Hop utilization refers to the percentage of alpha acids that undergo isomerization and remain in the final beer. The utilization of bitter compounds typically does not exceed 40% in commercial breweries and can be as low as 25% (31).
Factors affecting utilization
Not all of the potential bitterness from the hop’s alpha acids is utilized, which can be attributed to several reasons:
Form of hops
The form of hops initially affects the rate of isomerization. Isomerization is slower and occurs at a much lower rate with whole hops or plugs, slightly faster with standard pellets, and greatest with extracts.
Boil conditions can influence isomerization in various ways. For example, the longer the boil continues, the more isomerization occurs. However, the reaction eventually reverses itself, degrading the iso-alpha acids.
The hopping rate also affects isomerization; as the hopping rate increases, the rate of isomerization decreases. This effect can be partially counteracted by adding bittering hops in multiple stages.
Fermentation conditions can impact the amount of remaining iso-alpha acids in the beer. During fermentation, loss of iso-alpha acids occurs as they are absorbed onto the yeast cell walls.
Maturation and filtration conditions
After fermentation, the conditions during maturation and filtration affect not only the level of bitterness but also the survival of other hop components in the final beer.