Spontaneous Combustion of Sushi Crunch

spontaneous combustion

Fires resulting from spontaneous combustion of self-heating products such as oil-based stains and certain cooking oils are relatively common. Typically, soiled linens, rags and sawdust are saturated with such products and serve as the first fuel for the fire. In recent years, there has been an increase in restaurant fires involving the spontaneous combustion of food products – including several reported fires involving what the sushi industry refers to as “sushi crunch.”  

The sushi crunch gives sushi rolls that crunchy, interesting texture and is prepared by deep-frying tempura batter. Once the batter is fried, it takes the form of a flake, much like a granule of Grape-Nuts cereal. However, in order for the batter to become the crunchy flake, it must be drained and allowed to cool and dry. This process often involves placing the fried batter into a colander or strainer to allow the oils to drain. Depending on the amount of crunch that is being prepared, it can take several hours for the oil to adequately drain and the flakes to cool.

We have seen numerous fires occurring at sushi restaurants determined to be the result of spontaneous combustion of the sushi crunch. In fact, in Madison, Wisconsin two  fires occurred at sushi restaurants within approximately one month of each other in 2019. According to the investigating fire officials, the fires originated within colanders containing a large volume of the crunch mixture that had been left to cool, and resulted from the self-heating of the mixture. Other similar fires have reportedly occurred in other states.

The fatty acids in the oils used to fry the crunch – typically soybean or canola oils – have a known propensity to self-heat, especially when the heat generated from oxidation of these oils has nowhere to escape. This recognized hazard is why proper handling of oil soaked linens is so important in the restaurant industry. However, the hazard associated with food products cooked with such oils appears to be less-known despite the fact that multiple fires have resulted from the preparation of products like sushi crunch.

To determine recovery potential, the subrogation professional should thoroughly investigate how the restaurant prepared the crunch, what the restaurant knew or should have known about the proper preparation of such crunch, what products were used, how the products were labeled, whether the restaurant was aware of the hazards associated with preparing the product, quality, use and function of the fire protection system, etc. Human factors and standard of care experts can certainly bring valuable insight to such claims in assessing the associated labeling and warnings, as well as what the recognized standard of care is within both the context of the manufacturing and labeling of such products and restaurants use of such products. Comparative negligence and spread theories should also be analyzed.  Now that you have seen cases of spontaneous combustion of sushi, have you seen it all?

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