Sure, we all love a "40" of "O.E." every now and then. But, that bad boy is missing something that makes beer unique. Hops. Most malt liquor is unhopped or only slightly hopped.
Hops are a critical ingredient in beer. These flowers from the female plant botanically classified as Humulus lupulus provide beer with the resins and essential oils that give beer its bitterness, aroma and to some extent flavor. There are a ton of resins and terpenes found in hops. Each variety of the 50+ types of hops, offers a different chemical profile. The possibilities are endless.
Hops have typically 3 uses in making beer. 1) Bittering 2) Flavor 3) Aroma. How a hop is used, depends on how long it is boiled during the brewing process.
Bittering hops are boiled in the wort for at least 60 minutes. A critical isomerization occurs during this time (see below). Flavor hops are added during the last 15 minutes of a boil, and aroma hops are added during the last 1-5 minutes of the boil. The role is determined by how oxidized the hop chemicals get during the boil.
I want to just consider the bittering aspect right now. Hops contain varying amounts of what are known as alpha acids. Many hops range from 4-15% alpha acids. Humulone (as seen in the figure below) is one example of an alpha acid. There are of course many others, but they are all phenolic compounds that are only slightly soluble in water. The alpha acids get isomerized to iso-alpha acids during the boil in the slightly acidic wort. The iso-alpha acids are more soluble in water and contribute the bitterness of beer. A good 60 minute boil is necessary to extract and isomerize the alpha acids. The % alpha acids is a good measure of how bitter a hop will make the beer.
Below is my propose mechanism for the isomerization of alpha acids to iso-alpha acids.