They are used primarily as a flavoring and stability agent in beer, to which they impart a bitter, tangy flavor, though hops are also used for various purposes in other beverages and herbal medicine. In the Middle Ages beers tended to be of a very low alcohol content and were commonly consumed as a safer alternative to untreated water. Each village tended to have one or more small breweries with a barley field and a hop garden in close vicinity. Early documents include mention of a hop garden in the will of Charlemagne's father, Pepin III. However, the first documented use of hops in beer as a flavoring agent is from the 11th century. Before this period, brewers used a wide variety of bitter herbs and flowers, including dandelion, burdock root, marigold, horehound (the German name for horehound means "mountain hops"), ground ivy, and heather. Hops are used extensively in brewing for their antibacterial effect that favors the activity of brewer's yeast over less desirable microorganisms and for many purported benefits, including balancing the sweetness of the malt with bitterness, contributing a variety of desirable flavors and aromas. Historically, traditional herb combinations for ales were believed to have been abandoned when ales made with hops were noticed to be less prone to spoilage.
The hop plant is a vigorous, climbing, herbaceous perennial, usually trained to grow up strings in a field called a hopfield, hop garden (nomenclature in the South of England), or hop yard (in "The West country" and U.S.A.) when grown commercially. Many different varieties of hops are grown by farmers around the world, with different types being used for particular styles (categories) of beer.
Hops (Humulus lupulus) originate from China from where it moved east- and west-wards. The first documented instance of hop cultivation was in 736, in the Hallertau region of present-day Germany, although the first mention of the use of hops in brewing in that country was 1079. However in a will of Pepin the Short, the father of Charlemagne, in 768 hopgardens were left to the Cloister of Saint-Denis. Not until the 13th century did hops begin to start threatening the use of gruit for flavoring—which was used depending on the taxes which the nobility levied on either hops or gruit (or gruut). Whichever was taxed made the brewer then quickly switch to the other. In Britain, hopped beer was first imported from Holland around 1400, but hops were condemned in 1519 as a "wicked and pernicious weed". In 1471, Norwich, England, banned use of the plant in the brewing of ale ("beer" was the name for fermented malt liquors bittered with hops; only in recent times are the words often used as synonyms). Hops were imported from France, Holland and Germany and naturally import duty was raised on those; it was not until 1524 that hops were first grown in the southeast of England (Kent) when they were introduced as an agricultural crop by Dutch farmers. Therefore, in the hop industry there were many words which originally were Dutch words, such as oast house, which is derived from the Dutch word eest huis which means "drying house"; scuppet, which is a large wooden spade used on the hop floor to turn the hops into the hanging pocket; or bale which is derived from the Dutch word schop. Hops were then grown as far north as Aberdeen as they were grown near breweries because of the infrastructure. It was another century before hop cultivation began in the present-day United States, in 1629 by English and Dutch farmers.
World production 
Hops production is concentrated in moist temperate climates, with much of the world's production occurring near the 48th parallel north. Hop plants prefer the same soils as potatoes, the leading potato-growing states in the United States are also major hops-producing areas. However, not all potato-growing areas can produce good hops naturally. Soils in the Maritime Provinces of Canada lack the boron which hops prefer, for example. Historically, hops were not grown in Ireland, instead being imported from England. In 1752 more than 500 tons of English hops were imported through Dublin alone.
Important production centers are the Hallertau in Germany (which, in 2006, had more hop-growing area than any other country on Earth), the Yakima (Washington) and Willamette (Oregon) valleys, and western Canyon County, Idaho (including the communities of Parma, Wilder, Greenleaf, and Notus). The principal production centres in the UK are in Kent (which produces Kent Goldings hops) and Worcestershire. Essentially all of the harvested hops are used in beer making.
|Hop producing country||2010 Hop output in metric tonnes (t)|
|Democratic People's Republic of Korea||1,900|
|New Zealand||830 |
Cultivation and Harvest 
The cultivation of hops requires a special environment. Production is usually limited to rich flood plains adjacent to rivers. Hops are a climbing plant. They are trained to grow up strings or wires which support the plants and allow them significantly greater growth with the same sunlight profile. Energy that would have been required to build structural cells is also freed for crop growth.
Male and female flowers of the hop plant usually develop on separate plants (that is, the plant is dioecious), although fertile monoecious individuals will appear occasionally. Because viable seeds are undesirable for brewing beer, only female plants are grown in hopfields, which prevents pollination. Female plants are propagated vegetatively; or male plants are culled, if plants are grown from seeds.
