Post image for The Science Behind Hops Part 1 – Alpha and Beta Acids

The Science Behind Hops Part 1 – Alpha and Beta Acids

by Brian

in Hops, Science!

Hops are a science all their own. Balancing alpha acids, beta acids, and oils all along with aroma, taste, and overall impression of a beer make choosing the right hop for your beer very tricky. Doing this well involves knowing a few key terms. Becoming a hop master takes a lot more information than I can give in one post, but this is a great place to start with understanding what all the information you get with hops really mean. Here is the CBA Science Behind Hops, Part 1: Alpha and Beta Acids.

Inside every hop a balancing act is going on between alpha and beta acids. These are what give hops the majority of their bitter flavor, along with many other characteristics that come from different styles of hops. Both alpha and beta acids are measured by percent by weight of the hop comprised of that acid.

Alpha Acids

 

Alpha acids are the most commonly referred to acids when it comes to hops, as these are where the hops get most of their bittering effect from. There are five main alpha acids, and they are:

  1. Humulone
  2. Cohumulone
  3. Adhumulone
  4. Posthumulone
  5. Prehumulone

 

Since each has a unique effect, here is the basics on each alpha acid.

Humulone1. Humulone

This is the primary alpha acid found in the majority of hops. This is where much of the bitter flavor in “hoppy” beers comes from. The humulone alpha acid is also known for it’s anti-bacterial, anti-cancer, and antioxidant properties. 

Humulone is known for a soft bitter flavor that is far from harsh. Citra hops are a great example of a hop that has high alpha levels and high humulone levels. Beers with them are bitter, but not harsh.

While humulone’s cancer-fighting powers are still are still being studied, studies are also being done on this alpha acid’s ability to fight pneumonia and bronchitis. This means that maybe that beer you’re drinking is doing you more good than just the enjoyment of a good beer! 

cohumulone2. Cohumulone 

The next alpha acid is cohumulone. The jury is out on whether this alpha acid is good or bad. In the past this alpha acid was considered less desirable due to the harsh bitterness it helps to impart in beer. Hop producers actually list this alpha acid out specifically due to this. 

Recently, however, with new varieties of hops coming to market, the harshness of this alpha acid has come into question. With these new varieties that are high in cohumulone, a good, even bitterness has been achieved. Studies are still being done on this to see why this is, but overall this is generally found in lower percentages.

3. The Rest

Not a lot is known about the remaining alpha acids, which are adhumulone, posthumulone, prehumulone. These three add to the overall effect of hops but how this is done still is not 100% determined yet. There is a lot of science that goes into understanding what these alpha acids do, so for a beginner’s guide we can leave it at that. There are a few good books out there on hops, if this really interests you, I recommend you find one and get some more information.

Alpha Acid Wrap-UP

Basically, humulone is a soft bitterness, cohumulone is a harsh bitterness, and the rest are kind of a mystery. When looking for a hop high in alpha acids, the general rule is high humulone and low cohumulone.

 

Beta Acids

 

The second type of acid found in hops are beta acids. If hops were a band, alpha acids would be the lead singer, and beta acids would be the 4th guitarist. Most people don’t really know what he does, but what he plays is still important to the song.

Beta acids are comprised of three main types. They are:

  1. Lupulone
  2. Colupulone
  3. Adlupulone

 

While alpha acids dissolve into solution almost immediately after being added to the boil, beta acids break down over time. This is best seen in beer storage and lagering. Beta acids are generally not talked about on their own, so for this guide we won’t go into each one. Just know that they break down over time and can change the profile of a beer when it’s aged or lagered.

Cross-section_of_hop_cone.svg

Wrap-Up

 

  • To wrap this up nice and neatly, alpha acids are generally the bitterness you taste in a beer, and they dissolve into solution immediately. They still take some time to release their bitterness, which is why timing of their addition to the boil is vital. The alpha acids isomerize in the boil to form isomerized alpha acids.
  • Beta acids take longer to break down and show up best in lagered or aged beers. Noble hops have the closest 1:1 ratio of alpha to beta hops, where most other hops have about a 2:1 ratio.
  • IBUs, or International Bitterness Units, are a direct measure of the iso-alpha acids in a beer. Basically, 1 IBU is equal to 1 milligram of iso-alpha acid per liter of beer.  

There is a lot more to alpha and beta acids, and a TON more to learn about hops as a whole. For now, this is a great start to understanding your hops better. In Part 2 of this series, we will look at Myrcene, Humulene, Caryophyllene, and Farnesene; all essential oil compounds found in hops.

 

Thanks for checking out this post on the science behind hops. Check out my series on the Hop Of The Week, and sign up for the CBA email list below for weekly updates and your chance at winning free glassware.

Until next time, 

Cheers!

 

 

Previous post:

Next post: