Hop utilization is the percentage of alpha acids that is isomerized and remains in the finished beer. The utilization of the bitter substances rarely exceeds 40% in commercial breweries and is often as low as 25% (31).
Factors Affecting Utilization
Not all of the bitterness potential from the alpha acid in the hop is utilized, which can be attributed to a number of reasons:
Form of Hops
The isomerization rate is initially affected by the form of hops. Isomerization is slower and at a much lower rate with whole hops or plugs, slightly faster with standard pellets, and greatest with extracts.
Boil conditions can affect isomerization in a number of ways. For instance, the longer the boil continues, the more isomerization takes place, though eventually the reaction reverses itself, degrading the iso-alpha acids.
Isomerization is also affected by hopping rate; as the hopping rate increases, the rate of isomerization decreases. This effect can be partially offset by adding bittering hops in stages.
Fermentation conditions can affect the amount of iso-alpha acids that remain in the beer in a number of ways. Loss of iso-alpha acids also occurs during fermentation as they are adsorbed onto the yeast cell walls.
Maturation and Filtration Conditions
After fermentation, maturation and filtration conditions affect the extent to which not only bitterness, but also other hops components survive in the finished beer.
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