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'''[https://en.wikipedia.org/wiki/Thioester Thioesters]''' are derived from an acid and a thiol. These include S-methyl hexanethioate and S-methyl heptanethioate and derivatives of these, which impart cabbagy, sulfury, and soapy flavors, and their low flavor threshold can have an impact on finished beer. '''Sulfides''' and '''polysulfides''' found in hops includes [[Dimethyl _Sulfide|dimethyl sulfide (DMS)]], dimethyl disulfide (DMSD), dimethyl trisulfide (DMST; cooked vegetable, onion). DMTS has been found in wide ranges in hops, from a few ppm to 1450 ppm, and has a very low flavor threshold (1 ppb). These compounds are volatilized during brewing and fermentation, and are generally only found in beers that are dry hopped <ref name="Peppard_1981" />.
Other thiol (organic sulfur) based compounds contribute to a pleasant aroma and flavor in beer, such as 4-mercapto-4-methyl-pentan-2-one (4MMP), which is found in high quantities in North American varieties such as Simcoe (highest amount), Summit, Apollo, Topaz, and Cascade hops, as well as varieties from Australia and New Zealand. The character of black currant, muscat-like aroma in beer brewed with these hops has been attributed to 4MMP. It is thought that 4MMP is only found in North American, Australian, and New Zealand hops and not European hops because European hops are often treated with copper ions, which has been shown to decrease the amount of 4MMP in hops. Interestingly, beers brewed with these hops showed a 33% increase in 4MMP after fermentation; it is thought that the precursor cysteine conjugate is responsible for the increase in 4MMP during fermentation <ref name="Kishimoto_2008" />. The volatile thiols 3-sulfanyl-4-methylpentan-1-ol (3S4MP; grapefruit <ref name="Cibaka_2016">[https://www.uclouvain.be/cps/ucl/doc/inbr/documents/JAFC_2016_64_8572_8582.pdf 3‑Sulfanyl-4-methylpentan-1-ol in Dry-Hopped Beers: First Evidence of Glutathione S‑Conjugates in Hop (Humulus lupulus L.). Marie-Lucie Kankolongo Cibaka, Laura Decourriere, Celso-JoséLorenzo-Alonso, Etienne Bodart, Raphael Robiette, and Sonia Collin. 2016.]</ref>), and 3-sulfanyl-4-methylpentyl acetate (3S4MPA; passionfruit, grapefruit <ref name="Cibaka_2016" />) have been identified in Nelson Sauvin hops as the compounds that give these hops their "wine-like, Sauvignon Blanc" character. Similar thiols have been described as the major contributors to the aroma of Sauvignon Blanc wines themselves: 3-sulfanylhexan-1-ol (3SH) and 4-methyl-4-sulfanyl-pentan-2-one (4MSP) <ref name="Kiyoshi_2009">[http://pubs.acs.org/doi/pdf/10.1021/jf8034622 Identification and Characteristics of New Volatile Thiols Derived from the Hop (Humulus luplus L.) Cultivar Nelson Sauvin. Kiyoshi Takoi, Marie Degueil, Svitlana Shinkaruk, Cécile Thibon, Katsuaki Maeda, Kazutoshi Ito, Bernard Bennetau, Denis Dubourdieu and Takatoshi Tominaga. 2009.]</ref>.
==Antimicrobial Properties==
Terpenes and terpenoids (monoterpene alcohols) can also be transformed by fermentation. Studies have found that geraniol and nerol can transform into linalool by a strain of ''S. cerevisiae'', as well as nerol and linalool to alpha-terpineol, which can then by further transformed to terpin. Geraniol can also be converted into citronellol. Linalool, nerol, and alpha-terpineol gradually decrease during fermentation and aging (perhaps being transformed into ethers), while nerol and citronellol gradually increase. Geraniol also decreases during fermentation, but not as drastically as linalool. Citronellol might be created from geraniol, but also glycosidic activity (although another study found that glycosidic activity in ''S. cerevisiae'' is not very strong). Likewise, dry hopping preserves linalool and alpha-terpineol, and limits citronellol <ref name="Praet_2012" />.
Sulfur based compounds known as ''thiols'' have also been shown to be produced by yeast fermentation from hop derived precursors (suspected to be S-glutathione). So far, science has found that these include the volatile thiols 3-sulfanyl-4-methylpentan-1-ol (3S4MP; grapefruit) and 3-sulfanyl-4-methylpentyl acetate (3S4MPA; passionfruit, grapefruit). 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" />.
In general, different yeast strains have a large impact on how hops are perceived in the final beer, including both perceived bitterness and flavors. For example, POF+ (phenolic positive) strains of ''[[Saccharomyces|Saccharomyces cerevisiae]]'' tends to mask the hop derived aromas in dry hopped beers <ref name="Sharp_Presentation" />. A beer hopped with the Tradition hop variety produced fruit flavors when fermented with Abbaye ale yeast, and woody/spicy flavors when fermented with US-05. When the beer was brewed with Citra hops, with US-05 the beer had sweet fruits/citrus flavors and more bitterness, but when fermented with the Abbaye ale strain the beer had a more one dimensional sweet fruit/floral flavor and less bitterness <ref>"Influence of yeast strain on hop aroma development in dry hopped beers." Christina Schönberger, Elisabeth Wiesen, Benedikt Matsche, Barth Innovations Yves Gosselin, Stephan Meulemans, Fermentis. Presentation slides at 35th Congress EBC.</ref>.