Rice cooker

A rice cooker or rice steamer is a container or kitchen appliance for cooking rice.

Overview

Rice cookers may be divided into a variety of rice cooking sauce pans or pots (e.g. risotto pan, paella pan, porridge pot) (Dell INSPIRON MINI 9 battery) , rice steamers, ceramic or plastic containers for microwave oven and gas/electrical appliances. Today the majority of home rice cookers are of electric type. In commercial or industrial use, there are many varieties, such as large gas or electric rice cookers(Dell LATITUDE C500 battery), a large-scale rice cooker that is called "rice boiler", and fully automatic versions which handle the whole process of rice cooking from washing rice to the end of the cooking cycle. Dedicated rice cookers date from long ago in human history. A ceramic rice steamer dated to 1250 BC is on display in the British Museum(Dell LATITUDE C600 battery).

Cooking rice has traditionally been a process which required attention to ensure the rice was cooked properly. Electric rice cookers automate the process by mechanically or electronically controlling heat and timing(Dell LATITUDE C800 battery), thus freeing up a heating element on the cooking range that had to be occupied otherwise for rice cooking. Although the rice cooker does not necessarily speed up the cooking process, with an electric rice cooker the cook's involvement in cooking rice is reduced to simply measuring the rice, preparing the rice properly and using the correct amount of water(Dell LATITUDE D400 battery). Once the rice cooker is set to cook, the rice will be cooked with no further attention. Many modern cookers have heat insulating casing and a warming mechanism. When the rice is determined to be fully cooked, the unit will automatically switch to the "keep warm" cycle(Dell LATITUDE D500 battery), thus preventing the rice from being overcooked and keeping the rice warm until it is ready to be served.

It takes about 30 minutes to 1 hour for most of electric rice cookers to complete cooking. Some advanced models can back-calculate the cooking start time from arbitrary given finish time(Dell LATITUDE D600 battery). The time required for cooking rice depends on amount of rice, power of the heating elements, and atmospheric pressure, thus it is not constant. Pressure-cooker models are not influenced by atmospheric pressure. The special features distinguish high-end models from lower-cost, simpler, models(Dell LATITUDE D800 battery).

Some types of rice dishes require special ways of preparation and are not suited to the mode of cooking represented by electric/gas rice cookers. These recipes include risotto, paella, and stuffed peppers(Capsicums) (Dell LATITUDE D820 battery).

In the early days of electric home rice cookers in Japan, the products were manufactured, marketed and purchased only within Japan. With the trend of Japanese cuisine spreading abroad, they were exported to Western countries. They were also exported to rice-consuming Asian countries as the average family income has improved and reduced manual labor is desired(Dell STUDIO 1450 battery). Many products are now manufactured in China, Korea, Taiwan, and Malaysia. Even some rice cookers intended only for Japanese domestic market are now manufactured outside Japan.

Traditional rice cooking methods and utensils(Dell VOSTRO 1400 battery)

Boiling: long grain rice e.g. basmati rice, Thai jasmine rice: Boiling pan

steaming: long grain rice, ibid: Steamer e.g. Mushiki (zhēng lóng)

absorption method with boiling: Japanese rice e.g Calrose rice: Asian traditional rice cooker on hearth, i.e. 釜

absorption method with oven: e.g. Paella, pilaf: Paella pan

absorption method with stirring: e.g. Risotto: Risotto pan

slow cooking: e.g. porridge: Porridge pot(Dell VOSTRO 1500 battery)

Electric rice cookers

Features, specifications, prices

For the modern home rice cookers, the smallest single-person model cooks 1 rice cup (180ml) whereas the largest cooks 10 rice cups (1.8liter). The prices varies greatly, depending on the capacity, features, materials used, the countries of origin(Dell XPS M1210 battery). Retail prices range US$20.00 to US$1,700.00). These days, the typical lower price models use electric heaters to heat the inner cooking bowl controlled by built-in microprocessors, whereas the high-end models feature various ideas of improved and better cooking methods and the prices also vary greatly(Dell XPS M1330 battery).

