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Hops
,→Thiols
Compounds other than iso-alpha acids present several challenges to traditional methods of measuring BU's. Many hop compounds other than iso-alpha acids that have varying levels of perceived bitterness 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). In addition to these challenges, iso-alpha acids and other hop compounds that contribute to bitterness degrade over time, thus the perceived bitterness of beer tends to become weaker as beer ages <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 models are generally based off of boil time, alpha acid percent of the hops used, weight of the hops used, post-boil volume of wort, and gravity of the wort. 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/20152021/0511/1210/aibus-modifiedand-ibuthe-measurementsmph-especially-for-late-hoppingmodel/ 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. Other limitations include differences in brewhouse size and efficiencies. For example, the Tinseth model was developed on a homebrew system using whole leaf hops (see the Experimental Brewing podcast interview with Glenn Tinseth link below).
See also:
==Hop Derived Compounds In Beer and Biotransformations==
[[File:Svedlund 2022.jpg|thumb|400px|An overview of the biotransformation reactions occurring in yeast. Abbreviations: 3MH 3-mercaptohexanol, 3MHA 3-mercaptohexyl acetate, Cys cysteine, GSH glutathione, TPA terpene alcohol. Credit: Henrik Svedlund.
Source: [https://link.springer.com/article/10.1007/s00253-022-12068-w Svedlund, N., Evering, S., Gibson, B. et al. Fruits of their labour: biotransformation reactions of yeasts during brewery fermentation. Appl Microbiol Biotechnol 106, 4929–4944 (2022). https://doi.org/10.1007/s00253-022-12068-w]]]
The flavor and aroma compounds found in leaf/pellet hops are different than the hop-derived flavor and aroma compounds found in finished beer (other than in the case of dry hopping). The brewing process (particularly boiling), and fermentation greatly affect the composition of flavor and aroma compounds that are found in beer. For example, boiling wort and hops isomerizes non-bitter alpha acids into bitter iso-alpha acids. During the boiling of the wort, many compounds found in hops are evaporated, such as many of the various sulfur compounds found in hops. The terpene hydrocarbons which make up most of the hop oil content in hops (myrecene, humulene, and caryophyllene) are completely removed by fermentation. It is believed that these terpene hydrocarbons stick to the yeast cells and fall out of solution during fermentation <ref name="Praet_2012">[http://www.sciencedirect.com/science/article/pii/S1373716311001636 Biotransformations of hop-derived aroma compounds by Saccharomyces cerevisiae upon fermentation. Tatiana Praet, Filip Van Opstaele, Barbara Jaskula-Goiris, Guido Aerts, Luc De Cooman. 2012.]</ref>.
===Thiols===
Sulfur-based compounds bound to a hydrogen atom known as ''thiols'' have also been shown to be produced by yeast fermentation from the hop derived precursors (suspected cysteine or glutathione via yeast β-lyase activity. This activity takes place within the yeast cells which uptake the precursors. The cysteine and glutathione precursors are also found in malt, hops, grapes and rice, with levels varying greatly depending on varieties of the plants. In addition to some strains of ''Saccharomyces cerevisiae'' that express the genes to produce thiols, strains of the yeasts ''Metschnikowia pulcherrima'', ''Torulaspora delbrueckii'', ''Lachancea thermotolerans'', ''Candida zemplinina'', and the bacteria ''Lactobacillus plantarum'' have also been found to be produce thiols <ref name="Svedlund_2022">[https://link.springer.com/article/10.1007/s00253-022-12068-w Svedlund, N., Evering, S., Gibson, B. et al. Fruits of their labour: biotransformation reactions of yeasts during brewery fermentation. Appl Microbiol Biotechnol 106, 4929–4944 (2022). https://doi.org/10.1007/s00253-022-glutathione)120.]</ref>. So far, science has found that these include the volatile thiols : * 3-mercaptohexan-1-ol (3MH; also referred to as 3-sulfanylhexan-1-ol, 3SH; ''tropical fruit'')* 4-mercapto-4-methylpentan-2-one (4MMP; also referred to as 4-methyl-4-sulfanylpentan-2-one, 4MSP; ''blackcurrant'') * 3-sulfanyl-4-methylpentan-1-ol (3S4MP; ''grapefruit'') and * 3-mercaptopentanol (3MP; also referred to as 3-sulfanylpentan-1-ol, 3SP)Acetylation (acetate) variations:* 3-sulfanyl-4-methylpentyl acetate (3S4MPA; ''passionfruit'', ''grapefruit'')* 3-mercaptohexyl acetate (3MHA; ''passionfruit'')Typically, in beer and wine, the amount of free thiols that are formed from these precursors is less than 1%, perhaps due to poor activity of β-lyase activity in acidic media and inhibition by polyphenols. These However, these thiols were found in beers dry hopped separately with Amarillo, Hallertau Blanc, and Mosaic hop varieties. The amounts of these two thiols were higher than expected based on the content of these thiols in the hops alone <ref name="Cibaka_2016" />. Dry hopping temperature plays a role, with with 18-24°C being optimum for 3Mh and 3MP, and 28°C being optimum for 3S4MP. Mash hopping can potentially increase thiols, while using copper in the brewing or winemaking process can reduce them <ref name="Svedlund_2022" />. [[Omega Yeast Labs]] has bioengineered a yeast strain called [https://omegayeast.com/news/cosmic-punch-new-thiol-boosting-strain Cosmic Punch™ (British V OYL-011)] to produce significant amounts of thiols from hops and malted grains. [https://berkeleyyeast.com/available-yeast-strains/ Berkeley Yeast] also offers bioengineered yeast strains that produce thiols. See also this [https://www.facebook.com/groups/MilkTheFunk/permalink/1373899592638251/ MTF thread speculating on how ''Brettanomyces'' might produce thiols].
