Hops Essential Oils

As a NEIPA lover, speaking of beer aroma is the most delightful thing to do! In this article, we will explore the science of hop oils and understand how they impact the beer flavor and aroma. Subscribe to this newsletter to receive new articles every week, and please like and share this article to help strengthen this work!

Hop oil compounds are a complex subject. There are hundreds of compounds, where several are not identified yet, interacting with each other and forming a wide variety of aromas and flavors we feel in beer. Many of them are too volatile or have poor solubilization in water and never pass through the beer. The essential oils of hops are divided into three groups: hydrocarbons, Oxygen-bearing, and sulfur-containing compounds.

Hydrocarbon Components

These compounds are formed exclusively by carbon and hydrogen. They represent 50 to 80% of the total hop oils and are found as terpenes or sesquiterpenes. The hydrocarbon has low solubility and high volatility; therefore, they are rarely seen in beer, except when using dry-hopping techniques.

Monoterpenes such as myrcene have the flavor of resin, pine, and herbal and, in some cases, could be present in higher concentrations (achieving 60% of the total hop oil compounds); nevertheless, the myrcene has a low impact in beer, only the compounds resulted by its oxidation and polymerization survive to see your glass!

During storage, some hydrocarbon compounds can suffer oxidation, transforming them into less volatile compounds.

Noble hops, those with flavor associated with spicy, usually have a high sesquiterpene/monoterpene ratio in the range of 2.5 to 4.

Oxygen-bearing Components

This group is composed of a complex mixture of alcohols, aldehydes, acids, ketones, epoxides, and esters. Many of them are not present in fresh hops and are created in pelletization or storage. The compounds more extensively studied are linalool, geraniol, carophyllene oxide, and humulene epoxide.

Linalool is an essential compound of oils, considered important to beer aroma due to its high solubility. It provides floral and fruit aromas to the beverage. Geraniol tends to provide floral and herbal perfume. Both linalool and geraniol have synergy between themselves. Some varieties famous for being rich in linalool and geraniol are Amarillo, Cascade, Centennial, and Columbus.

Geraniol, when in contact with yeasts in fermentation, can be converted into β-citronellol (lime and lemon scents), linalool, or α-terpineol (fat, anise, and mint) in a process called biotransformation.

The caryophyllene oxide and humulene epoxide are associated with spicy and herbal flavors. Another widely used index to evaluate noble characteristics in hops is H/C (humulene to caryophyllene), where noble hops score above 3.5; however, many studies point out that the ‘noble’ notes result from the oxidation of humulene and caryophyllene.

Sulfur compounds

Sulphur-containing compounds represent a problem for beer. They are added to beer due to malt or fermentation; nonetheless, hops can be a source too. When the iso-alpha-acids are exposed to sunlight (wavelengths of 400 to 500 nm) it results in sulphury mercaptan, a compound responsible for the skunky off-flavor. Another reason is when sulfur was dosed in excess during cultivation to control fungus infestation. To understand better about sulfur compounds, read this article.

If you enjoy the article, please like and share it! And comment on your experience with hop aromas!