Hops are the female flower cones, also known as strobiles, of the hop plant (Humulus lupulus). They are used primarily as a flavoring and stability agent in beer, though hops are also used for various purposes in other beverages and herbal medicine. The first documented use in beer is from the eleventh century. Hops are used extensively in brewing today for their many purported benefits, including balancing the sweetness of the malt with bitterness, contributing a variety of desirable flavors and aromas, and having an antibiotic effect that favors the activity of brewer's yeast over less desirable microorganisms.
Bittering hops usually have a high alpha acid. The bitterness qualities that hops add are from the alpha acids in the lupulins. When boiled, a reaction occurs that creates bitterness and adds a natural preservative to the beer. First noted when India Pale Ale was sent from England to their troupes in India.
Aroma hops are noted for their lower alpha acid contents and their fragrance. When added towards the end of the boiling process, these hops produce different levels of hoppy, piney, woody and fruity aromas.
The following description are from one of the leading Hop Suppliers,
New high alpha variety, low co-humulone, Popular in IPA's
a Unique Proprietary variety that was found...alpha 8-10%
Released in 1972 from OSU breeding program as a new variety. Characterized by a medium strength aroma, with a low bittering value, alpha 4-7%
A relatively new hop variety on the market. Can be used for aroma, with a strong Cascade-like aroma, as well as for bittering, medium to high bittering, alpha 8-11%.
Released by the US(OSU Corvallis, OR.) High Alpha Breeding Program in 1985. Has a good quality earthy aroma, alpha 11-13%.
High yield and high alpha acids potential, high oil content; brewing characteristics similar to Centennial Great for dry hopping. Alpha 14 – 17%
Similar oil profile as Hallertauer pleasant continental-type aroma; suitable for flavoring beers and ales when Hallertauer-type aroma is desired. alpha 3-5%.
Originally developed in the UK in both Kent and Sussex counties. Traditional aroma hop, mild and spicy aroma, alpha 4.0-5.5%.
Originally developed in the UK in the county of Kent, its flowery aroma has characterized some of the best English bitters, alpha acid 5-6%
This variety is a traditionally popular German hop from Hallertau region, good aroma type, low bittering qualities alpha 3-5%.
Hallertauer hybrid released in 1983. Aroma hops similar to imported noble aroma European hops. best use is in German style lagers as a finishing hop. Alpha(2 to 6%).
Spicy, citrusy, super-high alpha bittering hop from the Pacific Northwest. Alpha 12-17% aka yakima magnum.
Hallertauer hybrid released in 1989 as a disease resistant variety, Aroma is mild and clean, with an alpha an 4-5%.
This is an English bred variety with some aroma but a high bittering quality, alpha 7-9%. It is difficult to grow.
Very new high alpha hop developed at the USDA hop research program Corvallis, OR alpha 9.8-17%
This is also a product of the US High Alpha Breeding Program developed at OSU Corvallis, OR. and was released in 1983. It is popular among growers because of its high yields, vigorous growth, and disease resistance. High alpha variety. Alpha Acid 11-16%.
This is also a German variety developed and grown in the US succesfully. Has a clean pleasant aroma and a medium bittering quality alpha 7-8%.
The original Bohemian pilsner hop, is a pleasant and mild aroma type, alpha 3-5%. It is difficult to grow.
New variety release 2000, unknown pedigree. Unique pine like aroma, used for aromatic and bittering qualities. Not overly vigourous growth. Alpha Acid 12-14%.
Unique lemony aroma... Developed in Japan at Sapporo Breweries. Pedigree; Brewer's Gold x Saaz. High yield potential. High alpha acid potential 13-16%
Dwarf variety strong aroma profile, citrus, grape-fruit flavor. It has been used for bittering and dry hopping. high alpha 18.0%
Similar to Saaz and Tettenanger. Pleasant European noble aroma. Origin: German Institute for Hop Research, Huell, Germany. Fair to good yields. Alpha 4 to 6%
Hybrid, suitable for replacing Saaz hops in brewery blends. Much higher yield potential than Saaz hops. aroma and oil composition very similar to Saaz. Alpha Acid 6-9% . Very good yield
A new release, pedigree unknown. Mild good aroma, Vigorous growth habit with a good yield. Popular in double IPA's Alpha Acid 14.5- 17.0
Released by the USDA in 1976 as a new aroma variety. A triploid hybrid of English Fuggle, characterized by low bittering values. A mild aroma. Medium yields. Alpha 4-6%