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The main compounds of interest to brewers in hops are their bitter acids and oils contained in the yellow-colored lupulin glands. There are at least 250 significant aroma and flavor compounds found in hop acids and oils. Alpha acids account for roughly 2-17% of dried hops by mass, beta acids account for roughly 2-10%, and oils account for roughly 0.5-3%, though the exact percentages will vary depending on factors such as the hop varietal, growing region, harvest time, and growth conditions for the year. The rest of the weight of hops is made up of 40-50% cellulose and lignin, 15% protein, 8-12% water (after drying), 8% minerals, 3-6% polyphenols and tannins, 1-5% lipids and fatty acids, 2% monosaccharides, and 2% pectin <ref name="Algazzali_2014">[http://www.asbcnet.org/publications/journal/vol/2016/Pages/ASBCJ-2016-1130-01.aspx The Bitterness Intensity of Oxidized Hop Acids: Humulinones and Hulupones. Victor Alexander Algazzali for the degree of Master of Science in Food Science andTechnology presented on August 8, 2014.]</ref>.

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 activity 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-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 to enhance the breakdown of glycosides in and 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. However, much of the work on hop derived glycosides has been done using hop oils. Sharp et al. (2017) found that when using pure beta-glucosidase extract on beer hopped with whole leaf hops that the amount of increased monoterpenes such as linalool, terpineol, citronellol, nerol, and geraniol is small and insignificant. The fatty alcohol 1-octanol (waxy, green, citrus, orange, aldehydic, fruity <ref>[http://www.thegoodscentscompany.com/data/rw1021071.html Octanol. The Good Scents Company. Retrieved 03/31/2017.]</ref>) was the only measured flavor compound that was increased significantly <ref name="Sharp_2017">[http://onlinelibrary.wiley.com/doi/10.1002/jib.418/abstract The effect of hopping regime, cultivar and β-glucosidase activity on monoterpene alcohol concentrations in wort and beer. Daniel C. Sharp, Jan Steensels, Thomas H. Shellhammer. 2017.]</ref>. The alcohol 1-octanol can be esterified into octyl acetate, which is a classically "citrusy" aroma, so perhaps certain yeasts can create this ester during mid-fermentation hopping <ref>[https://www.facebook.com/groups/MilkTheFunk/?comment_tracking=%7B%22tn%22%3A%22R%22%7D Preiss, Richard. Milk The Funk Facebook group. 03/31/2017.]</ref>. See [[Glycosides]] for more information.

Dry hopping can contribute to bitterness in beer through oxidized alpha acids and oxidized beta acids. Alpha acids will also dissolve into the beer, which are estimated as being 10% as bitter as iso-alpha acids. Dry hopping also has a linear impact on the pH of beer regardless of the starting IBU or pH: the pH rises by 0.14 per pound of hop pellets per barrel of beer in a beer that started with a pH of 4.2 (~0.5 ounces per gallon) <ref name="Maye_2016" /><ref name="Shellhammer, Vollmer and Sharp, CBC 2015"/>. This rise in pH might be less in more acidic beers that are dry hopped since pH is a logarithmic scale.

Although the mechanisms are not fully understood, dry hopping inhibits ''Lactobacillus''. This is probably due to non-isomerized alpha acids, other acids, or the small amount of isomerization of alpha acids that happens in beer at room temperature <ref>[http://scottjanish.com/zero-hot-side-hopped-neipa-hplc-testing-sensory-bitterness/ Janish, Scott. "Zero Hot-Side Hopped NEIPA | HPLC Testing for Sensory Bitterness". ScottJanish.com. Retrieved 03/09/2017.]</ref>. See the links below.

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 Hl of finished beer <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 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). 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.