Changes

[https://www.tandfonline.com/doi/full/10.1080/03610470.2021.1878684 Kishimoto et al. (2021)] reported similar results when making beers with forcibly aged hops. They aged Magnum hop pellets (14% AA) at 40°C and exposed to air for a number of different days: 3, 5, 7, 10, 14, 21, 30, and 90 days. The hops aged for 14 days had 9.8% AA, 21 days had 4.4% AA, 30 days had 1.2% AA, and 90 days had 0% AA. The IBU (measured with a spectrophotometer using Method Beer-23A from the American Society of Brewing Chemists) for the different beers made with the aged hops was more or less the same despite how much alpha acids were left in the aged hops. However, beers brewed with the different aged hops reflected a rapid decrease in iso-alpha acids in the beers made with the aged hops. Perceived bitterness also decreased for the beers made with the aged hops, but not as much as the decrease in ppm of iso-alpha acids, again demonstrating the oxidized hop compounds carry some bitterness, but less bitterness than iso-alpha acids <ref name="Kishimoto_2021" />. See Figure 5 from Kishimoto et al. (2021):

[[File:Kishimoto 2021 Fig5.jpg|600px|[https://www.tandfonline.com/doi/abs/10.1080/03610470.2021.1878684 Toru Kishimoto, Satoko Teramoto, Akiko Fujita & Osamu Yamada (2021) Evaluation of Components Contributing to the International Bitterness Unit of Wort and Beer, Journal of the American Society of Brewing Chemists, DOI: 10.1080/03610470.2021.1878684.] Uploaded with permission from Toru Kishimoto.]] It is therefore advised that brewers ask hop providers that offer aged hops what the original alpha acid percentage was when the hops were fresh, as well as the variety. This could be an important factor when determining how bitter the aged hops will taste, and potentially also how much they will negatively impact lactic acid bacteria growth. See also:* [[Hops#Aged_Hops_in_Lambic|"Aged Hops in Lambic" below]] and [https://www.facebook.com/groups/MilkTheFunk/permalink/2503097546385111 this MTF thread on IBU's from aged hops].]