Speaking of tarte Tatin…

Reader Caitlin wants to know why, when she makes tarte Tatin with tart apples like Granny Smiths, they seem to melt away with heat.

That’s a great question, for as much as I love Granny Smith apples (my grandfather loved to eat them with sharp cheddar cheese) I never recommend them for baking. When it comes to exposing apples to heat you want hard, sweet-tasting apples. Tart apples are better for things like apple sauce.


It all has to do with the behavior of starch molecules, which are abundant in apples. Starches, as you’ll recall from other posts on the subject, are long molecules — chains of sugars — that plants use for structural purposes.

At room temperature these starch molecules are usually quite rigid. But heat them and a funny thing happens: they start absorbing moisture. This has the effect of engorging the apple’s cells, which are bags of mostly water. When that happens the cells blow up, then pop, then collapse, with the result being that the flesh turns to mush. Here it helps to think of potato flesh: very starchy, hard when cold, mushy when cooked. Starchy apples behave in the same way.

Granny Smith apples can be either sweet or starchy depending on when they’re picked. Like all apples, they convert starch to sugar as they ripen. This is a process that begins in the inside of the fruit and works its way outward.

If a Granny Smith is picked too early (which is easy to do since ripe or underripe they’re still green) the starch conversion process won’t be complete and the result will be breakdown as detailed above — but mostly around the outside of the apple slices, which is what gives the impression that the slices are “melting”.

That makes Granny Smiths risky for baking. Not entirely unsuitable mind you, just…risky. So of you go the Granny route make sure to taste one first to make sure it’s not too tart. Otherwise, well, you know what to do.

Oh, and, in case you were wondering, mealiness in an eating apple is also related to moisture and cells, but in that case the cells are leaking water as a result of overripeness. The cell walls are simply breaking down, which likewise causes them to collapse.

Thanks for a great question, Caitlin!

12 thoughts on “Speaking of tarte Tatin…”

  1. On the Tarte Tatin note, EVERY time I make one, I end up with fruit syrup all over my kitchen counter after I flip it. I try to be really good at applying constant pressure during the flip, but it seems like no matter what I do, I have a huge mess to clean up. I flip right after it comes out of the oven. Should I wait longer for the juices to set up? Or do I just need to keep practicing? 🙂

    1. Hey Erin!

      Hm…that’s a bit of a puzzle. Can you direct me to the recipe you’re using? I’m curious.

      – Joe

      1. I wonder if Erin P is baking the tarte tatin in a glass dish? I have noticed that when I do that I also have a lot of liquid. I really like it that way, but it’s true that it’s messier and you get a sort of poached finish on the fruit instead of a sticky caramel.

        1. Interesting observation, Jen. I’ve never tried that, but there may indeed be a difference. Thanks!

          – Joe

          1. I think I know what’s going on, Erin. Pluots like their cousin the plums are very watery on the inside, even more so than an apricot. I think what’s happening is the sugar is drawing out that water, forming a thin syrup, and running everywhere. You shouldn’t have the same issue with apples which are firmer and don’t leech their water as easily.

            Best of luck with the next version!


            – Joe

  2. That’s interesting, Joe, because I so often see the Granny Smith apple recommended for baking. (That and Golden Delicious, which I’m always hesitant to buy, on account of the Red Delicious being so dreadful. Well, to my mouth, anyway.)

    I’m a Cortland fan, myself, but I can buy them from the local orchards. I know they’re not widely available in chain grocery stores.

    I hadn’t thought of the matter of ripeness, though of course it makes sense.

    Thank you.

    1. Hey Ted!

      Granny Smith can be great for baking provided it’s ripe. Personally I think it’s over-recommended these days. A bit of a fad if you ask me. But I’m with you on Red Delicious — yuck. Goldens however are not only better to eat they bake very, very well. I’ll put up a post on baking apples since you brought it up. Thanks!

      – Joe

  3. Great post Joe! Boy did I miss you! The best apple pie I ever made had sweet very crisp apples of three different varieties in it. It was perfect in every way, and now I know why! All is right in my baking world now that Joe Pastry is on the case! Thanks Joe!


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