Alpha acid

Iso-alpha acids (iso-α-acids) are typically produced in beer from the addition of hops to the boiling wort.

Alpha acid percentages vary within specific varieties depending on growing conditions, drying methods, age of the hop, and other factors.

For example, this list shows the typical range of alpha acids found in some common varieties (percentages are based on total dried weight).

For instance, lager styles use hop varieties with a low alpha acid content (such as Saaz and Hallertauer) while IPA styles use hop varieties with a high alpha acid content (such as Cascade, Centennial and Chinook).

[3] The iso-α-acids have no effect on Gram-negative bacteria, and therefore the brewer must rely on maintaining proper sanitiation and anaerobic conditions of the finished beer to ensure shelf stability.