Growing up in an Asian household, I would say that rice cookers were always a part of the whole eating experience. For the longest time, my mind would always connect rice cookers with the presence of rice: without a rice cooker, how would we cook rice? To my surprise though, not everyone was aware of the beauties of the rice cooker. Some of my friends would ask “Why do you need one? Why not just use the stove/microwave?” Pfft. The beauty of the rice cooker is that apart from adding the correct amount of water, there’s no human intervention necessary. No stirring, no watching–it was all taken care of, and in the end if you added the right amount of water you’d have perfectly cooked rice. It was so easy and convenient that I could be forgiven for thinking that they were so common place in Canada. Who knew that so many didn’t know what it was?
Anyway, how does the rice cooker get the rice to be just right? I guess the better question is: how does it know when to turn off? I wasn’t sure either until it was explained to me in an episode of Daily Planet back when Natasha Stillwell was still hosting with stalwart Jay Ingram. It was on their “You Asked For It” segment. Turns out the mechanics behind it are pretty much based on stuff you learnt in high school science.
Anyway, the rice cooker basically has a heating element and a thermostat trigger. So, in the pot you add your rice and water. When you press the button the heating element applies heat to the pot. Easy enough, right? Well, the water in the pot eventually heats up to the point where it starts boiling. At this point, even though the heat is still being applied the rising temperature of the water is basically halted. How? Why? Well, it’s a matter of state changes.
Do you remember what happens when water changes state between ice and liquid or liquid and steam? When you apply heat or cool it down the temperature changes within its solid, liquid or gas state. Once you get to that borderline though between water states, and heat you apply or heat given off doesn’t cause the temperature to move. Instead, all of the heat is used in the process of phase transition.
Wha…?
So, when moving from ice to water, when you hit 0 and apply heat, the ice won’t get any hotter until it’s water. When moving from water to steam, the water won’t get hotter than 100 until it’s steam. OK, so how does this apply to the rice cooker? Well, the water just boils the rice. The thermostat will read that the temperature is 100. Eventually the water will boil away and the rice will be cooked. When the water has boiled away, the heat being applied will cause the temperature of the pot contents to rise. The thermostat will sense this rise in temperature and switch the heating element off. The result? Perfectly cooked rice.
Good to know, eh? Turns out you can also use the rice cooker to cook other things. An old roommate used to use his rice cooker to make soup. Unfortunately, it’s not the kind of thing that you can leave out on the counter–not during the summer. Blech. There are videos on YouTube that show that you can even make bread in a rice cooker.
Yeah, gotta try that sometime.
Science lesson: over.
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