The Food Lab: The Science of Pie Dough
Author: J. Kenji López-Alt Managing Culinary Director, The Food Lab, Serious Eats
Link to article
What I'm after: The kind of crust that's substantial enough that it doesn't sog-out from a juicy filling but tender enough that it flakes in your mouth into buttery shards. A crust with substance, but not chew. A crust that divides along deep faults into many distinct layers separated by tiny air spaces and that cracks when bent. A crust that is never leathery or pliant, but not so tender or crisp that it crumbles instead of flakes. And of course, it should have a deep butteriness coupled with a balanced sweet and salty flavor.
Life of Pie
On paper, a classic American pie crust is a mind-bogglingly simple recipe. Combine flour with a bit of salt and sugar, cut in some butter and/or shortening, then add just enough cold water to get it to come together into a disk. Roll it out, and bake. That's it.
Perfectly incorporated butter
The underlying difficulty in the technique comes during the first stage of cutting the butter into the flour. It's simply impossible to accurately cut butter into flour to the same degree on a consistent basis. Don't cut it in quite enough, and you need to add extra water to absorb the excess dry flour, resulting in the over-formation of gluten, and a tough, leathery crust. On the other hand, cut it just bit too far, and you end up with way too little dry flour. Rather than having well-structured flaky layers, you end up with a crust that crumbles into sandy pieces.
Overly-incorporated flour leads to a crust that's short and crumbly
This is the reason why you sometimes need to add a couple tablespoons of water and other times up to twice as much to get the dough to come together—it's got nothing to do with the relative humidity of the air as many books will have you believe. Indeed, in the short time that it takes to make a pie crust, flour will absorb approximately 0.1 percent of its weight in water, even in the most humid of environments. That's a small enough amount to effectively be zero.
So how does the simple action of cutting butter into flour result in layers and layers of flaky pastry? It's all got to do with the balanced interaction of gluten and fat.
How Pie Crust Really Works
To summarize, here's what we've got as we're forming a pie dough: Dry flour, completely uncoated by fat, that absorbs water when you add it, forming gluten that then gets stretched out into wide layers. Pure pockets of fat that will flatten out into long, wide, thin sheets as you roll out your dough, separating the layers of gluten-enforced flour from each other so that rather than forming a solid, leathery mass, they separate and gently puff as they bake. A f lour/fat paste that functions much in the same way as pure fat does. As it bakes, the fat melts and a tiny amount of individually separated flour bits will deposit themselves and become incorporated into the gluten-enforced layers. And if this flour/fat paste functions similarly to pure fat, doesn't that imply that we can completely replace the pure fat with this paste? Indeed, we can.
Why Do I Care?
So it's all very interesting, but the question here is, why should you care? How does this make forming pie crust any easier?
In two ways. First off, it completely removes the variability of a traditional pie crust recipe. By measuring out a given amount of flour and fat and combining them together until they form a near homogeneous paste and then adding the remaining dry flour to that paste, you are very strictly defining exactly how much flour is used for gluten formation and how much ends up coated with fat. No more trying to visually judge whether your fat is properly cut. No more adding ice water a drop at a time until a dough is formed. The dough comes out the same, every single time.
The other key advantage is that your dough becomes much more pliable. The fat/flour paste formed at the beginning is much softer and more malleable than pure butter is, which means that your final dough rolls out smoothly and easily with little to no risk of cracking like a traditional pie crust.
Tips To Perfect Pie Crust
Finally, let me offer you a few tips to make the most out of your crust, no matter what recipe you decide to use.
1. Weigh Your Flour
Get yourself a scale, then do yourself a favor and throw out your dry measuring cups. Honestly. Do it. You will not regret it. Weighing dry ingredients by volume is simply not accurate. Depending on how tightly packed it is, the weight of a cup of all-purpose flour can vary by as much as 50 percent. 50 percent!!!. No such problems with a scale. Five ounces of flour (the equivalent of one cup) is five ounces of flour, no matter how tightly it's packed.
2. Use a Food Processor
If there's one reason to own a food processor, it's to make pie crust. Nothing is as efficient or as consistent at cutting fat into flour. A stand mixer will do the job reasonably well; a pastry cutter will, too, though it requires much more work. You can even get a decent crust using just your fingers. But if you've got the processor, use it.
3. Keep Everything Cold
Just like with grinding meat, the key to great pie crust is to make sure that your fat doesn't melt too much. If your home is too hot, make sure that you re-chill your dough as you work with it. In the summer with my oven on, the apartment pushes 80°F. Under these conditions, I'll put my dough back in the fridge for ten minutes immediately after incorporating the fat, for at least 2 hours after forming the dough into a disk and wrapping it, and for another 10 minutes after draping it in the pie plate before trimming and fluting the edges.
The temperature of your water has less of an effect than people lead you to believe. A couple tablespoons of warm water won't significantly chill a pound or two of butter and flour. Still, it doesn't hurt to use cold water or even ice water.
4. Use a Spatula to Incorporate Water
Your processed flour and butter are sitting there in the bowl of your food processor and you're tempted to save yourself a bit of cleanup by just adding the water directly in there, right? Don't do it! Sure, it'll work out ok, but you won't form nearly the same level of flakiness as you do if you incorporate with a spatula.By using the spatula to fold the water into the crust, you give flaky layer formation a head-start even before you pull out the rolling pin.
5. Use a Tapered Rolling Pin
While the ball-bearing-based heavy-duty cylindrical rolling pin might be better for whacking husbands over the head in cartoons or fitting into Norman Rockwell paintings, the slender, slightly tapered French-style rolling pin offers far more control, is easier to clean and store, and is cheaper to boot.
