Hop Oils: Difference between revisions

Revision as of 03:59, 13 July 2025

Hops Oils 101

Those compounds classified as hydrocarbons are highly volatile, not very soluble, and are perceptible in finished beer only when added very late in the boil or post-fermentation. Myrcene is almost always the most prominent, constituting 50 percent or more of the oils in hops varieties such as Cascade and Simcoe. It has a green, herbaceous, and resinous aroma associated with fresh hops that will be scrubbed away during boiling and fermentation but that will provide distinctive piney character to a dry-hopped beer.

The oxygenated hydrocarbon compounds are more soluble and aromatic. Their aromas, or new ones resulting from the fermentation process, are more likely to show up in finished beer. They include linalool, geraniol, citronellol, and hundreds of other compounds. The most prominent of them will constitute less than 1 percent of the hops oils.

Thirteen Hops-Odor Compounds to Know

caryophyllene » woody
citronellol » citrusy, fruity
farnesene » floral
geraniol » floral, rose, geranium
humulene » woody, piney
limonene » citrusy, orange
linalool » floral, orange
myrcene » green, resinous, piney
nerol » rose, citrusy
pinene » spicy, piney
3-mercaptohexanol » guava, tropical
3 mercaptoheyl acetate » muscat, passion fruit
4-mercapto-4-methyl-pentan-2-one » black currant, tropical

Hops by Compound

Geraniol-rich Hops
- Aurora, Bravo, Cascade, Centennial, Chinook, Citra, Mosaic, Motueka, Styrian Golding
Linalool-rich Hops
- Amarillo, Cascade, Centennial, Citra, Glacier, Millennium, Mount Hood, Nugget, Pacifica, Willamette
Hops that Contain 4-mercapto-4-methylpentan-2-one (4MMP)
- Apollo, Cascade, Centennial, Citra, Chinook, Cluster, Equinox, Mosaic, Simcoe, Summit

https://beerandbrewing.com/hops-oils--aroma-uncharted-waters/

Terpenes

Many different terpenes are found throughout the plant world. Terpene is a general term describing compounds made of one or more isoprene groups (C5H8) (Qian, 2013). Hop analysis typically focuses on mono- and sesqui- terpenes, which consist of 2 and 3 isoprene groups, respectively.

Farnesene:

A sesquiterpene exhibiting a noble and woody aroma profile. Interestingly, farnesene is only found in trace amounts in most modern varieties, and some actually have no detectable farnesene. Most of the varieties containing high levels of farnesene are traditional European varieties.

Hydrocarbons

As the name implies, ‘hydrocarbon’ can describe any compound that is made up of only hydrogen and carbon atoms. While all terpenes are hydrocarbons, not all hydrocarbons are terpenes.

Monoterpenes

Hydrocarbons made of 2 isoprene units. All monoterpenes are made of 10 carbon, and 16 hydrogen atoms (C 10H16). The most common hop monoterpenes are myrcene and β-pinene. Monoterpenes are very volatile and will usually not survive when added in hot-side additions.

Myrcene

A monoterpene, usually the largest component of a hop’s ‘total oil’ (up to about 75%, although some varieties have significantly less). Myrcene is extremely volatile, and while it contributes heavily to raw hop aroma, it will generally not survive the brewing process due to low solubility. Myrcene has an herbal, woody, and somewhat carrot-like aroma.

Sesquiterpenes

Hydrocarbons made of 3 isoprene units. All sesquiterpenes are made of 15 carbon, and 24 hydrogen atoms (C 15H24). The most common hop sesquiterpenes are β-caryophyllene, farnesene, and α-humulene. Like monoterpenes, sesquiterpenes are very volatile, and will usually not survive when added in hot-side additions.

Terpenes

A class of compounds that consist of varying quantities of isoprene units (C5H8). Typically representing a large portion of the ‘total oil’ fraction of a hop, with the monoterpene myrcene usually being the most prevalent.

α-humulene

A sesquiterpene exhibiting grassy, herbal, and woody aromas. It is highly volatile and generally will not survive the brewing process.

β-pinene

A monoterpene, β-pinene smells pine-like. It is far less abundant in hops than myrcene, making up only about 1% of the total oil, maximum. Like myrcene, β-pinene is very volatile, and will only transfer to beer during dry hopping.

β-caryophyllene

A sesquiterpene with a very woody aroma, sometimes cedar-like. Other aroma notes include floral and spicy. β-caryophyllene contributes to the character of noble hops and is found in lower levels in newer American hops. It generally does not survive the brewing process.

