Understanding Hops and the art of “hop bursting”

A quick little disclaimer…the first half of this post is going to be fairly “technical”.  More often then not home brewers tend to simply follow recipes in terms of hop additions, or look solely at the alpha acid level and pick their hops from that.  As we get more into creating our own recipes, I think it is important and also fairly interesting to truly understand how hops work and how to go about selecting the proper amount of hops for any particular beer.

However before I inundate you with a bunch of math formulas, and since I am writing this early on a saturday morning, here is a little good morning tunage.


As I go along in this blog I want to take time to focus in on each individual ingredient that plays a major role in the brewing of beer, hops will be my first undertaking.

First off, why do we use hops.  Surprisingly hops play several roles in the formulating of quality beer.  First, hops provide the bitterness level for any given beer.  This bitterness provided by the hops alpha acids (more on those later) helps define beer styles and also works as a balancing agent with malt, making sure beers don’t become to sweet or malty.  Second hops provide unique flavors and aromas to your beer.  With the endless varieties of hops available today, brewers have the opportunity to tweak hop flavor and aroma to find their own perfect combination.  Finally and perhaps most importantly hops work as an anti-bacterial agent, helping to destroy bacteria and allow the yeast to work properly; furthermore hops are also a preservative allowing for beer to be aged and stored without going bad.  When we look back at some of the early usages of hops, we think of the creation of the IPA (India Pale Ale) story and how the hops were used as a preservative in order to ship beer from England all the way to India.  (Sadly there was no overnight, next day delivery at this point in history)

Fantastic looking hops

When trying to understand the hop plant, especially as a brewer we look directly at the female flowers or cones.  In the world of brewing we use the female cones instead of the male cones for one major reason.  The female cones contain lupulin glands home of the all important alpha and beta resins, as well as other specific oils that help create unique flavors and aromas.  When we look at hops at our LHBS these resin levels are displayed as alpha and beta acid %’s.

Package of hops displaying the alpha and beta acid %’s

What exactly are alpha and beta acids, and what effect do they have on beer?  Well let’s first look at alpha acids.

Alpha Acids: The alpha percentage is what effects and helps a brewer know the amount of bitterness that a particular hop will impart in the beer.  The higher the % the more bitterness will be added to the beer.  Furthermore these acids are not very soluble.  Because of this, they require a much longer amount of time in the boil.  If you have ever been curious as to why bittering hops are added right at the beginning of the boil, now you know.  Alpha acids contain a trio of important chemicals, humulone, cohumulone and adhumulone.

Beta Acids: Unlike the alpha acids beta acids don’t impart bitterness, instead the oils in this acid will impart flavor and aroma.  Unlike alpha acids beta acids are very soluble and will release flavor when boiled between 10-30 minutes and aroma at any point under 5 minutes.  Of course the higher the beta % the more flavor and aroma that hop has to release.

My friend Pat recently sent me this link, and this page is a great resource for anyone looking to see the different acid levels of just about any hop available today.  Furthermore the page provides useful information in the growing of each hop type and also some suggestions for beer style usage and possible substitutions.  Check it out here

The next question is how do we apply this acid information to hop selection when it comes to brewing.  In other words how do we figure out our utilization and IBU levels based on these numbers.  I’ll be honest just about any brewing software will automatically do this for you, and after I walk you through the actual formulas I’m sure you will ALWAYS use the brewing software.  That being said it is kind of neat to see how the math actual works, and you never know who you can impress by knowing this stuff.

First how do we calculate a beers IBU’s.  IBU’s or international bittering units describe the bitterness level of a given beer.  The higher the IBU’s the more bitter the beer will be.  Beers with a high malt content need more IBU’s in order to balance out the sweetness.

To calculate IBU’s we use what is considered the most accurate formula created by Glenn Tinseth…

IBU’s = Utilization * (# ounces of hops *(Alpha%/100) * 7490/gallons of wort)

The problem with the above formula is it requires the hop utilization based on a beers target original gravity.  In order to calculate that we use the following formula…

U = (1.65 * .000125^(O.G. – 1))*((1-2.72^(-.04 * Boiling Time))/4.14

I know what your thinking…What the hell does ^^^^^ mean?  So let’s try and break it down using a basic hop such as cascade.  The cascade hops I have in front of me right now have an AA% of 8.9  To keep it simple we are going to brew a beer with a target O.G. of 1.060  with a target IBU level of 35.  We will be using a 60 minute bittering addition and a 15 minute flavor addition.  Our first step is to calculate utilization, which will require two separate calculations one for the 60 minute addition and the other for the 15.

[60 minute utilization]   (1.65 * .000125^(1.060-1)) * ((1-2.72^(-.04*60)) / 4.14 = 21.14% for whole hops (add 10% for pellets 23.25%)

[15 minute utilization]   (1.65 *.000125^(1.060-1)) * ((1-2.72^(-.04*15)) / 4.14 = 10.5 % for whole hops (11.5% for pellets)

We now have our utilization numbers required to calculate IBU’s remember that our target IBU’s is 35.

so for my 60 minute addition of cascade hops at 8.9% AA I am thinking of using 1 ounce.  Therefore my IBU calculation would look like…  (I’m using pellets)
IBU = 23.25 * (1 * (8.9/100) * 7490 / 5  giving me right around 31 IBU’s

For the 15 minute addition using a quarter ounce of cascade…
IBU = 11.5 * (.25 * (8.9/100) *7490 / 5 giving me 3.8 IBU’s

With both calculations completed I now add the two together 31 +3.8 for a total of 34.8 IBU’s.  (Pretty damn close 🙂

Once you have calculated your utilization the IBU formula is a good place to change the amount of hops being used to see the overall effect it will have on your beers bitterness.

Now I doubt any of you reading this are getting antsy over using this formula for practical application, but it is interesting to see how hops and their alpha acids actually effect your beer.

Now that we have learned about hops and understand how to utilize them….horrible pun intended, let’s move on to something fun…HOP BURSTING!

But first a hilarious intermission….

So what exactly is “hop bursting”?

Bursting is a technique that allows us to add an irrational amount of hops to a beer providing a ton of hop flavor and aroma without adding an overwhelming amount of bitterness.  Have you ever seen a recipe that uses over 8 ounces to a pound of hops and wondered how that wouldn’t taste like liquid aspirin?  The answer is quite simple, hop bursting.

As we discussed earlier in the post, bitterness levels rely on a hops alpha acid level.  We also learned that in order to extract the most alpha acids the hops need to be boiled for at least 60 minutes.  Therefore if they are boiled for less time, less of the alpha acids get utilized and therefore less bitterness is imparted.  Now even adding hops at 15 minutes will impart a percentage of bitterness which is why the formulas we previously discussed are important.

With hop bursting we are adding almost all late addition hops (from the final 15 minutes on) that are generally high in beta acids to maximize flavor and aroma.  By bursting or adding a large amount of hops at this point in the boil, we can maximize the amount of flavor and aroma we get while at the same time limiting the amount of bitterness in the beer.

This is a technique that is widely used, especially in those super hoppy IPA’s that have a ton of hop flavor but a balanced and drinkable bitterness.  Hope bursting is a fun way to experiment with different hops without completely destroying your beer.  Not only is bursting fun and experimental but it also cuts down on the need for dry hopping, which for those looking to make their beer as clear as possible, will help in preventing sediment and hop cloudiness.

So there you have it, the process of bursting.  Next time you are wanting to make a hoppy beer, give it a try, skip the generic bittering hops and load the beer up with late addition hops.  You will still get enough bitterness to balance your beer, but the hop flavor and aroma will be INTENSE!


Categories: Beer


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