Tests show an unknown poison in the popular mushroom. A research group studying wild sugihiratake mushrooms thought to cause a fatal acute-brain disorder said Monday the fungi are toxic enough to kill mice. Although they have yet to identify the toxin, professor Hirokazu Kawagishi of Shizuoka University said, “The toxin is a multimolecular substance that is water soluble and resistant to high heat.”
The findings were reported at a meeting with officials of the Ministry of Health, Labor and Welfare. In the experiment, mice were given large doses-about 10 times what they would normally eat-of wild sugihiratake mushrooms collected from mountains in the Koshinetsu region.
In the first stage, the mushrooms were ground up and dissolved in water. Five of six mice died after eating the mixture. Next, the mixture was boiled for 30 minutes at 100 degrees. All three mice that ate the stewed mushrooms died. In the third stage, the mixture was filtered and separated into a high polymer mix and one with smaller particles. Three mice that ate the mix after the liquid was drained died. Three fed the filtered mix, however, survived.
The experiment, however, does not prove a a link between the sugihiratake and acute encephalopathy in human brains. But researchers said they are a step closer to eliminating bacteria or viruses as its cause. The pearly white, meaty sugihiratake, long considered edible, are regularly eaten in the Tohoku and Shinetsu regions. It has so far been blamed for at least 17 deaths in the Tohoku and Hokuriku regions this season.
Fumitake Gejo, professor at Niigata University, one of the researchers, had noted the correlation between eating the mushrooms and brain fever. “When we conducted a follow-up investigation on patients, many replied they had consumed (the mushroom) in soups and in stir-fries,” he said. “The findings match our suspicions that the toxin must be water soluble and heat resistant.”
If so, no amount of cooking will make them safe for consumption. Local mushroom pickers said they noticed they came out a few weeks earlier this year.
Specialists have been pointing out that trace components in mushrooms may surge due to a shift in their environment. There have been sporadic cases of acute-brain disorder springing up in the past after the consumption of the popular mushroom.
“It is possible that the toxic level of the sugihiratake suddenly rose this year, prompted by outside stress factors such as a rise in temperature,” Kawagishi said. “We would like to pinpoint (the toxin) before next mushroom season starts.”