasts and
microbiota Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found t ...
present in the brewery (such as ''
Brettanomyces ''Brettanomyces'' is a non-spore forming genus of yeast in the family Saccharomycetaceae, and is often colloquially referred to as "Brett". The genus name ''Dekkera'' is used interchangeably with ''Brettanomyces'', as it describes the teleomorph ...
'') are allowed to settle to create a spontaneous fermentation, and are then conditioned or matured in oak barrels for typically one to three years.


Conditioning

After an initial or primary fermentation, beer is ''conditioned'', matured or aged, in one of several ways, which can take from 2 to 4 weeks, several months, or several years, depending on the brewer's intention for the beer. The beer is usually transferred into a second container, 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 flavours and harmful compounds such as
acetaldehyde Acetaldehyde (IUPAC systematic name ethanal) is an organic chemical compound with the formula CH3 CHO, sometimes abbreviated by chemists as MeCHO (Me = methyl). It is a colorless liquid or gas, boiling near room temperature. It is one of the mos ...
. ;Kräusening Kräusening is a conditioning method in which fermenting
wort Wort () is the liquid extracted from the mashing process during the brewing of beer or whisky. Wort contains the sugars, the most important being maltose and maltotriose, that will be fermented by the brewing yeast to produce alcohol. Wort ...
is added to the finished beer. The active yeast will restart fermentation in the finished beer, and so introduce fresh carbon dioxide; the conditioning tank will be then sealed so that the carbon dioxide is dissolved into the beer producing a lively "condition" or level of carbonation. The kräusening method may also be used to condition bottled beer. ;Lagering
Lager Lager () is beer which has been brewed and conditioned at low temperature. Lagers can be pale, amber, or dark. Pale lager is the most widely consumed and commercially available style of beer. The term "lager" comes from the German for "storage" ...
s are stored at cellar temperature or below for 1–6 months while still on the yeast. The process of storing, or conditioning, or maturing, or aging a beer at a low temperature for a long period is called "lagering", and while it is associated with lagers, the process may also be done with ales, with the same result – that of cleaning up various chemicals, acids and compounds. ;Secondary fermentation During secondary fermentation, most of the remaining yeast will settle to the bottom of the second fermenter, yielding a less hazy product. ;Bottle fermentation Some beers undergo an additional fermentation in the bottle giving natural carbonation. This may be a second and/or third fermentation. They are bottled with a viable yeast population in suspension. If there is no residual fermentable sugar left, sugar or wort or both may be added in a process known as priming. The resulting fermentation generates CO2 that is trapped in the bottle, remaining in solution and providing natural carbonation. Bottle-conditioned beers may be either filled unfiltered direct from the fermentation or conditioning tank, or filtered and then reseeded with yeast. ;Cask conditioning Cask ale (or cask-conditioned beer) is unfiltered, unpasteurised beer that is conditioned by a secondary fermentation in a metal, plastic or
wooden Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin tha ...
cask. It is dispensed from the cask by being either poured from a tap by gravity, or pumped up from a cellar via a
beer engine A beer engine is a device for pumping beer from a cask, usually located in a pub's cellar. The beer engine was invented by John Lofting, a Dutch inventor, merchant and manufacturer who moved from Amsterdam to London in about 1688 and patented ...
(hand pump). Sometimes a
cask breather A cask breather (sometimes called a cask aspirator) is a type of demand valve used to serve draught beer. The cask breather enables the empty space created when beer is drawn from a beer cask to be filled with carbon dioxide from an external sourc ...
is used to keep the beer fresh by allowing carbon dioxide to replace oxygen as the beer is drawn off the cask. Until 2018, the
Campaign for Real Ale The Campaign for Real Ale (CAMRA) is an independent voluntary consumer organisation headquartered in St Albans, England, which promotes real ale, cider and perry and traditional British pubs and clubs. With just under 155,000 members, it is th ...
(CAMRA) defined real ale as beer "served without the use of extraneous carbon dioxide", which would disallow the use of a cask breather, a policy which was reversed in April 2018 to allow beer served with the use of cask breathers to meet its definition of real ale. ;Barrel-ageing Barrel-ageing ( US: Barrel aging) is the process of ageing beer in wooden barrels to achieve a variety of effects in the final product.
Sour beer Sour beer, also known as Sours, is beer which has an intentionally acidic, tart, or sour taste. Traditional sour beer styles include Belgian lambics, gueuze and Flanders red ale, and German gose and Berliner Weisse. Brewing Unlike modern brewing, ...
s such as
lambic Lambic () is a type of beer brewed in the Pajottenland region of Belgium southwest of Brussels and in Brussels itself since the 13th century. Types of lambic beers include gueuze, kriek lambic and framboise. Lambic differs from most other beers ...
s are fully fermented in wood, while other beers are aged in barrels which were previously used for maturing
wine Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are m ...
s or
spirits Spirit or spirits may refer to: Liquor and other volatile liquids * Spirits, a.k.a. liquor, distilled alcoholic drinks * Spirit or tincture, an extract of plant or animal material dissolved in ethanol * Volatile (especially flammable) liquids, ...
. In 2016 "Craft Beer and Brewing" wrote: "Barrel-aged beers are so trendy that nearly every taphouse and beer store has a section of them.


