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Hops

Hop flower in a hop yard in the Hallertau , Germany Cross-section drawing of a hop bines .","txt":"Full grown hops bines."}]]}"> Fully grown hops bines ready for harvest on the ...

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Hop flower in a hop yard in the Hallertau, Germany
Cross-section drawing of a hop
Full grown hops bines.
Fully grown hops bines ready for harvest on the Yakama Indian Reservation
Humulus on a house

Hops are the flowers (also called seed cones or strobiles) of the hop plant Humulus lupulus,[1] a member of the Cannabaceae family of flowering plants.[2] They are used primarily as a bittering, flavouring, and stability agent in beer, to which, in addition to bitterness, they impart floral, fruity, or citrus flavours and aromas.[3] Hops are also used for various purposes in other beverages and herbal medicine. The hops plants have separate female and male plants, and only female plants are used for commercial production.[4] The hop plant is a vigorous climbing herbaceous perennial, usually trained to grow up strings in a field called a hopfield, hop garden (in the South of England), or hop yard (in the West Country and United States) when grown commercially. Many different varieties of hops are grown by farmers around the world, with different types used for particular styles of beer.

The first documented use of hops in beer is from the 9th century, though Hildegard of Bingen, 300 years later, is often cited as the earliest documented source.[5] Before this period, brewers used a "gruit", composed of a wide variety of bitter herbs and flowers, including dandelion, burdock root, marigold, horehound (the old German name for horehound, Berghopfen, means 'mountain hops'), ground ivy, and heather.[6] Early documents include mention of a hop garden in the will of Charlemagne's father, Pepin the Short.[7]

El lúpulo también se utiliza en la elaboración de cerveza por su efecto antibacteriano sobre microorganismos menos deseables y por supuestos beneficios, como equilibrar la dulzura de la malta con el amargor y una variedad de sabores y aromas. [ 3 ] Se cree que las combinaciones tradicionales de hierbas para cervezas se abandonaron después de que se observó que las cervezas elaboradas con lúpulo eran menos propensas a deteriorarse. [ 8 ]

Historia

El primer cultivo documentado de lúpulo data del año 736, en la región de Hallertau , en la actual Alemania. [ 9 ] En 768, Pipino el Breve , padre de Carlomagno , legó jardines de lúpulo al claustro de Saint-Denis en su testamento . [ 10 ] La primera mención del uso del lúpulo en la elaboración de cerveza alemana data del año 1079. [ 11 ]

No fue hasta el siglo XIII que el lúpulo comenzó a amenazar el uso del gruit como saborizante. El gruit se utilizaba cuando la nobleza imponía impuestos al lúpulo. Cualquiera que fuera gravado obligaba al cervecero a cambiar rápidamente al otro. [ 12 ]

En Gran Bretaña, la cerveza lupulada se importó por primera vez de Holanda alrededor de 1400, sin embargo, el lúpulo fue condenado hasta 1519 como una "mala hierba perniciosa y dañina". [ 13 ]

En Alemania, el uso del lúpulo también fue una elección religiosa y política a principios del siglo XVI. No se pagaba ningún impuesto al lúpulo a la Iglesia Católica, a diferencia del gruit. Por esta razón, los protestantes preferían la cerveza lupulada. [ 14 ]

El lúpulo utilizado en Inglaterra se importaba de Francia, Holanda y Alemania y estaba sujeto a aranceles de importación ; no fue hasta 1524 que se cultivó por primera vez en el sureste de Inglaterra ( Kent ), cuando los agricultores holandeses lo introdujeron como cultivo agrícola . En consecuencia, muchas palabras utilizadas en la industria del lúpulo derivan del neerlandés . Posteriormente, el lúpulo se cultivaba incluso en Aberdeen , al norte , cerca de las cervecerías para facilitar el acceso a la infraestructura. [ 15 ]

Según los Quinientos Puntos de Buena Agricultura de Thomas Tusser de 1557 :

Así exalto el lúpulo por su provecho, pues fortalece la bebida y da sabor a la malta; y bien fermentado y conservado, perdurará, y el trago se mantendrá, si no se bebe demasiado rápido. [ 16 ]

