Parts of a Rice Cooker
Rice cookers are usually electric appliances, much like a crockpot or slow cooker. The insulated outter container is equipped with a heating device, thermal sensors and controls. A removable pot or basin with a non-stick coating or enamel coating fits snugly inside of the container. Some rice cookers come with removable covers, while others have a lid attached to the outter container.
How a Rice Cooker Cooks
After rice and water are measured into the basin, the basin is placed into the container. The container is closed, and the heating element is turned on by flipping a switch. The heating device inside the container begins to heat up the water in the pot to its boiling point. The boiling water is absorbed by the rice, while the cover or lid keeps steam from escaping.
Quick Science Lesson: Water and the Boiling Point
Under normal heating conditions, water cannot heat past its boiling point, which is 212 degrees Fahrenheit (100 degrees Celsius). Any hotter than that, and the water converts to steam. Thus, as long as liquid water remains in the pot, the water will absorb the heat from the heating mechanism, not the rice. Because the water cannot get any hotter than 212 degrees, the pot cannot get hotter than 212 degrees. The thermal sensor monitors this.
How Rice Cookers Prevent Burning and Overcooking
Once it has absorbed all of the water, the rice itself can be heated past 212 degrees F, leading to overdone or burnt rice. Once the rice cooker's thermal sensor detects the pot going above 212 degrees, it means the water has all been absorbed. At that point, the rice is done. To prevent the rice from cooking any further, the sensor automatically trips the shut-off switch for the heating mechanism. This immediately stops the cooking process.
Keeping Rice Warm After Cooking
Many rice cookers come equipped with a warming setting. With this, as soon as the thermal sensors detect the pot going over 212 degrees F, rather than shutting the rice cooker off, it turns the heating to a much lower setting. This is temperature is not hot enough to cook the rice further, but warm enough to prevent any bacteria from growing in the rice. This setting usually keeps rice warm for hours after it finishes cooking. Without a warming setting, rice should not remain in a rice cooker for more than a half hour.