Recipe
Author: J. Kenji López-Alt Managing Culinary Director, The Food Lab, Serious Eats
Link to article
What I'm after: The kind of crust that's substantial enough that it doesn't sog-out from a juicy filling but tender enough that it flakes in your mouth into buttery shards. A crust with substance, but not chew. A crust that divides along deep faults into many distinct layers separated by tiny air spaces and that cracks when bent. A crust that is never leathery or pliant, but not so tender or crisp that it crumbles instead of flakes. And of course, it should have a deep butteriness coupled with a balanced sweet and salty flavor.
Life of Pie
On paper, a classic American pie crust is a mind-bogglingly simple recipe. Combine flour with a bit of salt and sugar, cut in some butter and/or shortening, then add just enough cold water to get it to come together into a disk. Roll it out, and bake. That's it.
Perfectly incorporated butter
The underlying difficulty in the technique comes during the first stage of cutting the butter into the flour. It's simply impossible to accurately cut butter into flour to the same degree on a consistent basis. Don't cut it in quite enough, and you need to add extra water to absorb the excess dry flour, resulting in the over-formation of gluten, and a tough, leathery crust. On the other hand, cut it just bit too far, and you end up with way too little dry flour. Rather than having well-structured flaky layers, you end up with a crust that crumbles into sandy pieces.
Overly-incorporated flour leads to a crust that's short and crumbly
This is the reason why you sometimes need to add a couple tablespoons of water and other times up to twice as much to get the dough to come together—it's got nothing to do with the relative humidity of the air as many books will have you believe. Indeed, in the short time that it takes to make a pie crust, flour will absorb approximately 0.1 percent of its weight in water, even in the most humid of environments. That's a small enough amount to effectively be zero.
So how does the simple action of cutting butter into flour result in layers and layers of flaky pastry? It's all got to do with the balanced interaction of gluten and fat.
How Pie Crust Really Works
To summarize, here's what we've got as we're forming a pie dough: Dry flour, completely uncoated by fat, that absorbs water when you add it, forming gluten that then gets stretched out into wide layers. Pure pockets of fat that will flatten out into long, wide, thin sheets as you roll out your dough, separating the layers of gluten-enforced flour from each other so that rather than forming a solid, leathery mass, they separate and gently puff as they bake. A f lour/fat paste that functions much in the same way as pure fat does. As it bakes, the fat melts and a tiny amount of individually separated flour bits will deposit themselves and become incorporated into the gluten-enforced layers. And if this flour/fat paste functions similarly to pure fat, doesn't that imply that we can completely replace the pure fat with this paste? Indeed, we can.
Why Do I Care?
So it's all very interesting, but the question here is, why should you care? How does this make forming pie crust any easier?
In two ways. First off, it completely removes the variability of a traditional pie crust recipe. By measuring out a given amount of flour and fat and combining them together until they form a near homogeneous paste and then adding the remaining dry flour to that paste, you are very strictly defining exactly how much flour is used for gluten formation and how much ends up coated with fat. No more trying to visually judge whether your fat is properly cut. No more adding ice water a drop at a time until a dough is formed. The dough comes out the same, every single time.
The other key advantage is that your dough becomes much more pliable. The fat/flour paste formed at the beginning is much softer and more malleable than pure butter is, which means that your final dough rolls out smoothly and easily with little to no risk of cracking like a traditional pie crust.
Tips To Perfect Pie Crust
Finally, let me offer you a few tips to make the most out of your crust, no matter what recipe you decide to use.
1. Weigh Your Flour
Get yourself a scale, then do yourself a favor and throw out your dry measuring cups. Honestly. Do it. You will not regret it. Weighing dry ingredients by volume is simply not accurate. Depending on how tightly packed it is, the weight of a cup of all-purpose flour can vary by as much as 50 percent. 50 percent!!!. No such problems with a scale. Five ounces of flour (the equivalent of one cup) is five ounces of flour, no matter how tightly it's packed.
2. Use a Food Processor
If there's one reason to own a food processor, it's to make pie crust. Nothing is as efficient or as consistent at cutting fat into flour. A stand mixer will do the job reasonably well; a pastry cutter will, too, though it requires much more work. You can even get a decent crust using just your fingers. But if you've got the processor, use it.
3. Keep Everything Cold
Just like with grinding meat, the key to great pie crust is to make sure that your fat doesn't melt too much. If your home is too hot, make sure that you re-chill your dough as you work with it. In the summer with my oven on, the apartment pushes 80°F. Under these conditions, I'll put my dough back in the fridge for ten minutes immediately after incorporating the fat, for at least 2 hours after forming the dough into a disk and wrapping it, and for another 10 minutes after draping it in the pie plate before trimming and fluting the edges.
The temperature of your water has less of an effect than people lead you to believe. A couple tablespoons of warm water won't significantly chill a pound or two of butter and flour. Still, it doesn't hurt to use cold water or even ice water.
4. Use a Spatula to Incorporate Water
Your processed flour and butter are sitting there in the bowl of your food processor and you're tempted to save yourself a bit of cleanup by just adding the water directly in there, right? Don't do it! Sure, it'll work out ok, but you won't form nearly the same level of flakiness as you do if you incorporate with a spatula.By using the spatula to fold the water into the crust, you give flaky layer formation a head-start even before you pull out the rolling pin.
5. Use a Tapered Rolling Pin
While the ball-bearing-based heavy-duty cylindrical rolling pin might be better for whacking husbands over the head in cartoons or fitting into Norman Rockwell paintings, the slender, slightly tapered French-style rolling pin offers far more control, is easier to clean and store, and is cheaper to boot.
Recipe