Category:Hops

Hops on the bine.

Hops are the dried flowers of the twining bine (Humulus lupulus) which is part of the hemp family. Hops are used to add bitterness as well as flavor and aroma to many modern beer styles.

The hop plant

The hop plant, Humulus lupulus, is a climbing bine which grows wild throughout the world. It is called a bine because, unlike grapes and other vines, the hop bine climbs by means of stiff hairs attached to the stem. The green, cone-like flowers of the hop plant are used to give beer bitterness as well as a characteristic hop flavor and aroma.

Use in brewing

Petals from the cone flower of the hop plant, or Humulus Lupulus, have been used as a main beer ingredient and for medicinal purposes for hundreds of years. In addition to acting as a preservative, hops lend three qualities to beer: bitterness, flavor, and aroma. How much of each quality a hop contributes to the final beer depends on how long the hop spends in the boil, as well as the variety of hop used.

History of hops in brewing

In early historical beer styles, various herbs and spices (called gruit) were used to flavor beer. There is some dispute over when and where hops first came into common use (though they seem to have become common in England around the 16th century), but once hops were introduced they quickly became an expected and indispensible ingredient. A few traditional or experimental beer styles still use herbs and spices in addition to, or occasionally instead of, hops. Historical reproductions of early, unhopped beer styles are occasionally brewed by enthusiasts.

Hops as a preservative

One reason hops won out over other herbs is the preservative effects hops have in beer. Gruits also lent a preservative effect, but hops are especially--and consistently--good for this purpose.

The preservative effect of hops also affected the development of certain beer styles; for example, India Pale Ale and several other styles intended for export had higher hop bitterness to preserve them on their travels, and often correspondingly higher alcohol levels to balance the beer's flavor.

Modern homebrewers rarely have to worry about adjusting hop levels to preserve beer, although they should be aware of the need for increased care if they are attempting to brew a gruit or other unhopped beer style.

Hop bitterness, flavor, and aroma

There is an inverse correlation between the amount of time the hops spends in the boil and the amount of actual hop flavor/aroma they impart, while the opposite is true for the amount of bitterness that is extracted. In other words, the longer the hops spend in the boiling wort, the more bitterness they impart, but the less actual hop flavor/aroma is retained. For these reasons, different hop varieties have different uses.

The reason has to do with what is extracted during (or after) the boil. The effective ingredients in hops are oils and resins. The oils give aroma and flavor, but boil off quickly (the aromas boil off especially fast). The resins provide bittering alpha acid, but are insoluble in water; they are partially soluble in boiling water, so a good rolling boil is needed to extract them. Generally speaking, bittering hops are boiled for over 15 minutes (usually for 1-1½ hours), while balancing flavor and aroma is more delicate, since the hops used for those purposes ("finishing hops") are usually added all at once. A rule of thumb is that flavoring hops are boiled for no more than 15 minutes, while aroma hops are boiled for no more than 5 minutes, or not boiled at all but added later. A brewer wanting a good compromise between aroma and flavor might add his finishing hops for the last 5 minuntes.

In previous days it was common to use the finishing ("wet") hops from a previous batch for the bittering in one's next batch. Unused ("dry") hops were then used for flavor/aroma, and then set aside to bitter the following batch. Hence the term "dry hopping", which nowadays refers to adding aroma hops after the boil to provide maximum aroma (but minimal flavor and no bittering)see dry hopping. The current usage of the term "wet hops" is for hops that have not been dried before use. This is also known as using "fresh hops".

Certain hops, known as bittering hops, are great for adding bitterness, as they have high alpha acid content, but they rarely lend much in the way of good flavor/aroma, so these are added at the beginning of the boil. On the other hand, Aroma hop varieties don't add much bitterness, as they have a low alpha acid content, but lend great hop flavor and aroma, so they are added later in the boil. Other varieties do well in both roles. See the Hop varieties page for more information on choosing bittering or aroma hops.

Although hops with high alpha acid levels are called bittering hops, they can be used for flavor and aroma. Aroma hops can be used for bittering, but because they have lower alpha acids levels, it takes more hops to achieve the same bitterness.

Hop varieties

Although all hops are a single species, there are dozens or hundreds of varieties of hops available to the homebrewer. The name a reseller or grower uses to describe a hop may tell you a number of things about it, including: the cultivar (genetically distinct subtype) the hop plant belongs to; the region in which the hop was grown; and maybe even the specific company who grew it.

Each of these hop varieties may differ significantly in flavor and aroma, from aggressive, citrusy or grapefruity aromas associated with American hops like Cascade and Amarillo to the almost indefinable floral or spicy aroma associated with the European noble hops like Saaz and Hallertau Hallertauer Mittelfrüher. Hops also vary greatly in the amount of alpha acid they contain, which affects how much bitterness they impart to beer. In addition to alpha acids, hops also contain beta acids, whose contribution to the finished product is small to negligible, though some homebrewers do pay careful attention to the beta acids of the hops they use.

For more information on the different hop varieties, how they are distinguished, and what the names of the different varieties mean, as well as lists of individual hop varieties available to brewers and homebrewers, please see the Hop varieties page.

Hop chemistry

The bittering, flavor, and aroma characteristics of hops are primarily created by two components of the hop: alpha acids and essential oils. The alpha acids are isomerized in the boil, yielding more bitterness the longer the hops are boiled. However, the essential oils evaporate quickly in boiling wort. Understanding these primary chemical components of the hop and the relationship between them will help the brewer better choose and use hops.

Hop products available to homebrewers

Whole hops

These are hops that have only been dried before packing. This is the form favored for flavor and aroma use and dry hopping. AKA hop cones.

Hop plugs

Whole hops that have been compressed in to standard sizes and weights.

Hop pellets

To form pellets some of the vegetative portion of the cone is removed and the remainder compressed and extruded into small, hard pellets. This improves shelf-life in storage and reduces the absorption of wort.

Hop Extract

Employs a chemical extraction process, using liquid CO2 is the most common method. This process separates the resins and oils from the vegetative portion. Further refinement splits the hop oils from the resins. The resin is stabilized and sold as "hop extract" for increasing the bitterness post-ferment. Hop oils can be used to improve the aroma of a beer that is lacking.

Hop cultivation

Hops are native to most of the world and relatively easy to grow. As a result, many home brewers who also enjoy gardening have tried growing their own hops.

External references

• General Reference
  • Wikipedia:Hops
• Hop variety charts
  • BYO Hops Reference Guide
• History of hops
  • A Short History of Hops