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Humulus lupulus

life science Maturity 5-7 Next article →

Humulus lupulus, commonly known as the hop plant, is a perennial climbing plant. It belongs to the Cannabaceae family, which also includes hemp and marijuana. As a perennial, it can live for up to 20 years. Every spring, the plant sends up new shoots from a cold-hardy rhizome. In the autumn, the plant dies back to this underground root system. Hops are essential to the brewing industry. They are used to provide flavor, aroma, and preservative qualities to beer.

Hop plant by Kent Ditch - geograph.org.uk - 5892896
Hop plant by Kent Ditch - geograph.org.uk - 5892896

The growth habit of the hop is unique. While many people call it a vine, it is more accurately described as a bine. This is because the plant has stiff, downward-facing hairs. These hairs provide stability and allow the plant to climb upward. The plant is also dioecious, meaning it has separate male and female plants. The male flowers, or staminate flowers, do not have petals. The female flowers, or pistillate flowers, have petals that envelope the fruit. These female flowers form fragrant, cone-shaped structures called strobili, which are commonly known as hops.

Humulus lupulus male flowers RF
Humulus lupulus male flowers RF

Inside these female cones, the plant produces specific structures. The fruit of the plant is an achene, which is a type of dry fruit that does not split open when it is mature. These achenes are surrounded by tepals. Concentrated on the fruit are glands that secrete lupulin. This substance is vital for the plant's chemical profile. The flowering process is triggered by longer summer days. In the Northern Hemisphere, this usually occurs around July or August. The fragrant flowers rely on the wind for pollination.

Humans have cultivated hops for many centuries. Historical records show that King Pepin donated hops to a monastery in Paris in 768 CE. Later, in 859 CE, documents from a monastery in Freising, Germany, recorded the cultivation of hops. Before hops became the standard, brewers used other plants like Myrica gale to flavor their drinks. Hops eventually became the preferred choice because they contain natural preserving agents. These agents help prolong the viability of a brew. Over thousands of years, human selection has enhanced the aroma, bitterness, and yield of various varieties.

Humle (Humulus lupulus)-2017-Ystad
Humle (Humulus lupulus)-2017-Ystad

The chemistry of Humulus lupulus is complex and highly valued. It contains several secondary metabolites, including myrcene, humulene, xanthohumol, myrcenol, and linalool. These compounds, along with tannins and resins, impact the flavor of products like beer. The characteristic bitterness in hop-based products comes from acids composed of prenylated polyketides. Specifically, iso-alpha acids are the main components responsible for bitterness. Other compounds help create the foam found in beer. Scientists have identified specific genes, such as geranyl diphosphate synthase and chalcone synthase, that influence these taste expressions.

There are five distinct varieties of the species distributed across the globe. The variety H. l. var. lupulus is found in Europe and western Asia. H. l. var. cordifolius is native to eastern Asia. In North America, there are three varieties: H. l. var. lupuloides in the east, H. l. var. neomexicanus in the west, and H. l. var. pubescens in the midwestern and eastern regions. There are also many cultivated varieties, or cultivars. One example is 'Aureus', a golden hop with yellow leaves. This cultivar is grown for ornamental use in gardens and holds a Royal Horticultural Society Award of Garden Merit.

Humulus lupulus 'Aurea' - Golden Hop
Humulus lupulus 'Aurea' - Golden Hop

Research into the hop plant continues to reveal new connections. The hop genome is quite large, appearing similar in size to the human genome. This complexity makes it difficult for scientists to identify all genetic properties. Interestingly, the hop shares about a 73% genomic overlap with Cannabis sativa. They also share significant overlap in the cannabidiolic acid synthase gene. Studies have also looked at the medicinal potential of hops. For example, extracts of bitter alpha-acids may act as sleep aides. Additionally, the antimicrobial properties of hop extracts have been used in natural deodorants.

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🖼️ Images & Media (4)
File:Humulus lupulus male flowers RF.jpg
Humulus lupulus male flowers RF.jpg
File:Hop plant by Kent Ditch - geograph.org.uk - 5892896.jpg
Hop plant by Kent Ditch - geograph.org.uk...
File:Humle (Humulus lupulus)-2017-Ystad.jpg
Humle (Humulus lupulus)-2017-Ystad.jpg
File:Humulus lupulus 'Aurea' - Golden Hop.jpg
Humulus lupulus 'Aurea' - Golden Hop.jpg
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