Why Do Rice Cookers Boil Over?


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My wife and I love our rice cooker because it boils or steams rice quickly; saving us time on dinner. But since I’ve noticed that sometimes I see large, soapy bubbles start leaking out, I’ve wondered why do rice cookers boil over?

I decided to figure that out. Here’s what I learned:

Rice cookers boil over because of the starch in the rice itself. As rice cookers come to a boil, the water boils, and when the boiling water mixes with the starch, it creates large bubbles and expands beyond the capacity of the rice cooker. Using overly-starch rice can also cause boil-overs.

But there’s a lot more to know about rice cookers and how to get the best results from them.

So, in this article, we’ll walk you through what rice cookers are, why they boil over, and how you can actually prevent your rice cooker from boiling over. We’ll also review the best types of rice to use in a rice cooker.

That way you get the convenience of using one without the mess. Let’s get going!

To understand why rice cookers boil over, it’s helpful to know what rice cookers are and how they work. Let’s take a look at what rice cookers are and why they tend to boil over.

If you’re looking to buy any small kitchen appliance, don’t forget to check out my Recommended Products Page (click to see my page) which breaks down all my best picks by category.

I always hand-select items that I either own, have used, or have researched well to ensure they are great items. I also give not only top of the line as well as inexpensive alternatives so my choices work for any budget.

What Are Rice Cookers?

Rice cookers essentially do what their name implies: they cook rice. It’s a little more than that, though.

Rice cookers are small kitchen appliances, much like a slow cooker or a Crock-pot. Once water and rice are measured into the rice cooker’s basin, a heating device inside the container starts to heat up the water until it reaches its boiling point.

As the water boils, it’s absorbed by the rice. This effectively cooks the rice!

Generally, if rice is cooked at temperatures exceeding 212° (Fahrenheit), it becomes burnt or overdone. Luckily, most rice cookers have a sensor that makes sure rice isn’t cooked at more than 212°.

This is great because not only does it prevent the rice from being burnt or overdone, but it’s still hot enough that it also prevents bacteria from growing or staying in the rice.

What Causes Rice Cookers to Boil Over?

We briefly mentioned this earlier, but the main reason why rice cookers boil over has to do with the rice itself rather than the rice cooker.

Rice cookers boil over if there is an excess of starch on the rice that’s being cooked. Rice is naturally starchy, and that’s hard to avoid. However, excess starch can be removed from rice to avoid the rice cooker from boiling over (which we’ll go through later on).

When there’s excess starch on the rice that’s being cooked in a rice cooker, the boiling water mixes with the starch and starts to create large, soapy, foamy bubbles. These bubbles make their way to the surface of the rice cooker and cause it to boil over.

As the starch and water continue to mix, not only can the rice cooker boil over, but the rice can also be turned into something like a gross “soupy” porridge.

Rice cookers may also boil over if there is too much water in the basin of the cooker. An excess of water plus starch in rice is a bad combination. It’s important to know the limit of water that can be placed in the basin and to make sure there isn’t too much!

What Rice Has the Least Starch?

Obviously, if starch is what causes rice cookers to boil over, it makes sense to consider using lower-starch kinds of rice, right?

There are two different types of starch found in rice:

  • Amylose
  • Amylopectin

Amylose helps keep rice kernels from getting mushy and you end up with a bowl of perfectly separated grains of rice in the finished dish.

For you keto fans, it’s worth noting that rice with a lot of amylose has a lower glycemic index number. Long grain white rice has the highest amount of amylose of any of the types of rice.

When you cook rice, no matter which type of starch is present, it will naturally get released into the water.

Amylopectin rice tends to be a lot stickier, and in fact, works great for things like rice pudding or maybe risotto. Most short-grain rice is high in amylopectin (and low in amylose).

So which type of starch is more likely to make your rice cooker boil over?

As you may have guessed from the descriptions, amylose starch will be less likely to cause your rice cooker to boil over. So if you routinely have this issue, try using one of these types of rice that are high in amylose starch and low in amylopectin starch:

  • Long grain white rice
  • Basmati
  • Jasmine

But also see my tips below which can help no matter what type of rice you are using.

Since Jasmine and Basmati are most-often used in Thai and Indian food respectively, if you’ve ever wondered about the differences between Thai and Indian curry, I have a recent article that covers those differences from A to Z, and I even touch on all the other countries that have curries.

What’s really surprising is that most of them don’t even use the leaves of the curry plant (but one does). Just click the link to read it on my site.

How to Prevent Your Rice Cooker from Boiling Over

By now you know how rice cookers work and the main reasons why they boil over. That brings us to our next (and pretty important) point: how to prevent your rice cooker from boiling over.

Luckily, there are actually several things you can do to prevent your rice cooker from boiling over.