These inventions include, e.g. microprocessor-controlled cooking cycles, employing pressure cooking, utilizing induction heating (IH) that can generate heat directly within the inner cooking bowl itself (all the IH type models are microprocessor-controlled), employing varying pressure control mechanism named "dual-pressure" method that creates repeated pressure/release cycles during the cooking(Dell XPS 1340 battery), using various materials (e.g. copper, pure carbon, ceramic, diamond powder coating) for the inner cooking bowl because of their higher heat conductivity, utilizing more than one induction heating element, or employing a mechanism to collect and return the boiled over liquid to the inner rice bowl(Dell XPS M1530 battery).

The pressure-cooking models can raise the water's boiling point higher, e.g. from 100 °C at 1.0atm up to about 110 °C at 1.4atm, and are generally believed to produce a better result. They are also suitable for cooking brown rice, which is richer in dietary fiber, more digestible. The pressure cooking models can also be used in high altitude areas(Dell XPS M170 battery) .

These extensive inventions and the non-metal materials (e.g. ceramic, carbon, diamond) that require increased manufacturing costs contribute to the high prices of these models.

Additional features

Stay-warm (keep-warm) feature: Majority of modern rice cookers are equipped with this function. (Some gas cookers also have electric stay-warm mechanism) (Dell XPS M1710 battery).

Many models feature an ability to cook sticky rice or porridge as an added value. Most can be used as steamers. Some can be used as slow cooking pots. Some other models can bake bread or in some cases have an added function to maintain temperatures suitable for fermentation of bread dough or yogurt(Dell XPS M1730 battery). Likewise, depending on the model, these days it is common to see many added functions other than cooking rice.

In the 2000s in Japan, it was popular to cook soups, stews or sponge cakes in electric rice cookers. Books have been published for these recipes(Dell XPS M2010 battery).

If the rice cooker is not suited for such uses, there is a chance that it may damage the appliance. In particular, it is quite possible that the Tefloncoating get scarred by the rough bottom of ceramic wares placed inside the inner cooking bowl(Dell Inspiron Mini 12 battery). In some cases, apparently there were troubles of causing rice to burn and stick to the bowl, damaging the packing parts, odors becoming persistent and tainting the rice cooked afterward. If such cooking was outside indicated usage of the appliance, it, of course, violates the warranty(SONY VGP-BPS9A/S battery). In some countries, electric rice cookers including Japanese models are regarded as automated universal electric cooking pots and their use in preparation of variety of food is rather standard.

History

The idea of cooking rice using electric heating is old. In 1937, late Japanese Imperial Army sanctioned Automobile-kitchen equipped with primitive rice cooking box(SONY VGP-BPS9/B battery). The rice cooking box was a rectangular wooden box with two electrodes attached to opposite ends. To cook rice, the box was filled with washed rice and require water and the current was applied. This caused the water boiling. When the rice is cooked, the reduction of the water caused the resistance and reduced the heat(SONY VGP-BPS9/S battery), then it automatically became a stay-warm state. This method, however, was not suitable for different water qualities or degrees of rice washing as such varied the amount of heat produced and the end results. It also presented a large risk of electrocution, thus was not suitable for employing it for home cooking(SONY VGP-BPS9A battery).

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(SONY VGP-BPS9A/B battery).

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(HP Pavilion DV6-1210SA battery). It was an imperfect idea. Many makers continued to experience failures in their ongoing trial-error approaches. At this stage, there was even a trial model which embedded heating element in traditional wooden rice container(SONY VGP-BPS11 battery).

The first practical electric rice cooker was invited by Yoshitada Minami,[1][2] 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) (SONY VGP-BPL11 battery).

In December 1956, the Toshiba Corporation placed the first commercially successful automated electric rice cookers on the market.[3] It used a double-chamber indirect rice cooking method. Rice was placed into the rice pot, and water into a surrounding container(SONY VGP-BPL12 battery). When the water in the outer pot boiled off, the temperature of the pot rose rapidly. A bimetallic thermostat then activated, and automatically turned off the cooker to prevent burning of the cooked rice. Soon, Toshiba was producing 200,000 rice cookers per month for the Japanese market. Four years later, rice cookers could be found in half of Japanese homes(SONY VGP-BPS12 battery).

