There's the fruit pie of your dreams, the one that cuts easily, with every slice revealing a jammy, vibrant fruit filling that gently oozes onto the plate. But if it's done wrong? The slice is more like a puddle, disintegrating when you try to serve it and leaving behind a lake of fruit juice in the middle of your pie pan. Or it's overthickened, the fruit filling so stiff it brings bouncy balls to mind. Given that moisture content changes from fruit to fruit and throughout the season, how can you ensure a just-right filling? Read on.

The key to achieving the former, and not the latter, is to thicken your fruit pie filling correctly. Essentially, this means adding a starch that can soak up the liquid released by the fruit as it bakes, lending structure to the fruit and helping it set in the oven.

You can thicken your fruit pie filling with lots of different starches — including all-purpose flour, cornstarch, tapioca, and more — and the amount you use will depend on the fruit you’re using. For instance, some fruits have more natural pectin and less moisture (such as apples) and thus need less thickener, while others, like strawberries, have little natural pectin and rely on that additional starch to set. It’s not an exact science, but to guide you, we have a whole Pie Thickener Chart. Our fruit pie recipes are also written with different thickening options best suited to the pie itself; if you’re following a King Arthur recipe, follow the quantity listed on the recipe for the best results.

While many different thickeners will work, they each yield slightly different results. For instance, some yield a different mouthfeel or more opaque appearance, while some might make a pie filling firmer.

Sliced apple pie with container of Instant ClearJel in the background Photography by Kristin Teig; food styling by Liz Neily
Instant ClearJel is one of our favorite pie filling thickeners.

The pie thickener options

  • All-purpose flour: the most common pie filling thickener, in part because it’s in just about everyone’s pantry.
  • Cornstarch: A fine white starch derived from corn, frequently used for its thickening properties when heated.
  • Instant ClearJelA modified starch made from corn that has been ground and processed to sort out specific starches with sought-after gelling properties; almost like cornstarch, but better. (Learn more: What exactly is Instant ClearJel, and why do bakers swear by it?)
  • Pie Filling EnhancerAn all-in-one pie thickener that combines Instant ClearJel with ascorbic acid for bright fruit flavor, and superfine sugar for better blending; unlike other thickeners, this replaces some of the filling’s sugar since it’s already included. 
  • Quick-cooking tapioca: A starch derived from cassava, quick-cooking tapioca is not frequently called for in recipes because it’s harder to find, though some pie bakers swear by it; the filling needs to sit at least 15 minutes before baking for tapioca to soften.

The testing method

As mentioned above, how you thicken and how much thickener you use will depend on the types of fruit and the pie recipe itself. But for this test, we baked five mini strawberry-rhubarb pies. Each filling used a different type of thickener, following the guidelines listed in our Pie Thickener Chart.

Five different mini strawberry-rhubarb pies sliced in half, all made with different pie thickener Photography by Rick Holbrook; food styling by Kaitlin Wayne
Different pie filling thickeners yielded slightly different results.

Overall pie thickener takeaways

In short, all of these pie thickener methods worked. They yielded a fruit filling that was stable instead of soupy; when we cut into each, the filling remained intact and did not run out onto the plate. I’d happily serve a slice of each to friends. 

Mini strawberry-rhubarb pie sliced in half Photography by Rick Holbrook; food styling by Kaitlin Wayne
Instant ClearJel was a top choice for the clear-yet-stable filling. 

The winners: Fruit pie fillings thickened with Instant ClearJel and Pie Filling Enhancer had the best texture — juicy without being gummy or starchy. These two fillings also had the clearest appearance, which really allowed the bright color of the fruit to shine.

Mini strawberry-rhubarb pie sliced in half Photography by Rick Holbrook; food styling by Kaitlin Wayne
While effective, all-purpose flour resulted in a pie filling that was more cloudy. 

The runners-up: The cornstarch-, tapioca-, and all-purpose flour-thickened fillings were slightly cloudy. In addition, the all-purpose flour also had a faintly starchy (though not noticeably unpleasant) mouthfeel, while the tapioca filling was more sticky.

To summarize: We recommend using Instant ClearJel or Pie Filling Enhancer, but cornstarch, flour, and quick-cooking tapioca will also work well if you don’t have other options available.

Three more tips for thickening fruit pie

Some additional pie tips to keep in mind:

Fresh from the farm? Up your pie thickener.

Fresh farmers market fruit, especially berries, is often juicier than fruit you buy at the supermarket. You’ll want to increase your thickener accordingly to account for this extra moisture. Because all fruit will vary, the amount you increase isn’t a perfect science, but we recommend upping the thickener by about 25% for particularly juicy fresh fruit.

Your pie style matters 

In past testing, we’ve found that a double-crust pie needs more thickener than an open-faced pie, or one with a lattice crust or pastry cutouts on top. Which makes sense: Even with vents in the top crust, that layer of pastry is preventing steam from escaping as the pie bakes. The liquid that would evaporate from an open-faced pie is trapped in a double-crust pie. Thus more thickener is needed to account for the extra liquid.

Pie with slice lifted to show cross section Photography and food styling by Liz Neily
For the perfect slice, wait for your pie to cool.
Don’t forget to wait before you slice!

Whichever thickener you use, wait until your pie is cool before slicing into it. This additional time gives the fruit filling a chance to fully set. If you cut too early, while the pie is still warm, it’s much more prone to slumping and leaking. We know it’s hard, but for the sturdiest slices, make sure to wait until your pie is fully cooled; in warm weather, this can take many hours, so plan accordingly! 

Learn more essential tips and techniques for the best pie in our guide on How to Bake Pie.

Cover photo by Rick Holbrook; food styling by Kaitlin Wayne.

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Strawberry-Rhubarb Pie
Strawberry-Rhubarb Pie
4.7 out of 5 stars 69 Reviews
2 hrs 12 mins
one 9" pie or two 6" pies
Recipe in this post
Filed Under: Tips and Techniques
Rossi crimping pie crust
The Author

About Rossi Anastopoulo

Rossi Anastopoulo grew up in Charleston, South Carolina, which is how she fell in love with biscuits. She didn’t have any bakers in her household (with the exception of her grandmother’s perfect koulourakia), so she learned at a young age that the best way to satisfy her sweet tooth was to make dess...
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