Hops are the female flowers of the plant known as humulus lupulus. Hops are used as a preservative, a bittering agent, and a brewing component to introduce hoppy aromas and flavours. They are especially good at stabilising head retention and clarifying the wort. Hops are cousins to cannabis in the Cannabaceae family, sharing several common terpenes such as myrcene, humulene, caryophyllene, aromadendrene, etc.
The first documented use of brewing with hops occurs in the 8th century when Benedictine monks used them for brewing beer in a Bavarian abbey outside of Munich, Germany. In Bavaria on 23rd April 1516, the Reinheitsgebot; The Beer Purity Law, was decreed by Duke Wilhelm IV at Ingolstadt, north of Munich, stating that "We wish...forthwith that...in all our towns and markets and in the countryside no other items can be used for beer than barley, hops, and water". Hops became the law in Bavaria from then on.
Before hops, bog myrtle, yarrow, and wild rosemary were common herbs used in brewing 'gruit' from the late 10th century (other ingredients include wormwood, juniper, burdock root, dandelion root, heather, horehound, marigold, and ground ivy). Gruit is often characterised as less bitter, light, herbal, and slightly floral (however tasting notes will vary due to the vast arsenal of herbs and botanicals used when brewing gruit, much like a Belgian Saison).
The exterior of hops are made up of soft leaf-like structures called 'bracts'. Inside the hop, there are many fleshy compartments known as 'bracteoles'. Within the bracteoles are the treasured 'lupulin glands' where the essential oils and resins are found.
Hops are plucked from 'strigs', the plant stem connecting them to the twisting vines known as 'bines', the climbing stem of the hop plant. Healthy hop bines can grow up to 12 inches per day, as well as growing up to 25-30 feet in length, and can yield 300-1000 grams of dried flowers per plant. These hop flowers are then taken to 'oast houses' for kilning (drying), hammer milled into a powder, and filled into moulds to create hop pellets.
Hops tend to grow tremendously well in countries that have high potato and corn yields, both sharing common denominators. Hops need 120 days of frost-free weather, plenty of water, space, and sunlight, soil with a pH of 6.0-7.0, and soil with fertilisers rich in potassium, phosphates, and nitrogen.
Ethiopia (40,074 tonnes), USA (39,536 tonnes), Germany (31,968 tonnes), Czech Republic (7,712 tonnes), and China (6,427 tonnes) are the five highest hop-producing countries. However, in terms of yield in kilograms/hectares: South Korea (6,756.2 kgs), Hungary (5,427 kgs), New Zealand (2,556.1), Australia (2,345.9), and Japan (2,079), appeared in the top five countries.
When hop are commercialised they are divided into four categories: bittering hops, aroma hops, noble hops, and dual purpose hops. These have varying alpha and beta acid content, essential oil content, and recommended hop additions.
Bittering hops are hops that have a high alpha acid content for bittering, these include: Admiral, Bravo, and Pride of Ringwood.
Aroma hops are hops that contain far less alpha acid content than bittering hops (typically less than 10%), these include: East Kent Golding, Hüell Melon, and Pacific Jade.
Noble hops refer to traditional Bavarian and Bohemian varieties that were used in brewing for centuries, these include: Spalt, Tettnanger, and Hallertau Mittelfrüh.
Dual purpose hops are hops with high amounts of both alpha acids (8-15%) and essential oils, these include: Azacca, Citra, and Mosaic.
Alpha acids are the principal components in lupulin, the resin of the hop cone. They are of great interest to brewers because they are the main bittering agent in hops. Chemically, alpha acids reside in the soft-resin fraction of the lupulin, which is soluble in hexane. Alpha acid analogues include humulone, cohumulone, and adhumulone, which, when isomerised to isohumulones (iso-alpha-acids) through the boiling process, bring bitterness to beer.
When dissolved in beer as iso-alpha-acids, the unit of measurement for bitterness is IBUs (International Bitterness Units). The hop's alpha acid value is then used by the brewer to formulate a recipe for the beer's final bitterness. Brewers adjust hopping rates based primarily on the selected hop's alpha acid content expressed as a percentage of the hop's weight (2-18%) and on the expected 'utilisation rate' of that hope in a given brewing system during a particular brewing process.
Terroir is a French term used to describe the environmental factors that affect a crop's phenotype. Hops can be radically affected by local climate, soil, sun, wind, and rain conditions. Many brewers are confident that terroir can distinguish one hop grown in one region to the same hop grown from another region.
German hops, like Hallertau Mittelfrüh (lightly flowery and spicy aroma), and Czech hops, like Saaz (noble, herbal character), are often characterised with soft, floral, woodsy, and earthy aromas.
English hops, like East Kent Golding (aromas of lavender, honey, thyme, spice, and earthy aromas) and Brewer's Gold (notes of spice and blackcurrant), are commonly associated with having grassy, floral, lemony, woodsy, minty, and tea-like aromas.
American hops, like Chinook (bouquet of pine and spice) and Centennial (earthy and floral with an element of citrus), have the broadest variety of aromas that are described as being citrusy, piney, floral, resinous, herbaceous, woodsy, and with many often giving off stone fruit aromas.
Australian hops, like Galaxy (citrus, peach, and passionfruit aromas), and New Zealand hops, like Motueka (tropical fruit and citrus notes), are widely known as expressing earthy, woodsy, tropical, and juicy aromas.
Very few Japanese hops exist commercially, these include Sorachi Ace (aromas of lemon, orange, dill, and cilantro) and Shinshuwase (lemon aromas). Hop varietals such as Toyomidori, Kitamidori, and Eastern Gold have been discontinued due to their susceptibility to downy mildew.
By Lucas Barker, a budding craft beer enthusiast of 2-3 years. 11/5/22
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