Hops Explained

What You Need to Know About Hops

Before the days of refrigeration, hops were used as a preservative in beer. The original Indian Pale Ales (I.P.A.'s) were born out of a need to preserve beer on the long sail from Britain to her colonies in India 200 years ago. The I.P.A's strong hop flavor and crisp bite are due to the large amounts of preservatives that were required to keep the brew fresh on such a long journey. Today, however, hops are primarily used to add bitterness to beer and counteract what would otherwise be a sweet, foamy concoction.

Hops are a vine plant that produces a cone-shaped flower. Within the flower are resins and oils which give it its special flavoring characteristics. The resins are referred to as alpha and beta acids. The oils contribute a certain flavor depending on the style of beer you are brewing.

The important thing to know is that the alpha-acids are used to measure the bittering capacity of the hops. When you purchase hops, you will notice that it will be rated with an AA (Alpha-Acid) percentage. If the hops you are using is 6.2% AA, then this means that 6.2% of the weight of the hop flower is Alpha-Acid resin.

As the hop flower ages, the resins oxidize and they lose their bittering capability. Since it is impossible to measure how much of the bittering is lost in your hops through oxidation, it is best to try to always use the freshest ingredients you can.

Measuring Bitterness: IBUs and HBUs

Incredibly, there is an objective way to measure bitterness in beer. The standard that has been developed is called International Bittering Units (IBU's for short), and you will see references to IBUs (or HBUs) on virtually every beer recipe you find.

One IBU is equal to the bittering that is produced by adding one milligram of alpha-acid to one liter of wort. IBUs are an accurate measure of the amount of bittering acids in the beer, but the bitterness you actually taste will depend on the level of sweetness in your wort. That is because the sweeter your beer is, the more hops will be required to produce an "equally" bitter tasting beer. The level of sweetness is, of course, determined by the amount of sugar in the wort. The sweeter the wort, the more IBUs you will need to counteract the sweetness.

Unfortunately, it is very difficult to measure IBUs accurately. For this reason, most recipes will refer to HBU's instead of IBU's. HBU stands for Home Bittering Unit, and is a more convenient method of measurement for homebrewers. Determining the actual IBU value of your wort assumes you know how much alpha-acid will dissolve in your beer. You may know that you plan on putting 1 ounce of 6% AA Target into your brew, but that doesn't mean that it will all dissolve. In fact, even with a 60 minute rolling boil you will probably only end up with about half of the bittering potential of your hops. If you are using extracts, then your utilization will probably be even lower than that. Additionally, you will lose some bittering to the protein sediment and krausen. Put it all together and you will only end up with about 30% of the potential bitterness of your hops.

Since the amount of Alpha Acid that is originally dissolved, and the amount that is lost during fermentation are generally unknowable factors to the homebrewer, HBU's are used to put a number on how much hops you should add to your brew.

But why do I need to know this?

Because when you buy hops, they will almost never have the same AA percentage as the hops that are referenced in the recipes you are making. In fact, many recipes won't even express the amount of hops in ounces or grams, they will only give you HBUs. Therefore, you need to understand how bittering units are measured in order to adjust your recipe to the specific bittering your hops have.

Fortunately this is easy. The way to calculate is as follows:

HBUs = (% AA) x (Weight of hops in ounces)

Therefore, if you are trying to produce 8 HBUs of bitterness and you have a pile of Nugget Hops with an AA of 6% then you would use the following equation to determine how much hops to use:

8 HBUs = 6 (%AA) x 1.33 oz

But does it really matter?

Probably not. If you are following a recipe that calls for 1 ounce of 6%AA Nugget Hops (which would be 6 HBUs), and you throw in 1 ounce of 7%AA Nugget instead, then your beer will just taste 16% more bitter. If you like bitter tasting beer anyway, then you might like it even better. On the other hand, if you prefer a sweeter tasting brew, then you might find that your results are just too bitter for your tastes. As with seasoning any food, you should adjust your hops to taste.

"Bittering" hops are just one application of hops in what is sometimes a four-part process of hopping beer:

Bittering Hops
Flavor Hops
Aroma Hops (a.k.a. Finishing Hops)
Dry Hops

Bittering Hops

In order to properly extract the bittering characteristics out of your hops and into your brew, you must boil your hops for at least 60 minutes at a rolling boil. This causes the oils and resins to break down and actually dissolve into the brew. The dissolved resins cause the flavors to balance properly, otherwise the flavors would remain separated in the same way that oil and water simply don't mix. Because of the length of the boil, you will likely not be able to discern the taste of the bittering hops by the end of the boil, however, the wort won't taste so sweet anymore. It will smell more like a pine tree, and may have certain pine qualities to the taste as well. When you first begin brewing, you will be following recipes that have already been tested. But as you learn more about hops varieties and how they are used, you may choose to make your own creative modifications.

