The “Proof” is in the Pie: How Alcohol Makes a Flakier Pie Crust

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(This article was originally published on Scientific American)

Happy 3.14, a day some are celebrating using proofs with pi but I’m opting to observe it instead with proofs in pie--80 proof to be exact.

There’s a whole science to pie crust and the secret to making a good one lies in achieving the right ratio of flour, liquid and fat. Variation in type and proportion of these three ingredients can result in vastly different pies--ones that can be flaky, crispy, mushy, crumbly, or tough. 

There are a few things to consider in pie crust making, beginning with the type of flour to use. The varying protein content of flour contributes to a dough’s texture and consistency. Lower protein flours are usually recommended. Pastry flour usually contains 8.5% - 9.5% protein, resulting in flaky and light crusts, but the lower protein levels also mean it can be a bit too delicate. Instead, many people use all purpose flour which has a slightly higher content (normally about 10% - 12% protein). Next, a type of fat is selected--although butter adds flavor, shortening can create a light and flaky texture. Those wanting the best of both worlds can opt for a shortening and butter combination. The final ingredient to consider is the liquid. This could be water, though some use milk or even vinegar. And, of course, there’s always vodka as an option. Say whaaaaat?

I learned of this option through a recipe in Cook’s Illustrated, from their quest to make a Foolproof Pie Dough. The vodka rationale isn’t to intoxicate your pie--it has to do with gluten. Liquids are essential to pie crusts because they bind the dough together; however, they can present challenges. When liquids are added to flour, two wheat flour proteins--gliadin and glutenin--form gluten, which can toughen the dough. So how do you bind fat and flour together but avoid gluten formation? The trick appears to be using a hard liquor such as vodka--since 80 proof vodka is only 60% water, it combines the dough but doesn’t contribute to gluten formation. 

In their cookbook, The Science of Good Cooking, Cook’s Illustrated explains “...gluten won’t form in alcohol. The ethyl alcohol in vodka and other liquors does not attach itself in the same way as water. Because of this, it does not hydrate the proteins, and therefore does not aid in gluten formation.”

It doesn’t have to be vodka; other liquors also work--Alton Brown has made an apple pie with an apple brandy crust, as well as a pecan pie with a bourbon crust. By substituting 50% of a liquid in a recipe with hard liquor, this technique can be applied with your favorite recipes--something I recently tried using this recipe for Meyer Lemon Meringue Pie from Chez Panisse.

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Chez Panisse Meyer Lemon Meringue Pie 

(via the New York Times)

INGREDIENTS

Flaky pie crust, enough for a 9-inch shell (see recipe*)

*I used 1 ½ tablespoons of water and 1 ½ tablespoons vodka.

THE FILLING:

2 Meyer lemons or other large lemons

2 eggs

3 egg yolks

6 tablespoons sugar

3 tablespoons salted butter, cut in 3 pieces

3 tablespoons unsalted butter, cut in 3 pieces

THE MERINGUE:

3 egg whites, at warm room temperature

1/4 teaspoon cream of tartar

6 tablespoons superfine sugar

1/2 teaspoon vanilla extract

PREPARATION

1. Prepare the shell. Roll the pastry into a 12-inch circle, 1/8-inch thick, and fit gently into the pan. Trim the edge a half-inch beyond the rim, fold under and crimp or pinch to make a decorative edge. Prick the bottom with a fork. Freeze the shell for 20 to 30 minutes.

2.Prepare the filling. Grate the zest from the lemons into a small, noncorrodable bowl. Strain in the lemon juice, then press through as much lemon pulp as possible.

3. In a heavy, noncorrodable saucepan, beat the eggs, yolks and sugar until just mixed. Stir in the lemon juice and pulp, then the six tablespoons of butter.

4. Cook, stirring constantly, over low to medium heat, until the mixture comes together and thickens enough to coat a spoon. Remove from heat, allow to stand five minutes, then whisk briefly to smooth. Set aside.

5. Preheat the oven to 375 degrees. Line the frozen shell with aluminum foil, weight with beans or pie weights and bake for 20 minutes, or until set and dry looking. Remove the weights and foil, turn the heat down to 350 and continue baking until shell is golden brown, about 12 to 15 minutes. Set aside and allow to cool slightly, but leave the oven on.

6. Spread the prepared filling in the shell and bake for 10 to 15 minutes or until the filling is just set. Remove pie and turn oven to 375.

7. Make the meringue. Beat the egg whites until frothy, add the cream of tarter and continue beating until rounded peaks form. Beat in sugar and vanilla.

8. Spread the meringue over the filling, making sure it meets the edges of the crust to make a seal. Swirl in a design with a knife or spatula and bake for about 10 minutes, or until the meringue is lightly browned.

9. Allow to cool completely, from one to two hours, but do not refrigerate.