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Tetrahydropyridine

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[[File:THP microbes.jpg|thumb|200px|right|Grbin et al. (1996) Survey of microorganisms that produce THP <ref name="Grbin_1996" />.]]
THP in wine ("mouse taint") was first described in wine by Müller-Thurgau and Osterwalder in 1913, although mention of an off-flavor in wine that 'is closely resembling the smell of a residence of mice' dates to 1894 in "A Treatise on wines" by J.L.W. Thudichum. Müller-Thurgau and Osterwalder attributed it to be produced by bacteria. They also established that the ability to detect THP varies from person to person <ref name="Grbin_1996" />. A 1908 text by the Germans Nessler and Windish linked THP off-flavors to wine that aged longer on lees, perhaps due to yeast autolysis <ref name="Snowdon" />. In the 1940's, some scientists proposed that THP was purely a chemical reaction, however, their evidence was inconclusive. In 1977, Tucknott et al. was able to identify that THP production was attributed to both ''Brettanomyces'' yeast and lactic acid bacteria, and that ethanol and L-lysine played a role in its production, and this was confirmed by Heresztyn et al. in 1986 <ref name="Grbin_1996">[httphttps://iwrdbdigital.sonomalibrary.org/cgi-bindigital/collection/p15763coll33/id/koha34976/opac-detail.pl?biblionumber=27016&shelfbrowse_itemnumber=19456 rec/1 Developments in the sensory, chemical and microbiological basis of mousy taint in wine. Grbin, P.R, Costello, P.J, Herderich, M. 1996.]</ref>.
The chemical analysis of THP has proven to be a difficult endeavor in science. In 1995, Herderich et al. out of Australia developed a method for chemically analyzing THP for the first time. It was at this time that all three forms of THP (ETHP, ATHP, and APY) could be identified consistently in contaminated wine. It was also during this time that the three forms of THP contributed to the flavor of various foods, such as tortilla chips and taco shells. For example, APY was found in the fermentation of cocoa in 1995. In 1995, Grbin et al. described ''Brettanomyces'' yeast as the yeast that produces THP, while wine strains of ''S. cerevisiae'' did not <ref name="Grbin_1996" />.
In 2000, the Australians Grbin and Henschke showed that some strains but not all of ''B. bruxellensis'', ''B. anomalus'', ''B. nardenensis'', and ''B custersianus'' produce THP, and that THP production was influenced by the carbon source, but not dependent on it (THP was still produced in dry wines with little available nutrients, and fermentation rate was not always related to THP levels) <ref name="Grbin_2000">[http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2000.tb00186.x/abstract PAUL R. GRBIN and PAUL A. HENSCHKE. 2000.]</ref>.
In 2007, the Australian team of Grbin et al. confirmed that higher lysine levels increased the amount of ATHP produced (but not ETHP), although with diminishing increases of THP as the lysine level was increased. They also discovered that L-ornithine also functioned as a precursor for THP production in ''Brettanomyces''. The group proposed a biochemical pathway for the different forms of THP in ''Brettanomyces'' <ref name="Grbin_2007" />.
==Detection Methods==

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