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Hops
,updated Hop Composition, first pass
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The main compounds of interest to brewers in hops are their bitter acids and oils. Alpha acids account for roughly 2-1217% 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<ref name="Algazzali_2014">[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>.
The primary '''alpha acids''' (humulones) in hops are humulone, cohumulone, and adhumulone. The ratio of these individual acids to each other can vary much like total iso-α-acid percent, though generally the primary acids are -------. While alpha acids are insoluble in wort, the isomerized acids which are formed during boiling are soluble. Isomerization leads to roughly a 70%/30% split between cis and trans iso-α-acids respectively, with cis iso-α-acids being more stable over time and more bitter<ref name="Schönberger and Kostelecky, 2012"> [http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.2011.tb00471.x/abstract Schönberger and Kostelecky, 2012]</ref>. Alpha acids themselves do not taste bitter, but isomerized alpha acids (iso-α-acids) contribute to the bitterness of beer and have antimicrobial properties. Isocohumulone is often cited as being more harshly bitter than the other iso-α-acids, but studies of taste perception of individual iso-α-acids have not agreed with this. However Isocohumolone is slightly more soluble than the other acids and therefore a hop with a higher cohumulone composition may result in a beer with higher iso-α-acid for hops of equal iso-α-acid percent and use in brewing but different iso-α-acid breakdown<ref name="Schönberger and Kostelecky, 2012"/>. Alpha acids are susceptible to oxidation and the alpha acid content of a hop will decrease with storage.