Some of the good things about technology is how it liberates individuals from tedious household tasks. Cooking rice is one of these. If you have ever cooked rice by hand, you’ll understand what a difficulty it can be. You have to keep a near watch on it get sidetracked and it will simmer dry, burn up the rice at the bottom side and spoiling the rest. Luckily, you don’t have to bother about this in highly modern kitchens, since an inexpensive device known as an automatic rice cooker takes care this for us, turning down the heat once the rice is ready to keep it hot without burning. How does an electric rice cooker do this?
The brief reply to this is by giving attention to the high temperature. The lengthy answer to this is by giving attention to the temperature in a fuzzy, relaxed sort of way. I’ll glance at the short answer in this article, and the long answer in the subsequent one.
The original automated home rice cookers arrived in the late 1950s from corporations like Toshiba. Industrial models had been around for a while prior to this, utilizing a range of methods to determine the perfect cooking of the rice, but the initial home models depend on the fact that water conducts heat better than rice does, and that it boils at 100℃ (212℉) at sea level.
Once you make use of a rice cooker, you place water and rice (normally in a 2:1 proportion) into a stainless-steel bowl, which has a heating component and a temperature measuring device below it. These are typically on springs to push them against the bottom of the cooking bowl to make sure they can conduct the heat well. The container is thin and made up of a metal like aluminum that conducts electrical energy nicely.
Once the automatic rice cooker is switched on, the heater begins heating up the container, which conducts the heat into the water and the rice. Because this mix is mainly water at this moment, it heats up till it starts to simmer. Once it starts boiling, the heat is passed off in the steam that emerges from the bowl. So, the temperature of the dish at the bottom side of the bowl won’t go much higher than 100℃ (212℉), since the water at the bottom of the bowl will boil, turning to steam and take off the heat.
In the Meantime, the rice is cooking, gripping the water into its formation, which is mostly comprised of starch. Starch is largely comprised of long chains of sugar molecules attached together, with a few more chemicals thrown in. When they are heated, these long sugar threads snatch onto passing water molecules in a process called hydrogen bonding: the hydrogen in the water feebly bonds to the oxygen atoms that are sticking out of the edges of this chain. Due to this, the rice grains soak up the water, and become less properly connected to each other, a method called gelatinization. If you kept adding up water, this would ultimately turn into a gooey substance. Nevertheless, you don’t want that to go on (unless you are making rice pudding or porridge) which is why you just add a specific amount of water: sufficient for the rice to soak up and swell up, but not plenty to break the structure down entirely.
Once the rice has wrapped up all the water, the heater is still pushing heat into the bowl alongside with the rice, but it doesn’t have any free water left to remove it by boiling, so the temperature of the bowl quickly climbs.
That abrupt temperature bump activates the process inside the rice cooker to turn the heat down or off, as the rice is done. The first rice cookers (and many cheap models today) used a bimetallic switch, where two metals enlarge at different rates when heated, activating at just over 100℃ and releasing a latch, producing the familiar “clunk” that lets you know the rice is completed.
That’s the short story. The long version has to contemplate a couple more issues: water boils at lesser temperatures at altitude, and the simple switch only allows you to have one trigger for doneness: you can’t regulate it for different kinds of rice that may absorb different amounts of water, or for different uses such as making porridge. Automatic rice cookers that can manage these use a different approach, called fuzzy logic.