Restaurant fires linked to tempura flakes

Deep-fried tempura flakes, a key ingredient sprinkled on sushi rolls for crunch and known as agedama or tenkasu, Japanese for “heavenly waste,” have been linked to a series of restaurant fires in Canada and multiple states.

Five of them occurred in Wisconsin, said Kara Nelson, a fire investigator in the capital, Madison, where two restaurants sustained more than $500,000 combined in fire damage. She has learned of similar fires in Minnesota, Virginia and Canada.

Nelson said she worked with the Bureau of Alcohol, Tobacco, Firearms and Explosives to pinpoint the unusual cause of the blazes, which she said were an example of spontaneous combustion.

The crunchy flakes are made by ladling drops of batter into a deep fryer — canola and soybean oils are commonly used. Nelson said both vegetable oils have a propensity to self-heat and keeping the mix densely piled in a pot or bowl does not allow the heat to dissipate.

It is no different than the chemical reaction that causes more wellknown substances to spontaneously combust, she said.

“It can happen in hay bales,” Nelson said. “It can happen in mulch piles.”

And in tempura flakes.

The first fire in Madison happened April 5 at Sumo Japanese Steakhouse & Sushi Bar, where security camera footage showed smoke billowing in the kitchen six hours after the crunch mix had been left in a metal colander to cool. Four hours later, flames engulfed the kitchen. The second fire broke out at Takara Japanese Restaurant May 9.

“Don’t leave it unattended,” she said of tempura flakes. “It can take anywhere from three to 10 hours for the heat process to start before it goes into ignition. We want to get the word out there.”