Tetrahydropyridine

Tetrahydropyridine (THP) and related compounds can give an "off flavor" that tastes grainy like Cheerios® or Cap'n Crunch® cereal, or at high levels sometimes "mousy" (like rodent urine). However, not everyone can taste these compounds, and some people may enjoy a low amount of THP flavor.

THP is produced by "wild" microbes like Brettanomyces, lactic acid bacteria such as Lactobacillus, and acetic acid bacteria. THP is a significant concern in sour beer, where these microbes are commonplace, but it may also occur in other beverages such as wine, cider, or mead, if wild microbes are present. It most often forms around the time of packaging, when THP production is stimulated by the presence of oxygen +/- fermentable sugar.

Best strategies to avoid THP:

• Minimize oxygen exposure prior to packaging and during packaging. (For beer, see low oxygen brewing cold-side methods)
• For fruit beers/wines: add yeast from an acid tolerance starter when you add the fruit.
• For carbonated beverages: Naturally carbonate rather than force carbonate, and add yeast from an acid tolerance starter at the time of packaging.
• Passivate all stainless steel parts that come into contact with the wort, beer, wine, etc., and use RO water in brewing and reconstituting wine kits. Iron is required for THP production, therefore removing sources of iron will reduce or prevent its formation.
• In wine, proper usage of sulfite inhibits the wild microbes that produce THP.

If THP forms, it typically ages out over a period of months, but it may take longer.

See also

Visit the Milk the Funk wiki for more information about THP.