Gyromitrin - Occurrence and Removal

Occurrence and Removal

Several Gyromitra species are traditionally considered very good edibles and several steps are available to remove gyromitrin from these mushrooms and allow their consumption. For North America, the toxin has been reliably reported from the species G. esculenta, G. gigas, and G. fastigiata. Species in which gyromitrin's presence is suspected, but not proven, include G. californica, G. caroliniana, G. korfi, and G. sphaerospora, in addition to Disciotis venosa and Sarcosphaera coronaria. The possible presence of the toxin renders these species "suspected, dangerous, or not recommended" for consumption.

Gyromitrin content can differ greatly in different populations of the same species. For example, G. esculenta collected from Europe is "almost uniformly toxic", compared to rarer reports of toxicity from specimens collected from the US west of the Rocky Mountains. A 1985 study reported that the stems of G. esculenta contained twice as much gyromitrin than the cap, and that mushrooms collected at higher altitudes contained less of the toxin than those collected at lower altitudes.

The gyromitrin content in false morels has been reported to be in the range of 40–732 milligrams of gyromitrin per kilogram of mushrooms (wet weight). Gyromitrin is volatile and water soluble, and can be mostly removed from the mushrooms by cutting them to small pieces and repeatedly boiling them in copious amounts of water under good ventilation. Prolonged periods of air drying also reduces levels of the toxin. In the US, there are typically between 30 and 100 cases of gyromitrin poisoning requiring medical attention. The mortality rate for cases worldwide is about 10%.