Filtering

Filtering stabilises the flavour of beer, holding it at a point acceptable to the brewer, and preventing further development from the yeast, which under poor conditions can release negative components and flavours. Filtering also removes haze, clearing the beer, and so giving it a "polished shine and brilliance". Beer with a clear appearance has been commercially desirable for brewers since the development of glass vessels for storing and drinking beer, along with the commercial success of
pale lager Pale lager is a very pale-to-golden-colored lager beer with a well- attenuated body and a varying degree of noble hop bitterness. The brewing process for this beer developed in the mid-19th century, when Gabriel Sedlmayr took pale ale brewing ...
, which - due to the
lager Lager () is beer which has been brewed and conditioned at low temperature. Lagers can be pale, amber, or dark. Pale lager is the most widely consumed and commercially available style of beer. The term "lager" comes from the German for "storage" ...
ing process in which haze and particles settle to the bottom of the tank and so the beer "
drops bright Bright beer is beer in which yeast is no longer in suspension. There are several methods used for clearing yeast from beer, from waiting for the yeast to drop of its own accord ("dropping bright") to filtering it. Dropping bright When the conce ...
" (clears) - has a natural bright appearance and shine. There are several forms of filters; they may be in the form of sheets or "candles", or they may be a fine powder such as
diatomaceous earth Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3  μm to le ...
(also called kieselguhr), which is added to the beer to form a filtration bed which allows liquid to pass, but holds onto suspended particles such as yeast. 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 colour and body from the beer. 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 removes almost all cloudiness. Sterile filtration removes almost all microorganisms. ;Sheet (pad) filters These filters use sheets that allow only particles smaller than a given size to pass through. The sheets are placed into a filtering frame, sanitized (with boiling water, for example) and then used to filter the beer. The sheets can be flushed if the filter becomes blocked. The sheets are usually disposable and are replaced between filtration sessions. Often the sheets contain powdered filtration media to aid in filtration. 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 regeneration. Common media include
diatomaceous earth Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3  μm to le ...
and
perlite Perlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial m ...
.