Flavor (Finishing) Hops

There is a difference between the bittering characteristic of hops and the flavor of hops. Different varieties of hops will lend unique flavors to your product. Some varieties, such as Cascade will deliver a citrus or flowery taste. Other varieties, such as a Hallertauer, have a distinctively spicier taste. If you were to boil these varieties of hops for a long period of time, the flavor would "cook out" of the brew, leaving only the bittering resins to dissolve in the solution. This is why brewers will add a second wave of "flavoring" hops to the kettle. These are added for the last fifteen minutes of the boil. They are generally more flavorful hops than the bittering varieties, and since you add them for the last fifteen minutes, their taste incorporates nicely into the wort, but it doesn't boil out. Most beer varieties with the exception of the sweetest ales and wheat varieties will use a flavor hop.

Aroma (Finishing) Hops

Of course, a large part of our tasting experience occurs through our sense of smell. Wine connoisseurs will often remark about a wine's nose, and believe it or not, there are a few beer aficionados running around who have been known to "swirl" a pint or two. Aroma Hops are added during the last minute of the boil. They don't stay in the wort long enough to affect the bitterness at all, but they do add substantial character to it's smell. Beer varieties that are characterized as more "hoppy" such as Pale Ales will always use an aroma hop.

Dry Hops

You may choose not to ever dry hop your beer, but if you do it adds a very green hoppy aroma and taste to the brew. Dry hopping is when brewers add raw hops into the fermenter with the beer as it ferments. The downside to dry hopping is that the hops are raw, and therefore not sanitary. Care must be taken to make sure you do not create an infection that gets out of control. You can lower the chances of unwanted infections by following these steps:

Add your dry hops after you have racked your brew to a secondary fermenter. Since most of the fermentation has already been completed by the time you rack your brew, the higher alcohol levels will inhibit the growth of bacteria. Also, since most of the simple sugars have already been consumed by your brewer's yeast, any wild cultures that may be introduced into the fermenter will not have enough food to eat to cause real harm
Finish up your fermentation as quickly as possible. Don't leave your brew sitting in the secondary fermenter with the dry hops any longer than necessary. As soon as fermentation is complete, bottle the product.
Once the brew has properly bottle conditioned, put it in a refrigerator. Don't store it on a shelf at room temperature. The cool refrigerator will inhibit bacteria and yeast growth.

Even following these suggestions, if you dry hop often enough, you will probably lose a few batches to infections. A good alternative to dry hopping is to add whatever hops you would have used for the dry hop phase into the wort during the last minute of the boil as additional Aroma Hops. This achieves the same objective of making the beer more "hoppy" but also removes the possibility of contamination.

Forms of Hops

Hops are shipped in a variety of formats. The primary ways you will find hops are in pellets, whole leaf, or plugs. On the whole, there is no convincing reason to use one form of hops over another. That said, these three forms are not exactly equal. Each has it's benefits.

Whole Leaf
Far cleaner than pellets, whole leaf hops are easily caught in a strainer or left behind when racking a batch of beer. You also have the satisfaction of using an ingredient that just looks much less "processed" than pellets or plugs. The downside to whole leaf: they are harder to measure accurately and may degrade faster than other forms.

Pellets
Extremely convenient and theoretically more durable, pellets are probably the most common form of hops for beginners. You will find that weighing out an exact amount of pelletized hops is very easy since they are so condensed. An ounce of pelletized hops comes out to less than a half cup in volume - far less than the equivalent whole leaf format. Because they are so tightly condensed, they are considered less susceptible to oxidation than whole leaf forms as well.

The downside to pellets: They disintegrate into a green mess in the brew kettle. Your only defense is to use a Muslin bag to contain as much of the green goo as possible.

Hop Plugs
For some reason, it is rare to find hop plugs these days, though occasionally you'll run across a few. Each plug generally weighs a half ounce, so it is pretty easy to measure the hops without using a highly accurate scale (as long as you want your hops in half-ounce increments). This ease of measurement is the primary benefit to plugs. They also have some of the benefits of pellets in that they are relatively compressed and may resist oxidation better than whole leaf. There really isn't any obvious downside to plugs except that they aren't whole leaf hops and they aren't pellets either. Therefore they tend to break up into smaller pieces than whole leaf (though not nearly as bad as pellets), and yet they are hard to measure accurately without a fancy digital scale the way whole leaf hops are.

Generally, you should be prepared to utilize your hops in whatever format it comes. Understanding the different formats is important to knowing how to deal with the product as you brew. If you are using pellets, it's a good idea to have a few Muslin bags laying around. If your hops arrive in whole leaf format, make sure you break out the strainer. If you have plugs, then you can use either a strainer or a Muslin bag.