Found in the lupulin glands of hop cones, these humulone compounds are insoluble in cold water and have no bitterness in their raw state. During the boiling of the wort, thermal isomerization converts them into iso-alpha acids, which dissolve into the liquid and create the characteristic bitter flavor. Brewers select hop varieties based on their percentage of these compounds to calculate the final International Bitterness Units of a batch.
These new pellets are testing at fourteen percent alpha acid, so cut the early boil addition by a few pounds to hit our target IBU.
High-alpha hops are typically added at the beginning of the boil for maximum isomerization, while low-alpha varieties are saved for late additions to preserve their delicate aroma oils.