The Science Behind Pies: How to Bake Any Kind of Pie

Pies. I love pies! Pies are so comfy, so tasty, so round. With that kind of treat, you’re allowed to skip the rest of the meal, and jump directly to the best part: that is the pie.

When I started cooking, I felt a bit lost. Most of the time, I didn't have half the ingredients and tools listed in the recipes I was trying to cook. Usually, I was blindly following the instructions and I didn't really understand what was going on. It was tasty, but I was frustrated. Something was missing in the process.

With this Instructable, I will explain the theory behind pies. After this tutorial, you will be able to create your own pie recipes, and you will no longer have to follow a recipe.

When baking, it is crucial to have fun. So let’s have fun and create some tasty pies!

Step 1: What Is a Pie?

A pie is a dessert composed of a crust and a filling. It can be a different combination of these two parts. For example:

Filling on top of a crust: it’s a filled pie (e.g.: Fruit pie)
Filling at the bottom and crust on top: it’s a top-crust (e.g.: The Tatin Pie)
Filling enclosed in the pastry shell: cobbler or two crusts pie (e.g.: Apple Pie)

CAUTION:

A dessert with the crust only, it’s a cookie.

A dessert with the filling only, it’s a pudding.

The Crust:

The crust is made of only three components: flour, fat, and water.

It can be any kind of flour or fat.
If you don’t put any fat, you will get a bread dough instead of a pastry batter. It’s good too, but it’s not a pie.
Any other ingredients you add will allow you to push further the taste boundaries of your pie. Don’t be afraid, be creative!

The Filling:

The filling can be anything!

You can use baked fruits, fresh fruits, custard with some fruits, fresh or baked. Curd, sugar filling, chocolate fudge, puree, nuts, caramel, etc. The list goes on and on depending on both your region history and what you have in your kitchen.

Now that we know what a pie is, let’s see exactly what happens when we bake it. Trust me, understanding what’s going on when the pie is cooking in the oven is kinda cool. It will guide our choices during the preparation and allow us to play around and improvise a perfect pie.

Step 2: The Baking Reaction

When you add the water to the dough (a), it creates a gluten network (b), holding the dough together (c). Without water, the fat will prevent the formation of gluten and will result in a very crumbly crust. But be careful, too much gluten will give a compact texture to your crust. While not enough gluten will result in difficulties to give the shape you want to your dough.

To get a good airy-flaky crust you need to have small pockets of fat coats with flour (d). Why? What makes up the fat is a group of water droplets trapped in oil (e). When baking, the water from the fat will evaporate and will be trapped into these pockets (f and g).

Baking timeline (approx.):

38°C = Complete melting of the fat (may vary depending of the kind of fat you are using).

100°C = Steam released from the fat pocket.

154°C = Mouth-watering smell due to the Maillard reaction.

175°C = It’s cooked! With light colorization, beginning of the caramelization.

180°C/190°C = Brown colorization due to the caramelization.

CAUTION: This is a baking timeline not a timeline of the oven temperature. The measurements indicate the temperature inside the pie. You can use a laser infrared thermometer if you want to check your pie’s temperature and understand where the pie is on the baking timeline.

Food and science go very well together. Tasty and satisfying. In the next part we will tackle the CRUCIAL choice of ingredients. Well not that crucial, in food everything is good if you put a lot of love into making it.

Step 3: Choosing the Fat for the Crust

We saw earlier that you only need some fat, some flour and some water to make a crust. Now let’s see there roles in the baking process.

The choice of ingredients is where you express your creativity and willingness to explore. I will give you here some guidelines and what to be aware of when you make your crust mix. Have fun and tell me in the comments what you have tried!

The fat:

The role of the fat is to:

Give taste
Release steam (thanks to the fat pocket)
Give the desired texture to the dough (crunchy, crispy, crumbly, chewy, etc.)

Fat is composed of many things. In pastry, we are interested in the percentages of fat/oil and water in the fat. Why? Because the more water there is in the fat, the more it will release steam into the pocket (see the Baking Reaction above). In the crust for a pie you don’t want too much air (like in a bread or a cake). We want to have «just enough » air.

For example :

Flaky or crumbly texture : a fat with a lot of water in it
Chewy or extra crispy texture : a fat with no water in it.