By-products

Brewing by-products are "spent grain" and the sediment (or " dregs") from the filtration process which may be dried and resold as "brewers dried yeast" for poultry feed, or made into
yeast extract Yeast extracts consist of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture media. They are often used to create savory flavors and umami taste sensations, a ...
which is used in brands such as
Vegemite Vegemite ( ) is a thick, dark brown Australian food spread made from leftover brewers' yeast extract with various vegetable and spice additives. It was developed by Cyril Callister in Melbourne, Victoria, in 1922. A spread for sandwiches, t ...
and
Marmite Marmite ( ) is a British savoury food spread based on yeast extract, invented by the German scientist Justus von Liebig. It is made from by-products of beer brewing ( lees) and is produced by the British company Unilever. Marmite is a vegan ...
. The process of turning the yeast sediment into edible yeast extract was discovered by German scientist
Justus von Liebig Justus Freiherr von Liebig (12 May 1803 – 20 April 1873) was a German scientist who made major contributions to agricultural and biological chemistry, and is considered one of the principal founders of organic chemistry. As a professor at t ...
.
Brewer's spent grain Brewer's spent grain (BSG) or draff is a food waste that is a byproduct of the brewing industry that makes up 85 percent of brewing waste. BSG is obtained as a mostly solid residue after wort production in the brewing process. The product is i ...
(also called spent grain, brewer's grain or draff) is the main by-product of the brewing process; it consists of the residue of malt and grain which remains in the lauter tun after the lautering process. It consists primarily of grain husks,
pericarp Fruit anatomy is the plant anatomy of the internal structure of fruit. Fruits are the mature ovary or ovaries of one or more flowers. They are found in three main anatomical categories: aggregate fruits, multiple fruits, and simple fruits. Aggre ...
, and fragments of
endosperm The endosperm is a tissue produced inside the seeds of most of the flowering plants following double fertilization. It is triploid (meaning three chromosome sets per nucleus) in most species, which may be auxin-driven. It surrounds the embryo and ...
. As it mainly consists of
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...
s and
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
s, and is readily consumed by animals, spent grain is used in
animal feed Animal feed is food given to domestic animals, especially livestock, in the course of animal husbandry. There are two basic types: fodder and forage. Used alone, the word ''feed'' more often refers to fodder. Animal feed is an important input to ...
.Heuzé V., Tran G., Sauvant D., Lebas F., 2016. Brewers grains. Feedipedia, a programme by INRA, CIRAD, AFZ and FAO. https://www.feedipedia.org/node/74 Last updated on 17 June 2016, 16:10 Spent grains can also be used as
fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
, whole grains in bread, as well as in the production of
flour Flour is a powder made by grinding raw grains, roots, beans, nuts, or seeds. Flours are used to make many different foods. Cereal flour, particularly wheat flour, is the main ingredient of bread, which is a staple food for many culture ...
and
biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
. Spent grain is also an ideal medium for growing
mushrooms A mushroom or toadstool is the fleshy, spore-bearing Sporocarp (fungi), fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the na ...
, such as
shiitake The shiitake (alternate form shitake) (; ''Lentinula edodes'') is an edible mushroom native to East Asia, which is now cultivated and consumed around the globe. It is considered a Medicinal fungi, medicinal mushroom in some forms of tradition ...
, and already some breweries are either growing their own mushrooms or supplying spent grain to mushroom farms. Spent grains can be used in the production of red bricks, to improve the open porosity and reduce thermal conductivity of the ceramic mass.


Brewing industry

The brewing industry is a global business, consisting of several dominant
multinational companies A multinational company (MNC), also referred to as a multinational enterprise (MNE), a transnational enterprise (TNE), a transnational corporation (TNC), an international corporation or a stateless corporation with subtle but contrasting senses, i ...
and many thousands of other producers known as
microbreweries Craft beer is a beer that has been made by craft breweries. They produce smaller amounts of beer, typically less than large breweries, and are often independently owned. Such breweries are generally perceived and marketed as having an emphasis o ...
or regional breweries or craft breweries depending on size, region, and marketing preference. More than are sold per year—producing total global revenues of $294.5 billion (£147.7 billion) as of 2006.
SABMiller SABMiller plc was a South African multinational brewing and beverage company headquartered in Woking, England on the outskirts of London until 10 October 2016 when it was acquired by Anheuser-Busch InBev. Prior to that date, it was the world's ...
became the largest brewing company in the world when it acquired Royal Grolsch, brewer of Dutch premium beer brand
Grolsch Grolsch Brewery (Koninklijke Grolsch N.V. - "Royal Grolsch"), known simply as Grolsch (), is a Dutch brewery founded in 1615 by Willem Neerfeldt in Groenlo. In 1895 the de Groen family bought the brewery. They had started their own brewery in E ...
.
InBev InBev () is a brewing company that resulted from the merger between Belgium-based company Interbrew and Brazilian brewer AmBev which took place in 2004. It existed independently until the acquisition of Anheuser-Busch in 2008, which formed Anheu ...
was the second-largest beer-producing company in the world and
Anheuser-Busch Anheuser-Busch Companies, LLC is an American brewing company headquartered in St. Louis, Missouri. Since 2008, it has been wholly owned by Anheuser-Busch InBev SA/NV (AB InBev), now the world's largest brewing company, which owns multiple glo ...
held the third spot, but after the acquisition of Anheuser-Busch by InBev, the new
Anheuser-Busch InBev Anheuser-Busch InBev SA/NV, commonly known as AB InBev, is an American-Belgian multinational drink and brewing company based in Leuven, Belgium. AB InBev has a global functional management office in New York City, and regional headquarters ...
company is currently the largest brewer in the world. Brewing at home is subject to regulation and prohibition in many countries. Restrictions on homebrewing were lifted in the UK in 1963, Australia followed suit in 1972, and the US in 1978, though individual states were allowed to pass their own laws limiting production.Papazian ''The Complete Joy of Homebrewing (3rd Edition)'',


