Myrcene is a type of essential hop oil and the most plentiful hydrocarbon of the hop oils. Like other essential oils, it develops in the hop cone’s lupulin gland and is formed throughout the entire hop cone maturation phase. As the hop cone ripens, trace amounts of oxygenated compounds of the essential oil appear first. They are followed by beta caryophyllene and humulene, and finally, by myrcene. The amount of myrcene continues to rise with ripening, while the amounts of beta caryophyllene and humulene do not. The percentage of myrcene, therefore, can serve as an indicator of the hop’s ripeness. The ratio of humulene to caryophyllene, on the other hand, can serve as a varietal indicator. Myrcene levels are typically 50% or more of the total oils at harvest time. In some instances, they even exceed 70%, as is often the case with such American varieties as Cascade and Centennial. See cascade (hop). Myrcene has a green and freshly herbaceous aroma that is distinctively “hoppy.” It has the lowest odor threshold—13 ppb—of the main hydrocarbons in hop oil, and is, therefore, the most potently aromatic. Beers that have been heavily dry-hopped with American hop varieties can have a pronounced myrcene aroma. Myrcene, however, is very volatile, which means that prolonged boiling causes virtually all of the myrcene to escape through the kettle stack, and very little remaining in the beer. The precursor to myrcene is the chemical geranyl pyrophosphate. Its oxidation, as well as its subsequent chemical rearrangements during the hop growth phase, can lead to a range of floral, fruity, and citrusy compounds. These include linalool (floral–citrusy), nerol (citrus, floral–fresh rose), geraniol (floral–rose, geranium), citral (citrus–lemon–candy like), and limonene (citrus– orange–lemon). See linalool. These latter compounds are considerably more water soluble than myrcene and are, therefore, readily extracted into the finished beer.

See also hop oils.