In England there were many complaints over the quality of imported hops, the sacks of which were often contaminated by stalks, sand or straw to increase their weight. As a result, in 1603, King James I approved an Act of Parliament banning the practice by which "the Subjects of this Realm have been of late years abused &c. to the Value of £20,000 yearly, besides the Danger of their Healths".[17]

Hop cultivation was begun in the present-day United States in 1629 by English and Dutch farmers.[18] Before prohibition, cultivation was mainly centred around New York, California, Oregon, and Washington state. Problems with powdery mildew and downy mildew devastated New York's production by the 1920s, and California only produces hops on a small scale.[19]

World production

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Growing zone for commercial hops and important international market beer hop growing areas.[20]:11[21]
Legend
  • Key:
  •   Growing range from 35° to 55° latitude
  •   48° N (highest productivity)
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Hops production is concentrated in moist temperate climates due to the plant's needs, with much of the world's production occurring near the 48th parallel north.[21]Climate change may impact future commercial production.[21] Germany and the United States account for three quarters of hop production with two thirds of the total surface area used for hop-growing worldwide.[20]:10 Hop plants prefer the same soils as potatoes and the leading potato-growing states in the United States are also major hops-producing areas.[22] Not all potato-growing areas can produce good hops naturally, however: for example, soils in the Maritime Provinces of Canada lack the boron that hops prefer.[22] Historically, hops were not grown in Ireland, but were imported from England. In 1752 more than 500 tons of English hops were imported through Dublin alone.[23]

Los centros de producción importantes hoy en día son Hallertau en Alemania, [ 24 ] Žatec ( Saaz ) en la República Checa , los valles de Yakima ( Washington ) y Willamette (Oregón), y el oeste del condado de Canyon, Idaho (incluidas las comunidades de Parma , Wilder , Greenleaf y Notus ). [ 25 ] Los principales centros de producción en el Reino Unido están en Kent (que produce lúpulo Kent Goldings), Herefordshire y Worcestershire . [ 26 ] [ 27 ] Esencialmente, como casi todo el lúpulo cosechado se utiliza en la elaboración de cerveza, los productores notables a nivel mundial están orientados a este mercado. Otras regiones notables para el mercado internacional de lúpulo para cerveza no mencionadas hasta ahora incluyen Spalt y Tettnang en Alemania, Lublin en Polonia, Celje en Eslovenia, Derwent Valley, Tasmania y High Country de Victoria en Australia, Marlborough en Nueva Zelanda, Villanueva del Carrizo en España, George en Sudáfrica. [ 20 ] : 11 [ 21 ] Entre los países con una producción notable se incluyen China, Francia, Japón, Canadá, Chile, Argentina y Ucrania. [ 20 ] : 11

Crecimiento temprano de lúpulo en un campo de lúpulo en el valle del río Yakima, Washington, con el monte Adams al fondo.

Cultivo y cosecha

Una superestructura de cables aéreos sostiene cuerdas que a su vez sostienen lizos .

Aunque el lúpulo se cultiva en la mayor parte de los Estados Unidos continentales y Canadá, [ 29 ] su cultivo para la producción comercial requiere un entorno particular. Dado que el lúpulo es una planta trepadora, se la guía para que crezca sobre enrejados hechos de cuerdas o alambres que la sostienen y le permiten un crecimiento significativamente mayor con el mismo perfil de luz solar. De esta manera, la energía que se habría requerido para construir células estructurales también se libera para el crecimiento del cultivo. [ 30 ]

El método de reproducción del lúpulo consiste en que las flores masculinas y femeninas se desarrollan en plantas separadas, aunque ocasionalmente se desarrolla un individuo fértil que contiene flores masculinas y femeninas. [ 31 ] Dado que las semillas polinizadas no son deseables para la elaboración de cerveza, solo se cultivan plantas femeninas en los campos de lúpulo, evitando así la polinización. Las plantas femeninas se propagan vegetativamente , y las plantas masculinas se eliminan si las plantas se cultivan a partir de semillas. [ 32 ]

Las plantas de lúpulo se siembran en hileras separadas por unos 2 a 2,5 metros (7 a 8 pies) . Cada primavera, las raíces producen nuevos tallos que se enraízan desde el suelo hasta un enrejado superior mediante cuerdas. Los conos crecen en lo alto del tallo y, antiguamente, se recolectaban a mano. La cosecha del lúpulo se volvió mucho más eficiente con la invención del separador mecánico de lúpulo, patentado por Emil Clemens Horst en 1909. [ 33 ] 

