Changes

===Chemistry and Characteristics===

During aging and if exposed to oxygen, compounds in hops oxidize into different compounds known collectively as "oxidative polar compounds" or OPC's. Hao et al. (2020) reported 39 different OPC's in aged hops, with 15 of them derived from alpha acids, 15 derived from isomerized alpha acids, and 9 from beta-acids <ref name="Hao_2020" />. Many of these oxidation derived compounds are considered "hard resins" (meaning they are soluable in alcohol) and contribute bitterness and antimicrobial properties to beer. Examples of "soft resins", which are not soluable in alcohol, are alpha and beta acids <ref name="Almaguer_2015">[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.160 Almaguer, C., Schönberger, C., Gastl, M., Arendt, E. K. and Becker, T. (2014), Humulus lupulus – a story that begs to be told. A review, J. Inst. Brew., 120: 289– 314. DOI: 10.1002/jib.160.]</ref>.

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! Oxidized Compound !! Precursor !! Beer Soluble (Y/N/?) !! Bitterness Level !! Notes

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| Humulinones (cohumulinone, n-humulinone, and adhumulinone) || alpha-acids (cohumulone, humulone, and adhumulone) || Y || 66% as bitter as iso-alpha-acids || In hops, alpha-acids are degraded to humulinones in the presence of air, with higher temperatures leading to more rapid conversion.

| Scorpiohumulinols A/B and dicyclohumulinols A/B || 4'-hydroxy-allohumulinones || ? || ? || Potentially makes up the majority (70%) of compounds derived from the degradation of 4'-Hydroxyallo-cis-humulinones in beer stored at 40°C over 12 weeks.

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