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[Photographs: J. Kenji Lopez-Alt]

Back in July, I wrote an article that tackled the basics of pie crust. Which is useful, for sure, but a pie without filling is, well, sort of like a bathtub without water in it: boring and functionless. Turns out that that article was merely the start of a three-part epic on pie.

So for the next two week's worth of articles here at the Food Lab, we're going to talk apple pie filling. This week, we'll start by figuring out exactly which apples make the best filling and why, then next week, we'll figure out the best way to cook them. Capice?

First off, an admission: I'm not much of a sweets person. Would I rather eat apple pie, or pizza pie? I often ask myself. You can guess what I reward myself with for answering that question correctly.*

*Okay, I'll tell you: it's pizza.

But just about now is the one time of year that I genuinely look forward to baking pies, if only because I truly love apple picking and need some way to get rid of all the excess apples I inevitably bring home. Being allergic to the raw fruit and having a wife who thinks that non-tropical fruits are not worth her time, they usually end up in baked desserts.

Thing is, if you think that making an apple pie is as simple as picking any old apple up from the orchard or the supermarket, chopping it up, tossing it with some sugar, cinnamon, perhaps a bit of cornstarch or flour to thicken up its juices and baking it, well, then I can only assume that you've probably ended up baking a few bad pies in your lifetime—I know that I have.

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Some apples just don't make good pies. They're too sweet, too mealy, too tart. They disintegrate when you cook them, they release too much liquid, they just taste funny.

Like burgers and pizza, I believe pie to be one of the truly perfect foods. A culinary endpoint that can be improved incrementally, but not fundamentally. The true beauty of a pie comes from that magical interaction between crust and filling. One sweet, tart, and fruity, the other buttery and rich, they complement each other in flavor and texture and create a dish that is so much greater than the sum of its parts. As such, each part deserves respect.

What I want in my apple pie filling is first and foremost apples that are completely tender, yet stay in distinct chunks with just a bit of al dente bite to them. Apples that turn to mush or worse, are mealy can ruin a good pie for me. I want those apples to be bound together with just a bare hint of a shiny glaze—not a torrent of juice that soaks the bottom crust or a sauce so thick that it become gloppy (if you want that, you can get it at McDonald's, two for $1). It should be sweet but never cloying with a bare hint of cinnamon—this is an apple pie, after all, not a cinnamon pie. Finally, it should taste overwhelmingly of fresh apples with a bright, clean flavor.

I rolled up my sleeves, made a few dozen batches of pie crust, then headed into the kitchen for some serious baking.

Apple Picking

I started with two batches of ten pies each, using ten of the most common apple cultivars widely available in the United States. My apologies if your favorite apple type was left off this list. With over 7,500 known cultivars of apples, it's absolutely impossible to test every single one of them.

I figured with these ten varieties, I should be able to find at least one that is available to everyone in the United States (you overseas readers'll have to do this research on your own).

Here's what I tried:

  1. Braeburn
  2. Cortland
  3. Empire
  4. Fuji
  5. Golden Delicious
  6. Granny Smith
  7. McIntosh
  8. Red Delicious
  9. Rome
  10. Royal Gala

To test them, I weighed out identical batches of each apple, cut them into quarter-inch thick slices, and tossed them with sugar, just a touch of cinnamon, and a bit of cornstarch to thicken their juices. I purposely left the cinnamon level very low and left out any other flavorings like vanilla or lemon juice in order to make sure that the apple flavor came to the forefront of each pie.

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After baking them all off, I allowed them to cool and rest at room temperature for 8 hours before tasting them to ensure that all of them had cooled down completely.

Color Coding

The array of textures and flavors that emerged was truly remarkable—even more varied than the differences between raw apples. Some, like Granny Smith and Empire were great at keeping their shape, resulting in the tender-but-firm chunks I look for in good apple pie. But Granny Smith is too tart and Empire is too sweet. Other apples showed the opposite problem—decent flavor, but lacking in texture.