El lúpulo se cosecha a finales del verano. [ 34 ] Las enredaderas se cortan, se separan y luego se secan en un secadero para reducir su contenido de humedad. Para secarlo, tradicionalmente el lúpulo se extiende en el piso superior del secadero y se calienta mediante unidades de calefacción en el piso inferior. Luego, el lúpulo seco se comprime en balas con una empacadora . [ 35 ] Actualmente, se suele secar en hornos con grandes ventiladores que fuerzan el paso de aire limpio y caliente a través de los lechos de lúpulo y se procesa posteriormente en pellets, que tienen propiedades de almacenamiento más prolongadas que el lúpulo entero. [ 36 ] : 25

Fotografía macro de lupulina en un cono de lúpulo.

Los conos de lúpulo contienen diferentes aceites, como la lupulina, una sustancia cerosa amarillenta, una oleorresina , que aporta sabor y aroma a la cerveza. [ 37 ] La ​​lupulina contiene lupulona y humulona , ​​que poseen propiedades antibióticas, suprimiendo el crecimiento bacteriano y favoreciendo el de la levadura cervecera. Tras la extracción de la lupulina durante el proceso de elaboración de la cerveza, los conos, de textura similar al papel, se desechan.

Trabajo migrante e impacto social

Hops harvest in the Kingdom of Bohemia (1898)
Hops harvest in Skåne, Sweden, in 1937

The need for massed labour at harvest time meant hop-growing had a big social impact. Around the world, the labour-intensive harvesting work involved large numbers of migrant workers who would travel for the annual hop harvest. Whole families would participate and live in hoppers' huts, with even the smallest children helping in the fields.[38][39] The final chapters of W. Somerset Maugham's Of Human Bondage and a large part of George Orwell's A Clergyman's Daughter 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.[40]

The often-appalling living conditions endured by hop pickers during the harvest became a matter of scandal across Kent and other hop-growing counties. Eventually, the Rev. John Young Stratton, Rector of Ditton, Kent, began to gather support for reform, resulting in 1866 in the formation of the Society for the Employment and Improved Lodging of Hop Pickers.[41] The hop-pickers were given very basic accommodation, with very poor sanitation. This led to the spread of infectious diseases and led to contaminated water. The 1897 Maidstone typhoid epidemic was partly as a result of hop-pickers camping near the Farleigh Springs which supplied Maidstone with water.[42][43]

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.[44]

Puget Sound region, Washington, c. 1893

In the United States, Prohibition had a serious adverse effect on hops production, but remnants of this significant industry in the western states are still noticeable in the form of old hop kilns that survive throughout Sonoma County, California, 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. This mechanization helped destroy the local industry by enabling large-scale mechanized production, which moved to larger farms in other areas.[45]

Chemical composition

In addition to water, cellulose, and various proteins, hops contain compounds that impart flavour and aroma to beer.[3][46]

Alpha acids

Isomerization scheme of humulone

Hops contain alpha acids or humulones. During wort boiling, the humulones are thermally isomerized into iso-alpha acids or isohumulones, which give a bitter flavour to beer.[47]

Beta acids

Structure of lupulone (beta acid)

Hops contain beta acids or lupulones, contributing aromas to beer.[48]

Essential oil

Myrcene contributes a pungent smell of fresh hops, together with humulene and caryophyllene, all representing 80-90% of the essential oil in hops.[46]

Flavonoids

Chemical structure of 8-prenylnaringenin

Xanthohumol is the principal flavonoid, with other prenylflavonoids including 8-prenylnaringenin and isoxanthohumol.[49] 8-prenylnaringenin is a potent phytoestrogen.[50]

Brewing

English brewers dry-hopping casks of beer (1918)
Hops sample

Hops are usually dried in an oast house or now kiln before they are used in the brewing process.[51] Undried or "wet" hops are sometimes (since c. 1990) used.[52][53][36]:25

The wort (sugar-rich liquid produced from malt) is boiled with hops before it is cooled down and yeast is added, to start fermentation.