Beside the water percentage, you must take a look at the melting temperature of the fat. Too hot, it will run into your flour while you are preparing the dough, which will make a very dense crust. Always cut your fat in small pieces, and chill them until "scoopable".

CAUTION: Using butter is the easiest solution, as the water you need is already trap into the fat. If you use shortening, you can make an emulsion with water first to make a reaction similar to butter. For oil you won’t be able to make as much different texture (but some tricks exists!).

Trying different kinds of fat is quite fun and it will expand your taste buds horizon. For example, you could use a mix of nuts oils (coconut, walnut, hazelnut, etc.), vegetable oil (flax seed, olive, peanut, etc.), or nuts butter (cashew, peanut, etc.). The quality of the fat can really make a difference and add a lot of taste and texture. Be careful! Combine them first and make them chill in the fridge, until you have a « scoopable » texture.

Step 4: Choosing the Flour for the Crust

The flour:

By flour, I mean anything that is dry. It could be any kid of cereal flour, starch or nut powder.

To any mix of flour, you can add a pinch of salt and sugar, this will add more taste to the crust, and bring the general taste of the pie together.

The role of the flour is to:

Give a structure to the dough (gluten network or subsitute)
Modify the density
Modify the taste and visual aspect

To make a crust, you need at least a little bit of elasticity.

The easiest solution is to use flour containing proteins, which, thanks to water, will enable the creation of gluten. As we saw earlier, a pie needs « just enough » gluten. Not enough gluten and the dough will fall apart (which is very hard to work). Too much gluten and our crust will be too compact (not the best sensation when you eat it).

For wheat and rye flour, choose a type of flour according to its gluten percentage. Bearing in mind that, the whiter the flour, the lower the gluten percentage will be (as the proteins are mainly found in the husk of the grain). For a pie dough we aim for a gluten pourcentage between 7 and 9%. In France and other countries, this corresponds to T45 or T55 flour. Thus, a soft or weak flour like cake flour, pastry flour, plain or all-purpose flour for the USA.

For other flours, since they do not naturally contain gluten, you can chose the right one according to its visual aspect and taste. You can then use a substitute to give more elasticity (eggs, banana purée, etc.). Almond powder for example, is used to add a "shortbread" aspect and some moisture to a dough. On the contrary, rice flour will bring more crunch. For a rustic look and taste, you can use chestnut flour. It's up to you, don’t be afraid to test and taste!

CAUTION: If you don’t want to follow a particular diet, it’s always better to mix different kind of items (fat or flour) and observe what going on. To start your experiment leave at least 1/4 of an item you know (normal butter or normal wheat flour).

Step 5: Choosing Water for the Crust

Water:

The role of water is to:

Activate the proteins from the flour into the gluten network

Yup, that’s it.

As a result, water is found in a lot of other liquids:

Fresh fruit juice: 90% water
Egg white: 82% water
Milk: between 75 and 89% water

Knowing that, you can use a liquid other than pure water and change the taste of the dough.

Step 6: The Balance of the Crust

To get the most out of each ingredient while keeping a nice texture, the best is to follow the same basic process for any kind of crust you make.

To know this ratio by heart is perfect to impress ourself while we are baking. Don’t overthink about precise measurements ingrams and don’t be scared of all the little steps which turn a simple recipe into a book (like this Instructable...). You only need to focus on a simple ratio and then choose your combination process.

Ratio:

Here we’ll talk in baker’s percentage. If you are not a rocket science specialist (that’s ok, neither I am) you can use a simple conversion of the pourcentage, like the example below. This ratio is based on the quantity of flour you chose to use. From there, you can calculate how much fat and liquide you will need.

So the following ratio:

100 % of flour
60 % of fat
20 % of liquid

Can be converted into the following proportions in grams:

100gr of flour
60gr of fat
20gr of water

If you choose to start with 200gr of flour, then you will need 120gr of fat and 40gr of water.

In other words, for 10 portions of flour, you need to add 6 portions of fat and 2 portions of water. If you split this ratio in half, we get 5 portions of flour corresponding to 3 portions of fat and 1 portion of water.

For information, a 20cm tart pan corresponds to 200gr of dough before baking.

CAUTION: This is not a volume ratio but a weight ratio! So don’t use cups, use a scale, like proper bakers!

In pictures, some examples for perfectly balanced dough. You can see the changes in ingredients depending on the type of crust.

