How To Use Cornstarch As Thickener


What is Slurry?

A slurry is a mixture of thickening agent and liquid to thicken soups and sauces. In Japan, we use potato starch (we call it katakuriko 片栗粉) to make a slurry. It is known to make a thicker texture than cornstarch can make.

However, since cornstarch is easier to get here in the United States and generally used in Chinese cooking, you can use cornstarch in place of potato starch in my recipes.

The liquid for a slurry is often water, but sometimes it can be a mixture of condiments or dashi (Japanese stock).

The benefit of thickening the sauce and soup is to trap all the delicious flavors, and because the thick sauce or soup coats the ingredients well, you can enjoy them together in one bite whereas a thin sauce or soup can slip through the ingredients and more challenging to stick on the food.


What is a Cornstarch Slurry?

Quite simply, a cornstarch slurry is cornstarch mixed with cool water. In this form, cornstarch can be drizzled into soups and sauces for thickening without any powdery lumps forming.

How to Make a Cornstarch Slurry:

To make a cornstarch slurry, we generally use a 1:1 ratio of cornstarch to water.

Simply mix 1 tablespoon water and 1 tablespoon cornstarch until the mixture is homogenous (you can adjust the amounts according to how much slurry a dish needs). The cornstarch disperses when it comes in contact with water (note that the cornstarch disperses rather than dissolves. This type of mixture, with one substance dispersed into another, is known as a colloid. Science!).

The secret to authentic Chinese stir fries is that easy!

The one thing to remember is that cornstarch can s

The one thing to remember is that cornstarch can settle and separate from the water quite easily (you can see how it clings to the bowl in the photo below), so it’s important to re-stir your cornstarch slurry right before using. Just use a clean finger or chopsticks to loosen and recombine your slurry right before you add it to food.

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Other options

There are a lot of options out there for soup thickeners, and you may find that cornstarch works great for you, or maybe it isn’t your ideal choice.

One thing to keep in mind is that many people say that cornstarch isn’t great for soups that will be reheated. It can dissolve if cooked too long, meaning it’ll lose its thickening effect if the soup is reheated too much, and it can get a strange somewhat spongy texture if frozen.

However, that doesn’t mean it isn’t a great option for certain soups and situations. Go ahead and experiment with different slurry recipes and amounts.

Also, check out arrowroot and tapioca as other thickener options. There are so many soup thickener options out there now, you’re sure to find one you love working with and tasting (or not tasting at all.) Happy soup making.

Now let’s talk about why you should be using a food mill. Or check out this post on the best indoor grills for burgers.

Use less thickening for open-faced pies

For a lattice or open-faced pie, use a little less thickening than for a double crust pie, because more of the liquid will evaporate during the baking process.

The average amount of cornstarch for 4 ounces of fruit is 1 to 2 teaspoons.

2. Add Slurry To Soup

Once the corn starch is completely dissolved, slowly pour the slurry into the main soup pot.

Stir the soup until the slurry is fully mixed.

By mixing the corn starch slurry with cool water before adding it to the soup, you’ll keep it from clumping when it is incorporated into the hot liquid.

Important! Do not add dry cornstarch directly to the soup as this will cause clumping.

Making a slurry

A slurry is the semi-liquid kind of paste you get when you mix the liquid with small solid things. In some cases, like in construction, it means mixing cement with water to make it easier to pour. In soup making, it means mixing liquid into the cornstarch before adding it directly to the soup.

Some people use water, some use stock, some even use wine. You can experiment to see what version of “slurry” you end up liking best with each soup. It’s a great opportunity to try something new and see what kind of new flavors you can bring out of old favorite recipes.

To make the slurry, add equal parts cornstarch and water (or wine or stock) in a bowl and mix them vigorously until you’ve formed a paste.

For each cup of soup you’re making, mix 1 tablespoon of cornstarch with 1 tablespoon of liquid. That is about the right amount of slurry to thicken your soup, but of course, this depends largely on personal taste and how much thickener you need for the recipe.

Try experimenting with how much thickener you use. It may be a little different from the flour you’ve used in the past. Be prepared to try a few versions before you’re completely satisfied.

A tip: make sure to use cold liquid when you’re making your slurry, then add it to the hot soup.

How to Use Cornstarch

This powder looks quite similar to flour, but it’s not. Lighter in nature I prefer it over the other and buy it in bulk I use it so often. A little goes a long way for sure with this stuff.

In the past my mom used to make a roux this way. Pouring flour into a pan on the stovetop after sauteeing vegetables it created a thick paste. This was used to thicken gravy at Thanksgiving. It worked okay…..