TERPENE ALCOHOLS

Terpene alcohols are closely related to terpenes. Unlike terpenes, terpene alcohols are oxygenated, making them an alcohol. By their nature, alcohols are more soluble than non-oxygenated terpenes due to their greater polarity. They therefore have a much greater retention rate into the final beer, and hops high in terpene alcohols are widely thought to benefit hot-side additions.

Terpene alcohols are also the subject of recent research investigating biotransformation. In a study by (Takoi, et al., 2012), β-citronellol, a compound not usually found in hops, was found to increase during fermentation. A prominent theory states that during fermentation certain strains of yeast are capable of metabolizing geraniol into β-citronellol, which has shown to amplify citrus/floral aroma profile in final beer. Enough geraniol must be present in the wort solution for conditions to favor this action.

Geraniol

Like linalool, geraniol is a monoterpene alcohol which commonly survives late boil and whirlpool additions. Its aroma profile is geranium-like and citrusy. Geraniol is thought to be at least partially biotransformed by certain strains of yeast into β-citronellol during fermentation.

Linalool

A monoterpene alcohol commonly used as a fragrance and flavoring in cosmetics and candy. It has a strong fruity and floral aroma, commonly described as similar to the aroma of Froot Loops™ cereal. High levels of linalool can act as a ‘booster’ to increase fruity flavor in beer. Linalool is beer-soluble and commonly survives the brewing process.

