2.2 Litre rice cooker

A rice cooker or rice steamer is an automated kitchen appliance designed to boil or steam rice. It consists of a heat source, a cooking bowl, and a thermostat. The thermostat measures the temperature of the cooking bowl and controls the heat. Complex rice cookers may have many more sensors and other components, and may be multipurpose.

Principle of operation (basic rice cooker models)

The bowl is filled with rice and water. During cooking, the rice/water mixture is heated at full power.
The water reaches a temperature of 100 °C (212 °F); it cannot get hotter than its boiling point (all the energy goes into vapourizing the water).
At the end of cooking there will be no free water left; most will have been absorbed by the rice, and some boiled off.
As heating continues, the temperature can now rise above boiling point; this makes the thermostat trip.
Some cookers switch to low-power “warming” mode, keeping the rice at a safe temperature of approximately 65 °C (150 °F); simpler models switch off.

Electric rice cookers
Features and specifications
For modern home rice cookers, the smallest single-person model cooks 1 rice cup (180 ml), whereas large models can cook 10 cups. Commercial models can cook 20 or more cups. As a possible source of confusion, model specifications and names may list either cooked or uncooked capacity. Rice roughly doubles in size during cooking; therefore, a 10 cup (uncooked) rice cooker can produce up to 20 cups of cooked rice. The prices vary greatly, depending on the capacity, features, materials used, and the country of origin.

The majority of modern electric rice cookers are equipped with a stay-warm or keep-warm feature, which keeps the rice at an optimal temperature for serving without over-cooking it. Some gas cookers also have electric stay-warm mechanism. However, the usefulness of this feature degrades over time, a microwave may be more energy efficient or better suited to reheat rice that will sit longer than four hours.

Some rice cookers use induction heating, with one or more induction heaters directly warming the pot. This can improve energy efficiency.

Most modern rice cookers use aluminium for the inner cooking bowl. There are some models that use stainless steel instead of aluminium. Various other materials, such as copper, pure carbon, ceramic, and diamond powder coating, may be used for higher heat conductivity or better taste.

The pressure-cooking models can raise the water’s boiling point higher, e.g., from 100 °C at 1.0 atm up to about 110 °C at 1.4 atm, which speeds cooking. The pressure-cooking models can also be used in high altitude areas, where the boiling temperature is below 100 Celsius. Pressure cookers are also suitable for cooking brown rice (which contains oils and bran fiber that cook differently from pure white rice starch). Some pressure rice cookers have a varying pressure control mechanism (named the “dual-pressure” method) that creates repeated pressure/release cycles during the cooking.

There also exist mechanisms to collect and return the boiled over liquid to the inner rice bowl.

Many cookers now have microprocessor-controlled cooking cycles, which are often used to adjust for rice and cooking type.

This means that if more water is added, the rice will cook for longer.