Agreeing on a definition for “quality of bitterness” is almost as hard as agreeing on a definition of “craft beer.” But understanding quality of bitterness is essential, and a reason why I like the way Polish homebrewers tweaked their scoresheet for their competitions, awarding six points for bitterness.
The International Bitterness Unit formula was established in the 1960s at a time the composition of hop cones was different than today. And because isomerized alpha acids are primarily responsible for the bitterness in beer, “many brewers consider iso-a-acids to be the only relevant bitter compounds in beer.” Scientists in Germany believe otherwise, maintaining that the majority of what they call “auxiliary bitter compounds” are desirable from a sensory perspective. Sensory panels reported that the harmonious aspect of bitterness increased with the quantity of ABC.1
Basically, “auxiliary bitter compounds” encompass all bitter compounds in hop resins which are transferred into beer and which are not iso-alpha acids. Few of the 8,000-plus brewers in the United States have the equipment needed to measure ABC.
If a brewer does not have that equipment what should they do? A few rules of thumb:
– High alpha varieties, particularly those with a low percentage of beta acids, will contribute little ABC.
– Short boiling times increase the concentration of ABC, because fewer alpha acids are isomerized.
– Late hop additions increase the concentration. Same reason.
– Dry hopping increases the concentration. Ditto.
– No surprise, quantity increases the concentration.
– Using hops with a high beta to alpha ratio increases concentrations. This is the flipside of the first item on this list. It is common to take a look at the alpha/beta ratio in a variety, but consider the beta/alpha instead.
The hops with the highest beta/alpha ratio (from 1.3:1 to 2.4:1) are all landrace varieties — found growing in the wild, sometimes centuries ago, and chosen for their brewing qualities — such as Saaz, Mittelfrüh, and Strisselspalt.
In contrast, starting with Brewer’s Gold, New World varieties have been bred to produce more alpha. Some examples (ratios will vary by lot):
– Cascade 1:1.2
– Centennial 1:2
– Citra 1:3.25
– Mosaic 1:3.4
– El Dorado 1:2.8
– Sabro 1:2.8
– Idaho 7 1:2.8
– Nelson Sauvin 1:2
– Galaxy 1:2.3
1 A. Foster, F. Schüll, A. and Gahr, “What are Auxiliary Bitter Compounds in Hops and how do they Affect the Quality of Bitterness in Beer?” Brewing Science 70 (2017), 203-209.