The double-chamber indirect cooking model took more time to complete cooking and also consumed more electricity. This model was gradually phased out since the 1960s. Today, electric rice cookers utilize an insulated outer container and an inner removable bowl, often coated with a non-stick surface(SONY VGP-BPS14 Battery), and stamped with water-level graduations marked in cups of rice used. The rice cup measure is normally based on the traditional Japanese measurement system 1 gō (合?), which has its origin in China (gě合). 1 gō (合?) is 180ml, approximately 25% smaller than the American measuring cup of 8 (US) fluid ounces / 240ml. 1 cup gō(合?) is regarded to produce enough cooked rice enough for a meal for one person(SONY VGP-BPS14/B Battery).

Initial models did not have a keep-warm feature and the cooked rice cooled down too quickly, thus it was often necessary to move the cooked rice to heat insulated serving containers. In 1965, Zojirushi Thermos company started selling electric rice cookers with a stay-warm function using a semi-conductor heat regulator(SONY VGP-BPS14/S Battery). The product sold 2,000,000 units per year. The other makers soon followed suit. The stay-warm function can typically keep rice warm for up to 24 hours. This not only keeps the rice at the desired temperature but also have benefit of suppressing growth of Bacillus cereus that is a cause of food poisoning. Another notable improvement was the use of electric timers(SONY VGP-BPS14B Battery).

In simple models, a mechanical thermostat is used to turn off the cooker when the water has boiled off. Since the 1980s, higher-end electric rice cookers use microprocessors to control the cooking process(SONY VGP-BPS22 battery), often incorporating a battery-powered memory and electronic timer that can be used to set the desired "ready time". Since 1990s, many models allow users to select desired cooking results for rice (e.g. soft, medium, firm, etc.), different types of rice, or some other ingredients than rice. Some models can be used as steamers(SONY VGP-BPS18 battery).

In the late 1980s, some higher-end electric rice cookers started using induction heating. This type aims to produce tastier cooked rice by controlling heating process more precisely. Some other pressure-cooking models use 1.2atm to 1.7atm (the limit of 1.4atm applies to home appliances) to raise the cooking temperature over 100 °C(SONY VGP-BPS22/A battery). Expensive models often provide steam-heating function.

In the 1990s, China started mass producing economical electrical rice cookers with limited functions and exporting them to many countries. Japanese makers have been attempting to compete by seeking a niche in models with added values by increasing features of products(SONY VGP-BPS22A battery).

In the 2000s, more deluxe models appeared on the market and attracted much attention. These models are characterized with non-metallic materials for inner cooking bowls to employ the thermal far-infrared waves in order to improve the taste of cooked rice. In 2006(SONY VGP-BPL10 battery), Mitsubishi Electric produced most expensive product which used an inner cooking bowl called "honsumigama" 本炭釜 that was made of hand-carved pure carbon. It has a better heat generating profile with induction cooking. Despite the high price (¥115,500, about US$1,400, at the time), it sold 10,000 units within 6 months after it was introduced(SONY VGP-BPS10 battery). It was a huge success and it set the trend of extremely high-end models in the market. There is also a product which uses pottery e.g. Arita-yaki for the inner cooking bowl. There existed pottery-based electric cooking appliances in China since the 1980s, and in recent years rice cookers have been also produced(Dell Latitude E6500 battery). Some other materials used for luxurious rice bowls are e.g. pure copper, ceramic-iron layers, diamond-coating. These rice cooker makers research on what the best cooked rice means (in taste and texture) and attempt to realize "the best cooked rice" in electric rice cookers by using various inventions(Dell Latitude E6400 battery). Most regard rice cooked either in a traditional rice cooker used in hearth or in a gas pressure cooker as references, and attempt to achieve the same or to exceed.

Restaurants that serve a lot of rice, particularly those specializing in Asian cuisine, often use industrial size rice cookers (Dell Latitude E5400 battery) (often they are gas pressure cookers but electric models exist too) that quickly and cheaply produce large quantities of cooked rice. A rice cooker 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(SONY Vaio VGN-FW31J Battery).

