The short answer to whether you should reheat sushi is no. Applying heat compromises both its safety and its quality, creating a risk of foodborne illness while destroying the delicate balance of flavors and textures. The primary concerns stem from the perishable nature of the raw fish and the specific characteristics of the vinegared rice. Attempting to warm refrigerated sushi is discouraged, as it moves the food into a temperature range that encourages bacterial growth.
Food Safety and Texture Degradation
Reheating sushi poses a food safety risk because it moves the food into the temperature “danger zone,” between 40°F and 140°F (4°C and 60°C). This range allows pathogenic bacteria to multiply rapidly. The brief, uneven heating provided by methods like a microwave is typically insufficient to reach the 165°F temperature required to kill all harmful microorganisms. The rice component carries a specific danger from the bacterium Bacillus cereus, which forms spores that can survive the initial cooking process. If the rice is left unrefrigerated for too long, these spores can germinate and produce heat-stable toxins that reheating will not destroy.
The quality of the sushi is also degraded by heat. Refrigeration causes the starch molecules in the vinegared rice to crystallize, making the rice hard and dry. Applying heat will only dry the rice out further and destroy the sticky, cohesive texture characteristic of proper sushi rice. Furthermore, the raw fish component, or neta, will partially cook when heated, even slightly. This results in an unappetizing change in texture, turning the fish rubbery, tough, or mushy.
Proper Handling of Leftover Sushi
Instead of reheating, handle leftover sushi through careful storage and consumption at a cool temperature. Sushi containing raw fish should be consumed within 24 hours of refrigeration to minimize the risk of spoilage and bacterial growth. Leftovers must be placed in the refrigerator immediately after purchase or preparation, as perishable food should not remain at room temperature for more than two hours.
To enjoy refrigerated leftovers, remove the sushi from the refrigerator and allow it to sit at room temperature for 10 to 15 minutes before eating. This brief period takes the chill off the rice and fish, allowing the flavors and aromas to become more noticeable without moving the food into the bacterial danger zone. The goal is to serve the sushi closer to its ideal temperature, which is slightly cooler than body temperature, rather than warming it with external heat.
An exception exists for rolls that contain only fully cooked ingredients, such as California rolls, cooked eel, or tempura shrimp. These cooked components can tolerate brief warming, such as a few seconds in a microwave, to improve the texture of the rice. This should only be done for the portion that will be eaten immediately, and never for rolls that contain any raw fish.