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Essential Oils

Essential Oils

How brewer’s get that hop burst in beer.
By Joe Bair

A simple way to enjoy hop aroma is by rubbing a few hop cones between your palms to create some heat for a few seconds, just until it turns sticky, and then inhale in cusped hands. What you smell is the “flashpoint” of the essential oils vaporizing. The amount of essential hop oils that go into the beer is less than a few hundredths of the weight of the cone (1-3 parts per million), so getting that rubbed hop smell in the beer must be understood. This is how brewers are making it hoppy just for you.

To begin with, hop packaging has improved. The hop merchant, wholesaler and homebrew store owner packaged the hops for their companies for name brand recognition which degraded the hops, because hops oxidize quickly. Now, the hop merchants package them just once in portion controlled, nitrogen flushed, oxygen barrier packages. Once you’ve opened your hop package, you should use them, or store your excess hops with the air expelled in your freezer, as oxidation happens faster at higher temperatures.

It is imperative to understand the delicate balance in timing and temperature of hop kettle additions for the bittering, flavoring and aroma. When you boil the hops you drive off the aromatic essential oils of the hops (homebrewers love the smell of hops in the brew house during the boil).

When I’m solar brewing and pressure cooking the wort, the bittering alpha acids isomerize more under pressure (past the 212ºF boiling ceiling) and the essential oils are not driven off, but go back into the beer making it mighty hoppy!

Hop Kettle Additions Made Easier:

Bittering or boiling cones, pellets or hop plugs or bittering hop Alpha acids (which are usually ethanol extract) are calculated by IBUs (International Bitter Units). When boiling the hops for an hour it just rearranges the atoms of the molecules (i.e. isomerize) so the Alpha acids will be released from inside the cones lupulin glands and dissolve into the wort. For most “glass of hops” US IPAs, try using a small amount of bittering hops (~3 IBUs) and 10x of “flavor” hops. Using less bittering hops benefits the malt flavors in the beer by not hiding it behind the less harsh tasting bittering hops.

Flavoring or finishing (ethanol extract): The semi-released hop resins play an important part in flavoring and finishing late kettle additions (over the last 30 minutes with particular emphasis on about 12 minutes) called “burst” hops additions. These lower alpha isomerization (~15%) flavoring resins fit somewhere in the middle and contribute to the sticky hop taste.

Aroma or nose hop (CO2 extract): Hop oil has been on the market for 40 years, it was originally extracted with steam which oxidized the oils and made some nasty tasting solvents. It was used for bittering only. Hop aroma oil is extracted using vacuum distillation with liquid carbon dioxide in a controlled environment which produces an amber to yellow colored oil. Hop varietals are different in aroma due to the composition of the volatile essential oils which change in a different year’s crops and location. It is now used in holistic therapies, which goes back to the original use of hops
as a calmative herbal remedy for childbirth in Southern Germany.

The four essential oils of hop aroma:
Myrcene, Caryophyllene, Humulene and Farnesene.
For the most hop emphasis, brewers should wait at least until the wort is cooled down below the boiling point of the hop oil and it is even, before adding the aroma hops below the flashpoint to be most efficient.

  • Myrcene

(flashpoint 103ºF, boiling point 147ºF) is the piney, grapefruit character you taste in American beers.

  • Caryophyllene

(flashpoint 200ºF, boiling point 262ºF) is the Earth, wood and pepper smell you find in English beers.

  • Humulene

(flashpoint 110ºF, boiling point 210ºF) is the continental European Noble hops herbal spicy flavor used in perfume. 

  • Farnesene

(79ºF flashpoint, boiling point 500ºF) is the “green apple” smell, but is usually in very small amounts.

There are four essential oils of hop aroma (see above), of course, it is complex and there are other oils (20-25% of the total oil content), too! The percentage of one oil to the other is just as important as the percentage of the oil itself. To find the hop oils, look them up by name and compare the oils of one to another.

I’ve seen homebrewers use a pillow case full of freshly picked hops to “wet” hop a five gallon batch. The displacement volume is messy and it oxidizes the beer. If you haven’t grown your hops but want the same effect, use hop aroma oil which is cold extracted with liquid CO2 and will not expose your beer to oxidation. Aroma hop oils are generally used in the secondary fermentor or before bottling or kegging. The reason being, the yeast metabolizes and alters the oils,
resulting in a different kind of aroma.

Extract and specialty grain brewers can boil the wort in half the time to get hoppy beers. If you do not want to boil for an hour, just boil for thirty minutes and add “burst” hops accordingly. The extract maker is usually the same malter of the grain so the DMS has already been boiled off. Since all-grain brewers need to boil wort for an hour for all grain to drive off the DMS, you should just add one half-ounce of bittering hops to reduce the surface tension to help avoid boil overs. Hop oils were originally made for brewing in warmer climates like Africa, where the storage and stability of whole or pelletized hop was not possible and required the hop extract.

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