I will admit it wasn’t always smooth and you

I will admit it wasn’t always smooth and you’d likely get a clump of thickener in your bite, it wasn’t pretty.

Now that I create my own easy Instant Pot recipes, and gravy for the holidays I have a different method. It works much better and is so simple to do. Instead of adding your thickener in your dish dry, it’s important to whisk it with some liquid first.

Then when you add it into your recipe and allow it to bubble a bit, your mushroom gravy or sauce(s) will become thicker without those pesky lumps!

How To Thicken Soup With Flour

Cornstarch has twice the thickening power of flour.

1 tablespoon of corn starch = 2 tablespoons of flour.

When a recipe calls for thickening with flour, substitute with half as much corn starch.

Whisk one tablespoon of flour in two tablespoons of room temperature water to make a slurry, then stir into the soup as it’s cooking.

Don’t add dry flour directly to the soup as it may clump. Simmer for about 15 minutes to cook out the raw flour taste.

Or, in a separate bowl, just mix 1-2 tablespoons of flour, with a cup of your soup’s hot liquid.

Whisk until all clumps are gone, then slowly add back to your pot while stirring.

You can experiment with rice, almond, or coconut flour as well.

Or make a roux

What is a roux?

A roux (pronounced “roo”) is also French and describes a paste created with equal parts flour and fat (melted butter, oil, or lard).

When using a flour slurry you have to simmer your soup for a while to cook out that raw flour taste. Using a roux speeds things up.

If you let your roux get really browned, it gives your soup a toasty flavor.

Here’s how to make a browned roux:

  1. Melt 1 tablespoon of unsalted butter in a skillet.
  2. Add 1 tablespoon of flour. Stir while cooking until fully incorporated and the roux is browned.
  3. Stir the cooled roux into your soup. Bring to a simmer (uncovered) and cook for at least 10 minutes.
  4. Adjust seasonings as needed.

Tip: You can also make a roux using corn starch

2. For Thickening Gravies

For gravies in dishes like Chicken Egg Foo Young, a larger amount of cornstarch slurry is needed.

It is very important to constantly stir the gravy with a whisk, so no lumps form. It’s also important to cook the gravy with the added cornstarch until it comes back up to a simmer before checking the thickness, as the heat “activates” the thickening agent.

And remember, hot gravy will thicken slightly as it cools, so be careful not to add too much!

Shrimp with lobster sauce is another one of those dishes that has a substantial amount of sauce in the dish. It’s usually best to thicken sauces before adding any final ingredients, like egg or scallions, so they don’t overcook.

Cornstarch Alternatives

Something to remember when you’re using cornstarch: If your sauce is quite acidic (like maybe it’s tomato-based), the acid will cause cornstarch to lose some of its effectiveness as a thickener. In that case, you can substitute arrowroot or tapioca starch. These two alternatives are also better options if what you’re making is something you’re planning to freeze because cornstarch can take on a spongy texture when frozen. Conversely, don’t use arrowroot to thicken a cream or milk-based sauce as arrowroot combined with milk can be a bit slimy.


Cornstarch has 7 grams of carbs per tablespoon, but more thickening power than flour, so you can often use less than what the recipe calls for. According to cornstarch manufacturers, you only need half as much cornstarch as flour to achieve the same thickening results. If your recipe only calls for one tablespoon of a thickener, cornstarch can be a low-carb option.

How to Substitute Gluten-Free Cornstarch for Flour

Sauces thickened with cornstarch are less opaque and will be glossier than ones with flour. Cornstarch is generally added to cold water and then to the sauce (whisk or shake in a small container to combine), and you do not have to worry about cooking it first. However, cornstarch can leave foods tasting chalky if undercooked.

How to Thicken Sauce with Cornstarch

Thickening a sauce with cornstarch is very similar to using flour, you just need different quantities. Be sure to thoroughly mix the cornstarch and water together, then pour into your sauce. Cook and stir over medium heat until thickened and bubbly. Heat two minutes more in order to completely cook the cornstarch. When using cornstarch as a thickening agent, here's how much you'll need:

  • Use 1 Tbsp. cornstarch mixed with 1 Tbsp. cold water (aka a cornstarch slurry) for each cup of medium-thick sauce.

Test Kitchen Tip: Be careful not to overcook cornstarch-thickened sauces as they can break down when overcooked (the starch loses its thickening properties when cooked too long).

Pie Thickeners in detail

Cornstarch – Pie Filling Thickener

Corn starch is somewhat flavorless, silky and thickens the pie filling at boiling point.

ClearGel ® The Best Pie Thickener

A secret no more. The failsafe way to thicken your fruit pies.