Botanicals 101: Hops
“What are hops???” The short answer is botanical ingredients (plants) that are used to give flavor (yum) and stabilise beer (good).
Historians believe hops first started to be used in brewing around 800 AD through discovery of their antibacterial properties - beer brewed with hops took longer to spoil. At the time, monks had the most knowledge of scientific advances in medicine and brewing, so it is only natural that the two practices were eventually combined. Before hops, brewers tried all kinds of herbal ingredients in an attempt to make their beer last longer and taste better, even poisonous herbs like hemlock and nightshade. Hops (Humulus lupulus) are from the Cannabaceae family, which means that yes, they are related to marijuana, but don't try smoking them (you won’t get high at all, plus it’ll taste super gross).
Hops contain acidic oils; brewers are generally mostly interested in the alpha acid content, which varies in strength depending on hop variety. Essentially, the higher the alpha acid content of the hop variety, the more bitterness it will give to the beer (yes, exactly, lower alpha acid content will mean less bitterness). High alpha acid content also takes longer to break down and give its bitterness, so those hops are added at the beginning of the boil. Lower alpha acid hops (also known as aromatic hops) are added at the end of the boil because they take less time to break down and a longer boil time would destroy some of their more delicate flavor notes. A brewer's goal is to achieve a final product that contains a certain balance between high alpha and aromatic hops, in addition to complementing the flavours from the malt bill. Hundreds of hop varieties exist today, with new varieties bred constantly. The writers of the Bear Flavored blog have put together a thorough cross-referenced list; use it the next time you need to demolish a craft beer nerd who brewsplains you while you try a new beer.
The bitterness level of the beer is measured by the IBU, or international bitterness units. A good rule of thumb is the more bitter a beer tastes, the higher its IBU will be. According to Amy Stewart’s Drunken Botanist, a good general reference would be:
Mass market American beers = 5-9 IBUs
Porter = 20-40 IBUs
Pilsner lager = 30-40 IBUs
Stout = 30-50 IBUs
IPA = 60-80 IBUs
Triple IPA = 90-120 IBUs
This is just a guideline though, since some experimental brewers have tried to push a beer's IBU level through the roof, regardless of style - some succeed in making a balanced and drinkable beer, most do not. 100-120 IBUs is generally the limit to bitterness that people can taste, so anything over that is usually just a gimmick. Personally, I am still recovering from the mega hoppy beer trend a few years back, so I reserve my bitter flavors for the cocktail world and prefer a nice Pilsner instead these days.
Back to CHEMISTRY: Iso-alpha acids are a type of alpha acid; they contribute to foam stability in beer. These acids are hydrophobic (translation: don’t like water) and are believed to provide support to bubbles. The acids work in coordination with hydrophobic proteins in the beer to preserve foam and keep the beer stable from brewery to consumer. The downside to these acids is that they are sensitive to light and break down, creating off-flavours in finished beer (technical phrase: they tend to photo-oxidise and turn to a compound called isopentenyl mercaptan, which gives that nasty skunky flavour in light-struck beer) (a good phrase to use on that craft beer nerd I mentioned earlier). This is why dark-colored beer bottles are preferable to light or clear bottles; they help protect the beer from damaging light. It's also why any beer advertised to be served with a slice of lime in the bottle neck is just a marketing trick (cough Corona cough).
It's possible to grow your own hops at home, if you've got space to support a sturdy trellis and live in the right climate. Hops grow best between the latitudes of 35-55 degrees North and South, and only the female cones contain the acid-rich oils desired by brewers (if you want to get technical, the alpha acids are found in a resin called lupulin in the cones). Hop vines like at least 13 hours of sunlight a day while they grow, which further narrows their geography. I also like 13 hours a day of sunlight, but it’s winter in Berlin right now so I have to take what I can get. Please comment any experience as to whether a S.A.D. light will work on a hop vine.