References

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Wiley-Blackwell Wiley-Blackwell is an international scientific, technical, medical, and scholarly publishing business of John Wiley & Sons. It was formed by the merger of John Wiley & Sons Global Scientific, Technical, and Medical business with Blackwell Publish ...
, 2005, * Bamforth, Charles; ''Beer: Tap into the Art and Science of Brewing'',
Oxford University Press Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print books ...
, 2009 * Boulton, Christopher; ''Encyclopaedia of Brewing'',
Wiley-Blackwell Wiley-Blackwell is an international scientific, technical, medical, and scholarly publishing business of John Wiley & Sons. It was formed by the merger of John Wiley & Sons Global Scientific, Technical, and Medical business with Blackwell Publish ...
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Aspen Publishers Wolters Kluwer N.V. () is a Dutch information services company. The company is headquartered in Alphen aan den Rijn, Netherlands (Global) and Philadelphia, United States (corporate). Wolters Kluwer in its current form was founded in 1987 with a ...
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CRC Press The CRC Press, LLC is an American publishing group that specializes in producing technical books. Many of their books relate to engineering, science and mathematics. Their scope also includes books on business, forensics and information tec ...
, 1994, * Esslinger, Hans Michael; ''Handbook of Brewing: Processes, Technology, Markets'',
Wiley-VCH Wiley-VCH is a German publisher owned by John Wiley & Sons. It was founded in 1921 as Verlag Chemie (meaning "Chemistry Press": VCH stands for ''Verlag Chemie'') by two German learned societies. Later, it was merged into the German Chemical Socie ...
, 2009, * Hornsey, Ian Spencer; ''Brewing'',
Royal Society of Chemistry The Royal Society of Chemistry (RSC) is a learned society (professional association) in the United Kingdom with the goal of "advancing the chemistry, chemical sciences". It was formed in 1980 from the amalgamation of the Chemical Society, the Ro ...
, 1999, * Hui, Yiu H.; ''Food Biotechnology'', Wiley-IEEE, 1994, * Hui, Yiu H., and Smith, J. Scott; ''Food Processing: Principles and Applications'',
Wiley-Blackwell Wiley-Blackwell is an international scientific, technical, medical, and scholarly publishing business of John Wiley & Sons. It was formed by the merger of John Wiley & Sons Global Scientific, Technical, and Medical business with Blackwell Publish ...
, 2004, * Andrew G.H. Lea, John Raymond Piggott, John R. Piggott ; ''Fermented Beverage Production'', Kluwer Academic/Plenum Publishers, 2003, * McFarland, Ben; ''World's Best Beers'',
Sterling Publishing Sterling Publishing Company, Inc. is a publisher of a broad range of subject areas, with multiple imprints and more than 5,000 titles in print. Founded in 1949 by David A. Boehm, Sterling also publishes books for a number of brands, including AAR ...
, 2009, * Oliver, Garrett (ed); ''The Oxford Companion to Beer'', Oxford University Press, 2011 * Priest, Fergus G.; ''Handbook of Brewing'',
CRC Press The CRC Press, LLC is an American publishing group that specializes in producing technical books. Many of their books relate to engineering, science and mathematics. Their scope also includes books on business, forensics and information tec ...
, 2006, * * Stevens, Roger, et al.; ''Brewing: Science and Practice'',
Woodhead Publishing Woodhead Publishing Limited was established in 1989 as an independent international publishing company of science and technical books. The company publishes books in association with The Textile Institute, Cambridge International Science Publishin ...
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External links


An overview of the microbiology behind beer brewing from the Science Creative Quarterly


{{Authority control Fermentation in food processing