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'''Oxidized beta acids''' produce some compounds that also contribute to perception of bitterness, specifically hulupones. Unlike humulinones which form relatively quickly from oxidation of alpha acids, hulupones form at a much slower rate <ref name="Dušek_2014" />. Also unlike humulinones, they survive boiling and fermentation. While some sensory analysis of beers containing oxidized beta acids describe the resulting bitterness as "harsh and clinging", another analysis by Krafta et al (2013) described the bitterness of oxidized beta acids in beer when added in their pure form at the beginning of the boil as "pleasant and not lingering". The more degradation of beta acids into oxidized beta acids that occurs in hops, the more bitter beers brewed with these hops will be <ref name="krofta_2013" />. Two other compounds other than hulupones have been identified as being produced by the oxidation of beta acids, epoxycohulupone and epoxyhulupone. Their effect on beer flavor is not yet known, however it is thought that hulupones have the greatest impact on beer flavor <ref name="Dušek_2014" />.
The bitterness of hulupones has received some debate among researchers. In 1973, a researcher found that hulupones are about 50% as bitter as iso-alpha acids. Briggs et al stated the complete opposite, and that hulupones are twice as bitter as iso-alpha acids. More recent studies using modern analysis techniques found that on a weight for weight basis, hulupones are 35-40% as bitter as iso-alpha acids in one study, and another found that they were 84% (+/- 10%) as bitter as iso-alpha acids (note that this is an average; tasters vary widely in how much bitterness they perceived from different bitter compounds) <ref>[https://www.researchgate.net/publication/307796892_The_effect_of_hop_beta_acids_oxidation_products_on_beer_bitterness The effect of hop beta acids oxidation products on beer bitterness. Karel Krofta, Světlana VRABCOVÁ, Alexandr Mikyška, and Marie JURKOVÁ. 2013.]</ref><ref name="Algazzali_2014" /><ref>[https://www.crcpress.com/Brewing-Science-and-Practice/Briggs-Boulton-Brookes-Stevens/p/book/9780849325472 Brewing Science and Practice. Dennis E. Briggs, Chris A. Boulton, Peter A. Brookes, Roger Stevens. 2004.]</ref>. While the taste threshold of iso-alpha acids is 5-6 mg/L in light lager, the threshold for hulupones has been measured to be 7-8 mg/L in light lager <ref name="Algazzali_2014" />.
Both humulinones and hulupones have been identified as forming due to the oxidation of hop acids. However, other researchers have reported that both of these bitter compounds formed during the boiling of hops, and another during the storage and aging of beer <ref name="Algazzali_2014" />.
Other compounds have been associated with the oxidation of beta acids and are extracted during wort boiling. These are described as giving a long-lasting, linger bitterness on the palate. They include hydroxytricyclo-lupulone, dehydrotricyklolupulone, and hydroperoxytricyklolupulone <ref>[http://www.sciencedirect.com/science/article/pii/S0308814609001770 Structure determination and sensory evaluation of novel bitter compounds formed from β-acids of hop (Humulus lupulus L.) upon wort boiling. Gesa Haseleu, Daniel Intelmann, Thomas Hofmann. 2009.]</ref>.
[[File:Lam Hop Oils.jpg|thumb|upright=2.5|[http://pubs.acs.org/doi/pdf/10.1021/jf00070a043 Data from "Aging of hops and their contribution to beer flavor" by Kai C. Lam, Robert T. Foster, and Max L. Deinzer.] '''Aged I''': 2 weeks at 90°F; '''Aged II''': 60 additional days at 90°F.]]