Black apple crumble!
I used the apple crisp recipe from Joy of Baking and I'm quite sure I followed it to the dot (didn't add blackberries, though, only apples). But for some reason, after I took it out, let it cool a little and cut into it, I saw that the apple had turned a strange purple/black color! These were perfectly good (not rotten or bruised) apples that I bought a few days ago. Any reason that this could have happened?
EDIT:
Here's a picture. I managed to salvage this one piece of cooked apple, since I had thrown out the rest of it - sorry for the crappy quality and excuse my face in the background! As you can see, half of it is tinged a strange purple/black!
Best Answer
Walnuts are most likely your culprit. Black walnuts have more of this tendency than common cooking walnuts, but I have had it occur with both. I especially have seen in with port chops stuffed with walnuts and applesauce getting a very purple stain to them. I have seen multiple theories on why purple, but with walnut breads a common suggestion seems to be that iron reacts with the walnut to cause the purple, and some flours are higher in iron than others.
And idea, but just a suggestion, is toasting the walnuts first might reduce this tendency. In fact, here is an article from Cook's Illustrated https://www.cooksillustrated.com/how_tos/6672-preventing-purple-walnut-bread. They indicate that they believe it to be Gallic acid in the walnuts doing it, and that blanching for 1 minute before using them will reduce the effect.
ETA: Looking up Gallic Acid was interesting. It was used as a key ingredient in "Iron Gall Ink" in the 12th through 19th centuries as a standard writing and drawing ink, giving some idea of its ability to color.
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The main reason your crumble topping isn't crunchy is probably because you haven't used Demerara sugar. Although, it could also be that you've got your topping ingredient quantities wrong: either too much or not enough flour and butter alongside the sugar.Why is my apple crumble not crumbling?
Red Delicious, Fuji, Ambrosia, Cortland or Gala apples are perfect. However, if you prefer a more tart crisp, use Golden Delicious or Granny Smith Apples.Stunning Apple Crumble \u0026 Black Forrest Gateau Dessert | MasterChef UK | MasterChef World
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Images: Torsten Dettlaff, energepic.com, cottonbro, cottonbro