Let’s walk through one of the most useful ones so you can enjoy your rice cooker and your rice without any “rice porridge” or a mess from boil overs.

1. Wash Your Rice Before Cooking

This is perhaps the biggest and most useful tip for preventing your rice cooker from boiling over. If you wash the rice before placing it in the rice cooker, you can remove the excess starch from the rice.

Removing the excess starch from the rice before placing it in the rice cooker prevents the biggest problem: boiling water and excess starch mixing to create a boil-over.

So, how do you wash your rice before cooking?

There are quite a few methods, and there isn’t really any one “proven” method for washing rice before cooking it. You may adopt a different method for washing your rice or find that one method works better than another.

That being said, we’ll walk you through one of the basic methods of washing rice.

How to Wash Rice

To wash your rice, you’ll need the following things:

  • Rice
  • A bowl (large or mixing size)
  • A strainer or rice-draining colander
  • Cold water

a). Pour Your Rice in the Bowl

To begin washing your rice, first, pour the rice you want to cook into the bowl. Make sure your bowl is large enough to have room to hold water and stir the rice.

b). Pour Water Over the Rice

Next, pour water over the rice. You can use tap water or whatever water you prefer. Your water doesn’t have to be ice cold, but it’s better if your water is somewhat cold rather than room temperature or hot.

Fill the bowl with water until the rice is completely covered. If you want a formula, try pouring in three times the amount of water as rice.

c). Use Your Hands to Stir the Rice

Next, wash your hands, because you’ll be using them! After your hands are washed, use your hands to stir the rice. Use light pressure to stir the rice around with your hands. You can also pick the rice up and move it around.

As the rice rubs against other rice grains, your hands, and the water, the excess starch on the rice begins to come off.

d). Pour Out the Starchy Water

After that, it’s time to pour out some of the starchy water. You can begin pouring the water straight from the bowl into another bowl or into the sink. You can also save the starchy water for other recipes if you wish!

Rice isn’t buoyant, and it will sink to the bottom of the bowl. Use your hand to block the rice from being poured out with the water as it comes out. You’ll notice that the water being poured out appears milky and cloudy.

That’s good – it means the starch has come off your rice!

2. “Punch” the Rice With Your Hands

After the water is poured from the rice (as much as you can), begin lightly “punching” the rice in the bowl with your hand. Do this a few times. This will again rub the rice against itself and get more of the excess starch off.

Rinse and Repeat

Once you’ve “punched” your rice quite a few times, pour more water into the bowl and repeat the process all over again. Repeat the process until the water you pour out is mostly clear.

3. Soak Your Rice (Optional)

Lastly, you can take the colander or strainer and pour your rice in it. This step is optional, but you can allow your rice to sit there for about thirty minutes to “soak.” Soaking your rice in the colander can lead to shorter cooking times.

Using Your Rice Cooker

Now that you’ve effectively washed your rice and gotten rid of the excess starch, you can use your rice cooker!

It’s pretty likely that washing the excess starch from your rice will prevent your rice cooker from boiling over. However, there’s something else you should pay attention to, and that’s the amount of water you place in the rice cooker.

Make sure that when you’re ready to use your rice cooker, you don’t use too much water or fill the basin of your rice cooker too full of water. This can also help prevent a boil-over!

Asian food naturally lends itself to having long-grain rice on the side.

But many people get confused about the different types of Asian cuisine. If you’ve ever wondered what the difference is between Vietnamese and Chinese food, I break down the key differences between the 2 in a recent article.

What really surprised me was how much healthier 1 is from the other. Just click the link to read it on my site.

Did I cover all you wanted to know about why rice cookers boil over and what to do about it?

In this article, we took a look at the world of rice cookers.

Rice cookers are awesome! They save us time, are easy to clean up, and you generally avoid having rice stuck or burned to the bottom of the pan. They are also pretty fool-proof in terms of getting perfectly textured rice every time.

But they do sometimes boil over or leak. Very frustrating as that obviously makes a mess and can affect the texture of the rice for our meal.

So today, we explored not only WHY they boil over but, more importantly, what you can do to make sure that NEVER happens again.

What’s your favorite rice to cook with?

If you’re looking to buy any small kitchen appliance, don’t forget to check out my Recommended Products Page (click to see my page) which breaks down all my best picks by category.

I always hand-select items that I either own, have used, or have researched well to ensure they are great items. I also give not only top of the line as well as inexpensive alternatives so my choices work for any budget.


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Jeff Campbell

Jeff was a leader for Whole Foods Market for over 2 decades and is now a recovering foodie. When he's not spending time with his wife & 3 daughters, he can usually be found practicing martial arts, making music, blogging on his main blog over at newmiddleclassdad.com or, of course, in the kitchen.

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