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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" />.
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>.
===Glycosides===
Hops contain glycosides, which are flavor compounds that are bound to a sugar molecule. In their bound form, glycosides are flavorless. Studies on hop compounds elude to the possibility of compounds being produced by glycosidic activity of ''S. cerevisiae'', however direct evidence of glucosidic acitivity in ''S. cerevisiae'' is lacking. Daenen (2008) reviewed the glycosidic activity of many strains of ''S. cerevisiae'', and found that only a few strains expressed any real glucosidic activity, and none that exhibited exo-beta-gluconase glucosidase which would be required to break glycosidic bonds in the beer/wort. Daenen did find that enzymatic activity from some strains of ''Brettanomyces'' can efficiently release these bound compounds and release their flavor and aromatic potential <ref name="Praet_2012" />. Beta-glucosidase enzyme can also be added to beer enhance the breakdown of glycosides in intensify hop derived flavors and aromas. For example, one study showed an increase in citrus, orange, grapefruit, and tropical pineapple in a Cascade dry hopped beer that had beta-glucosidase enzymes added to it <ref>"Optimizing hop aroma in beer dry hopped with Cascade utilizing glycosidic enzymes (presentation slides)." Kaylyn Kirkpatrick from New Belgium Brewing Co. Young Scientist Symposium, Chico, CA 2016.]</ref>. There is also some evidence to support that there is higher glucosidase activity in seeded hops, which are generally not used in the brewing industry <ref>"Seeded and "Unseeded Hops - a Quality Comparison (presentation slides)." Martin Zarnkow. EBC 2015.</ref>. See the [[Glycosides]] page for details.
==Aged Hops==