The effect of hops on the finished beer varies by type and use, though there are two main hop types: bittering and aroma.[3] The characteristics are also determined by the soil the hops are grown on and for example clay-loamy soils can have low yields but excellent aroma and taste.[20]:16

Bittering hops have higher concentrations of alpha acids, and are responsible for the large majority of the bitter flavour 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) flavour.

Bittering hops are boiled for a longer period of time, typically 60–90 minutes, and often have inferior aromatic properties, as the aromatic compounds evaporate during the boil. The degree of bitterness imparted by hops depends on the degree to which alpha acids are isomerized during the boil, and the impact of a given amount of hops is specified in International Bitterness Units. On the other hand, unboiled hops are only mildly bitter.

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. Farnesene is a major component in some hops.[3] The composition of hop essential oils can differ between varieties and between years in the same variety, having a significant influence on flavour and aroma.[3]

Dual-use hops 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.[54] Hop acids also contribute to and stabilize the foam qualities of beer.[3]

Flavours and aromas may be described as "grassy", "floral", "citrus", "spicy", "piney", "lemony", "grapefruit", and "earthy".[3][55]

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.

Dried extracts and pellets may replace whole hops in the brewing process to improve efficiency, cost, and storage life, typically at temperatures between −1 and −5 °C (30 and 23 °F).[36]:25

Varieties

Breeding programmes

There are many different varieties of hops used in brewing. Historically, hops varieties were identified by geography, i.e., from the towns of Hallertau, Spalt, and Tettnang in Germany,[56] or a region, such as the Neomexicanus hops of New Mexico.[57] Others were named for the farmer recognized as first cultivating them, including Goldings or Fuggles from England,[58] or by their growing habit, like the Oregon Clusters.[59]

Around 1900, a number of institutions began to experiment with breeding specific hop varieties. The breeding program at Wye College in Wye, Kent, was started in 1904 and rose to prominence through the work of Prof. E. S. Salmon. Salmon released Brewer's Gold and Brewer's Favorite for commercial cultivation in 1934, and went on to release more than two dozen new cultivars before his death in 1959. Brewer's Gold has become the ancestor of the bulk of new hop releases around the world since its release.[60]

Wye College continued its breeding program and again received attention in the 1970s, when Dr. Ray A. Neve released Wye Target, Wye Challenger, Wye Northdown, Wye Saxon and Wye Yeoman. More recently, Wye College and its successor institution Wye Hops Ltd., have focused on breeding the first dwarf hop varieties, which are easier to pick by machine and far more economical to grow.[61] 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 US 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 US have lately been the more significant breeders of new hop varieties, including dwarf hop varieties.

In New Zealand, where hop cultivation commenced in 1842,[36]:7 hops have been developed into varieties such as Pacific Gem, Motueka and Nelson Sauvin, being used in a "Pacific Pale Ale" style of beer.[62] By 1985 80% of New Zealand hop production was exported.[36]:7

Noble hops

Mature hops growing in a hop yard in Germany

The term "noble hops" is a marketing term that traditionally refers to certain varieties of hops that became known for being low in bitterness and high in aroma.[63] They are the European cultivars or races Hallertau, Tettnanger, Spalt, and Saaz.[64] Some proponents assert that the English varieties Fuggle, East Kent Goldings and Goldings might qualify as "noble hops" due to the similar composition, but such terms are not applied to English varieties. Their low relative bitterness, but strong aroma, are often distinguishing characteristics of European-style lagers, such as Pilsener, Dunkel, and Oktoberfest/Märzen. In beer, they are considered aroma hops (as opposed to bittering hops);[63] see Pilsner Urquell as a classic example of the Bohemian Pilsener style, which showcases noble hops.

As with grapes, the location where hops are grown affects the hops' characteristics. Much as Dortmunder beer may within the EU be labelled "Dortmunder" only if it has been brewed in Dortmund, noble hops may officially be considered "noble" only if they were grown in the areas for which the hop varieties (races) were named.

