Changes

ATHP/ACTPY (which has two forms: 2-acetyl-3,4,5,6-tetrahydropyridine and 2-acetyl-1,4,5,6-tetrahydropyridine) has a much lower flavor threshold than ETHP (see [[Tetrahydropyridine#Thresholds_and_Quantities_Found_in_Mousy_Wine|Thresholds]]), and has been historically cited as the cause of mousy off-flavors detected in wine. In wine, its aroma cannot be detected due to the low pH of wine (it can be detected if the pH is raised), only the flavor. It is easier to detect in higher pH wines. ATHP is the form of THP that is the major contributor to the aroma of freshly baked bread, corn tortilla chips, and crackers. How different foods/wines/beers interact with ATHP on the palate may explain the different flavors that are detected by people, as well differing concentrations and peoples' ability to detect ATHP <ref name="Snowdon"></ref>. In food, ATHP has a slightly different form (6-Acetyl-1,2,3,4-tetrahydropyridin). Its formation in food is due to cooking and thought to be associated with Maillard reactions <ref name="Adams_2005" />.

APY/ACPY (2-acetyl pyrroline) is a more volatile but more potent form of THP. It has a significantly stronger odor and lower odor threshold in wine than ATHP. It can also be found in damp pearl millet, white bread, taco shells, tortilla chips, boiled potatoes, roasted sesame seeds, pan-fired green teas, cured tobacco leaves, peanut and pumpkin seed oils, honey, several soy-based products, and more aromatic rice such as Indian Basmati. APY is primarily produced by heterofermentative LAB. In foods, APY formation is due to cooking and thought to be associated with Maillard reactions <ref name="Snowdon"></ref><ref name="Grbin_1996" /><ref name="Adams_2005">[http://pubs.acs.org/doi/abs/10.1021/cr040097y Chemistry of 2-Acetyl-1-pyrroline, 6-Acetyl-1,2,3,4-tetrahydropyridine, 2-Acetyl-2-thiazoline, and 5-Acetyl-2,3-dihydro-4H-thiazine:  Extraordinary Maillard Flavor Compounds. An Adams andNorbert De Kimpe. 2005.]</ref>.

There have been anecdotal reports of other forms of mousy off-flavors. During growth of lactic acid bacteria (LAB), mousy off-flavor detection fluctuated with high levels detected early on, and lower levels detected towards the end of growth. This indicates that there may be a transient, strain-dependent form of THP that can occur during malolactic fermentation. There have also been a sensory detection of mousy off-flavors at different levels than the documented levels of ATHP, ETHP, and APY, which were not associated with LAB or ''Brettanomyces'' <ref name="Snowdon"></ref>. ===Sulfur-Containing Forms===Sulfur-containing versions of THP exist in many vegetables and processed meats and are important aspects of their aromas. These include 2-Acetyl-2-thiazoline (the sulfur containing version of APY) and 5-Acetyl-2,3-dihydro-4 H -1,4-thiazine (the sulfur containing version of 6ATHP). These are formed in meat during processing, for example in beef and chicken broths, roasted beef, etc. They are characterized as being similar to APY and ATHP, and have a roasty, popcorn-like odor and low thresholds. These are chemically formed during cooking and food processing and are not associated with biological metabolism or fermentation <ref name="Adams_2005" />.