Humulus

Although frequently referred to in American literature as the hops "vine", it is technically a bine; unlike vines, which use tendrils, suckers, and other appendages for attaching themselves, bines have stout stems with stiff hairs to aid in climbing. In British literature the term "vine" is generally reserved for the grape genus Vitis. Humulus is described as a twining perennial herbaceous plant which sends up new shoots in early spring and dies back to the cold-hardy rhizome in autumn. Hop shoots grow very rapidly, and at the peak of growth can grow {{convert|20|to|50|cm|abbr=off|in|sigfig=1}} per week. Hop bines climb by wrapping clockwise (except for Humulus japonicus) around anything within reach, and individual bines typically grow between {{convert|2|and|15|m|abbr=off|ft|sigfig=1}} depending on what is available to grow on. The leaves are opposite, with a {{convert|7|to|12|cm|in|abbr=on|frac=4}} leafstalk and a heart-shaped, fan-lobed blade {{convert|12|to|25|cm|in|abbr=on|frac=4}} long and broad; the edges are coarsely toothed. When the hop bines run out of material to climb, horizontal shoots sprout between the leaves of the main stem to form a network of stems wound round each other.{{cite book | editor-last = Brickell | editor-first = Christopher | title = The Royal Horticultural Society A-Z Encyclopedia of Garden Plants | year = 2008 | page = 550 | publisher = Dorling Kindersley | location = United Kingdom | isbn = 9781405332965}}

Male and female flowers of the hop plant are dioecious, developing on separate plants. Female plants, which produce the hop flowers used in brewing beer, are often propagated vegetatively and grown in the absence of male plants. This prevents pollination and the development of viable seeds, which are sometimes considered undesirable for brewing beer owing to the potential for off-flavors arising from the introduction of fatty acids from the seeds.[http://www.agroatlas.ru/cultural/Humulus_lupulus_K_en.htm Interactive Agricultural Ecological Atlas of Russia and Neighboring Countries. Economic Plants and their Diseases, Pests and Weeds. Humulus lupulus.] {{webarchive|url=https://web.archive.org/web/20120310182625/http://www.agroatlas.ru/cultural/Humulus_lupulus_K_en.htm |date=2012-03-10 }}

The characteristic bitterness imparted by the addition of hops to the brewing process is mainly due to the presence of bitter acids, which are prenylated acylphloroglucinol derivatives.{{cite book |last1=Verzele |first1=M. |title=Chemistry and analysis of hop and beer bitter acids |last2=De Keukeleire |first2=D. |publisher=Elsevier |year=1991 |isbn=978-0-444-88165-6 |location=New York}} Bitter acids are divided into the alpha-acids, with humulone the major compound, and the beta-acids, with lupulone the major compound; the alpha-acids isomerize during the brewing process to form iso-alpha acids, which themselves have a bitter taste.{{cite journal |last1=Jaskula |first1=Barbara |last2=Kafarski |first2=Pawel |last3=Aerts |first3=Guido |last4=De Cooman |first4=Luc |date=August 2008 |title=A Kinetic Study on the Isomerization of Hop α-Acids |journal=Journal of Agricultural and Food Chemistry |volume=56 |issue=15 |pages=6408–6415 |doi=10.1021/jf8004965 |pmid=18598038}} These hop acids are vinylogous acids, with acidic ring enols in conjugation with ring and substituent carbonyl groups.{{cite journal |last1=Urban |first1=Jan |last2=Dahlberg |first2=Clinton J. |last3=Carroll |first3=Brian J. |last4=Kaminsky |first4=Werner |date=28 January 2013 |title=Absolute Configuration of Beer′s Bitter Compounds |journal=Angewandte Chemie International Edition |volume=52 |issue=5 |pages=1553–1555 |doi=10.1002/anie.201208450 |pmc=3563212 |pmid=23239507}}{{cite journal |last1=De Keukeleire |first1=Denis |date=February 2000 |title=Fundamentals of beer and hop chemistry |journal=Química Nova |volume=23 |issue=1 |pages=108–112 |doi=10.1590/S0100-40422000000100019 |doi-access=free}} Plants in the genus Humulus produce terpenophenolic metabolites.{{cite book |last1=Page |first1=Jonathan E. |title=Recent Advances in Phytochemistry |last2=Nagel |first2=Jana |year=2006 |isbn=9780080451251 |volume=40 |pages=179–210 |chapter=Biosynthesis of terpenophenolic metabolites in hop and cannabis |doi=10.1016/S0079-9920(06)80042-0}} Hops also contain xanthohumol, a prenylated chalcone, and other compounds.{{cite journal |last1=Stevens |first1=Jan F |last2=Page |first2=Jonathan E |date=May 2004 |title=Xanthohumol and related prenylflavonoids from hops and beer: to your good health! |journal=Phytochemistry |volume=65 |issue=10 |pages=1317–1330 |doi=10.1016/j.phytochem.2004.04.025 |pmid=15231405|bibcode=2004PChem..65.1317S }}

File:환삼덩굴 잎.JPG leaves]]

{{As of|2020|10}}, the following species were accepted:{{cite web |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30027247-2 |title=Humulus L. |author= |date=2017 |website=Plants of the World Online |publisher=Board of Trustees of the Royal Botanic Gardens, Kew |access-date=14 October 2020 }}

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• Humulus americanus Nutt.
• Humulus cordifolius Miq.
• Humulus lupulus L.
• Humulus neomexicanus (A.Nelson & Cockerell) Rydb.
• Humulus pubescens (E.Small) Tembrock
• Humulus scandens (Lour.) Merr. (syn. ''Humulus japonicus Siebold & Zucc.)
• Humulus yunnanensis Hu

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For brewers' hops, which are specific cultivars, and propagated by asexual reproduction, see the article, "List of hop varieties".

Hops are boiled with the wort in brewing beer and sometimes added post-ferment; they impart a bitterness, flavor, as well as aroma to the finished product.{{cite journal |last1=Almaguer |first1=Cynthia |last2=Schönberger |first2=Christina |last3=Gastl |first3=Martina |last4=Arendt |first4=Elke K. |last5=Becker |first5=Thomas |title=Humulus lupulus - a story that begs to be told. A review: Humulus lupulus - a story that begs to be told |journal=Journal of the Institute of Brewing |date=September 2014 |doi=10.1002/jib.160 |doi-access=free }}

In pharmacy lupulus is the designation of hop. The dried catkins, commonly referred to as hop cones, of the female plant of H. lupulus are used to prepare infusion of hop, tincture of hop, and extract of hop.{{Cite Collier's|wstitle=Hop}}

Some of the compounds hops contain are under preliminary research for their potential health properties.

{{Reflist}}

• [https://www.ars.usda.gov/pacific-west-area/corvallis-or/national-clonal-germplasm-repository/docs/ncgr-corvallis-humulus-germplasm/ Jeanine S. DeNoma: Humulus Genetic Resources (USDA ARS National Clonal Germplasm Repository)]
• [https://www.uvm.edu/~pass/perry/hops.html Hops varieties research]
• [https://pfaf.org/User/plant.aspx?LatinName=Humulus+lupulus Plants for a Future: Humulus lupulus]

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Category:Medicinal plants

Category:Stem vegetables

Category:Dioecious plants

Category:Rosales genera

Category:Taxa named by Carl Linnaeus