Business Insider Edition

A string of sushi restaurant fires in the US were caused by spontaneously combusting tempura flakes

Bill Bostock , Business Insider US
 Jul 20, 2019, 09:58 AM
Security camera footage of a fire breaking out at Sumo Steakhouse.
Madison Fire Department
  • Seven fires at sushi restaurants in the US were caused by spontaneously combusting tempura flakes, investigators have found.
  • A reaction between oxygen and oils used in tempura batter caused fires in five Wisconsin restaurants, as well as venues in Minnesota, Virginia, and even Canada.
  • Kara Nelson, a fire investigator with the Madison Fire Department, told ABC News: "The oil will combine with the oxygen in the air and in that chemical process, it releases heat."
  • Staff at Madison's Sumo Steakhouse and Sushi Bar told fire crews: "After being deep-fried, the flour is left to drain and cool for a day. In this case, the deep-fried flour ignited on its own overnight, resulting in a fire."
  • The tempura flakes are also known as "crunch," or "tenkasu" in Japanese.
  • For more stories, go to Business Insider SA.

Fires at multiple sushi restaurants in North America were caused by spontaneously combusting tempura flakes, investigators have found.

The flakes - known colloquially as "crunch," but "tenkasu" in Japan - are made with an oil which self-heats and "can create an environment for a fire to occur," the City of Madison, Wisconsin said in a statement on July 11.

Investigators said fires at Madison restaurants Sumo Steakhouse and Sushi Bar on April 5, and at Takara Japanese Restaurant on May 10, were categorically caused by the flake mixture.

Five other fires caused by tempura have broken out at restaurants in recent months, with some in Wisconsin, as well as in Minnesota, Virginia, and even Canada, Kara Nelson, a fire investigator with the Madison Fire Department, told ABC News.

The combined damage from the two fires in Madison was $575,000 (R8 million), the city wrote.

This security tape from inside Sumo Steakhouse and Sushi Bar shows the moment the tempura batter combusted in the dead of night.

In their report on the Sumo Steakhouse and Sushi Bar fire, Madison Fire Department wrote: "Restaurant staff report that flour is routinely deep-fried for use in some of their sushi products."

"After being deep-fried, the flour is left to drain and cool for a day."

"In this case, the deep-fried flour ignited on its own overnight, resulting in a fire."

Nelson told ABC News: "The oil will combine with the oxygen in the air and in that chemical process, it releases heat."

She said the two oils most likely to react and cause fires are vegetable oil and canola oil.

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