Hops as most of us know, are used in brewing beer. The hop cones contain different oils that add flavor to the beer and make it foamy. The cones grow high on the vine and had to be picked by hand. The mechanical hops separator patented by Emil Horst in 1909 made the harvest easier. Hop plants are planted in rows about six to eight feet apart and are male and female. It’s the buds from the female plants that are used to flavor beer. Each spring the roots send forth new vines that would be started up strings that were attached from the ground to an overhead trellis. Harvest came near the end of summer when the vines were pulled down and the buds were then taken to a hop house for drying. Hop houses were two story buildings. The top floor had a slatted floor that was covered with burlap. Here the buds would be poured out and raked even. The bottom floor was where the heating unit was located that was used to dry the hops. When the hops were dry they were moved to a press. The press was a sturdy box with a plunger. Two long pieces of burlap were laid into the hop press at right angles and the hops were poured in and compressed into bales.
Emil Clemens Horst 
E. Clemens Horst (March 18, 1867 - May 24, 1940) was a major figure in the cultivation, harvest and sale of hops. He emigrated to the US in 1874 from Tuttlingen, Baden-Wuretemberg Germany, eventually moving to San Francisco in 1902. By 1904 he was supplying Oregon hops to the Guinness Brewery in Ireland - and by 1912, Horst owned the largest number of acres of hops under cultivation in the world with offices in Chicago, New York, London. Horst Company was headquartered at 150 Pine Street, San Francisco, California.  Prior to World War II, Horst Company was the only exporter of hops to Germany.
The cultivation of hops requires rich flood plains. One of Horst’s oldest and most productive hop ranches was the site of Campus Commons in Sacramento along the American River. Another nearby ranch of Horst's was based in Horstville, which was nearby Wheatland, CA. Until 2009, when Google released a digitized version of the 1916 Commission on Industrial Relations, the Horstville ranch was often confused with the neighboring Durst Ranch. The Durst Ranch was the site of the Wheatland Hop Riot on August 3rd, 1913.
Horst revolutionized the process of growing and processing hops with his 1909 patented mechanical separator that harvested the hops while discarding the vine and leaves. The process was further developed in 1939 (US Patent #2139046)  by his son-in-law, Edouard Thys, founder of Thys Company which, among other industrial parts, manufactured the parts for the portable hop picking machine.
A film produced between 1900 and 1910 entitled Horst Hop Ranch, depicts the processing of hops and their shipment to market. The 35mm nitrate film was housed in a Thomas A. Edison film can that initially suggests that this may be one of the earliest commercial films in California. Careful examination has revealed that the film is a reversal copy and that there are three distinct sections to the film. The first part is the hop separator in operation on the “Campus Commons” ranch. The second section is scenes in hop fields at Hopland, California or in Oregon. The third section is on the weighing and transportation of bales of hops by the Oregon Railway and Navigation Company probably near Portland, Oregon.
Migrant Labor and Social Impact 
The need for massed labor at harvest time meant hop-growing had a big social impact. Around the world, the labor-intensive harvesting work involved large numbers of migrant workers who would travel for the annual hop harvest. Whole families would partake and live in hoppers' huts, with even the smallest children helping in the fields. The final chapters of W. Somerset Maugham's Of Human Bondage contain a vivid description of London families participating in this annual hops harvest. In England, many of those picking hops in Kent were from eastern areas of London. This provided a break from urban conditions that was spent in the countryside. People also came from Birmingham and other Midlands cities to pick hops in the Malvern area of Worcestershire. Some photographs have been preserved.
Particularly in Kent, because of a shortage of small-denomination coin of the realm, many growers issued their own currency to those doing the labor. In some cases, the coins issued were adorned with fanciful hops images, making them quite beautiful.
In the US, Prohibition had a major impact on hops productions, but remnants of this significant industry in West and Northwest are still noticeable in the form of old hop kilns that survive throughout Sonoma County, among others. Florian Dauenhauer of Santa Rosa in Sonoma County, became a manufacturer of hop-harvesting machines in 1940, in part because of the hop industry's importance to the county. Ironically, this mechanization helped destroy the local industry by enabling large-scale mechanized production, which moved to larger farms in other areas.Dauenhauer Manufacturing remains a current producer of hop harvesting machines.
