I figured it would be a good idea to write a basic summary of the acids in hops. I suppose should start by saying that there three main compound groups in hops that provide our sought after bitterness, aroma, and flavor. These groups are the hard resins, soft resins, and the essential oils. The consensus is that hard resins aren’t important and don’t contribute much of anything in terms of flavor and aroma. As such, I am going to ignore them… forever.

Instead, I am going to focus on the soft resins. They are considered the most important because they contain the alpha acids (humulone, cohumulone, and adhumulone) the primary bittering agent for your brew. These unadulterated chemicals don’t actually contribute to the bitterness. They first must be isomerized (chemically re-oriented) by heating before they can be dissolved into the wort (the longer the boil the more isomerization). Cohumulone is the most effective bittering alpha acid because it readily dissolved into the wort. Typically, the high alpha acid mega brewer hops are high in cohumulone to get more bang for there buck. This contributes to the understanding that these hops are bad for homebrewing, craft brewing, or brewing simply brewing for flavor. As you contribute large amounts of one bittering compound, you lose the balance of flavors contributed by the others. Also, because less hops are needed for the desired bitterness, there are less essential oils being extracted. These compound contribute important citrus, herbal, floral, and even piney flavors. As a side note, old stale hops are hops that have undergone oxidation. This alters the alpha acids in such a way that they can not be isomerized, and, therefore, can not be dissolved into the wort. So throw away your old hops cheesey smelling hops.. they are useless (except for lambics and compost).

Beta acids are the other soft resin. They are lupulone, colupulone, adlupulone. These are generally not recognized for bitterness because they are not naturally soluble and dont isomerize to become soluble. On the contrary, beta acids must oxidized to create bitterness, the opposite of the alpha acids. Therefore, as a beer ages the bitterness from beta acids can become more prevalent as the bitterness from the alpha acids is reduced from oxidation. This isn’t really a fair trade-off because the flavor from these compounds is commonly described as vegetal, which is not a good thing. Most LHBS don’t usually give the beta acid percentage, but I know Austin Homebrew Store does. The rule of thumb is that a 2:1 ratio of alpha acids to beta acids is good. This allows the beer to mature gracefully without tasting like a rotten artichoke.

Wikipedia also claims that the beta acids create DMS, which give off a corn aroma/flavor and is created during boiling. But, I dont buy this at all. DMS is a byproduct of S-methyl methionine, which is made from methione a common amino acid, and is found in malt not hops. The only possible connection is the use of sulfur containing chemicals to block mildew that are used on hops, which may react to create DMS during the boil. There are also sulfur containing essential oils, but i have not been able to find much info. on them. Therefore, don’t trust wikipedia, and leave your brewpot at least partially cracked until the last ten minutes of the boil. That will release the DMS.

J