Hop Aroma Oil Survivability in Beer Brewing01/12/2021
This week I take a look at how well hop oils survive the brewing process to make it into the finished beer. Some oils and hop varieties do much better depending upon when they are added when brewing.
What is Aroma Oil Survivability?
Aroma oil survivability is simply a measure of how well an aroma oil (or the aroma oils from a particular hop variety) make it into the finished beer. The basic idea is that if you introduce hops into the brewing process either in the boil, whirlpool or dry hopping, some oils are lost at each subsequent stage in the brewing process. For example whirlpool additions may be lost due to fermentation, aging, centrifuge, filtering, or packaging.
Recent Research Into Aroma Oil Survivability
Yakima Chief has published some of the more recent research in this area, particularly with respect to their hop varieties. In particular they have published the Survivable Compounds Brewer’s Handbook and accompanying Poster which highlight their findings. What I really like about their work is that they have taken a very complex subject and made it approachable and readable for the average brewer.
The Yakima labs measured how well 7 key aroma compounds survive the brewing process and provided recommendations for many hop varieties on when best to use them. The seven compounds are: linalool, geraniol, 2-Nanonone, 2-Methylbutyl Isobutyrate, Methyl Geranate, Isoamyl Isobutyrate and 3-Mercaptohexanol. There findings were that some hop varieties preserved these aroma oils well even if used early in the brewing process while others were better used late.
Hops That May Be Used Early in Brewing
While Yakima’s research was focused on the varieties their farmers grow, they did cover many of the major craft brewing hop varieties. Their results are summarized in the poster chart here.
The hops with aroma oils that survived the best even when used in late kettle, whirlpool or dry hopping include: Centennial, Cryo Pop Blend, Idaho 7, Mosaic, Citra, Ekuanot, Simcoe, Crystal, Loral, Comet and Chinook. Not surprisingly we see some of the most desirable IPA hops in this list.
While you could potentially use these in a late boil, they are probably better used in the whirlpool, late fermentation or dry hopping.
Hops Best Used After Fermentation
A second group of hops were found to be not as survivable by Yakima, and they recommend using this post-fermentation. This group includes: Talus, Sabro, El-Dorado, Palisade, Amarillo, Ahtanum, Willamette, Cashmere, HBC 630, Cascade and Azacca. Using these post-fermentation keeps more of the aroma oils above in the finished beer.
What About Myrcene?
Notably absent in the Yakima study is myrcene which is a major aroma oil compound in many US pacific north-west hops and provides a piney finish to the beer. For many hop varieties, it is the dominant aroma oil. Fortunately, we already know that myrcene is quite volatile, and it survives best post-fermentation.
Myrcene, however, is an interesting compound. Highly valued in many of the early Craft Beer IPAs, it has become slightly less popular now in an era of fruity IPAs and New England hazy IPAs. While it provides a great piney finish, in some of the newer styles it can actually mask other more fruity aroma oils like linalool and gerainiol because myrcene is fairly strong and also present in larger quantities.
So depending on the style, some brewers have been working to minimize the impact of myrcene by using “early aroma” hops listed above in the whirlpool where the remaining aroma oils will survive but a large percentage of the myrcene will not.