What's the Best Pie Filling Thickener?

Flaky crust, juicy filling—a perfect fruit pie is all about balance. But pies need thickeners to keep them from being a runny mess. The right thickener can transform a watery fruit filling into a luscious, perfectly slice-able masterpiece. Some pie recipes use flour to thicken the filling, while others rely on cornstarch or tapioca. What's the difference between each, and how do you choose the right one for your recipe? The difference between the thickeners is mostly about how they look and taste, the temperature at which they begin to thicken, and how long they hold their structure after cooking. Read on to find out which is best for your pie.

Flour

Teaspoon for teaspoon, you will need to use about twice as much flour as you would cornstarch or tapioca to achieve the same thickening effects. Adding too much flour to your pie filling will turn it cloudy and pasty, with a distinctly floury taste. For this reason, flour works best with fruits that are less juicy, and/or are naturally high in pectin—a naturally occurring thickening agent—such as apples and blueberries.

Cornstarch

Just like the name suggests, cornstarch is derived from corn. Cornstarch is faster-acting than flour and forms a smooth, relatively clear filling. Just be aware that too much cornstarch can create a slimy texture. When cornstarch is combined with acidic ingredients such as rhubarb or lemon juice, it can cause the texture to break down over time. This isn't a problem if you expect your pie to get gobbled up in one day, but if you're looking forward to leftovers, or if you plan to freeze your pie, it's best to use a different thickener.

Tapioca

Tapioca-it's not just for pudding! This old-school ingredient may be what your great-grandmother used to thicken her pies, and it's still great for making a perfect fruit pie with a clear, stable filling. Tapioca is derived from cassava (also known as yuca or manioc), a starchy root native to South America. Tapioca comes in several different forms, but the one you want for pie-making is instant (otherwise known as quick-cooking) tapioca. When using tapioca as a thickener, allow the pie filling to sit for at least 15 minutes to absorb the juices before spooning it into the crust. Tapioca can be substituted in a one-to-one ratio for cornstarch.