Is it possible to interchange flour, cornstarch and potato starch when you are thickening something?

-Robin

Dear Robin,

They could be interchangeable, but let me explain how that could be tricky.

Flour is the strongest thickener. Not only does it thicken a liquid, but when you reheat the liquid, it will remain thick. It won’t break, meaning the solids separate from the liquid.

Cornstarch also thickens, but it generally will break at one point or another if you store that thickened liquid for any length of time.

Potato starch is equally fragile.

What you want to do is think about how you are going to use the sauce. For example, in Chinese cooking cornstarch is the classic thickener. If you want to do a gravy with your turkey, flour is really dependable. That gravy will hold in the fridge for several days or freeze beautifully. It will come out just the way you made it, and it will be beautifully thickened.

Whenever you use any of these things, you have to dilute them with water and stir until there are no lumps. You have to add them to simmering liquid.

They are not really interchangeable. (Learn more about selecting the correct starch.) But in a pinch, you could substitute cornstarch for flour. 

-Lynne

Lynne Rossetto Kasper
Lynne Rossetto Kasper has won numerous awards as host of The Splendid Table, including two James Beard Foundation Awards (1998, 2008) for Best National Radio Show on Food, five Clarion Awards (2007, 2008, 2009, 2010, 2014) from Women in Communication, and a Gracie Allen Award in 2000 for Best Syndicated Talk Show.