Potato starch and corn starch are both effective for thickening and for use in baked goods. You will be able to use either one in most recipes and wind up with very similar results. That said, there are some differences between the two as each of them is better for some applications than for others.
If you are choosing between the two, there are a few important questions to consider. Let’s review in another SPICEography Showdown: potato starch vs. corn starch.
How do potato starch and corn starch differ?
Like wheat flour, corn starch is a grain starch and potato starch is a root starch. Grain starches and root starches have different characteristics but can be used in many of the same applications.
Potato starch is made from refined starch that has been extracted from potatoes. Like other root starches, potato starch thickens at lower temperatures. Potato starch should be added at the end of the cooking time and you should avoid boiling it.
Corn starch can handle high temperatures; in fact, it is best to cook it thoroughly to keep your dish from taking on a chalky taste. Acidic ingredients can diminish the thickening power of corn starch. Sugar is another ingredient that can affect its thickening ability as a high concentration of sugar limits the ability of corn starch granules to swell and thicken a liquid.
Both starches produce a thickened liquid that is clearer than liquids thickened with wheat flour; however, potato starch will be the clearer of the two. Liquids thickened with corn starch will still be slightly opaque.
If your recipe calls for one, can you use the other?
Both are used in a similar way—by making a slurry with water. Both are also interchangeable in most recipes, but there are exceptions.
You can use potato starch as a corn starch substitute to thicken soups, gravies, and pie fillings as long as they are not going to be cooked for extended periods after being thickened.
You can use corn starch in place of potato starch in the same soups, gravies, and pies as long as the acidity and sugar content is low. You can use it in place of potato starch for thickening a beef stew as you may want to add the thickener early in the cooking process rather than at the last minute.
Is one better for you?
Potato starch is a resistant starch, so it does not get digested in the stomach or small intestine. Resistant starch does not cause the spike in blood sugar or insulin that other starches cause. It also has significant amounts of vitamin B6 and various minerals.
Corn starch contains small amounts of certain minerals, but not enough of them to make it nutritionally valuable. It also does not provide any vitamins.
When should you use potato starch? When should you use corn starch?
Use corn starch when you need to thicken a dish at the start of the cooking process. Macaroni and cheese is a good example of a dish that is cooked after the addition of a thickener. Potato starch does not handle long cooking times well and so would not be ideal for this type of dish.
Use potato starch to thicken dishes at the last minute. Add it to soups, gravies, and pie fillings if other methods have failed to give them the right texture.