How do you thicken potato soup without flour?

Quick Answers

Here are some quick answers to common questions about thickening potato soup without flour:

What are good flour substitutes for thickening soup?

Some good flour substitutes for thickening soup include cornstarch, arrowroot starch, potato starch, tapioca starch, instant mashed potato flakes, pureed vegetables, xanthan gum, cream, milk, and butter.

What ratio do you use for cornstarch as a thickener?

As a general rule, use 1-2 teaspoons of cornstarch whisked with 2 tablespoons cold water per 1 cup of soup to thicken. Bring the soup to a simmer before adding the cornstarch slurry while stirring constantly.

Does potato starch thicken as well as cornstarch?

Yes, potato starch works very similarly to cornstarch as a thickener. Use about 1-2 teaspoons per cup of liquid. It provides a clear, glossy thickness.

Can you use instant mashed potatoes to thicken soup?

Yes, instant mashed potato flakes can be whisked into hot soup at the end to thicken it up nicely. Start with 1-2 tablespoons per batch and adjust as needed.

Potato soup is a comforting, hearty soup that is perfect for chilly weather. It is often thickened with flour or a roux to give it a creamy, velvety texture. However, some people need to avoid flour due to food allergies, gluten intolerance, or other dietary restrictions. Thankfully, there are a number of easy alternatives for thickening potato soup without flour.

Replacing flour requires carefully considering the texture and mouthfeel you want the soup to have. Flour not only thickens, but also adds body, absorbs liquid, provides opacity, and stabilizes fat emulsions. When removing flour, you may need a combination of techniques to achieve the ideal consistency.

In this article, we will explain both the purpose of flour in soup and why you may need to omit it. We’ll also give you 10 of the best substitutes and techniques to effortlessly thicken flourless potato soup.

Reasons to Omit Flour from Soup

Here are some of the most common reasons people need to avoid flour as a thickener:

  • Celiac disease or gluten sensitivity – Those with celiac disease or gluten intolerance must avoid flour, which contains the gluten protein.
  • Wheat allergies – Some people have an allergy specifically to wheat flour.
  • Carb restriction – Low carb and keto diets often limit flour and starchy thickeners.
  • Paleo or whole foods diet – The Paleo diet avoids all grains, including wheat flour.
  • Sensory issues – Some people, especially children, do not like the texture flour gives.
  • Prefer clean label – Many seek to avoid modified starches and gums for a “cleaner” ingredient list.

Fortunately, none of these require you to give up enjoying thick, creamy potato soup! With a simple substitute, everyone can savor comforting bowl of soup.

Purpose of Flour in Soup

Before examining substitutions, let’s first understand the important functions flour performs in soup:

  • Thickening – Flour thickens liquids through its starches absorbing moisture. This increases viscosity.
  • Mouthfeel – It provides a smooth, creamy texture fans of potato soup enjoy.
  • Opaqueness – Flour particles diffuse light for an opaque, not clear, soup.
  • Emulsification – It can help stabilize fat droplet emulsions for a rich texture.
  • Absorption – Flour soaks up excess moisture in the soup.
  • Flavor – It provides some neutral background flour flavor.

When using substitutes, we need to find alternatives that can perform some or all of these functions to match the expected potato soup texture.

Top Thickeners for Potato Soup

Here are 10 of the best ways to thicken flourless potato soup:

1. Cornstarch

Cornstarch is one of the most widely used flour substitutes in cooking. To use it, first whisk 1-2 teaspoons of cornstarch with 2 tablespoons cold water per cup of soup. Then, stir the slurry into simmering soup until thickened. Cornstarch provides opacity and thickening power similar to flour.

2. Arrowroot

Like cornstarch, arrowroot starch can be mixed with cool water then stirred into hot soup to thicken it up. Use about 1 teaspoon per cup of liquid. Arrowroot results in excellent clarity and a glossy texture.

3. Potato Starch

Potato starch is an apt choice for potato soup! Use it the same way as cornstarch. It delivers thickening, but minimal changes to flavor or mouthfeel. Potato starch is also gluten-free.