@@ Line 82: / Line 82: @@
 '''Linalool'''
 * A monoterpene alcohol commonly used as a fragrance and flavoring in cosmetics and candy. It has a strong fruity and floral aroma, commonly described as similar to the aroma of Froot Loops™ cereal. High levels of linalool can act as a ‘booster’ to increase fruity flavor in beer. Linalool is beer-soluble and commonly survives the brewing process.
-== '''Thiols''' ==
-'''Nerol'''
-* A monoterpene alcohol with a rose and citrus aroma. An isomer of geraniol. Not usually detectable by YCH analysis.
-'''β-citronellol'''
-* A monoterpene alcohol with an aroma similar to citronella candles. Not thought to be found in hops, but has been detected in beer. It is believed that this compound is produced by metabolism of geraniol by yeast during fermentation.
-'''SULFUR-CONTAINING COMPOUNDS'''
-Sulfur compounds represent an increasingly important area of study in hop aroma science. They are difficult to detect using a traditional GC-MS and are usually found in extremely small concentrations in hops, potentially two orders of magnitude less than terpenes (ASBC). However, the human nose is excellent at detecting sulfur compounds. An example: the aroma threshold for myrcene is about 20ppb, while 4MMP (a common sulfur compound found in hops) is detectable at around 0.05ppb, or about 400 times less (ASBC)! Sulfur-containing compounds are now thought to be an integral part of the aroma profile of a beer, incentivizing brewers to harness their power in the brewing process. Common confusion surrounds the prefixes mercapto and sulfanyl, which are generally interchangeable. Using mercapto- is not now suggested by the IUPAC. However, much of previously completed research on sulfur-containing compounds use the mercapto- prefix, along with much of modern brewer parlance. In the following descriptions, the sulfanyl- prefix will be used in text, but the mercapto- abbreviation will also be listed.
-'''Polyfunctional Thiol or Thiol'''
-In chemistry, a blanket term for an organic compound containing a sulfhydryl functional group(-SH). In the brewing world, it is a broad term covering a group of compounds, often contributing positive beer flavor and aroma.
-'''4-methyl-4-sulfanylpentan-2one (4MSP or 4MMP)'''
-* A polyfunctional thiol, and one of the better-known sulfur compounds in the brewing world. Research suggests that 4MSP is not present in European varieties (Kishimoto, Morimoto, Kobayashi,Yako, & Wanikawa, 2008). 4MSP is usually described as having a blackcurrant aroma. At higher concentrations the aroma can become unpleasant, expressing as a “catty” or cat-urine-like.
-* Interestingly, the threshold at which 4MSP becomes unpleasant varies substantially among individuals, similar to the flavor perception of cilantro. When dissolved in a beer matrix, it is thought to add tropical and wine grape-like flavors.
-'''3-sulfanylhexan-1-ol (3SH or 3MH)'''
-* A polyfunctional thiol commonly found in hops. It has a tropical and grapefruit aroma. 3SH can be converted by yeast into 3SHA (3MHA).
-'''3-sulfanylhexyl acetate (3SHA or 3MHA)'''
-* This compound is found readily in hoppy beers, but not usually found in hops (Kishimoto, Morimoto, Kobayashi, Yako, & Wanikawa, 2008) . Like its relative 3SH, it has a grapefruit and tropical aroma. When present in high concentrations it can provide a passionfruit flavor. Whirlpool and activefermentation dry hopping additions containing varieties high in 3SH are thought to maximize the potential for 3SHA by maximizing contact time between hop compounds and actively fermenting yeast.
-'''3-sulfanyl-4-methylpentyl acetate (3S4MPA or 3M4MPA)'''
-* A polyfunctional thiol with a rhubarb and grapefruit aroma. In a study by Takoi Et al. on Sauvignon Blanc wines, it was concluded that 3S4MP and 3S4MPA worked synergistically to enhance flavor (Takoi, et al., 2009).
-'''3-sulfanyl-4-methylpentan-1-ol (3S4MP or 3M4MP)'''
-* A polyfunctional thiol with an aroma of rhubarb and grapefruit. It has an extremely low odor threshold of 0.07ppb. Like 3SHA, its concentration increases during fermentation (ASBC).
-'''ESTERS AND KETONES'''
-'''2-methylbutyl isobutyrate'''
-* An ester derived from hops which typically survives the brewing process. Like most esters, it lends a fruity aroma, specifically apricot.
-'''2-nonanone'''
-* A ketone with a variety of different aromas. It can range from sweet and fruity to cheesy, buttery, and waxy.
-'''Methyl geranate'''
-* A methyl ester derived from hops which typically survives the brewing process into finished beer. It lends a fruity and floral aroma and is usually the only hop-derived methyl ester that survives into beer.
-'''Butanoic acid 3-methylbutyl ester'''
-* An ester derived from hops which typically survives the brewing process. It lends a fruity, sweet, and tropical aroma.
-== '''Averado and Berkley yeast tests''' ==
-=== Thiol Test Recipes ===
-'''Cold Pressed Hazy IPA'''
-* · 2-Row Malt for Base, 25% malted wheat & oats make up the grist.
-* · Mash Hopping with High Precursor Motueka Lot from Freestyle Hops, just 0.25 lbs / bbl.
-* · Whirlpool at 175, 0.75 lbs / bbl same Motueka lot.
-* ·  Ferment with Tropics yeast at 68 deg.
-* · Dry Hop 2.75 lbs / bbl with 40% HBC 586, 40% El Dorado, 20% Sabro Cryo.
-* · Centrifuged to less than 200 EBC
-'''Contains No Juice Hazy IIPA'''
-* 2-Row Malt for Base, 25% all wheat, incl. high protein red wheat from Mecca Grade.  Mash Hopping with US Cascade Hops
-* Whirlpool at 175, 2 Kg of Idaho 7 Full Spectrum Plasma & 0.5 lbs. / bbl Simcoe
-* Ferment with Tropics yeast at 68 deg.
-* Dry Hop 5 lbs / bbl with blend of Mosaic, Citra Cryo, Waimea & Nelson hops.
-=== '''Takeaways – Brewing Process''' ===
-* High-Precursor hops in Mash & Whirlpool (cooled to 175)
-* Thiol Yeast for Fermentation (Tropics used in these examples).
-* Moderate Dry Hop seems to prevent decrease of 3MH, although difference between 2.75 and 5 lbs was 2,000 ng/L – moderately perceptible. More efficiency with raw materials
-* Comparing with Berkeley’s lab trials (unhopped): these beers were tested after packaging (3-4 weeks old), vs. Fresh and in the lab. Likely higher at packaging.
-* At what point is the thiol threshold so far beyond perception that there’s little difference between x and y? (i.e. the “100 IBU” fatigue example). Odor Activity Values!
-* Vengeful Barbarian shows importance / reliance of monoterpene alcohols to generate hop flavor. Thiols just part of the story.
-* We know we’re going to get a TON of 3MH concentration from using thiol releasing yeast, focus on good hops to do the rest of the work.
-=== '''Incorporating Thiols & Monoterpenes in Recipes''' ===
-* Results from VB show us that Thiols are only part of the story. Must take into account:
-* Presence of Monoterpene Alcohols: Geraniol, Linalool, Citronellol
-* Ester compounds found in hops like 2MIB
-* Knowing Free Thiols & Monoterpene Alcohol Concentrations, a brewer can extrapolate when planning dry hops.
-* 1 Kg T90 Nelson hops / bbl = 1300 ng/L of potential 3S4MP if 100% extraction occurs.
-* 1 Kg T90 Sabro Cryo hops / bbl = 497.84 ppm of potential Geraniol if 100% extraction occurs.
-* Thinking about how much ”special sauce” could be going into your DH, rather than a blind lbs / bbl benchmark.
-* Establish Odor Activity Values for various compounds, then determine how to get there with hops.