Starch & Thickener Conversion Chart

When to Use Each Thickener

Choosing the right thickener depends on five factors: the acidity of your dish, whether it will be frozen, how glossy or opaque you want the result, cooking temperature, and whether the recipe is gluten-free. Using the wrong thickener can produce a sauce that breaks down in the freezer, turns cloudy in a delicate dessert, or develops an unpleasant slimy texture.

Cornstarch — The Standard

Cornstarch is the benchmark thickener in American cooking. It is pure starch extracted from corn endosperm, weighs 128g per cup, and produces a glossy, relatively clear sauce when cooked through. Cornstarch begins thickening at 62°C (144°F) and reaches full thickening power between 72–80°C (162–176°F). Do not overcook cornstarch-thickened sauces — sustained boiling for more than 1–2 minutes causes the starch granules to break down and the sauce will thin and become watery again. Cornstarch also breaks down in acidic conditions (pH below 4) and after freezing and thawing, making it unsuitable for fruit pies that will be frozen or vinegar-heavy sauces.

Arrowroot — Best for Acidic and Frozen Dishes

Arrowroot starch, extracted from the tropical arrowroot plant, is a direct 1:1 substitute for cornstarch by weight and volume. Its key advantages: it tolerates acidic ingredients without breaking down, and it maintains its thickening after freeze-thaw cycles — making it the preferred starch for fruit sauces, vinaigrette-based dressings, and dishes intended for the freezer. Arrowroot also thickens at a lower temperature (approximately 60°C / 140°F), so it requires less cooking time. The result is crystal-clear and glossy. One limitation: arrowroot develops a slightly slimy texture if overcooked past 80°C (176°F). Add it at the end of cooking and don't boil for more than 30 seconds.

Tapioca Starch — Ideal for Pies and Chewy Textures

Tapioca starch (also called tapioca flour) is derived from cassava root and is particularly valued in fruit pie fillings and bubble tea (boba). It produces a glossy, somewhat chewy-textured thickening. In fruit pies, tapioca starch holds the fruit juices without making the filling gluey, and it remains stable after baking without the breakdown problems associated with cornstarch. It is a 1:1 substitute for cornstarch. Tapioca is also freeze-thaw stable and acid-tolerant. Note that instant tapioca pearls and tapioca starch are different products — for thickening sauces, use the starch/flour form, not the pearls.

Potato Starch — For Creamy Soups and GF Baking

Potato starch weighs more per cup (150g) than cornstarch (128g) because its granules are denser. Use 0.75 tablespoons of potato starch for every 1 tablespoon of cornstarch — it is a more powerful thickener by weight. Potato starch creates a creamy, opaque texture rather than a clear gloss, which works well in cream soups, casseroles, and gluten-free baking blends. It withstands higher temperatures than cornstarch without breaking down, making it the starch of choice for dishes that require extended cooking. However, it does not freeze well in sauces — use arrowroot or tapioca for frozen preparations.

Rice Flour as a Thickener

White rice flour (158g/cup) is used as a thickener primarily in Asian cuisines. It creates a milky, opaque appearance and a slightly starchy, filling result. Use 2 tablespoons of rice flour for every 1 tablespoon of cornstarch. Rice flour must be cooked thoroughly — at least 5 minutes of simmering — to eliminate a raw flour taste. It is commonly used to thicken Chinese sauces, Korean soups, and as part of gluten-free flour blends where it contributes body and structure.

All-Purpose Flour — For Roux and Gravies

All-purpose flour (125g/cup) is the oldest and most traditional thickening method in Western cuisine, forming the base of sauces from bechamel to country gravy. Its thickening power is roughly half that of cornstarch — use 2 tablespoons of flour for every 1 tablespoon of cornstarch. Flour must always be cooked first, either in a roux (fat + flour cooked together) or by simmering in liquid for at least 2–3 minutes to eliminate the raw starch taste. A roux involves cooking equal parts butter and flour over medium heat until the desired color is reached: white roux (1–2 minutes) for bechamel, blonde roux (5–7 minutes) for veloute, and dark roux (20–45 minutes) for gumbo and Cajun applications. Flour is not suitable for gluten-free cooking.