4. Tapioca Starch

Tapioca starch, also called tapioca flour, offers another neutral, gluten-free, and flavorless thickening option. Use about 2 teaspoons per cup of soup. It turns clear and gluey when cooked.

5. Instant Mashed Potatoes

For rich body similar to flour, whisk in instant potato flakes after cooking. Start with 1-2 tablespoons per batch, adding more to reach desired thickness. The potato flakes also lend potato flavor.

6. Pureed Vegetables

Blending cooked vegetables like potatoes, cauliflower, or white beans into the soup will thicken it without adding gluten or starches. You control the thickness based on how much you puree.

7. Roux

Though roux is made from flour and butter, you can create starch and gluten-free versions using substitutes. Try rice flour, tapioca flour, or cornstarch with olive oil or butter.

8. Xanthan Gum

This gluten-free polysaccharide powder is made from fermented sugars and used to replicate the properties of gluten. Use just 1⁄4-1⁄2 teaspoon per batch. It is very powerful!

9. Gelatin

Unflavored gelatin like Knox can thicken while providing protein content. Dissolve 1 teaspoon in the hot soup, without boiling. Let sit 5 minutes to thicken.

10. Egg Yolks

For a velvety texture, temper in 1-2 egg yolks per batch at the end of cooking. The fat emulsifies and proteins thicken. Use caution for food safety.

Choosing the Best Thickener

With so many options available, how do you choose what’s best for your potato soup recipe? Consider these factors:

  • Dietary needs – Pick gluten-free, keto, or paleo-friendly substitutes as required.
  • Flavor contribution – Starches and gums are relatively flavorless.
  • Texture – Ingredients like potato flakes most closely mimic flour’s mouthfeel.
  • Appearance – Starches produce clear gels; flours make opaque sauces.
  • Convenience – Thickeners like xanthan require exact measuring for best results.
  • Stability – Flour and egg yolks stabilize emulsions; gums stabilize starches.

Considering these aspects will guide you to the ideal substitute to match the soup experience you want to create.

Tips for Thickening Without Flour

Once you’ve selected a thickener, there are some easy tips to ensure soup perfection:

  • Mix starches with cool water before adding to prevent clumping.
  • Simmer soup after adding thickeners to activate them fully.
  • Start with less thickener and add more as needed for desired texture.
  • Whisk sauces frequently while simmering to maximize thickening power.
  • Puree vegetables after cooking until smooth for cleaner thickening.
  • For roux, cook the flour substitute with the fat briefly before adding liquid.
  • Give gums 5-10 minutes after adding to fully hydrate and thicken.

With a steady hand and these tips, you’ll effortlessly whip up the perfect thick and creamy flourless potato soup.

Thick and Creamy Potato Soup Recipes Without Flour

Want some recipe inspiration to try thickening potato soup without flour? Here are 3 delicious ideas:

Simple Potato Soup

Made creamy with milk and thickened with cornstarch, this straightforward soup lets the potato flavor shine. Recipe yields 6 servings.


  • 3 lbs russet potatoes, peeled and diced
  • 4 cups low-sodium chicken or vegetable broth
  • 1 cup whole milk or heavy cream
  • 3 tablespoons unsalted butter
  • 1 teaspoon salt
  • 1⁄2 teaspoon pepper
  • 1 onion, chopped
  • 2 cloves garlic, minced
  • 2 bay leaves
  • 2 teaspoons cornstarch + 2 tablespoons water


  1. In a large pot over medium-high heat, melt the butter.
  2. Cook the onions until soft, about 5 minutes.
  3. Add the potatoes, garlic, bay leaves, salt, and pepper. Cook 2 minutes more.
  4. Pour in the broth. Bring to a boil then reduce heat and simmer 20 minutes until potatoes are very soft.
  5. Discard bay leaves. Using an immersion blender, puree the soup until smooth. Otherwise, use a countertop blender in batches.
  6. In a small bowl, whisk together the cornstarch and water. Pour mixture into the hot soup while stirring.
  7. Add the milk or cream. Heat through but do not boil. Adjust seasonings.
  8. Serve soup warm, garnishing with extras like bacon bits, chives, or shredded cheese if desired.

