Vol. 2, No. 2, June 2018
What follows is an oversimplification of research reported in the 2017 November/December issue of BrewingScience (“What are Auxiliary Bitter Compounds in Hops and how do they Affect the Quality of Bitterness in beer?). Basically, the words “auxiliary bitter compounds” encompass all bitter compounds in hop resins which are transferred into beer and which are not iso-alpha acids.
The majority of the substances are considered desirable from a sensory perspective. They reduce lingering bitterness and contribute to the quality and harmony of bitterness. The ratio of non-specific bittering units (IBU) to the specific iso-alpha acids (not something that can be measured at home or, in fact, at most of the breweries in the United States) serves as an indicator of the amount of auxiliary bitter compounds in beer.
The ratio is equal to 1 in beers brewed with one hop addition of high-alpha hops at the beginning of the boil, in which case the bittering units would be almost equivalent to the iso-alpha content. A higher ratio indicates more compounds.
If a brewer does not have equipment to measure the ratio what is she to do? (A quick aside here: Thank goodness drinkers won’t be seeing some sort of ABC measurement on menu boards at their favorite breweries). 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, because fewer alpha acids are isomerized.
– Late hop additions increase the concentration. More of the same.
– 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. The hops with the highest beta/alpha ratio (from 1.3:1 to 2.4:1) are all landrace varieties — chosen rather than bred — such as Saaz, Mittelfrüh, and Strisselspalt.
In contrast, New World hops currently popular for late and dry hopping, and whose names (Citra, Mosaic, Galaxy, etc.) end up plastered on the sides of cans, have ratios more like 1:2.3, 1:3.3, or 1:3.6.