Unfortunately, I didn't find a single apple that was completely successful both in terms of flavor and texture.

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But there was an interesting phenomenon I noticed when I accidentally left out a few bags of sliced apples for a bit too long:

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I noticed as the apples were sitting that depending on the variety, they browned to a different degree. Some, like Red Delicious, turned dark brown almost immediately. On the other hand, even after several hours, Granny Smiths showed only a hint of browning.

I arranged the apples on a plate in order of level of browning.* What immediately struck me was that the least tart apple—the Red Delicious—was all the way at one end, while the most tart apple—the Granny Smith—was all the way at the other end.

*Note: the order they are arranged in is by level of browning relative to their original color, which is why some appear to be out of order in the photograph.

This makes sense: acid can inhibit the browning oxidation reactions that take place in fruit flesh when it is exposed to the air. For this same reason, cooks will store trimmed artichokes in acidulated water—it prevents browning.

But what does this mean for my fillings?

Well, there's another thing that acid does: it strengthens pectin, the cement-like glue that holds together the cells of fruit. So looking at this arranged spectrum of apples is actually a pretty good indication of how well each fruit is going to hold up during baking. The further right along the browning scale, the firmer the apple should be in the finished pie.

After arranging the pies in this same order and examining their fillings, turns out that indeed, it is true. As you can see in the photos, the pies start off with very mushy fillings that get progressively firmer.

Here are all of my tasting notes. Afterwards, I'll discuss how flavor is a factor.

Red Delicious

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Flavor: Very sweet and one-dimensional.
Texture: Mealy flesh that turns to mush when cooked. Skin is thick and can be quite bitter. They may look good on the supermarket shelf for a long time, but are only really tasty when fresh picked.
Pie Rating (1-10): 1; Completely mushy with a very one-dimensional, cloying flavor. This reminded me of bad applesauce.
Best uses?: Eating out of hand, but only when very fresh.

McIntosh

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Flavor: Sweet and mildly tart with very white flesh.
Texture: Tender and slightly grainy.
Pie Rating (1-10): 3; it holds up better than, say, Red Delicious in pies, but still turns quite brown and mushy.
Best uses?: Apple sauce or eating out of hand.

Braeburn

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Flavor: Very sweet and mildly tart with a unique citrusy aroma, similar to Granny Smith (of which it is a descendent). It becomes almost pear-like in flavor when it cooks.
Texture: Quite crisp and not much graininess. This texture seems to indicate that indeed it has a fairly strong structure of pectin.
Pie Rating (1-10): 7; it manages to soften fully while still retaining a good deal of texture when baked into an apple pie due to its density. It could be slightly firmer when baked. Great golden color.
Best uses?: Pies, tarts, sauce, eating plain.

Rome

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Flavor: Very mild when eaten out of hand, not very sweet, but develops in flavor when cooked.
Texture: They have a thick skin and very firm flesh. Despite having a reputation as being a good baking apple, I found them unsuitable.
Pie Rating (1-10): 3; They turn dark brown and mushy as they baked.
Best uses?: Sauce.

Fuji

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Flavor: Quite sweet and fresh tasting, not cloying.
Texture: Crisp flesh that stays good for a long time. The texture is almost pear-like in its moisture level and crunchiness.
Pie Rating (1-10): 2; The mild flavor does not get enhanced by baking. Watery but tart.
Best uses?: Eating out of hand.

Golden Delicious

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Flavor: Sweet, tart, and almost buttery. Well balanced and rich, especially when cooked.
Texture: Very fresh it's quite crisp, but can border on mealy when held for too long off the tree. When baked, it softens but retains a bit of texture
Pie Rating (1-10): 8; the best flavor I got out of any single apple—this is what apple pie should taste like. I just wish it were slightly firmer.
Best uses?: Pies, sauce, apple butter.