WATER & BINDER*:

When we add a binder (egg for example), we lower the percentage of water. Because a binder is, in most cases, made of water.

SUGAR*:

5 % of sugar: you won’t taste it that much, but it will bring the taste of the pie together.
20 % of sugar: this proportion is perfect to taste the sweetness of the sugar in the crust.
50 % of sugar: that is sweet ! Use this proportion for a shortbread crust or pâte sablée only.

Step 7: The Combination Process of the Crust

The best way to make a crust, is the way you feel the most comfortable with Try an easy type of dough, do it a few times until you’re familiar with it. Have fun. When you are comfortable with one, you can explore the other types of dough without becoming frustrated. I’m always using the basic ratio with this basic process and put whatever I have in my kitchen.

(see table above)

This type of table represents a recipe in a very minimalist way, I use it a lot because I like to see at a glance the whole recipe and what are the steps I have to do simultaneously to save time.

Same recipe as the BASE ONE in other words:

Mix the different types of flour together.
Cut the fat into 1cm dices.
Crumble the fat dices into the dry.
Add the liquid until almost combined.
Fraiser (a french word that means : to smear the dough. It’s the exact opposite of kneading).
Form a ball and chill the dough.
Roll the dough and use it for your pie!

Same recipe as the BASE ONE with all the details:

Mix together the flour with a whisk. This help getting a perfect balance of each dry ingredients in the dough.
Cut the fat into 1cm dices. And chill them until they are hard or scoopable. Depending on the fat, it can turn into liquid from 20°C (See the Fat section above). If your kitchen is hot, or you are planning in doing a big batch of crust, you will have to harden the fat. With cold temperatures and cold hands, a scoopable fat will be hard enough for the dough.
Crumble the fat dices into the dry ingredients. With your hands or with blades. With your hands you can crush the fat with the tips of your fingers. Depending on the size of the fat pockets you create, you will get different textures. The bigger the chunks of fat, the flakier the crust. For a crumblier dough, you will need very small fat pockets.
- Almond size chunk = flakier
- Pea size = normal flakiness
- Sand size = crumbly
Add your water until almost combined. Use a cold water if possible to keep the fat at the same temperature. Be careful, do not overwork the dough. Here’s why:
- The more flour is kneaded with water, the more gluten is formed. The risk is that the dough will be too elastic and compact.
- If you work the fat too much, there is more risk that the fat will melt and soak the flour. This will turn into a very hard crust.
Fraiser. This technique consists in stretching the fat pockets while preventing the gluten from forming. It also allows the dough to be homogeneous. To do this, push the dough onto the work surface with the palm of your hand until it is completely smeared before re-forming a ball and repeating the movement. I only do it 4 or 5 times per batch. You can do it a few more times, but I honestly don't see the difference.
Give a ball shape to the dough. Chill the dough. Until you get a texture similar to hard butter. That should be around 30min in a freezer or 1h in the fridge. This time is important for the gluten to relax and the fat to regain its structure. If you skip this resting time, the dough will shrink considerably during cooking.
Roll the dough. First, flour the surface and the dough. Roll out the dough, with a quarter turn each time. Repeat the operation until you get a flat dough of about 0.4cm high.

There you go! You can use this process for most types of pies. Except for the sweetcrust pastry, where you will have to form fat and sugar pockets, which create the melt-in-the-mouth feeling as well as a special crunchiness for the crust.

Step 8: Assembling the Pie

Even if we talked mainly about the dough, we haven't seen the filling yet. Yet that's what you start with when you want to make a pie.

The filling belongs more in the cooking than the pastry category. You can try anything you want and have fantastic results. The fastest and very tasty way, is to peel fruits, coat them with sugar, and put it on top of the crust before cooking for 45 minutes at 180°C. It’s fast and always good!

When you feel confident enough you can make a puree, a curd, or a flan and top it with your fruits. Progressively, you can move on to more complexe fillings like a lemon curd or chocolate fudge. Why not mix different types of layers?

For a filled pie, you can follow this diagram to make sure you have the right dough for your filling. As a general rule for a top-crust (e.g.: The Tatin Pie) or a two crust pie (e.g.: Apple Pie), it is always easier to use a Shortcrust shell pastry.

Step 9: TIME TO EAT

That’s it folk! I hope I covered everything and that you now feel confident enough to make any kind of dough according to your imagination. If you have any question or want more advice: leave a comment!