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Happy Pi Day! We are huge fans of homophones here at SciShow, so we put together a whole bunch of fun facts and tasty tips about PIES! Get it?!

Hosted by: Hank Green
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[SciShow Intro Plays]

Hank: In honor of this Pi Day, we thought we’d talk about pie. No, not pi, pie! Tender crust with fruit inside. The filled dessert that is superior to all the other desserts. That pie. From the crust, to the filling, to the presentation, there’s a science to making the perfect pie.

Let’s start with the crust. The best pie crusts tend to be light, crisp, and above all flaky. And the key to making a light, crispy, flaky pie crust? Vodka. Normally, two of the main ingredients in pie crust are wheat flour and water. But wheat flour contains two proteins -- gliadin [GLY-a-din] and glutenin [GLUE-ten-in] -- that can combine to form a delicate pie crust’s worst enemy: gluten.

The proteins combine when they’re exposed to water, and the more you work the dough, the more gluten will develop. Generally, more gluten is a good thing -- if you’re baking bread, that is. Gluten is sticky and elastic, and it makes bread dough chewy. But gluten also makes pie crust tough. So, what you want is a pie crust dough that sticks together enough to roll out properly, but stays flaky.

And replacing about half of the water with vodka turns out to be a great way to do that. Vodka is 40% ethanol, and those proteins that make up gluten won’t dissolve in ethanol the way they do in water. But, since the ethanol still adds moisture, you can still work with the dough. Most -- though not all -- of the alcohol will cook off in the oven, so you won’t end up with a particularly boozy pie crust, just a delicious one.

Then there’s the filling, which you probably don’t want getting all runny and soggy. Problem is, fruit has a lot of water in it, and plant cells tend to break down when you cook them, which lets that water loose inside your pie. One ingredient that can help keep the water from escaping is something that occurs naturally in the fruit itself: a carbohydrate called pectin, which normally helps hold cell walls together. In pie filling, pectin will form a jelly-like mesh that holds water in place. So, more pectin means a thicker pie filling, which in turns means a pie bottom that’s less soggy. For thicker pie filling, you can choose fruits with more pectin, like apples. You can even add an apple to a pie made with low-pectin fruits, like strawberries, for more thickening power. And, a little acid will make pectin stronger and more stable, so some bakers add lemon juice to pie filling. However, heat destroys pectin, so even a pie with lots of pectin can turn to mush if you overcook it.

Finally, you can improve both the look and flavor of your finished pie with what’s known as the Maillard [my-YAHR] reaction -- aka the most delicious chemical reaction of all time. It was named after an early twentieth century French chemist who was trying to figure out how to make proteins. And it’s actually more than just one chemical reaction -- it’s a whole category of them. The Maillard reaction is what happens when proteins react with certain sugars at around 140 degrees Celsius. The reaction can form all kinds of different products, depending on the proteins and sugars involved, but generally, it’s what makes bread develop a crust, and cooked food turn brown. It’s also usually considered something that makes food extra-delicious, and there’s an easy way to help the reaction along in your pie -- or pretty much any pastry, for that matter. All you have to do is brush some egg white over the crust while it bakes. The protein in the egg white will react with sugars in the crust, setting up a Maillard reaction and giving your pie that deep golden brown color.

So, happy pi day everybody, and we hope these tips help you impress your friends. And if you want to spice up your dessert conversation with some facts about the math version of pi, we have a couple of videos that might help as well.

Thanks for watching this special Pi day episode of SciShow, and thanks especially to SR Foxley, our Patreon president of space who helps to make this show possible. If you want to help support this show, just go to And do not you forget to go to and subscribe!