Changes

Beer bitterness is often described in terms of International Bitterness Units (IBU), or more accurately, Bitterness Units (BU). The European Brewery Convention has adopted the [https://europeanbreweryconvention.eu/new-international-method-on-bitter-compounds-in-dry-hopped-beers/ “E.B.C. Bitterness Units,” ] determined in a similar wayand recently updated for dry hopped beers to account for humulinones, as a uniform method that best expresses the true bitter flavor value of beer <refname="asbc_ibu">[https://www.asbcnet.org/Methods/BeerMethods/Pages/default.aspx ASBC Methods of Analysis website. Retrieved 02/11/2022.]</ref>.These measurements seek to measure the amount of iso-alpha acids, which contribute the majority of bitterness to beer. There are, however, other compounds that contribute to bitterness, such as oxidized alpha and beta acids (see [[Hops#Chemistry_and_Characteristics|Aged Hops]] below). These methods include using [https://en.wikipedia.org/wiki/Spectrophotometry spectrophotometry], [https://en.wikipedia.org/wiki/High-performance_liquid_chromatography High-Performance Liquid Chromatography-Ultraviolet (HPLC-UV)], and [liquid chromatography–mass spectroscopy liquid chromatography–mass spectroscopy (LC–MS)]. Compounds other than iso-alpha acids present several challenges to traditional methods of measuring BU's. Many hop compounds other than iso-alpha acids are detected at the same wavelength as iso-alpha acids using spectrophotometry. In addition, oxidized alpha acids are known to contribute to bitterness. As a result, updated methods of using High-Performance Liquid Chromatography-Ultraviolet (HPLC-UV) and liquid chromatography–mass spectroscopy (LC–MS) are generally recommended for measuring bitterness units in dry hopped beers (although models that account for bitterness contribution from compounds other than iso-alpha acids have not yet been completed) <ref>[https://www.chromatographyonline.com/view/liquid-chromatography-mass-spectrometry-analysis-of-hop-derived-humulone-and-isohumulone-constituents-in-beer-the-bitter-truth-of-hops-utilization-during-brewing Liquid Chromatography–Mass Spectrometry Analysis of Hop-Derived Humulone and Isohumulone Constituents in Beer: The Bitter Truth of Hops Utilization During Brewing. Bruce C. Hamper, Nicholas Viriyasiri, Aaron Boland, Lorna Espinosa, Hunter J. Campbell, Kurt Driesner, Michael McKeever. January 1, 2022. LCGC Europe, January 2022, Volume 35, Issue 01. Pages: 32–37.]</ref><ref name="asbc_ibu"/>. Measuring BU's directly requires costly laboratory equipment, and so researchers and enthusiasts have made some progress in creating models that attempt to estimate bitterness units. These include the [http://www.realbeer.com/hops/research.html Tinseth] model, the Garetz model, and the [http://realbeer.com/hops/FAQ.html#units Rager] model. These models are often used in brewing software, such as [https://beersmith.com/blog/2021/09/23/hop-utilization-models-for-beer-brewing-compared/ BeerSmith™] and [https://www.brewersfriend.com/ibu-calculator/ Brewer's Friend]. [https://alchemyoverlord.wordpress.com/2015/05/12/a-modified-ibu-measurement-especially-for-late-hopping/ Other models] have been proposed as potential updates to older models to address their limitations in regard to newer hopping techniques such as whirlpool hopping and dry hopping. See also:* [http://scottjanish.com/dry-hopping-effect-bitterness-ibu-testing/ "Dry Hopping Effect on Bitterness and IBU Testing" by Scott Janish.]* [https://www.experimentalbrew.com/podcast/episode-32-ibu-lie Experimental Brewing interview with Glenn Tinseth (52 minutes in).]