In 137, the Japanese Imperial Army sanctioned an automobile-kitchen equipped with a primitive rice cooker. The rice cooker was a rectangular wooden box with two electrodes attached to opposite ends. To cook the rice, the box was filled with washed rice and water, and then a current was applied. This caused the water to boil. When the rice was cooked, the reduction of the water caused an increase in resistanc9e and reduced the heat, then it automatically became a stay-warm state. This method, however, was not suitable for different water qualities or degrees of rice washing and as such varied the amount of heat produced and the end results. It also presented a high risk of electrocution, thus it was not suitable for home cooking.
In 1945, the Mitsubishi Electric Corporation of Japan was the first company to produce a commercially available electric rice cooker. The Mitsubishi product was an aluminum pot with a heating coil inside. It had no automatic turn-off facility, and it required constant monitoring during cooking.
In the early development phase, electric home rice cookers used the simple concept of simply heating the rice to cook and turning off the heater when the temperature rose to a certain point. This method, however, is influenced too greatly with seasonal changes in room temperature and often produced under-cooked rice. Many makers continued to experience failures in their ongoing trial-and-error approaches. At this stage, there was even a trial model which embedded the heating element in a traditional wooden rice container.
The first practical electric rice cooker was invented by Yoshitada Minami,[2][3] who had an association with Toshiba Electric Corporation. It became possible to cook rice practically by employing the triple-chamber rice cooker (that provided heat insulation by air layers).
In December 1956, the Toshiba Corporation placed the first commercially successful automated electric rice cookers on the
Bibliography: http://en.wikipedia.org/wiki/Rice_cooker