By Mike Retzlaff
Whether you find the analysis on the hop packaging, the HOP UNION web site, or elsewhere, there are plenty of things to consider when choosing hops to go into that next batch of beer.
The compounds in hops that are responsible for bitterness are the alpha acids. There are five but the major three are humulone, cohumulone and adhumulone. All are bitter and occur in varying proportions depending on the hop variety, where it’s grown, the weather conditions of that season, etc. Hops high in cohumulone have a harsher bitter character than those with low cohumulone levels. These hops with high levels are better suited for late boil additions, in the whirlpool, hop-back, or for dry hopping. High levels are generally considered to be 34% of the total alpha acid level or higher. For a number of years, I’ve shunned Cascade hops in my brewing. Drinking a beer loaded with Cascade hops is like swallowing hack saw blades; at least for me. I didn’t really know if this was real or imagined. Once I learned how the level of cohumulone in hops affects the perception of bitterness, it all made sense. Cascade hops have a cohumulone level of 38% to 40% of the alpha acids. I find them very harsh and generally substitute Amarillo and Centennial. Cascade is still a great hop when used for flavor and aroma. Many of the available New Zealand hops have high cohumulone levels too. As a comparison, noble hops have a 16% to 24% cohumulone level. Adhumulone usually comprises about 15% of the total alpha acid content – across the spectrum of varieties. It possesses a component, that when oxidized, produces isovaleric acid which has a cheesy aroma. See Aged Hops.
Alpha acids aren’t very soluble in wort. When wort is boiled with hops, the alpha acids undergo a chemical reaction called isomerization. The alpha acids, once isomerized, are soluble in wort, and these iso-alpha acids are what transmit bitterness into the finished beer.
Hops also contain beta acids. Beta acids are not bitter and are generally ignored by brewers. Their significance comes into play when analyzing the characteristics of different hop varieties. They aid in determining how much the hops have degraded over a period of time. Beta acids are not soluble nor do they isomerize. Some of their components, if oxidized, can add harshness to a finished beer.
In addition to alpha and beta acids, hops also contain essential oils. These hop oils are responsible for the hop aroma and flavor in finished beer. These oils are extremely volatile and evaporate very quickly at elevated temperatures. Most of these hop oils are lost within minutes when added to the boil. The heat of the boil changes the character of these oils as well. These oils can influence mouthfeel (body) perception. The major hop oil constituents of significance are myrcene, humulene, and caryophyllene. The aroma from the volatile oils is best preserved by either late hopping, whirlpooling, in a hop-back, or dry hopping so these components aren’t driven off by excessive or sustained heat.
There are a number of hops which are “traditional” for certain beer styles. Their aroma and flavor have become part of that style. Modern hop breeding offers us many alternatives to these traditional varieties. When choosing hops for a particular beer, there are some general guidelines which can be found in many places.
Use common sense and a little thought in selecting your hops. It does not make any sense to hop a beer with a subtle hop such as Tettnanger or Saaz and then dry hop with something aggressive like Warrior or Columbus. Galaxy hops remind me of the aroma of hard candy. Lemon Drop hops taste and smell like, um, lemon drops. Many other hops have their own qualities. It seems inappropriate to add citrus or tropical fruit aroma and flavor to a Munich Dunkel. It’s only reasonable to match the hops to what beer you’re producing unless you have some exotic effect in mind. Please don’t get me wrong; I am a hardy proponent of the “what if?” mindset but you should have a plan – a set goal.
When reading the descriptions and specifics of a particular hop, the total percentage of alpha acids, percentage of cohumulone, and total oils are the figures to watch. Using the properties of the individual hops to their best advantage will turn out to be to your best advantage too.