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How To Thicken Soup With Cornstarch

by Gina Elizabeth
How to thicken soup with cornstarch

If your soup is too thin, you’re not alone. You can easily thicken soup with corn starch.

What is Cornstarch?

Cornstarch is a powdered thickening agent. The molecules present in the cornstarch are similar to little sponges. They can soak up the water as well as expand when they do all that soaking.

Cornstarch to Water Ratio

To thicken your soup using cornstarch, make a mixture of liquid and cornstarch in equal parts. Prepare the slurry using a cold liquid and later add your slurry to the soup. To prepare the slurry, use the 1:2 ratio, i.e., one tablespoon cornstarch with two tablespoons of water.

What do I do if my soup is too watery?

How to Thicken Soup With Corn Starch

1. Make A Corn Starch Slurry

For each cup of liquid, you want to thicken, start with 1 tablespoon of corn starch in a small bowl. Add an 1 tablespoon of cold water and stir until a smooth slurry forms. Whisk the slurry into the hot, simmering liquid. Simmer uncovered until thickened.

You can also mix milk or half & half with cornstarch until smooth. Add more slurry until your soup reaches the desired thickness.

Tip: Use a sealed mason jar to shake the mixture until all clumps are removed.

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.

3. Heat the Soup

Heat the soup to boiling for 1 minute, then reduce the heat and simmer (uncovered) until the starchy taste is cooked away. Don’t cook too long, the starch may break down and your soup will thin out again.

Cooking with corn starch is easy when you follow a few simple guidelines:

  • Stirring. Gradually stir cold liquids into corn starch until completely smooth. Continue to stir gently during entire cooking period. Stirring too vigorously may cause mixture to break down and thin out.
  • Temperature. Cook over medium-low to medium heat. Cooking over high heat can cause lumping.
  • Cooking time. After boiling 1 minute, the starch granules will have swelled to their full capacity, causing the mixture to thicken. Overcooking thickened soup may cause it to thin out as it cools.

Serve and enjoy!

You can also substitute corn flour, cornmeal, polenta, or masa harina for corn starch. Note that corn thickening ingredients may dilute the soup’s meaty flavor if you add too much.

Tip #1: Do not use coarse-grind cornmeal, it won’t dissolve properly in the soup.

Tip #2: Add shredded or grated cheese to thicken your soup further.

Cornstarch Not Thickening

For every cup of the liquid that you wish to thicken, you must use one tablespoon of cornstarch and add an equal proportion of cold water to form a smooth paste. This is the slurry. Next, you must whisk your slurry by putting it in the simmering, hot liquid that you wish to thicken. Let it boil and then simmer until the starchy taste is cooked away. You shouldn’t cook it longer since the starch can break down, whereas the liquid will be thin again.

Remember, cornstarch requires heat for starch granules to swell as well as absorb water. So, if you want your mixture to thicken, make sure you heat the cornstarch at a high temperature. Also, let the cornstarch as well as the liquid mix boil lightly for 5-10 minutes. After this time, it will begin to thicken and bubble.

[READ: How To Cook A Turkey For The First Time]

More Soup Thickening Methods

You can’t beat the classics.

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

How To Thicken Soup With Reduction

Strain your soup through a sieve then pour it back in the pot along with a half of the liquid. Simmer with the lid off, for about 5-10 minutes. This will thicken soup without adding extra ingredients.

  • Note that the flavor of your soup may be more concentrated using this method.
  • Keep your soup uncovered as it cools to allow the steam to vent. Soup will thicken further as it cools.

A simple straining and reduction will do the trick but can take longer than other methods. If you’re in a pinch use corn starch or flour to thicken your soup fast.

What is reduction?

Reduction is simmering or boiling a liquid (without a lid) such as a stock, soup, stew, sauce, juice, wine, vinegar until the desired concentration or thickness is reached by evaporation.