Hop resins are composed of two main acids: alpha and beta acids. Alpha acids have a mild antibiotic/bacteriostatic effect against Gram-positive bacteria, and favor the exclusive activity of brewing yeast in the fermentation of beer. Alpha acids are responsible for the bitter flavor in the beer.
Beta acids do not isomerize during the boil of wort, and have a negligible effect on beer taste. Instead, they contribute to beer's bitter aroma, and high beta acid hop varieties are often added at the end of the wort boil for aroma. Beta acids may oxidize into compounds that can give beer off-flavors of rotten vegetables or cooked corn.
The effect of hops on the finished beer varies by type and use, though there are two main hop types: bittering and aroma. Bittering hops have higher concentrations of alpha acids, and are responsible for the large majority of the bitter flavor of a beer. European (so-called "noble") hops typically average 5–9% alpha acids by weight (AABW), and the newer American cultivars typically range from 8–19% AABW. Aroma hops usually have a lower concentration of alpha acids (~5%) and are the primary contributors of hop aroma and (nonbitter) flavor. Bittering hops are boiled for a longer period of time, typically 60–90 minutes, to maximize the isomerization of the alpha acids. They often have inferior aromatic properties, as the aromatic compounds evaporate off during the boil.
The degree of bitterness imparted by hops depends on the degree to which otherwise insoluble alpha acids (AAs) are isomerized during the boil, and the impact of a given amount of hops is specified in International Bitterness Units (IBUs). Unboiled hops are only mildly bitter. On the other hand, the nonbitter flavor and aroma of hops come from the essential oils, which evaporate during the boil.
Aroma hops are typically added to the wort later to prevent the evaporation of the essential oils, to impart "hop taste" (if during the final 30 minutes of boil) or "hop aroma" (if during the final 10 minutes, or less, of boil). Aroma hops are often added after the wort has cooled and while the beer ferments, a technique known as "dry hopping", which contributes to the hop aroma. The three major components of the essential oil of hops are myrcene, humulene, and caryophyllene, which comprise about 60–80% of the oil for most hop varieties. farnesene is a major component in some hops. The composition of hop essential oils can differ a lot between varieties and between years in the same variety. About 250 components of essential oils have been identified. 22 of these are known to have significant influence on the flavor and aroma.
Today, a substantial amount of "dual-use" hops are used, as well. These have high concentrations of alpha acids and good aromatic properties. These can be added to the boil at any time, depending on the desired effect.
Flavors and aromas are described appreciatively using terms which include "grassy", "floral", "citrus", "spicy", "piney", "lemony", "grapefruit", and "earthy". Many pale lagers have fairly low hop influence, while lagers marketed as Pilsener or brewed in the Czech Republic may have noticeable noble hop aroma. Certain ales (particularly the highly-hopped style known as India Pale Ale, or IPA) can have high levels of hop bitterness.
Hop varieties 
Wye College which was established as an agricultural college in Wye, Kent in 1894 as part of London University has had a very significant effect on the breeding of Hop varieties in the early 19th century in the U.K. but since then as well in the world. Prof.E.F. Salmon was the first breeder of new hop varieties in the world and started there in 1906. He bred in 1919 two significant varieties Brewers Gold and Bullion from which many newer varieties have been cultivated not only in the U.K. hop breeding stations but all over the world. In 1934 he bred the variety Northern Brewer specifically for Scottish & Newcastle Breweries, situated in the North of England, hence is name was given Northern Brewer. Many breeding stations throughout the world have used this variety in their breeding program since then. The second significance of Wye College breeding of hops was in the seventies by Dr. Ray A. Neve, first with the new varieties Wye Target, Wye Challenger, Wye Northdown, Wye Saxon, Wye Yeoman and secondly by the breeding of the first world dwarf hop varieties, which are far more economic to grow for the Hop farmers, was carried out by Dr. Ray Neve. Wye College have also been responsible for breeding hop varieties that will grow with only 12 hours of daily light for the South African hop farmers. Wye College was closed in 2009 but the legacy of their hop breeding programs, particularly that of the dwarf varieties, is continuing as already the U.S.A. private and public breeding programs are using their stock material.