Xanthan Gum — Gluten-Free Baking Essential

Xanthan gum is a polysaccharide produced by bacterial fermentation, not a starch at all. It functions as both a thickener and an emulsifier, and it is the standard gluten replacement in gluten-free baking. In sauces, use 1/8 teaspoon per cup of liquid — this tiny amount provides significant thickening because xanthan gum is thousands of times more powerful than starch by weight. In gluten-free baking, it mimics gluten's binding and elasticity: use 1/4 teaspoon per cup of gluten-free flour in cookies, 1/2 teaspoon per cup in cakes, and 1 teaspoon per cup in breads. Xanthan gum hydrates instantly in liquid without heating, which distinguishes it from all starch-based thickeners.

Temperature Activation of Starches

All starch thickeners work by gelatinization: starch granules absorb water and swell when heated, forming a viscous network. Different starches gelatinize at different temperatures, which affects when to add them to hot dishes:

• Arrowroot: 60–65°C (140–149°F) — thickens at the lowest temperature
• Cornstarch: 62–72°C (144–162°F) — standard range
• Tapioca starch: 60–70°C (140–158°F) — similar to cornstarch
• Potato starch: 56–66°C (133–151°F) — thickens at relatively low temperature
• Rice flour: 65–73°C (149–163°F) — requires a full simmer
• All-purpose flour: 52–60°C (126–140°F) gelatinizes, but flavor elimination requires 85°C+ (185°F+)

Freezing Stability of Thickened Sauces

Not all starch-thickened sauces survive freezing and reheating. When starch gels freeze, the water molecules rearrange into ice crystals that physically disrupt the starch network. Upon thawing, the gel collapses and the sauce becomes thin and watery — a process called syneresis (or "weeping").

Freeze-thaw stability by thickener:

• Cornstarch: Poor — breaks down significantly after freezing. Do not use for sauces or soups intended for the freezer.
• Arrowroot: Good — maintains structure through freeze-thaw cycles.
• Tapioca starch: Good — stable after freezing, which is why it's preferred for fruit pies.
• Potato starch: Moderate — better than cornstarch but not as stable as arrowroot or tapioca.
• All-purpose flour: Moderate — flour-thickened sauces (like bechamel) can be frozen but may require whisking upon reheating to restore smoothness.
• Xanthan gum: Excellent — freeze-thaw stable, maintains viscosity perfectly.

Making a Slurry vs. a Roux

There are two primary methods for incorporating starch thickeners into sauces:

The Slurry Method

A slurry is the correct method for pure starch thickeners (cornstarch, arrowroot, tapioca, potato starch). Never add dry starch directly to hot liquid — it will seize and clump immediately. Instead:

1. Measure the starch into a small bowl or cup
2. Add an equal volume of cold water (2 tablespoons water per tablespoon starch)
3. Whisk vigorously until completely smooth and lump-free
4. With your sauce at a simmer, slowly pour in the slurry while stirring continuously
5. The sauce will thicken within 30–60 seconds. If it needs to be thicker, make a second slurry — do not add dry starch

The Roux Method

Roux is used exclusively with flour-based thickening. A roux is made by cooking equal weights of fat (butter, oil, or drippings) and flour before adding liquid:

1. Melt 2 tablespoons butter (28g) in a heavy saucepan over medium heat
2. Add 2 tablespoons flour (16g) all at once and whisk until combined
3. Cook, stirring constantly, for 1–7 minutes depending on the desired color
4. Add liquid gradually — cold liquid whisked into hot roux prevents lumps
5. Simmer for at least 5 minutes after all liquid is added to fully cook the starch

One tablespoon of cornstarch provides the same thickening as approximately 2 tablespoons of all-purpose flour in a roux, and a cornstarch-thickened sauce will be lighter, glossier, and require less cooking time.

Common Thickening Mistakes

• Adding dry starch to hot liquid: Always make a cold-water slurry first
• Overcooking cornstarch: Extended boiling breaks down the starch network, thinning the sauce
• Using too much xanthan gum: Even 1/4 teaspoon too much produces a slimy, unpleasant texture
• Using cornstarch in a tomato or lemon sauce: Acidity degrades cornstarch; use arrowroot instead
• Not cooking flour long enough: Raw flour tastes chalky — always cook for at least 2–3 minutes
• Freezing a cornstarch-thickened sauce: It will be watery upon thawing; use arrowroot or tapioca instead
• Measuring xanthan gum by volume: Its compressibility makes volume measurements highly inconsistent — measure by weight when possible

Related Tools