Great pie dough is easy for some and a quest for others. Flour, salt, butter, water — how can it be so challenging? Sometimes, recipes call for one extra ingredient: a splash of vinegar in the cold water that brings the pie dough together.

What does that vinegar do? The most common answer — that it affects gluten development — isn't actually that useful. If you had a mass spectrometer at home, you could measure the teensy difference vinegar makes in the tensile strength of gluten strands in the dough, which in theory makes it a bit more tender.

But there are two much more important perks to using vinegar: it provides a little insurance against overworking the dough. And, that splash of vinegar will keep your dough from oxidizing and turning gray.

Pie dough via @kingarthurflour
Fresh All-Butter Pie Dough with vinegar (right) and without (left).

Putting vinegar to the test

To watch the oxidation process play out, I made two batches of our All-Butter Pie Dough and mixed 1 tablespoon of vinegar into the ice water of the second batch.

Pie dough via @kingarthurflour
Three-day-old All-Butter Pie Dough with vinegar (right) and without (left).

Here's the same recipe after three days. The water-only version has become noticeably grayer. It was also a bit more slack to work with when rolled out.

Pie dough via @kingarthurflour
Top row: water only, oxidized dough baked with egg wash (left) and without (right). Bottom row: vinegar dough, egg washed (left) and without (right).

What happens if your dough is gray and oxidized, and you bake it anyway? Good news. It'll be fine. While the oxidized dough was a little floppier to work with and didn't hold the pattern of the pie top cutters, the look and flavor of the baked dough were pretty much the same.

In the end, if you prepped your dough without vinegar, forgot about it, and worry you'll have to start over, fear not. Use your gray dough and give it a little egg wash on top before baking.

Pie dough best practices

The biggest determining factor in the quality of your pie crust is the technique used to make it. Vinegar, buttermilk, lemon juice, and vodka all change the interaction of the liquid and gluten in the dough. But the difference between a dough with acid in it and one without (when made with the same technique) is infinitesimal. In other words, no ingredient can cure poor execution.

So remember the essential rules of pie baking:

  • Keep your fat cold, and leave half of it in larger chunks, bigger than you think they should be.
  • Add liquid, but not too much.
  • Fold the dough to bring it together, and don't be anxious if it's a little crumbly, as long as it feels damp.
  • This is where overworking is a risk; as long as the dough is mostly holding together, you don't need to spend a lot of time kneading it.
  • Chill in disks with round, smooth edges. If you do, you'll get smooth edges when you roll it out.

When it comes to pie dough, practice makes perfect. The most essential pastry ingredient is confidence. But if you're a busy baker and aren't sure when you'll be making the leap from dough to oven, a little splash of vinegar (or lemon juice) in your recipe is a good idea.

If you're a visual learner, check out the video tutorials in our Complete Guide to Perfect Pie Crust.

Our thanks to Anne Mientka for the photos in this post.

Susan Reid
The Author

About Susan Reid

Chef Susan Reid grew up in New Jersey, graduated from Bates College and the Culinary Institute of America, and is presently the Food Editor of Sift magazine. She does demos, appearances, and answers food (and baking) questions from all quarters.