Although there is only one hop species (Humulus lupulus) that is used for brewing beer, there are a number of varieties (technically known as “cultivars”) in that species, each with its own spectrum of characteristics. Varieties of hops are chosen for the properties of bitterness, flavor, or bouquet that they will lend to the beer. Hop varieties can be roughly divided into two classes, bittering hops and aroma hops, although there are hops that can be considered dual-purpose.
Hops that are bred to be high in alpha acids are referred to as high-alpha acid hops or bittering hops such as Chinook, Apollo, Summit, Columbus, and Nugget. Alpha acid is listed as a percentage weight of the total hop weight (w/w) based on a range of values at harvest. A rating below 5 percent alpha acid content indicates low bittering values; 5 to 8 percent alpha acid indicates an assertive medium range of bitterness; and 8 to 14 percent alpha acid indicates a very powerful bittering value.
Aroma hops, with low- to medium alpha levels, mainly impart characteristic hop aromas to beer. In Europe, aroma hops are mostly grown, with a smaller but growing emphasis on bittering hop varieties. The aroma varieties that are grown in Germany often are referred to as “noble” hops. The three recognized noble hops are Hallertauer Mittelfrüh, Tettnang Tettnanger, and Spalt Spalter. Czech Saaz is the primary aroma variety grown in the Czech Republic. Some consider the English varieties Fuggle and East Kent Golding to be noble.
Dual-purpose hops tend to have intermediate levels of alpha acids together with desirable aroma properties. Hops such as Citra, Challenger, Northdown, El Dorado, and Simcoe are being used at all stages.
Hop Producing Countries
Washington state produces over 70 percent of all hops grown in the U.S., with the Yakima Valley accounting for the majority of it. Willamette Valley in Oregon and Treasure Valley in southwestern Idaho are the other two major hop-growing regions.
Different cultivars are important for the production of specific styles of beers. For instance, Bullion (a strong odor, high myrcene, and high alpha acid hop) is suitable for strongly bittered ales, but would not be suitable for final hopping of light lager. Goldings is suitable for pale ales. Refer to Appendix A, Hop Varieties for a list of hop cultivars along with their technical parameters and recommended uses in brewing.
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