Typically, a rice cooker contains an insulated outer container containing a heating element, into which is fitted an inner removable bowl, which is sometimes non-stick or teflon-coated, which often has graduations marked in cups of rice (white). Whereas less expensive and older models use simple electronics and mechanical and thermal sensors, high-end rice cookers use microprocessors to control the cooking process and often incorporate a timer which can be used to set the desired "ready time". Some higher-end rice cookers use induction heating. 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. New rice cookers normally include a small measuring cup, and a plastic paddle for serving the cooked rice. The rice cup measure is normally 180 ml, approximately 25% smaller than the American measuring cup of 8 (US) fluid ounces / 250 ml.
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, also known as "the ja", is a standard appliance in kitchens in many Asian countries and in many Asian households; indeed a recent survey showed that over 95% of Japanese kitchens feature such a device
Different kinds of rice require different amounts of water. Usually, there are graduated marks for the right amount of water only for white rice, but sometimes there are separate scales for brown rice (as more water is required) or for cooking other food in the appliance.
Once the lid is closed and the cooking cycle has been activated, the rice cooker does the rest. Higher-end models give a countdown in minutes to the "ready time," or beep when done. Many people prefer to let the rice soak for a while before cooking the rice; additionally, some like to allow the rice to "rest" for a while after cooking before eating the rice. Higher-end models automatically time the soaking and resting periods.
A microwave rice cooker is a microwavable container designed specifically for cooking rice. It consists of three parts: an outer bowl, a fitted lid with steam vents, and an inner bowl with a finely perforated base. A measured amount of dry rice is placed within the inner bowl, which is then washed through with running water to remove surface starch powder from the grains. The water is then allowed to drain through the base of the bowl prior to cooking. This process may need to be repeated until the water draining out is clear. The inner bowl is then placed within the outer bowl and a small amount of water is added, so that the rice is just about covered. The lid is then fitted and the combined bowls are microwaved at full power for between 8 to 15 minutes (depending on the rice type, power output of the appliance and personal texture preference). Cooking occurs with the water boiling away and steaming the grains. It is very important to follow the manufacturer's instructions regarding the length of time and amount of water added, otherwise the rice can burn.
Microwave rice cookers work well for cooking American long-grain rice, but not so well for stickier varieties such as Japanese rice.
Some rice cookers are designed to accommodate a basket above the rice. This basket is generally used to steam vegetables, holding them in the steam coming off the rice. Most types of dumpling and buns can also be cooked this way.
Publication No. WO/2009/151229 Published on Dec. 17, Assigned to Qlif for Rice Cooker Lid Lifting Device, Autonomous Automatic Rice Cooker (South Korean Inventor)
Dec 18, 2009; GENEVA, Dec. 23 -- Sung-Gon Kim, South Korea, has developed a rice cooker lid lifting device and an autonomous automatic rice...