Aroma Hop: The Odd One Out

Hops are the flowers of the hop plant (Humulus Lupulus) and are used primarily as a bittering, flavouring, and stabilising agent in beer. They are added to the brew to balance the finished product through bitterness, flavour, and aroma. There are two types of hops used in quality beer brewing: aroma hops and bittering hops. Aroma hops are hops with strong and forward aromas and flavours that work well for late additions and dry hopping. They can have high or low alpha acid contents, but the most important characteristic is the amount of flavour and aroma they provide. Aroma hops are usually added to the wort later to prevent the evaporation of the essential oils, to impart hop taste or hop aroma.

Aroma hops are added to the brew at the end of the boiling process or during fermentation

Hops are the flowers of the hop plant, *Humulus lupulus*, and are used primarily as a bittering, flavouring, and stabilising agent in beer. They are added to the wort in three stages during the boil: bittering, flavour, and aroma. However, not all beers will have three additions; some may have only one, while others may have up to five or six.

Aroma hops are hops with a strong and forward aroma and flavour that work well for late additions and dry hopping. They can have high or low alpha acid contents, but the most important characteristic is the amount of flavour and aroma they provide. Aroma hops are typically added to the wort later in the process to prevent the evaporation of essential oils, which are responsible for the aroma. They are usually added during the last 5 to 30 minutes of the boil, or at flameout (when the kettle is removed from the heat). Adding hops at flameout will produce the maximum amount of aroma. Aroma hops are also often added after the wort has cooled and while the beer ferments, a technique known as dry hopping, which also contributes to the hop aroma.

The timing of adding hops for aroma depends on the desired final product. If using aroma hops, it is likely that their aroma is being sought, rather than their bittering properties. Therefore, they are usually added later in the process.

Aroma hops are typically low in alpha acids, with a percentage of less than 10%. They also usually have a 1:1 ratio of alpha to beta acid contents, which makes it difficult to add enough bittering to a beer. Since alpha acids isomerise at temperatures above 175°F (79°C), bittering can still occur with these hops, but it will not be significant.

The essential oils that contribute to the aroma of hops include myrcene, humulene, caryophyllene, and farnesene. These oils will evaporate quickly if left in the boil for too long. Most aromatic hop oils are best extracted at temperatures between 160–170°F (71–76°C).

Aroma hops have strong and forward aromas and flavour

Aroma hops are an essential ingredient in brewing, adding a wide range of flavours and aromas to beer. They have strong and forward aromas and flavours that can be fruity, resinous, piney, citrusy, floral, herbal, spicy, or earthy. Hops contain essential oils that contribute to these specific aromas.

Aroma hops are typically added to the wort later in the brewing process to prevent the evaporation of the essential oils, thereby imparting a "hop taste" and "hop aroma". They are often added after the wort has cooled and while the beer ferments, a technique known as "dry hopping", which contributes to the hop aroma.

Aroma hops are usually low in alpha acids, with a percentage of less than 10%. They also have a 1:1 ratio of alpha to beta acid content, which makes it difficult to add enough bitterness to a beer. Since alpha acids isomerize at temperatures above 175°F (79°C), bittering can still occur with these hops, but the low amounts will not be significant.

The specific combination of terpenes in a beer can vary depending on the hop variety, the timing of the hop addition, and the brewing technique. For example, dry hopping enhances the hop aroma without adding additional bitterness.

Some popular hop varieties known for their aromatic qualities include Cascade, Citra, Amarillo, Chinook, and Centennial.

They can have high or low alpha acid contents

The alpha acid content of hops is indicated as a percentage of the total weight of the hop. Hops with a higher alpha acid content will contribute more bitterness to the beer than hops with a lower alpha acid content. The alpha acid content of hops varies within specific varieties depending on growing conditions, drying methods, age of the hop, and other factors. For example, lager styles use hop varieties with a low alpha acid content, such as Saaz and Hallertauer, while IPA styles use hop varieties with a high alpha acid content, such as Cascade, Centennial, and Chinook.

The alpha acid content of hops can be determined in a lab using the ASBC method, which involves several reagents and a spectrophotometer. This process cannot be easily performed at home with homegrown hops. The alpha acid content of hops is important in brewing beer, as it determines the amount of bitterness contributed to the beer.

Bittering hops, which are used to add bitterness and stability to the beer, typically have higher concentrations of alpha acids. These hops are boiled for a longer period of time, usually 60-90 minutes, to isomerize the alpha acids and increase bitterness. The degree of bitterness imparted by bittering hops depends on the degree of isomerization during the boil, and this impact is specified in International Bitterness Units (IBU).

On the other hand, aroma hops usually have a lower concentration of alpha acids, typically around 5%. Aroma hops are added to the wort later in the brewing process to prevent the evaporation of essential oils, which contribute to the "hop taste" and "hop aroma". Aroma hops are often added during the final 10-15 minutes of the boil or through a technique called "dry hopping", where hops are added after the wort has cooled and during fermentation.

Dual-purpose hops, which can be used for both bittering and aroma purposes, have high amounts of both alpha acids and essential oils. These hops can be added at any stage of the brewing process and are commonly used in Pale Ales and IPAs.

Aroma hops are often added to the beer after it has been brewed, in a process known as dry-hopping

The term "dry-hopping" originated with British brewers centuries ago and initially referred to adding hops to a cask shortly before shipment. Today, dry-hopping refers to any addition of hops after the wort has been cooled, typically in the primary or secondary fermenter, or directly into a keg. This technique allows brewers to maximise the flavour and aroma of the final beer, as the volatile oils in the hops are not boiled off during dry-hopping.

The essential oils in hops are responsible for their aroma and flavour. However, these oils are volatile and can be easily lost during a long boil. Therefore, dry-hopping is done on the ""cold side" of brewing, after the beer has moved from the kettle into fermentation tanks. By avoiding boiling, dry-hopping preserves the essential oils in hops, resulting in a more intense aroma and flavour in the beer.

Different methods of dry-hopping exist, such as using nylon bags filled with hops and suspending them inside fermentation tanks. The type of hops used for dry-hopping is also important. Aroma hops, which have lower alpha-acid percentages (typically less than 10%), are commonly chosen for dry-hopping to avoid excessive bitterness. Popular varieties of aroma hops used for dry-hopping include Cascade, Crystal, Willamette, East Kent Golding, and Saaz.

While dry-hopping enhances aroma and flavour, it does not add bitterness to the beer. To achieve the desired level of bitterness, brewers still need to add bittering hops during the boil, as boiling is necessary to convert the alpha acids in hops into iso-alpha acids, which create bitterness.

Popular aroma hops include Crystal, Fuggle, El Dorado, Pacifica, and Zythos

Aroma hops are hops with strong and forward aromas and flavours that work well for late additions and dry hopping. Popular aroma hops include Crystal, Fuggle, El Dorado, Pacifica, and Zythos.

Crystal hops are often used for their citrus, floral, dark fruit, tropical fruit, dank, or herbal notes. Fuggle hops, meanwhile, are known for their black pepper, dank, citrus, earthy, spicy, and black tea notes.

El Dorado is a newer variety of aroma hop, released to the public in 2010. It is known for its uniquely fruity flavour profile, with bold tropical fruit flavours and aromas of pear, watermelon, stone fruits, and even candy. El Dorado hops have high alpha acids, lots of oils and resins, good storage stability, and an exceptional yield, making them an excellent commercial variety.

Pacifica hops are known for their floral, pine, cedar, and berry notes, while Zythos hops can add flavours and aromas of orchard blossom, ripe fruit, and floral notes to a brew.

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