  • 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%)
  • 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%)
  • Žatec (Saaz): Noble hop, named after Žatec town, used extensively in Bohemia to flavour pale Czech lagers such as Pilsner Urquell. Soft aroma and bitterness. (Alpha acid 3–4.5% /Beta acid 3–4.5%)

Los lúpulos nobles se caracterizan mediante análisis por tener una calidad aromática resultante de numerosos factores en el aceite esencial, como una proporción alfa:beta de 1:1, bajos niveles de alfa-ácidos (2–5%) con un bajo contenido de cohumulona, ​​bajo mirceno en el aceite de lúpulo, alto humuleno en el aceite, una proporción de humuleno:cariofileno superior a tres y una mala capacidad de almacenamiento que los hace más propensos a la oxidación. [ 63 ] En realidad, esto significa que tienen un potencial de amargor relativamente constante a medida que envejecen, debido a la oxidación de los beta-ácidos, y un sabor que mejora a medida que envejecen durante períodos de almacenamiento deficiente. [ 63 ] [ 65 ]

Otros usos

2-metil-3-buten-2-ol

El lúpulo se utiliza en infusiones , así como en refrescos como el julmust (una  bebida carbonatada similar a la gaseosa, popular en Suecia durante diciembre), la Malta (un refresco latinoamericano ), el kvass y el agua de lúpulo . [ 66 ] El amarasato , un suplemento dietético extraído del lúpulo, se comercializa para suprimir el apetito. [ 67 ] Además, tanto los brotes jóvenes como las flores jóvenes son comestibles y se pueden cocinar como los espárragos . [ 68 ] [ 69 ] [ 70 ] 

El lúpulo puede utilizarse en la medicina herbal de forma similar a la valeriana , como tratamiento para la ansiedad, la inquietud y el insomnio. [ 71 ] Una almohada rellena de lúpulo es un remedio popular para el insomnio. [ 72 ] Estas indicaciones tienen evidencia limitada en humanos. [ 73 ] El lúpulo carece de evidencia sólida que respalde su eficacia para cualquier afección médica específica, aunque generalmente se considera seguro. [ 73 ]

El lúpulo es de interés para la terapia de reemplazo hormonal y se encuentra en investigación básica para el posible alivio de problemas relacionados con la menstruación. [ 74 ]

Toxicidad

La dermatitis a veces es consecuencia de la cosecha de lúpulo. Aunque pocos casos requieren tratamiento médico, se estima que el 3% de los trabajadores sufren algún tipo de lesión cutánea en la cara, las manos y las piernas. [ 75 ] El lúpulo es tóxico para los perros . [ 76 ]

Véase también

  • Artemisa , una hierba utilizada históricamente como amargo en la producción de cerveza.
  • Rhamnus prinoides, a plant whose leaves are used in the Ethiopian variety of mead called tej

