Science of Pumpkin Pie

Homemade pumpkin pie is one of my all-time favorite dishes. I can live without pumpkin lattes, pumpkin scones, pumpkin juice, and even pumpkin M&Ms (really?!?), but I couldn’t manage an entire fall without at least a few pumpkin pies. Since Halloween is right around the corner it’s the perfect time to learn the science of pumpkin pie while also making a family favorite!

When we think of baking, we often don’t think of science, even though science is what drives the deliciousness of everything we bake. And here’s the thing, kids LOVE to bake. So why not use a little of your baking time to learn new vocabulary, discover new types of chemistry, and to dive into comprehensive science?

In this blog post, you will not only find one of our favorite pumpkin pie recipes, but you will also learn some cool scientific facts behind the making, and tasting, of pumpkin pie.

To learn about the science of pumpkin pie we have to make a pumpkin pie. If we didn’t it would be like doing the moon-Oreo project without letting your kids eat an Oreo. Below is most of our secret family recipe. I was chided by my 8-year-old when I mentioned putting up the ‘real’ recipe she was not cool about it. Apparently, our spice blend (which I stumbled upon) has to be kept a real family secret. I will say, when it comes to holiday cooking, cardamon and anise are two of my favorite spices.

That last sentence might get me in trouble…

Our favorite pumpkin pie recipe

Ingredients for the pie filling:

• 1 can pumpkin (or 15 ounces fresh baked pumpkin flesh)
• 1 can of evaporated milk (12 oz)
• 1/4 c white sugar
• 1/4 c brown sugar
• 2 large eggs
• 1 tbsp dried milk (optional)
• 1 tsp cinnamon
• 1/2 tsp ginger
• 1/2 tsp nutmeg
• 1/2 tsp salt

Ingredients for the pie crust:

• 1 1/4 cup flour
• 1/4 tsp salt
• 1/2 cup (2 sticks) butter, cold
• 1/4 cup ice water

Making your pumpkin pie crust

1. Combine the flour and salt in a large bowl.

2. Cube the butter and cut it into the flour salt mix. The mixture should start off as a mix of very chunky butter and very fine flour/salt. By the end, the mix should look more like small crumbs.

3. Add water, 1 tbsp at a time, until the dough just forms.

4. Chill your dough in the refrigerator for a few hours, or turbocharge the cooling by placing it in your freezer while you make the pie filling.

Making your pumpkin pie filling

1. Preheat your oven to 425

2. Mix your dry ingredients together in a small bowl (sugars, salt, dry milk, and spices).

3. Beat your eggs and add in the pumpkin, mix well.

4. Mix in the dry ingredients.

5. Blend in your can of evaporated milk and pour the filling into your pie crust.

6. Bake for 15 minutes at 425F and then lower the temperature to 300F for another 45 minutes or until the center reaches 175F. Allow the pie to cool before serving.

The science of pumpkin pie crust.

That pie crust recipe seems simple right? Just a few ingredients, not too much work, but yet replicating a deliciously buttery, flaky, light, but distinct pie crust can be ridiculously difficult.

Why does the recipe call for 1/4 cup of water when I might only need 1 tbsp? The amount of water you add to your flour/salt/butter mixture completely depends on how well you cut your butter into your flour/salt mix.

Imagine you just toss in the cubed butter and then start to add the water. You would need a lot of water to moisten the flour and bring it together since the butter wouldn’t be doing too much work.

Now imagine the other option, you cut the butter in so much that there is no crumble to the mix, instead it is just a homogenous (that means all alike) mixture or very thick dough. In this case, you wouldn’t need to add any water at all since the mix already came together with the moisture of the water.

In both of these cases, you won’t have a nice flaky pie crust, and we can learn why through science!

If we don’t cut the butter into the flour then we need to add a whole bunch of water to make the dough come together. This extra water combines with the flour and creates more starch. This starch is like glue and is why flour mixed with water can become a sticky disaster. As we blend the extra water with the flour we create too much of the starch glue and our crust becomes leathery.

