
Hops
Ahhh, hops. Every brewers friend. It balances sweetness with it bitterness. It adds flavor and aroma to many styles of beer. Even in beers where you may think there is no hops, chances are it is there in the background providing just enough bitterness to prevent the beer from appearing sweet, even if there is not much hop aroma or flavor. But the focus on hops is almost always the Alpha Acids, and to a much lesser extent the beta acids. Since the focus of this article is not on those two components, I will only briefly brush through their role in hops before I hit on the main topic of my posting, co-humulone.
Almost all the matter that benefits beer is found in the lupulin in the hop cone. You can easily identify lupulin in the hop cone as the yellow powdery and slightly sticky substance under the cones of leaves (see picture below). The alpha acids, which when isomorized in the boil, contribute bitterness to the beer, as well as some mild preservative qualities because of their antiseptic properties as well. The Beta acids also contribute a slight bitterness, however, since they don’t isomerize, but rather become soluble through oxidation, high amounts of beta acids can contribute to off-flavors such as a vegetal aroma for example. This lupulin also has the other oils and resins that contribute flavor and aroma as well as co-humulone.

Lupulin
So why is understanding co-humulone important? By understanding what it does, you can control the type of bitterness your beer has. If you have ever had an IPA with say 60 IBU’s (International Bittering Units) that you just loved, but then had another that was stating it was also 60 IBU’s but you found the bitterness quite off-putting, it could have been the co-humulone level of the hops used in each beer. In short, it is the level of co-humulone in the alpha acids that will dictate the type of bitterness the beer will have. Higher co-humulone hops tend to have a more bracing or harsh bitterness, while lower levels of co-humulone tend to have a softer more rounded bitterness. Think Amarillo, and the type of bitterness it provides compared to Chinook.
So here is where you can really start to have fun with recipe formulation and playing with hop varieties. I consider lower co-humulone levels to be that of 25% of total alpha acid, anything below 20% I consider to be quite low. Most of you nobel hop varieties fall in this range (15%-25% co-humulone), but some American varieties, some of the newer varieties in particular fall in here as well. See the bottom of the post for a list of low co-humulone US variety’s of hops.
Now there is some debate on if co-humulone really affects the type of bitterness. From my personal experience, it does. I have brewed a few IPA’s using the traditional Chinook, Cascade, Centennial, and other “traditional” American hops, and I have made IPA’s using the newer varieties like Amarillo, Glacier, Simcoe, and Horizon. I found that I prefered the newer varieties as opposed to the traditional. I never knew why until I discovered the effect co-humulone level has on bitterness.
I do have to say though, that if you are brewing for competition, it may be a good idea to add a small amount of higher co-humulone hops to the boil. The reason is that judges, and other beer geeks, have come to expect a certain type of flavor and bitterness when it comes to American IPA’s. I have found that all low co-humulone IPA’s seem to be described as “not having the bitterness expected for an IPA” and such. I don’t really think that is the case, but rather the bitterness is more well-rounded and not as sharp. My low co-humulone IPA’s are quite bitter if you pay attention, it’s just the bitterness is…..different. But keep that in mind if you enter one in a competition.
Below you will find a link to a hop data sheet, you can use this to research hop varieties from the US, UK, Germany, and other countries. These data sheets are helpful for finding a particular hops alpha acid, beta acid, and co-humulone range as well as getting aroma profiles, primary usage, and alternatives if you can’t get that particular hop near you. Below that I listed the low co-humulone American hops I know of.
US Low Co-humulone varieties
- Amarillo
- Citra
- Glacier
- Crystal
- Golding
- Hallertau
- Horizon
- Mt. Hood
- Santium
- Simcoe
- Summit
- Tettnang
- Vanguard










