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Forms of '''Tetrahydropyridines'''(THP), specifically 6-Acetyl-2,3,4,5-tetrahydropyridine (ATHP or ACTPY), 2-ethyltetrahydropyridine (ETHP), and 2-acetyl-1-pyrroline (ACPY or APY) <ref name="wikipedia">[http://en.wikipedia.org/wiki/6-Acetyl-2,3,4,5-tetrahydropyridine 6-Acetyl-2,3,4,5-tetrahydropyridine. Wikipedia. Retrieved 3/210/2015.]</ref>, which are classified as ketones <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1034461653248715/?comment_id=1034611563233724&offset=0&total_comments=29 Humbard, Matt. Milk The funk Discussion. 3/10/2015.]</ref>, are commonly attributed to the "mousy", "urine" (in high amounts) "cheerios" or "Captain Crunch" (in low amounts), "breakfast cereal", or more generically, "cracker biscuit" flavor in sour beers. The flavor is detected towards the end of the swallow. Diacetyl is sometimes mistakenly indicated as a potential cause of this flavor in sour beers. However, Tetrahydropyridines are the accepted cause. The flavor tends to age out of sour beers after 2-3 months (it is unknown whether cold or room temperature storage speeds this up), although the exact mechanism for this is not fully understood <ref>[http://www.homebrewtalk.com/f127/cheerios-character-after-bottling-504468/#post6516169 Tonsmeire, Michael. Homebrewtalk.com post 1. 11/21/2014. Retrieved 3/10/2015.]</ref>. Many brewers have noticed that pitching rehydrated wine yeast at bottling reduces the amount/duration of this flavor <ref>[http://www.homebrewtalk.com/f127/cheerios-character-after-bottling-504468/#post6522207 Tonsmeire, Michael. Homebrewtalk.com post 2. 11/21/2014. Retrieved 3/10/2015.]</ref>.

[[Brettanomyces]], [[Lactobacillus]], and [[Pediococcus]] can produce forms of ''Tetrahydropyridine''. In Brettanomyces, ATHP and ETHP are produced by metabolizing the amino acids L-Lysine and D-Lysine, along with ethanol and a glucose or fructose molecule. Oxygen has a stimulatory effect in it's production, but this is probably because ''Brett'' has a higher biomass formation under aerobic conditions <ref>[http://www.brettanomycesproject.com/dissertation/introduction/ Yakobson, Chad. The Brettanomyces Project; Introduction. Retrieved 3/10/2015.]</ref><ref>[http://pubs.acs.org/doi/abs/10.1021/jf071243e The Role of Lysine Amino Nitrogen in the Biosynthesis of Mousy Off-Flavor Compounds by Dekkera anomala. Paul R. Grbin, Markus Herderich, Andrew Markides, Terry H. Lee, and Paul A. Henschke. J. Agric. Food Chem., 2007.]</ref><ref name="Oelofse">[http://scholar.sun.ac.za/handle/10019.1/8437 Significance of Brettanomyces and Dekkera during Winemaking: A Synoptic Review. A. Oelofse, I.S. Pretorius, and M. du Toit. 2008.]</ref>. The level of THP production varies widely between species and strains of ''Brett'', with some strains not producing it at all and some producing very high amounts above taste threshold. Additionally, THP production appears to require glucose or fructose, which explains why THP may be seen more often in stuck wine fermentations rather than wine that has finished fermenting. ATHP production by ''Brett'' was observed in wine with glucose or fructose added, along with synthetic growth media, suggesting that the type of growth substrate does not effect production <ref>[http://www.ncbi.nlm.nih.gov/pubmed/18194246 Growth and volatile compound production by Brettanomyces/Dekkera bruxellensis in red wine. Romano A, Perello MC, de Revel G, Lonvaud-Funel A. J Appl Microbiol. 2008 Jun.]</ref>.

* [https://www.facebook.com/groups/MilkTheFunk/permalink/1034461653248715/ Milk The Funk Threadon March 10, 2015.]* [https://www.facebook.com/groups/MilkTheFunk/permalink/1134644959897050/ milk The Funk Thread on Aug 25, 2015.]