If we blend (instead of cut) our butter into the flour the dough needs no water. Since you wouldn’t need to add much water there would be no formation of the starch complex that happens when water and flour mix. Since there is no glue your crust ends up being far too crumbly, almost like chewable sand grains.

So the key to your perfect pie crust lies in perfectly cutting the butter into the flour – not too much, and not too little.

How does the kneading affect your pie crust?

Adding water initially makes the starch glue, but over time, with enough pushing and pulling, we change the characteristics of the dough by developing two proteins, gliadin, and glutenin. Glutenin is a protein that likes to bond, or hold hands with, other proteins. Thus by kneading you begin to make networks of these proteins that spread throughout the dough. You want just the right amount of these proteins in your dough. Too much and your dough will be leathery, too little and it will be crumbly.

Making a perfect pie crust every time.

It would be hard to get your butter-flour crumbles to the same size each and every time you bake a pie. How can you make a reproducible flaky delicious pie crust?

One idea would be to take a set amount of chilled butter (say 1tbsp) and a set amount of the flour (maybe 1 cup) and blend it into a nice smooth paste. Then cut in the remaining dry flour and bits of butter before adding your water. This would give you an even distribution of flour-butter globules every time. Of course, you would have to try out various proportions to get the texture perfect for your family!

The science of pumpkin pie filling.

Here is a great question that I’m sure you know the answer to – what makes your pumpkin pie a pie, and not a goupy soup?

There is one ingredient responsible for pulling the whole shebang together – can you think of what it is?

If you thought of the eggs, then you’re right! Egg whites are a mixture of water, protein, and a few vitamins.

How do eggs hold your pumpkin pie together?

The eggs provide the structure of our pie. As mentioned earlier, the egg white is mostly protein and water. When heat is added to the protein it denatures (that is, it changes its natural shape). As the proteins are bumping around and denaturing you can imagine them becoming like long, tangly strings. The water that was between globs of protein is now spread along these long tangled chains, making it appear drier. As you continue to bake the pie, the water from the egg whites gets squeezed out of the increasingly tangled web and evaporates. You can imagine, if you cook your pie (or any egg) too much the network squeezes out too much of the water and becomes rubbery – a texture that no one wants!

The egg yolk adds fat and emulsifiers to our pie filling. This fat helps create a smooth dough and prevent the overcooking of the egg proteins. In fact, the addition of cream cheese can often help create smoother, creamier, custard pies like the pumpkin pie for this very reason. If you find your pies are always full of pumpkin pie ‘curds’ you may want to either add more fats, like an extra yolk or cook it at a lower temperature.

The emulsifiers in the egg are the intermediaries between fats, which hate liquids, and liquids, which hate fats. These emulsifiers help blend the flavors of spices that often need to be paired with fats to be delicious on our tongues.

How important is mixing the filling of your pumpkin pie?

You’ll notice that in this pie filling, and in most recipes, we mix our dry ingredients in one bowl, wet ingredients in another, and then combine the two together.

This mixing of dry ingredients helps to evenly disperse the spices, sugars, and extra fats (like the dry milk) throughout the pie dough. This ensures that the first slice of pie isn’t one big bite of sugar while the second slice is dull.

When we add the beaten eggs and pumpkin together in their own bowl and mix, we ensure that the firming quality of the coagulating proteins in the eggs is evenly spread out. Again, this ensures that one slice of the pie isn’t like mush while another slice is a frittata.

Since the pumpkin pie filling doesn’t have any flour in it, we don’t need to worry about over-mixing the filling like you would with a pancake batter. However, this is another great reason to mix dry ingredients in one bowl, wet ingredients in another, and then combining. In recipes with flour involved, this preparation technique requires less mixing of the liquids with the flour, ensuring light, fluffy, delicious pancakes (or cakes, 0r cookies…).

Basically, mixing creates a homogeneous mixture. Homogeneous means everything is the same. So one slice of your pie will have the same amount of each ingredient as another slice of the pie. Thus, each slice tastes the same.

I hope you enjoyed learning with baking and eating a delicious pumpkin pie this fall! Now you know a little bit more about the science of pumpkin pie.