Hops, Part Two
by Sophie Nelson, [email protected]
The last time we chatted about beer ingredients, I gave a little history and country-specific information about hops. The use of hops in beer, however, is much more complicated than simply throwing the little, green flower into some liquid. There’s a whole lot of chemistry behind the process, and I’ll now pass some of it on to you.
Hops are generally used in the form of little pellets, which are made by drying the hops, breaking them up, then forming them into pellets. In this form, they have a longer shelf life and more easily provide bitterness.
Wet hopping involves using fresh hops instead. This can be a trickier because once the hops are picked, they must be used that day to avoid going bad. Wet hopping creates a more green, grassy flavor in beer.
The last form of hopping is through an extract called Isohop that’s a concentrate of alpha acids. Miller is famous for using this extract in order to make beer that cannot be affected by light. Without it, Miller beer would become light struck and skunk in its clear glass bottle.
Hops are used for three things in beer, which I touched on in Part One: bitterness, aroma and flavor. Each hop is distinctive in its variety and in the location where it was grown, and each is measured for its bittering abilities in alpha acids, and for its flavor and aroma in resins and aromatic oils. Different hops are more useful for different beers, and they can make or break a style attempt. Not only does the hop’s composition affect the beer, but the point at which it’s added also has an effect.
Hops are added during the boil: one of the first brewing stages after the malted barley has been combined with water and has created a sweet liquid called wort. The wort is transferred to a boil kettle, where it boils for about 90 minutes. This is where some scientific understanding is needed.
The bittering capabilities of beer are measured in alpha acids, which, when boiled, go through a process called isomerization. This creates bitterness in the beer. The amount of alpha acids that are isomerized in the liquid is called International Bitterness Units (IBUs). The longer the alpha acids are boiled, the more bitter the liquid, and the higher the IBUs. This lets brewers choose whether they’re going to add hops earlier to create a more bitter beer, or later to brew a less bitter beer.
Hops can also be added after the boil, but for different reasons. A common example is a technique called dry hopping, when hops are added after the beer has gone through its first stage of fermentation. With dry hopping, the liquid is not hot enough to isomerize the hops,
so no bitterness is added. Instead, the process allows volatile oils and resins to add some aroma and flavor to beer. Some hop types are better for flavoring; others are better for aroma.
Four hops are known for their low alpha acids – or bittering capabilities – and high aromatic oils and resins. These “noble hops” are Tettnanger, Hallertau and Spalt from Germany, and Saaz from the Czech Republic. Because of the terroir qualities of hops, a noble hop that’s grown anywhere but in its original location is not considered a noble hop. These are vital for giving distinctive flavors and smooth bitterness to German and Czech lagers.
In the U.S., different styles rely on different hop varieties as well. Last time, I mentioned West Coast-style IPAs, which are known for citric, piney bitterness. New England IPAs, however use less-bitter hops with more flavor and aroma qualities to add light, fruity flavors, along with oats and other adjuncts to make the body smoother and creamier than their West Coast counterparts. Try some different styles to see what you think!