Use science (and some booze) to make the best pie ever
One of the staples of the holiday season is pie. While you may have Grandma’s tried-and-true recipe, do you know what goes on at the molecular level?
Here are five scientific tips from UCLA’s Science and Food blog that you can apply in the kitchen this holiday season.
1. Think of butter as a gas
Butter is really just a bunch of teeny tiny water droplets dispersed in fat:
In the oven, these water droplets convert from liquid to gas.
This means that the chunks of butter you see in your dough are really just big pockets of air waiting to happen. More air gives you a flakier crust.
While butter with higher butterfat content generally is considered to be of better quality, when it comes to baking pie, a slightly lower fat content (and higher water content) may be a good thing.
2. Fruit filling and steam vents
As a pie bakes, water from the apples — or other fruit — converts from liquid to gas, which causes air pockets to expand the crust.
While baking, the apples shrink in volume and soften. This can result in a big space between crust and filling.
Smaller pieces of fruit will cook more quickly, but they also tend to lose more liquid since they have a higher surface-area-to-volume ratio.
For a truly fruit-packed pie, try slicing the apples flat instead of cutting them into wedges, and pat them down in the crust to make sure they lie flat, which minimizes collapse later.
Make sure to cut vents in the center of the top crust — those aren’t just to make the pie look pretty! Apples lose a third of their weight from evaporation and that steam needs a place to go to prevent your pie from swelling.
3. Sometimes the best pie is a day-old pie
Temperature is important for a nice pie texture.
Letting the pie cool isn’t just for preventing a burned mouth.
Because molecules flow more quickly past each other at higher temperatures, hot pie filling straight from the oven will be runnier.
Eating your pie the day after you bake it allows plenty of time for the pie to cool down and the filling to set.
As the pie cools, the pectin molecules of your fruit also spend more time interacting with each other. This results in a more solid, gel-like filling that will take longer to seep out of the pie when it’s cut and served on a plate.
A little bit of cornstarch, tapioca or flour can also help solidify the filling.
4. Types of flour
Different types of flour have different protein counts, based on the type of wheat the flour was made from.
Bread flour has a particularly high protein count. When mixed with water, it forms dense gluten networks that are great for chewy breads and bagels.
But for a flaky pie crust, you don’t want extensive gluten networks.
Flours with lower protein content — such as pastry flour or cake flour — will create a less dense gluten network and a more tender crust. The challenge is that this type of flour can be more fragile to work with as a dough.
Have you ever added vodka to your apple pie? There’s a scientific reason for boozing up a pie crust.
Gluten develops in dough when two wheat proteins in flour (glutenin and gliadin) are mixed with water. The proteins begin to stick to each other because they don’t like to interact with water.
As the flour and water are mixed into dough, the glutenin and gliadin molecules form extensive networks:
These networks give structure and stability to dough. Ideal pie dough has just enough gluten to hold everything in the dough together without becoming too dense.
So how do you bind the fat and flour together into dough, but minimize gluten formation? A little trick is alcohol.
Vodka is roughly 60 percent water and 40 percent ethanol, which means that only 60 percent of it is actively aiding in gluten development. This moistens the dough and makes it easier to roll without forgoing the flaky texture.
Ready to test some of these tips? The Science and Food blog has some great pie recipes to experiment with:
For a step-by-step (and scientific) guide to pie making, take a look at the video below with UCLA biophysicist Amy Rowat: