The rice cooker knows that the rice is done and will turn itself off once all of the water has boiled away or is absorbed by the rice and the internal temperature rises above 212 degrees Fahrenheit. A thermostat inside the rice cooker will turn it off once it reaches this temperature knowing that the water is gone and the rice is done.
Rice cookers are made to safely turn off once the rice is finished cooking. Adding twice as much water to rice in the cooker to start with, it will heat up and the rice will boil and steam when it reaches 212 degrees Fahrenheit.
Once the water is fully absorbed by the rice, the temperature rises above this level which is detected by the thermostat and the rice cooker will turn off.
How rice cookers know the rice is done
The rice cooker does not know necessarily that the rice is done but will detect a rise in temperature which happens when the water is gone. If there is not enough water to rice, the rice cooker will turn off before the rice is cooked leaving hard, uncooked rice.
Add twice as much water to rice to get a delicious, perfectly cooked rice. Choosing a lower starch good quality rice like basmati will prevent the excess forming starch bubbles and boiling over. Rinsing the rice can also help to remove starch and prevent it boiling over.
How does a rice cooker thermostat work
Rice cookers can be as simple as an outer shell which holds the heating element and thermostat and an inner aluminum pan which holds the rice.
The rice and water is put inside the aluminum pan that sits inside the rice cooker. The weight of the pan, rice and water will push down a spring loaded thermostat which will allow the pan to sit on the heating device.
When the rice cooker is turned on, the heating pad heats up, boiling the water in the rice cooker and creating steam. This gradually cooks the rice and it will absorb the water and expand.
Water boils at 212 degrees Fahrenheit or 100 degrees Celsius and will not go above this temperature as long as there is water in the dish.
The spring loaded thermometer at the bottom measures the temperature of the pan and when all of the water in the rice cooker is absorbed the temperature will rise and it will turn the rice cooker off.
Most rice cooker pans are made of aluminum because it is a low cost metal that transfers heat very effectively. They can have a non-stick coating which makes it easier to remove the rice when it is done.
Benefits of a rice cooker for perfect rice
The benefit of using a rice cooker instead of the stove top is that you can dump in the water, rice and turn it on allowing the rice cooker to do all of the work.
You do not need to stir, or even lift the lid of the rice cooker as it cooks. Leaving the lid on is actually essential for delicious fluffy rice as it will trap the steam and make it light, fluffy and delicious.
At the end of the cooking process, using a non-stick spoon simply give the rice a stir and the cooker will automatically move to a warm function which keeps your rice hot and ready to eat.
I always like to turn off the rice cooker eat it straight away and then store the rice in the fridge quickly. Do not leave your rice on the warm setting for too long, it can dry out and never leave the rice in the rice cooker while it is turned off as it can grow bacteria.
How to avoid overcooking rice in a rice cooker
There are some easy ways to avoid overcooking rice in a rice cooker.
Measure your rice and water
Make sure you add the right amount of rice and water in the correct ratio to avoid the rice overcooking and going soggy. Measuring twice as much water to rice will give you a delicious, well cooked rice that will not be gluggy or stuck together.
Measure the rice using a cup first, then fill the cup up again with twice as much water. Using the same cup will help you to remember how much rice and water to put in. For me, I like to use about ½ a cup per adult which will need 1 cup of water.
My rice cooker holds 4 cups which is more rice than my family could eat in a night but if you are entertaining you could go for the large 10 cup rice cooker which is great for big groups.
Use good quality rice
I had never considered the type of rice that I buy but after choosing a very cheap rice I could really notice the difference. A good quality basmati rice will be easy to cook right, it will be lower in starch so won’t bubble everywhere and always seems to cook to perfection.
A good quality rice makes me look like a better cook than I am as the rice ha a delicious flavor that works for Thai and Indian curries and even works for stir fry.
Longer grain rice works better in rice cookers as it won’t go gluggy if you put the right amount of water in.
How does a rice cooker know when the rice is done? | Summary
Rice cookers are simple, low cost machines that are clever in the way that they know the rice is done. A simple mechanism that detects the heat of the pan and turns it off when it heats above rice boiling point is all the rice cooker needs for perfect rice.
I use my rice cooker at least 5 times a week as we cook so many types of curry including Thai green curry, Indian butter chicken and chicken tikka marsala a few times per week.
A good rice cooker will make you look like a great cook with very little effort.