Basic principle of operation (basic rice cooker models)

The bowl in the rice cooker is usually removable, and beneath it lies a heater and a thermostat. These form the main components of the rice cooker. A spring pushes the thermostat against the bottom of the bowl for good thermal contact to ensure accurate temperature measurement(SONY Vaio VGN-FW32J Battery). During cooking the rice/water mixture is heated at full power. The temperature cannot go above 100 °C (212 °F) — as any heat put into the rice/water mixture at that point will only cause the water to boil. At the end of cooking, some of the water will have been absorbed by the rice and the rest is boiled off(SONY Vaio VGN-FW17W Battery). Once the heating continues past that point, the temperature exceeds the boiling point. The thermostat then trips, switching the rice cooker to low power "warming" mode, keeping the rice no cooler than approximately 65 °C (150 °F). Simple rice cookers may instead turn off at that point(SONY Vaio VGN-FW31E Battery).

Cooking rice with an electric rice cooker

The rice is measured and added to the inner bowl or washed in a separate bowl (it is not recommended to wash rice in the inner bowl itself) in order to remove loosened starch and residual bran. Strainers are often used in the washing and draining process. For better texture and taste, some types of rice, e.g. Japanese rice or Calrose rice which is suited for absorption method, require pre-cooking water absorption(SONY Vaio VGN-FW139E Battery). The water absorption step typically involves letting the rice stand for at least 5 min after draining water from the washing step and soaking the rice in the measured water for at least 15 min (or some claim it to be 1 hour) before cooking. The water draining step is believed to make it the water measurement more accurate(SONY Vaio VGN-FW139E/H Battery), if the water is measured and added after the initial water absorption that takes place in the washing step. Some people prefer to achieve the water absorption by simply leaving the rice soaking in the rice cooker overnight before starting cooking in the morning. Some other types of rice, e.g. long-grain rice or scented rice such as jasmine rice(SONY Vaio VGN-FW31M Battery), do not require washing or the water absorption step. The water for cooking is added to the inner bowl by using measuring cups or simply filling up to the appropriate graduated mark in the inner bowl. Although cold water is normally added, boiling water is used for cooking sushi rice(SONY VAIO VGN-FZ21E Battery).

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(SONY VAIO VGN-FZ21Z Battery).

Once the lid is closed and the cooking cycle has been activated, the rice cooker does the rest. Most models give a countdown in minutes to the "ready time," or beep when done. After cooking cycle is completed, it is recommended that the rice is to "rest" for 5 minute for post-absorption and then to be stirred to prevent the grains from clinging to each other too hard(SONY VAIO VGN-FZ21J Battery). Some rice, e.g. long-grain or scented rice, do not seem to require this post-absorption step.

Some higher-end models automatically time the soaking (pre-cooking water absorption) and the resting periods, therefore, there is no need to manually manage the water absorption or time these steps(SONY Vaio VGN-FW11 Battery).

Rice types and rice cookers

There are 3 different types of Asian rice: Oryza sativa subsp. indica i.e. Indian rice (long grain rice e.g. basmati rice and Thai jasmine rice), O. sativa subsp. javanica i.e. Java rice (large grain rice) and O. sativa subsp. japonica i.e. Japanese rice (medium grain rice e.g. Calrose rice, short grain rice e.g. most Japanese rice and risotto rice). In addition, Oryza glaberrima is known as African rice(SONY Vaio VGN-FW11M Battery).

Each rice cooker model may be optimized to cook a certain type of rice best. For example, most Japanese rice cookers are optimized for cooking Japanese rice and may not be the best for other types of rice. The typical method of cooking long grain rice is boil-and-strain and/or steaming method(SONY Vaio VGN-FW11S Battery). The absorption method used in Japanese rice cookers will produce slightly different texture and taste, usually stickier rice.

Japanese rice cookers used overseas

Since the 1980s, electric rice cookers were manufactured in China and Korea, who focused on simple feature models because of the market trend which regarded the price competition to be more important than rich features(SONY Vaio VGN-FW21E Battery).

