Succulent Science: The Role of Fats in Making a Perfect Pastry

Summary

Key Concepts

Baking, pastries, fats

Credits

Teisha Rowland, PhD, Science Buddies

Introduction

Have you ever wanted to bake the perfect pie to help warm up the cold holiday season? No matter whether it is apple, pumpkin, chocolate, pecan or pumpkin pie, every good pie needs a well-made pie crust. If the pastry crust is heavy or chewy then that can really affect how much you enjoy the pie. But how do you make a pastry crust that is light and flaky? In this scrumptious science activity, you will find out by investigating how the temperature of fat used (in dough) can affect a pastry’s texture and taste, all while baking your very own pastry crusts!

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Background

Going to a bakery can be fun adventure – there is usually a display of delicious sweets and pastries to tempt the palate and the eyes. Many of these treats are made using wheat flour. Wheat flour is an interesting substance. When you mix water with other powdery substances, you just get a paste. But when you mix water with wheat flour, you get a very different material, one that is the base for so many tasty foods, such as breads, pastas and pastries, including pie crusts. Pie crusts (also called pastry shells) were first developed in the Middle Ages to contain and preserve meat preparations, resulting in dishes like the Cornish pasty.

The taste and texture of a pastry depends upon the makeup of its dough, which typically contains water, flour and fat. Gluten proteins in flour allow the dough to be plastic (it can change its shape) and elastic (it bounces back and returns to its original shape), and turn into a fluffy baked good. The fat in the dough, on the other hand, helps give the final product its texture and flavor. Get ready to make homemade pastry crusts to find out how differently prepared fats affect them!

Materials

Ice water
One cup of butter. Using butter in individually wrapped sticks makes it easy to measure the required amount.
Small pot
Large mixing bowl
A fork
Measuring cups and spoons
Three cups of flour
One teaspoon of kosher salt
Pastry blender or two dinner knives
Ruler
Plastic wrap
Timer, clock or stopwatch
Refrigerator
Oven
Large, hard cutting board
Rolling pin
Two aluminum pie pans, each 9 inches in diameter
Oven mitts
Hot pad
Volunteers (at least 3) to do some pastry shell tasting!

Preparation

Wash your hands and make sure all of your cooking equipment is clean and your ingredients are out and ready to use.
Prepare ice water by filling a small bowl with ice cubes and then adding cold water until the bowl is nearly full. Add fresh ice cubes as they melt.
Right before you’re ready to start, get ½ cup of butter melting in a small pot on the stove, on low heat. Keep the butter warm and melted until you are ready to use it.

Instructions

Measure 1 1/3 cup of flour and place it into the large mixing bowl. Measure ½ teaspoon of kosher salt and mix it completely into the flour with the fork.
Add ½ cup of cold, refrigerated butter to the flour mixture and use the pastry blender to work the butter into the flour. If you do not have access to a pastry blender, use two dinner knives to “cut” the butter into the flour. Blend or cut the butter into the flour for approximately 7-10 minutes. The result should be small, pea-size (or smaller) pieces of fat-coated flour. How hard is it to mix the cold butter with the flour?
Once the flour mixture is the right texture, add 3 tablespoons of ice water to the bowl. Use the fork to blend the water into the flour mixture. How easily does the water blend in?
Once the water is completely blended into the flour mixture, quickly gather the dough into a ball and flatten it into a 4-inch-wide disk with your hands. How well does the dough collect into a ball?
Wrap the dough with a piece of plastic wrap and put it into the refrigerator for 20 minutes. At the same time, preheat the oven to 425 degrees Fahrenheit.
While the first batch of dough is in the refrigerator, prepare a second batch, but this time use the melted butter you prepared. Again, measure and mix together 1 ½ cup of flour, ½ teaspoon of kosher salt and then blend in the ½ cup melted butter. How hard is it to mix the melted butter with the flour?
After the butter is mixed in, blend in 3 tablespoons of ice water, collect the dough into a ball, and flatten it into a 4-inch-wide disk. How easy was it to blend in the water and collect the dough into a ball this time?
Wrap the dough with a piece of plastic wrap and put it in the refrigerator for 20 minutes.
When the first batch of dough is ready, lightly flour the rolling pin and the large, hard cutting board. Roll the dough disk from the center out, in each direction, forming approximately a 12-inch circle. How easy is it to make the circle?
Transfer the dough to the 9-inch pie pan. To do this, a trick you can use is to flip the pie pan upside down and place it on top of the rolled-out dough. Then carefully flip the dough and pie pan over (by putting your hand underneath the cutting board) so that the dough is now on top of the pie pan.
Gently press the dough against the bottom and sides of the pie pan. Trim any dough that is hanging over the edge of the pie pan with a knife. Prick the bottom and sides of the dough with a fork.
Bake the pastry shell for 15-18 minutes at 425 degrees Fahrenheit.
While the first batch of dough is baking, you can prepare the second batch when it is done refrigerating. Prepare the second batch as you did the first batch (using a new pie pan). How easy is it to roll this dough into a 12-inch circle?
Once you have prepared the pastry shell using the second batch of dough, also bake it for 15-18 minutes.
When the pastry shells are done baking, carefully remove them from the oven (using oven mitts). Place each pie pan on a hot pad to let it cool. The pastry shell should be golden brown. How does each baked pastry shell look compared to each other? How are they similar, and how are they different?
Once the pastry shells have cooled, gather your volunteers and have them look at, and taste pieces of, each shell. Which pastry shell is the flakiest? Which is most tender? (You can define tenderness as how easy it is to chew a piece of the shell, or how soft it is in your mouth when you chew it.)
How do you think the type of butter (melted or refrigerated) used affected how the pastry shells turned out?

Extra: Repeat this activity but skip the step where you chill the dough in the refrigerator. Is chilling the dough required to make a good pastry shell?

Extra: Try this recipe using lard and/or vegetable shortening instead of butter. Does using one of these other ingredients make a good pastry shell? How do pastry shells made with these different types of fats compare?

Extra: If you have access to a microscope, you could do a closer inspection of the pie crusts. How do the pie crusts compare to each other when viewing them through a microscope?

Observations and Results

Did you and your volunteers find the pastry shell made using refrigerated butter to be bumpier, less tender and flakier than the pastry shell made using melted butter?

When mixing the butter into the pastry shell dough, you probably found it much harder to mix in the cold butter (which was sold and difficult to break into pieces) than to mix in the melted butter (which was a liquid and so should have easily blended together with the flour, salt and ice water). When rolling out the chilled disk of dough, you should have similarly found it much easier to roll out the dough with the melted butter than the dough made with the cold butter. Overall, the melted butter should have more easily coated and separated the flour particles from each other, which resulted in a smoother pastry shell when using the melted butter compared to the cold butter. You and your volunteers may have also generally found the pastry shell made using melted butter to be less flaky and more tender than the pastry shell made using cold butter, although some people may differ in their opinions.