See also:
===Aged Hop Suppliers===
* [https://www.yakimachief.com/commercial/hop-wire/introducing-the-ych-aged-hops-program YCH offers 1-2 oz bags for homebrewers and 44 lb bags of aged hops; contact for more information.]
* <s>[http://www.hopsdirect.com/choice-debittered-aged-hops-leaf/ Hops Direct "Choice Debittered/Aged Hops" (Leaf - Cascade).]</s>
* <s>[https://hopsdirect.com/products/choice-debittered-pellets Hops Direct "Choice Debittered/Aged Hops" (Pellet - Columbus).]</s>* [https://www.freshops.com/shop/hop/aroma-hopproduct/lambic-hops/ Freshhops "Lambic Hops" (Leaf - Willamette)".]* [httphttps://www.yakimavalleyhops.com/Lambic2oz_pproducts/hopslambichops3.htm lambic-hop-pellets Yakima Valley Hops "Lambic / Aged Hops" (Pellet).]
* [http://www.farmhousebrewingsupply.com/lambic-hop-blend-4-oz-2015/ Farmhouse Brewing Supply "Lambic Hop Blend" (Pellet - Blend of varieties that are aged for ~5 years and then pelletized <ref>Private correspondence with Dustin Carver by Farmhouse Brewing Supply. 03/22/2016.</ref>).]
* [httphttps://www.themaltmiller.co.uk/index.php?_a=viewProd&productId=592 The Malt Miller (UK).]* [http:/product/www.brewstore.co.uk/specially-aged-fuggles-hops-100-grams Brew Store UK / The Malt Miller (Leaf - Fuggles).]* [http://www.brewstore.co.uk/specially-aged-hallertau-hops-100-grams Brew Store UK (Leaf - Hallertau).]
* [https://northwesthopfarms.com/products/lambic-aged-hops Northwest Hop Farms (BC, Canada).]
* [https://bsgcraftbrewing.com/lambic-hop-blend BSG sometimes offers aged pellet hops for commercial brewers; contact for details.] See [https://www.facebook.com/groups/MilkTheFunk/permalink/4326634927364688 this MTF thread] on experiences with these hops.
[[File:Cantillon aging hops.jpg|thumbnail|right|Brasserie-Brouwerij Cantillon aging their hops; image provided by Dave Janssen.]]
Modern lambic traditionally uses aged hops at a moderate rate to help limit and select for microbes and regulate acid production. Modern Lambic brewers cite rates in the range of roughly 450 grams of hops per hectoliter of finished beer (0.6 ounces per gallon) <ref name="Jean Van Roy on Basic Brewing Radio"> [http://hwcdn.libsyn.com/p/e/a/2/ea26e00136fe1638/bbr05-30-13cantillon.mp3?c_id=5723890&expiration=1443888327&hwt=8dd886677defabdd73669cdc262ef446 Jean van Roy on Basic Brewing Radio] </ref> (~43 min in) (see also the notes pertaining hopping rates on the [[Cantillon]] page), with some brewers possibly going above this range. The age of hops used depends on the producer and their preferences/stock. Cantillon uses hops that are roughly 3 years old<ref>D. Janssen personal communication with Jean Van Roy, 9-Nov-2013</ref>, while 3 Fonteinen reports using hops that are over 10 years old<ref name="Drie Fonteinen on Belgian Smaak"> [http://www.belgiansmaak.com/armand-debelder-michael-blancquaert-drie-fonteinen/ Drie Fonteinen on Belgian Smaak] </ref> (~48 minutes in). Jester King reported using 0.66 - 0.75 pounds of whole leaf aged hops per BBL (0.34-0.39 ounces per gallon) in their spontaneously fermented ales <ref>Averie Swanson. "Sour Power! A Pro Brewer Spontaneous Fermentation Roundtable". HomebrewCon seminar. 2018.</ref> (~31:00 mins in). Lambic brewers either add their hops while still collecting wort, sometime before the wort comes to a boil<ref>[https://www.facebook.com/groups/Lambic.Info/permalink/1831338433787524/ Video of Cantillon wort reaching a boil from Bill on Lambic.info]</ref> (also known as "first wort hopping"), or shortly after boil is reached<ref name="Drie Fonteinen on Belgian Smaak"/> (~48 min in). The hops are then boiled with the wort for essentially the full length of the boil <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1593059604055581/?comment_id=1593928187302056&reply_comment_id=1593938693967672&comment_tracking=%7B%22tn%22%3A%22R9%22%7D Conversation with Dave Janssen on MTF. 02/24/2017.]</ref><ref>[http://www.lambic.info/Brewing_Lambic#Hopping "Brewing Lambic", section "Hopping". Lambic.info website. Retrieved 02/24/2017.]</ref>. The resulting lambic beers are often surprisingly bitter, especially when young. Historically, there is [http://www.horscategoriebrewing.com/2016/04/hops-in-spontaneous-fermentation.html some evidence] that lambic brewers used a combination of aged hops and fresh dried hops. Not all aged hops are the same; different varieties/sources result in different levels of residual alpha/beta acids (probably not zero), oxidized acids, IBU's, perceived bitterness, and inhibition of lactic acid bacteria. Varieties with high acids and hop oils probably have more residual acids and oils, and aging times/conditions may not be ideal enough to completely age high alpha/beta/oil hop varieties. Therefore, it is impossible to give a blanket statement on how much aged hops to use given a specific lot of aged hops. Andrew Holzhauer from Funk Factory Geuzeria suggests tasting aged hops for bitterness and adjusting the amount of hops depending on how bitter they taste <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2723907944304069/?comment_id=2723956477632549&reply_comment_id=2724104977617699&comment_tracking=%7B%22tn%22%3A%22R%22%7D Andrew Holzhauer. Milk The Funk Facebook group on how much aged hops to use. 06/13/2019.]</ref>, while James Howat from Black Project suggests making a small batch and having the wort/beer analyzed for IBU's and adjusting accordingly.
For example, homebrewer Caleb Buck performed an experiment comparing two different hopping rates for spontaneously fermented beer at home using whole leaf aged hops that were independently tested to have 0.5% alpha acids and 0.2% beta acids and were obtained from Hops Direct in Junuary 2016 <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2302073339820867/?comment_id=2302314029796798&reply_comment_id=2303737466321121 Caleb Buck. Milk the Funk Facebook group thread on Caleb's aged hop experiment. 10/01/2018.]</ref>. The two rates tested were 0.3 ounces of aged hops per gallon and 0.6 ounces per gallon, both added at the beginning of the boil <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/3970005893027595/?comment_id=3970763046285213 Caleb Buck. Milk The Funk Facebook group. Addendum to when hops were added to the boil for his associated hop experiment. 10/14/2020.] </ref>. Samples of the two worts were sent to Sweetwater Science Labs to perform IBU analysis using the ASBC standard IBU test. Interestingly, the results were 72 IBU and 127 IBU respectively. The unexpectedly high IBU might be due to the variety of aged hop, as well as oxidized hop acids showing up in the standard IBU test (see Peacock's data [[Hops#Acids_2|here that showed that aged and fresh dried hops produce a similar IBU]]). After about 7 months, one of the 0.3oz/gal batches got down to a pH of 3.6, a second batch at 0.3oz/gal got to a pH of 4, while the 0.6oz/gal batches remained within a pH of 4.2 - 4.3. From this experiment, Caleb will attempt using only 0.15 oz/gal of aged hops which should be closer to 30 IBU and so that more acidity can be achieved. James Howat from Black Project Spontaneous Ales suggests making sample wort with the hops that will be used for a larger batch and sending that sample off for IBU testing in order to more easily achieve the desired IBU's. More detail can be found on [http://www.archaicpursuit.com/2018/08/2017-coolship-experiment-hopping-rate.html?m=1 Caleb Buck's collected data on cooling rates, acidity from hopping rates, and other collected data over a multi-year, multi-batch experiment] and [http://hwcdn.libsyn.com/p/b/d/2/bd2703ec2214a5c7/bbr09-27-18souribus.mp3 Caleb's interview on this experiment on BasicBrewing Radio].