Rice cooker
A rice cooker is a self-contained electrical appliance, used primarily for cooking rice. There are also gas and open flame variants as well. The preparation of rice has traditionally been a tricky cooking process that requires accurate timing, and errors can end up with inedible undercooked or burnt rice. Rice cookers aim to avoid these problems by automatically controlling the heat and timing in the preparation of rice, while at the same time freeing up a heating element on the range.
Typically, a rice cooker contains an insulated outer container containing a heating element, into which is fitted a non-stick or teflon-coated inner removable pot, which often has graduations marked in cups of rice (white). High-end rice cookers use microchips to control the cooking process, whereas less expensive and older models use simple electronics and mechanical sensors.
To cook white rice, the rice is measured and optionally rinsed, then added to the inner pot. Cold water is measured and added or simply added up to the appropriate graduation in the inner pot. Sometimes there are separate scales for brown rice (as more water is required) or for cooking other foods in the appliance.
Once the lid is closed and the cooking cycle has been activated, the rice cooker does the rest. Fancy models give a countdown in minutes to the "ready time," and beep when done, whereas less expensive and older models simply click or ring a bell when done.
Rice cookers are typically used for the preparation of plain or lightly seasoned rice, but more elaborate recipes are possible using a rice cooker, and there are cookbooks devoted entirely to dishes prepared using a rice cooker. One of the most unusual dish that could be made by using a rice cooker is a beef stew. By simply adding ingredients and setting it to "warm", a rice cooker would keep them at around 60 degrees Celsius. In few hours, stew would be ready for serving.
Many rice cookers can keep rice warm safely for up to 24 hours. This helps to avoid the dangers of food poisoning due to Bacillus cereus.
Small, basic rice cookers can be purchased in the US at discount retailers often for as low as $10-$15, and units with large capacity and different selectable electronically-controlled cooking cycles can cost up to $100 or more. Restaurants that serve a lot of rice, particularly those specializing in Asian cuisine, often use industrial size rice cookers that quickly and cheaply produce large quantities of cooked rice. A rice cooker is a standard kitchen tool in Japan.
Rice cookers, when purchased, normally include a small "cup" measure and a plastic paddle for doling out the cooked rice.
Basic principle of operation
The bowl in the rice cooker is usually removable, and beneath it lies a spring and thermostat. These form the main components of the rice cooker. The spring in the bottom is simply to ensure contact of the thermostat to the base of the cooking bowl. In a rice cooker the amount of rice and water are exacly measured. During cooking the mixture is continuously heated. The temperature cannot go above 100 ° C as any energy put into the system at that point will only cause the water to boil. At the end of cooking all of the water will have been evaporated or absorbed. If the heating continued past this point the temperature would become greater than 100 ° C. The thermostat trips at this temperature, and switches the rice cooker to "warm" mode (say 65 ° C).