How To Thicken Soup With Mashed Vegetables

Mashed or pureed vegetables are another classic choice for easily thickening your soup. Mash some of veggies (and potatoes) then place the vegetables back in the pot. Simmer with the lid off, for about 5-10 minutes or until your soup is thickened.

How to add mashed legumes to soup

Simply add mashed legumes (beans or lentils) to your soup, mix, and simmer (without a lid) until the soup thickens.

  • Mashing legumes releases their natural starches and helps thicken the soup, while maintaining flavor.
  • If the soup isn’t thick enough, simply add more mashed legumes and simmer longer.
  • Season with extra salt and spices to taste.

How to mash legumes after soup is cooked

If you’ve cooked your soup with whole legumes already, just use a potato masher to mash up some (not all) of your soup. The legumes will release their starches and thicken the soup.

If you don’t have a potato masher, pick about a third of the legumes out of your soup and use a fork — or blender — to mash your beans/lentils.

Couldn’t be easier.

How To Thicken Soup With Potato Starch

In case you were wondering — yes, you can make a potato starch roux. Browned potatoes taste really good, and a potato roux is delicious!

Here’s how:

  1. Melt 1 tablespoon of unsalted butter in a skillet.
  2. Add 1 tablespoon of potato starch. 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 about 10 minutes.
  4. Adjust seasonings as needed.

Or add a tablespoon of instant potato flakes to hot soup. Stir thoroughly. Let cook for a minute. The potatoes will absorb some of the liquid and thicken it. Potato flakes lighten the color and flavor slightly.

You get similar results with a rice flour roux. No surprise there, browned rice always tastes good.

Did you know?

Other ingredients commonly used to thicken soups and broths include rice, lentils, flour, and grains –Wikipedia

Soup Q&A

What can be used instead of corn starch to thicken soup?

Best Substitutes for Corn Starch

  1. Wheat Flour
  2. Arrowroot
  3. Potato Starch
  4. Rice Flour
  5. Grated Cheese
  6. Ground Flaxseeds
  7. Psyllium Husk
  8. Collagen Powder

How is soup served?

In the United States, soup is served in a bowl and either precedes the main course — or is the main course.

Can you use corn starch in place of arrowroot or potato starch when thickening soup?

Corn starch has the same “thickening power” as arrowroot, potato starch and tapioca, and you should substitute the same amount. So use the same amount in recipe substitutions.

What is the difference between corn flour and cornstarch?

Corn flour made from finely ground, dried corn. And cornstarch is a fine powder made from the starchy part of a corn kernel. Cornstarch is primarily a thickener. While corn flour is used like other cooking flours.

What are the advantages of using corn starch rather than flour?

Corn starch thickens with a satiny smoothness and glossy appearance. It adds no taste of its own to mask the flavor of foods. Recipes thickened with corn starch have a brighter, more translucent appearance than those thickened with flour. Corn starch also blends more easily with cold liquids than flour because it doesn’t absorb liquid until it’s cooked.

Why isn’t corn starch thickening my soup?

  • If there is not enough liquid, the corn starch granules will not fully swell and remain thickened when the mixture cools.
  • Too much fat or eggs in a soup can interfere with the swelling of the corn starch granules and prevent thickening.
  • Acid ingredients such as lemon juice, vinegar or tomato will reduce the thickening ability of the starch or prevent the mixture from thickening.
  • Excessive or vigorous stirring may break the starch cells and cause the mixture to thin out.
  • Simmering or boiling too long may cause the starch cells to break and the mixture to thin.
  • Freezing corn-starch thickened soups will rupture the starch cells and cause the mixture to thin out.

How do you thin soup that’s too thick?

  1. Add about 1/4 cup of beef/chicken broth or tomato juice for each 1 cup of soup. A little at a time.
  2. Stir the soup to evenly distribute the new liquid.
  3. Cover the pot with a lid to avoid evaporation.
  4. Re-season if desired.
  5. Keep adding liquid a quarter cup at a time until it reaches the right consistency.