Particular hop varieties are associated with beer regions and styles, for example pale lagers are usually brewed with European (often German, Polish or Czech) noble hop varieties such as Saaz, Hallertau and Strissel Spalt. British ales use hop varieties such as Fuggles, Goldings and W.G.V. North American beers often use Cascade hops, Columbus hops, Centennial hops, Willamette, Amarillo hops and about forty more varieties as the U.S.A. have lately been the more significant breeders of new hop varieties, including dwarf hop varieties.
Noble hops 
The term "noble hops" traditionally refers to varieties of hops which are low in bitterness and high in aroma. They are the European cultivars or races Hallertau, Tettnanger, Spalt, and Saaz. They are not bred as "modern" hop varieties but they are wild hops found and named for a specific region or city in which they were first found or by the farmer which found them or first propagated them. They contain high amounts of the hop oil humulene and low amounts of alpha acids cohumulone and adhumulone, as well as lower amounts of the harsher-tasting beta acids lupulone, colupulone, and adlupulone.
Their low relative bitterness but strong aroma are often distinguishing characteristics of European-style lager beer, such as Pilsener, Dunkel, and Oktoberfest/Märzen. In beer, they are considered aroma hops (as opposed to bittering hops); see Pilsner Urquell as a classic example of the Bohemian Pilsener style, which showcases noble hops.
As with grapes, the land where the hops were grown affects the hops' characteristics. Much as Dortmunder beer may only within the EU be labelled "Dortmunder" if it has been brewed in Dortmund, noble hops may only officially be considered "noble" if they were grown in the areas for which the hops varieties (races) were named.
English noble varieties are Fuggle, East Kent Goldings and Goldings. They are characterized through analysis as having an alpha:beta ratio of 1:1, low alpha-acid levels (2–5%) with a low cohumulone content, low myrcene in the hop oil, high humulene in the oil, a ratio of humulene:caryophyllene above three, and poor storability resulting in them being more prone to oxidation. In reality, this means they have a relatively consistent bittering potential as they age, due to beta-acid oxidation, and a flavour that improves as they age during periods of poor storage.
- Hallertau or Hallertauer–The original German lager hop; named after Hallertau or Holledau region in central Bavaria. Due to susceptibility to crop disease, it was largely replaced by Hersbrucker in the 1970s and 1980s. (Alpha acid 3.5–5.5% / beta acid 3–4%)
- Saaz–Noble hop used extensively in Bohemia to flavor pale Czech lagers such as Pilsner Urquell. Soft aroma and bitterness. (Alpha acid 3–4.5% /Beta acid 3–4.5%)
- Spalt–Traditional German noble hop from the Spalter region south of Nuremberg. With a delicate, spicy aroma. (Alpha acid 4–5% / beta acid 4–5%)
- Tettnang–Comes from Tettnang, a small town in southern Baden-Württemberg in Germany. The region produces significant quantities of hops, and ships them to breweries throughout the world. Noble German dual-use hop used in European pale lagers, sometimes with Hallertau. Soft bitterness. (Alpha acid 3.5–5.5% / beta acid 3.5–5.5%)
Other uses 
The only major commercial use for hops is in beer, although hops are also an ingredient in Julmust, a carbonated beverage similar to soda that is popular in Sweden during December, as well as Malta, a Latin American soft drink. Hops are sometimes added to some varieties of kvass. They are also used for flavor in some tisanes.
Hops are also used in herbal medicine in a way similar to valerian, as a treatment for anxiety, restlessness, and insomnia. A pillow filled with hops is a popular folk remedy for sleeplessness, and animal research has shown a sedative effect. The relaxing effect of hops may be due, in part, to the specific chemical component dimethylvinyl carbinol. Hops tend to be unstable when exposed to light or air and lose their potency after a few months' storage.
Dermatitis sometimes results from harvesting hops. Although few cases require medical treatment, an estimated 3% of the workers suffer some type of skin lesions on the face, hands, and legs. Hops are toxic to dogs, resulting in life-threatening hyperthermia.
Hops contains humulone, isohumulone and humulene which are bitter-tasting compounds. It also contains the natural phenols xanthohumol, isoxanthohumol and the most estrogenic phytoestrogen known, 8-prenylnaringenin.
See also 
- Gruit, an old-fashioned herb mixture used for bittering and flavoring beer, popular before the extensive use of hops
- Mugwort, a herb historically used as a bitter in beer production
- Oast house, a building designed for drying hops
- Rhamnus prinoides, a plant from which an extract is used, mixed with honey, to ferment a mead called tej in Africa
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