Some visitors to Japan desired to buy Japanese domestic models as souvenirs, due to their ability to produce better tasting cooked rice and the multiple features. Since the Japanese domestic models use 100 volts only, they cannot be used in most other countries without adapters and power converters(SONY Vaio VGN-FW21J Battery). In Akihabara Electric Town, various models that are modified to be able to operate under 110V/220V-240V are sold in boxes that are labeled with English. A few rice cooker makers (see below) produce export models for use abroad.

Online vendors sell mid-range to low-end models outside Japan. So far, however, it seems that the high-end models are available only to Japanese domestic market(SONY Vaio VGN-FW21L Battery).

Rice cooker techniques

Rice cookers are typically used for the preparation of plain or lightly seasoned rice. More elaborate recipes are possible using a rice cooker, and there are cookbooks devoted entirely to dishes prepared using a rice cooker. Dishes that can be made in a rice cooker include beef stew(SONY Vaio VGN-FW21M Battery). By simply adding ingredients and setting it to "warm", a rice cooker would cook that at about 65°C (150°F). In a few hours, the stew is fully cooked and ready to eat.

Some rice cookers are designed to accommodate a basket, 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(SONY VGP-BPS13Q Battery).

Production

There were approximately 85 million rice cookers made in 2005. Most of the rice cookers were made in China, Korea and Japan, with 70% of the production in China. Most of Chinese production was from ZhanjiangCity and Lianjiang City in Guangdong Province(SONY VGP-BPS13B/Q Battery).

Microwave rice cookers

A microwave rice cooker is a microwavable container designed specifically for cooking rice. Some container consists of three parts: an outer bowl, a fitted lid with steam vents, and an inner bowl with a finely perforated base. Some others have only one container and the double-layered lid fitted with a steam vent(SONY VGN NR11S/S battery).

A measured amount of dry rice is placed within the bowl. For long-grain rice or scented rice (e.g. basmati rice, Thai jasmine rice), neither washing or soaking is usually necessary unless contaminating dirt is suspected. For Japanese rice (e.g. Calrose or medium/short grain rice) (SONY VGN NR11M/S battery), the rice is washed to remove surface starch powder and the trace of rice bran from the grains. For washing, a generous amount of water is added to the rice then the mixture is stirred a few times with a hand quickly. The water is then drained immediately while the lighter starch is still in the water, and the heavier rice grains settle at the bottom of the container(SONY VGN NR11Z/S battery). The washing process may need to be repeated about 3 times until the water draining out is clear of starch. The excessive washing, however, is believed to be detrimental, since it will remove too much water-soluble nutrients, e.g. vitamins(SONY VGN NR11Z/T battery).

With the 3 part model, 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 cooker is microwaved at full power for between 8 and 15 minutes (depending on the rice type, power output of the appliance and personal texture preference) (SONY VGP-BPS13A/Q Battery). 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. This method works well with long-grain rice that does not release much starch and is conventionally cooked with boil/strain or steam method(SONY VGP-BPS21/S Battery).

The microwave rice cookers can also be used for cooking Japanese rice, or medium- or sort grain rice, but the absorption method should be used. The rice is washed to remove starch well and allowed to stand to absorb water for at least 15 min before cooking(SONY VGP-BPS21 Battery). The water absorption step is essential, otherwise the cooking may result in cooked rice which is still too hard. The regular amount of water as the conventional cooking method can be used. The container is placed in the microwave and it is brought up to the boil at high power(SONY VGP-BPS21B Battery). Then, it can be cooked at low or low-medium power until all the water is evaporated (about 20 min - 30 min, depending on the rice type) and not much steam is coming out. The container is then left to stand for 5 min before the rice is stirred for serving(SONY VGP-BPS13B/S Battery).

Gas rice cookers

Most gas rice cookers are of pressure cooker type and have larger capacity than home rice cookers (1 to 2 litres). They are more commonly used for commercial and industrial purposes. Different from conventional gas pressure cookers(SONY VGP-BPS13A/S Battery), they are designed for easier rice-serving and easier cleaning. In general, it is believed that gas pressure cookers produce better cooked rice than conventional electric rice cookers that do not employ pressure cooking. Some are equipped with a heat insulating outer layer and electric keep-warm feature(SONY VGP-BPS13S Battery).