How do you fix salty soup gluten free?

How to Thicken Soup with Gluten-Free Starches, Just Add:

  1. Cooking collagen powder
  2. Arrow root powder or kuzu root starch (Japanese arrow root)
  3. Any corn based thickener like cornstarch, masa harina, tortilla chips, polenta…
  4. Finely chopped raw broccoli or raw mushrooms
  5. Gluten-free dry noodles while chili is cooking
  6. Precooked onion, corn, okra, drained tomatoes
  7. Low-sodium cheese like mozzarella or goat cheese
  8. Tomato paste

How to I thicken my keto soup?

  • Reduction: Simmer (without a lid) until liquid reduces
  • Cooking collagen powder
  • Remove some of the veggies. Mash or blend them, then add back to the chili. The starches in veggies will help thicken the soup.
  • Arrow root powder
  • Finely chopped raw broccoli or raw mushrooms
  • Chia seeds
  • Add precooked cauliflower to make the soup chunkier
  • Grated parmesan or cheddar cheese
  • Xanthan gum (sparingly)

How do I thicken soup with cheese?

Stir in cheese and let it melt for a little extra thickness at the end. Add 1 cup of shredded cheese to the whole pot of soup, or sprinkle shredded/grated cheese directly on top of your bowl and mix.

How do I thicken soup upon serving?

If you want to thicken soup after it has been served, simply add these ready to eat thickeners as toppings or mix-ins.

  • Crackers. Crumble a few saltine crackers and stir them into your individual serving of soup. Start with 3 or 4 crackers, adding more to bring the soup to your desired thickness.
  • White Bread. Thickens so quickly! Stir in pieces white bread into the soup, then give it time to soak in the extra liquid. Check the consistency after a few minutes and add more if needed.
  • Bread crumbs. Use fresh, dried, or frozen bread crumbs. If your soup is still too watery, add more.
  • French’s Fried Onions. Sprinkle a handful into a large individual serving of hot soup. Stir thoroughly. Sooogood!

If you want to stay low-carb, add cheese instead.

Cheddar Cheese

Cheeses take the wheel.

Shredded cheese contains citric acid which acts as an emulsifier. This binds the cheese to the liquid in your soup and thereby thickens it.

Cream Cheese

I’m not sure if I’m more excited for the cream cheese or the soup.

Add cream cheese to further thicken your soup:

  • Mix equal parts hot liquid from the soup and softened cream cheese, until smooth
  • Add the mixture into the soup
  • Let simmer for about 15 minutes

So. Much. Flavor.

Parmesan Cheese

What doesn’t love Parm?

Serve topped with grated Parmesan cheese and a dollop of sour cream.

There’s no such things as too much cheese.

  • Stir fry finely chopped mushrooms before adding to the soup
  • Or add them directly to the soup and hour before it is done

What ingredients thicken soup while cooking?

If you don’t mind altering your recipe, you can addnon-traditional ingredients to thicken your soup.

Raw Broccoli

Raw broccoli soaks up a lot of liquid as it cooks. Just use chopped broccoli instead of beans.

  • Use raw broccoli (not frozen) and only the florets.
  • Chop the broccoli very finely.
  • The broccoli cooks down — after about an hour — and shrinks to the point you can hardly see it anymore.

Don’t knock it ’til you’ve tried it! The broccoli takes on the flavor of the soup and tastes great.

Who said soup can’t have veggies?

Mushrooms

You can also add fresh mushrooms to your soup. Do not use canned or frozen mushrooms.

Uncooked Noodles

If the soup is not chunky enough. Add uncooked noodles to simmering soup to soak up extra liquid. Most pasta cooks in8 to 12 minutes. Test for doneness after about 4 minutes of cooking by testing it.

Elbow macaroni or small pasta shells are a great choice of pasta for soup.

Ground Seeds

Ground seeds = game changing.