References

  1. ↑"University of Minnesota Libraries: The Transfer of Knowledge. Hops-Humulus lupulus". Lib.umn.edu. 13 May 2008. Archived from the original on 5 March 2012. Retrieved 20 May 2012.
  2. ↑"Cannabaceae | Description, Genera, & Species". Encyclopedia Britannica. Retrieved 16 September 2020.
  3. 12345678Schönberger C, Kostelecky T (16 May 2012). "125th Anniversary Review: The Role of Hops in Brewing". Journal of the Institute of Brewing. 117 (3): 259–267. doi:10.1002/j.2050-0416.2011.tb00471.x.
  4. ↑Willy H. Verheye, ed. (2010). "Hops and Hop Growing". Soils, Plant Growth and Crop Production Volume II. EOLSS Publishers. p. 194. ISBN 978-1-84826-368-0.
  5. ↑Hornsey, Ian S. (2003). A History of Beer and Brewing. Royal Society of Chemistry. p. 305. ISBN 978-0-85404-630-0.
  6. ↑"Understanding Beer – A Broad Overview of Brewing, Tasting and Analyzing Beer – October 12th, 2006, Beer & Brewing, The Brewing Process". www.jongriffin.com. Jongriffin.com. Archived from the original on 15 March 2012. Retrieved 20 May 2012.
  7. ↑Michael Jackson (1988). The New World World Guide to Beer. Running Press. p. 18. ISBN 978-0-89471-884-7.
  8. ↑F. G. Priest; Iain Campbell (2003). Brewing microbiology. Springer. p. 5. ISBN 978-0-306-47288-6.
  9. ↑Ian Hornsey (31 October 2007). Brewing. Royal Society of Chemistry. p. 58. ISBN 978-1-84755-028-6.
  10. ↑Unger, Richard W. (2007). Beer in the Middle Ages and the Renaissance. Philadelphia, Pennsylvania: University of Pennsylvania Press. pp. 53–54. ISBN 978-0-8122-1999-9.
  11. ↑H.S. Corran (23 January 1975). History of Brewing. David and Charles PLC. p. 303. ISBN 978-0-7153-6735-3.
  12. ↑Verberg, Susan (2020). "From Herbal to Hopped Beer: The Displacement of Regional Herb Beer Traditions by Commercial Export Brewing in Medieval Europe". Brewery History. 183: 9–23 – via ResearchGate.
  13. ↑Richard W. Unger (2004). Beer in the Middle Ages and Renaissance. University of Pennsylvania Press. p. 100.
  14. ↑Mika Rissanen. "The Reformation had some help from hops". www.academia.edu. Retrieved 21 September 2016.
  15. ↑Pocock, D. C. D. (1959). England's diminished Hop-acreage. Geographical Association. pp. 14–22.
  16. ↑Knight, Charles (1832). "Antiquity of Beer". The Penny Magazine. p. 3.
  17. ↑Adam Anderson (1764). An Historical and Chronological Deduction of the Origin of Commerce. Vol. 1. p. 461.
  18. ↑Charles W. Bamforth (1998). Beer: tap into the art and science of brewing. Plenum Press. p. 245. ISBN 978-0-306-45797-5.
  19. ↑Knight, Paul D. "HOPS IN BEER". USA Hops. Hop Growers of America. Archived from the original on 10 June 2015. Retrieved 11 June 2015.
  20. 12345Stark, C.; Gillespie, J. (2021). Suitability of New Zealand cropping regions to support hop production(PDF) (Report). Lincoln, New Zealand: Bio-Protection Research Centre. pp. 1–35. Retrieved 25 December 2025.
  21. 1234Mozny, M.; Trnka, M.; Vlach, V.; Zalud, Z.; Cejka, T.; Hajkova, L.; Potopova, V.; Semenov, M.A.; Semeradova, D.; Büntgen, U. (10 October 2023). "Climate-induced decline in the quality and quantity of European hops calls for immediate adaptation measures". Nature Communications. 14. 6028. doi:10.1038/s41467-023-41474-5.
  22. 12"Hops industry has great potential for Atlantic Canada". peicanada.com. 12 December 2012.
  23. ↑"The London magazine, 1752", page 332
  24. ↑Summary of Reports: Nürnberg, Germany, 14 November 2006, International Hop Growers' Convention: Economic Committee
  25. ↑"NCGR-Corvallis Humulus Genetic Resources". www.ars-grin.gov. Ars-grin.gov. Retrieved 20 May 2012.
  26. ↑Norman Moss, A Fancy to WorcestersArchived 29 September 2007 at the Wayback Machine, Agricultural research Service, US Department of Agriculture
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  30. ↑Keegstra, Kenneth (1 October 2010). "Plant Cell Walls". Plant Physiology. 154 (2): 483–486. doi:10.1104/pp.110.161240. ISSN 1532-2548. PMC 2949028. PMID 20921169.
  31. ↑C. C. Ainsworth (15 June 1999). "5 Sex Determination in Plants". Sex Determination in Plants. Current Topics in Developmental Biology. Vol. 38. Garland Science. pp. 167–223. doi:10.1016/s0070-2153(08)60247-1. ISBN 978-0-203-34599-3. PMID 9399079.
  32. ↑"Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries. Economic Plants and their Diseases, Pests and Weeds. Humulus lupulus". www.agroatlas.ru. Agroatlas.ru. Archived from the original on 10 March 2012. Retrieved 20 May 2012.
  33. ↑"Innovative Hopping Equipment: New Belgium's Dry Hop Dosing Skid". Craft Brewing Business. 22 October 2013. Retrieved 4 May 2021.
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Further reading

  • "Oregon Brewers Played an Outsized Role in Popularizing IPA". All Things Considered. NPR. 1 June 2024. Retrieved 1 June 2024.