Compound Interest has made understanding the chemical compounds in beer as they relate to flavor and aroma easier for us all.

The below infographic, created by CI and available for purchase as a poster, brings light to the topic of where the defining flavors and aromas of beer stem from; namely, alpha acids, beta acids, essential oils, and esthersA great deal of these chemicals form as a result of the addition of hops during the brewing process.

After the wort, or the sugar-rich liquid resulting from the breaking down of barley, is transferred from the mill to the brew kettle, hops are added along with any other flavor-inducing ingredients. Before the yeast is added to the fermentation process, the hops react chemically with the mashed barley, infusing the beer mixture with various aromas and imparting a bitterness that gives many beers their defining personality.


Below, we point out interesting facts/a further breakdown of the four most significant types of compounds that are found in hops. To read Compound Intererest’s full article (which we highly recommend reading for a full understanding of the topic), head here.

Alpha Acids

  • This is where most of the bitterness from the hops comes from
  • Humulone is the most dominant alpha acid in the majority of hops. To make beers that have varying levels of bitterness, hops with different compositions are used
  • During brewing, alpha acids are broken down to form iso-alpha acids, which are soluble compounds responsible for much of the bitter flavor

Beta Acids

  • Beta acids give a much harsher bitterness than do alpha acids, but contribute less to flavor building because they are insoluble
  • They oxidize (instead of isomerize, like alphas do) to produce their bitter flavor during fermentation
  • This takes a longer time, and because of this, the effect is more powerful if the beer is fermented for a longer time

Essential Oils

  • Essential oils from the hops give the beer most of its aroma and flavor
  • Out of the over 250 essential oils in hops, humulene contributes most to beer’s distinguishing hoppy aroma
  • Because they evaporate easily, the oils are “collected” when the hops are added at a later stage in the brewing process
  • American hops have higher quantities of myrcene, which lends a citrus or piney flavor


  • Esters contribute fruity flavors in beers
  • They form when the organic acids in hops react with the alcohol in beer and a molecule found in hops, called acetyl coenzyme
  • The amount of esters that appear depends on the type of beer; lagers have small concentrations, while ales have high concentrations
  • The final concentration of esters in beer depends on, but is not limited to, these conditions during brewing: pH, temperature, and agitation of the mixture