Whenever you need to thicken stew or soup, add ground pumpkin or chia seeds. They don’t have a lot of flavor and the chia seeds will get a gel coating on the outside after a bit.

Quinoa

The newest use for quinoa is probably the best.

Red quinoa blends into the soup. Add a 1/4 cup an hour before soup is done. Quinoa soaks up excess liquid and makes soup more hearty.

Important! Quinoa is a “high risk” gluten-free grain for people with celiac disease. It is often grown and harvested with wheat, barley and rye.

The following plant based ingredients will add extra nutrition and thicken your soup without changing the flavor:

Nutritional Yeast

Only sounds fancy: Nutritional yeast has a cheesy, nutty or savory flavor. Its a complete protein, containing all nine essential amino acids. One tablespoon of nutritional yeast contains 30–180% of the RDI for B vitamins.

  • Alternatively, you can add water to collagen in a separate bowl and mix until smooth. Then add the mixture to your soup. Cook over medium heat stirring the mixture constantly until your soup thickens.

Kuzu Root Starch

Also known as Japanese Arrow Root, it comes in rock-like granules.

  • Mix 1 tablespoon of kuzu root starch with 1 tablespoon of water, then add to simmering soup until thickened.
  • No change in flavor or texture

Tomato paste

Most of the time, tomato paste is used as a basic ingredient in making soup. Mix the tomato paste just before serving, in the final half hour of your cooking.

Add the tomato paste, a little at a time, stirring and checking the thickness to ensure that you achieve your desired thickness level.

Tomato paste works wonders in thickening pastes, stews, and soups.

Should I cook soup covered or uncovered?

Bring soup to a boil and then simmer for 2 or more hours. Alternating between covered and uncovered will control how thick the soup turns out. 

What is the best pasta to use for adding bulk to soup?

  • Elbow macaroni
  • Small shells
  • Curly spirals (fusilli and rotini)
  • Penne
  • Ziti

How do you thin soup that’s too thick?

  1. Add about 1/4 cup of beef/chicken broth or tomato juice for each 1 cup of soup. A little at a time.
  2. Stir the soup to evenly distribute the new liquid.
  3. Cover the pot with a lid to avoid evaporation.
  4. Reseason if desired.
  5. Keep adding liquid a quarter cup at a time until it reaches the right consistency.

How do you fix salty soup gluten free?

How to Thicken Soup with Gluten-Free Starches, Just Add:

  1. Cooking collagen powder
  2. Arrow root powder or kuzu root starch (Japanese arrow root)
  3. Any corn based thickener like cornstarch, masa harina, tortilla chips, polenta…
  4. Finely chopped raw broccoli or raw mushrooms
  5. Gluten-free dry noodles while soup is cooking
  6. Precooked onion, corn, okra, drained tomatoes
  7. Low-sodium cheese like mozzarella or goat cheese
  8. Tomato paste

What is masa harina?

Instant corn flour (masa harina) is a common way to thicken soup in Texas. Masa harina is a corn flour that comes from ground nixtamalized corn. Masa harina is pre-cooked and holds onto water better than corn meal. The corn flavor isn’t very strong (most people probably won’t notice).

Masa harina is typically used in Latin America for making corn tortillas, tamales, pupusas, and other dishes. Wikipedia

How to I thicken my keto soup?

  • Reduction: Simmer (without a lid) until liquid reduces
  • Cooking collagen powder
  • Remove some of the veggies. Mash or blend them, then add back to the soup. The starches in veggies will help thicken the soup.
  • Arrow root powder
  • Finely chopped raw broccoli or raw mushrooms
  • Chia seeds
  • Add precooked cauliflower to make the soup chunkier
  • Grated parmesan or cheddar cheese
  • Xanthan gum (sparingly)

Can I use xanthan gum to thicken my soup?

Xanthan gum can create lumps if you apply it directly to your soup, so mix with a little cold water first before incorporating it into your pot of soup. This thickener should be added sparingly due to the health risks associated with it’s usage.

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