Loaded Baked Potato Soup

All the taste of a baked potato in creamy, thick soup. Arrowroot starch replaces flour beautifully. Makes 8 servings.


  • 4 lbs russet potatoes, peeled and cubed
  • 6 cups chicken or vegetable broth
  • 1 cup whole milk
  • 8 ounces cream cheese
  • 6 slices cooked crumbled bacon
  • 1⁄4 cup sour cream
  • 2 tablespoons unsalted butter
  • 1⁄2 teaspoon onion powder
  • 1⁄2 teaspoon garlic powder
  • 1⁄2 teaspoon salt
  • 1⁄4 teaspoon pepper
  • 1⁄4 cup arrowroot starch


  1. Simmer the potatoes in the broth until very fork tender, about 15 minutes after reaching a boil.
  2. Reserve 1 cup of broth then drain and transfer potatoes to a blender. Puree until smooth.
  3. Return potato puree to the pot. Add all remaining ingredients except arrowroot starch and mix well.
  4. In a small bowl, whisk together arrowroot starch with reserved broth
  5. Add arrowroot slurry to the soup, stirring constantly. Bring to a low simmer.
  6. Cook 5 minutes until slightly thickened. Season with more salt and pepper if desired.
  7. Top bowls of soup with bacon, sour cream, and shredded cheddar cheese.

Low Carb Cauliflower Soup

With cauliflower as the main ingredient, this soup is low carb, creamy, and flourless. Yields 6 servings.


  • 1 large head cauliflower, chopped
  • 1 medium white or yellow onion, diced
  • 3 cloves garlic, minced
  • 4 cups chicken or vegetable stock
  • 2 cups whole milk
  • 2 ounces cream cheese
  • 1⁄4 cup olive oil
  • 2 teaspoons xanthan gum
  • 1⁄2 teaspoon salt
  • 1⁄4 teaspoon black pepper
  • 1⁄4 cup grated parmesan cheese


  1. In a large pot over medium heat, cook the onion in the olive oil until soft, about 6 minutes.
  2. Add the cauliflower and garlic. Cook 5 minutes more.
  3. Pour in the broth and bring to a boil. Reduce heat and simmer 15 minutes until cauliflower is very tender.
  4. Use an immersion blender to puree the soup smooth, or blend in a regular blender in batches.
  5. Return the soup to low heat. Add the cream cheese and milk, stirring frequently until melted and combined.
  6. Sprinkle the xanthan gum into the soup while whisking briskly to prevent clumping.
  7. Continue simmering 5 minutes to fully activate the thickener.
  8. Season soup with salt and pepper as desired. Top bowls with grated parmesan.

Frequently Asked Questions

Can I use all-purpose flour in soup if I don’t have specific thickening flours?

Yes, all-purpose flour can be used to thicken soup in a pinch. Just keep in mind it contains gluten. Start with 1-2 teaspoons whisked with water per cup of soup. All-purpose flour results in a slightly less smooth texture than starches.

Do I have to use exact measurements for these thickeners?

Exact measurements are not mandatory, but highly recommended especially for powerful thickeners like xanthan gum or cornstarch. When using new ingredients, start with less than the recommended amount, then add more as needed. You can always thicken the soup further, but it’s hard to reverse over-thickening.

Can I thin out soup that was thickened too much?

Yes, you can thin overly thickened soup by stirring in additional broth, milk, or water to reach the desired consistency. You may also need to bring it back up to a simmer so the starches dilute evenly again.

Do I have to puree some of the soup to thicken it?

Pureeing vegetables in the soup will help thicken it without using starches or thickeners. However, it is not required. Pureeing adds thickness from natural fibers while maintaining the whole food ingredients.

Can I freeze potato soup made without flour?

Definitely! Soups thickened with starches freeze very well. Allow the soup to cool fully before transferring to airtight freezer containers. Label and freeze up to 3 months. Defrost in the refrigerator before reheating.


By understanding the purpose of flour and considering substitutes’ properties, you can effortlessly thicken flourless potato soup. Cornstarch, arrowroot, potato starch, and other options like instant mash or xanthan gum make excellent gluten-free and low carb thickeners. Follow thickening tips and recipes for guaranteed potato soup success without flour!

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