Cortland

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Flavor: Similar to a McIntosh, but much sweeter and tarter. Like its cousin, it's got very white flesh and a mild flavor.
Texture: Tender and slightly grainy,
Pie Rating (1-10): 4; it does quite well in pies texturally—softening without breaking down—but lacks in flavor.
Best uses?: Apple sauce or eating out of hand.

Empire

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Flavor: Very sweet and very tart with a good level of juiciness, they are a cross between a McIntosh and a Red Delicious, and show flavors from both.
Texture: Despite their tender/grainy ancestry, their texture is quite firm and crunchy.
Pie Rating (1-10): 3; when baked, they have nice texture, but become cloyingly sweet. The acid is still present, but it's not enough to fight against the sugar level.
Best uses?: Eating out of hand.

Gala

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Flavor: Mild and sweet with a fair amount of tartness, they're one of the most popular apples around for their small size and good resistance to bruising.
Texture: Very thin-skinned with a grainy texture.
Pie Rating (1-10): 6; when baked, they hold their shape, but the graininess can get overwhelming. I prefer my pie apples to be supple and smooth-textured.
Best uses?: Eating out of hand.

Granny Smith

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Flavor: Very bright and tart with a distinct citrus aroma and white wine-like nose. Texture: Very firm, crunchy, and slightly grainy.
Pie Rating (1-10): 5; it holds up almost indefinitely when cooking. They have good brightness, but not much apple-y flavor.
Best uses?: Eating out of hand.

Now some very astute readers might have noticed the one glaring exception here: Braeburns are low in acid, yet remain relatively firm as they bake. Why is this?

It all has to do with air. Braeburns are relatively dense apples with not much air in between their cells. (You can see this by dropping them into a bucket of water next to say, a McIntosh. Braeburns will float up much more slowly.) Apples with lots of air will collapse on themselves like a deflating ballon as they cook. Very dense apples—like Braeburns—will retain their shape better, even as they completely soften.

So as you can see, for the most part texture certainly does improve with more tartness, but good texture along does not a good pie make.

Some folks suggest mixing two varieties of apple—one to provide texture, the other for flavor—but this never made sense to me. Say we combine some Granny Smiths with some Romes. What you end up with is a pie that's got nice firm chunks of apple interspersed with brown apple mush. It's like replacing every third model in a runway show with a Vogon. The models are still there, but you're too distracted by the gross stuff to be able to enjoy the nice stuff at all.

Nope, a single apple would have to do it for me, and the best ones in the running are the Golden Delicious and the Braeburn. They're the ones I use for all of my baking purposes.

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Now, the question is, since both Golden Delicious and Braeburns have great, well-balanced flavor, but neither is quite firm enough when baked, is there something I can do to improve upon their texture?

Indeed there is, and this article is riddled with hints on how to do it. Unfortunately, we've run out of time today, and will have to get to the final installment in our pie-athon next week.

A Last Word On Freshness and Seasonality:

You may think that the whole "local, seasonal" movement is getting a bit out of hand, and oftentimes, I tend to agree. But there are certain foods for which it truly makes sense. Apples for pies are one of them

See, if you aren't buying apples directly from the orchard or picking them yourself in the fall, chances are that they've been in long term storage. Apples are stored in atmospherically controlled rooms for up to 10 months before being put on supermarket shelves. This holding wreaks havoc with their cell structure, causing them to ripen at a vastly increased pace once they're taken out of storage.

This means that if you buy an apple from the supermarket in, say, June, most likely that apple was picked last October. Within a day or two, it goes from being crisp and bake-able to mushy and unsuitable for pies.

My advice? Don't bake apple pies except in the fall and early winter. If you absolutely must have that spring or summer pie, look for apples that are refrigerated and get them into your own refrigerator as soon as possible. Do not let them sit at room temperature for too long before cooking them.

As for what to do with the leftovers of 20 pies? If you ask me nicely, I might share with you a great way to make friends with your neighbors.

About the author: J. Kenji Lopez-Alt is the Managing Editor of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.

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