Bite into an apple and leave it on the table for a while, and the cut surface will turn brown. Has it gone bad?
Actually, the apple is bandaging itself. The flesh contains a protein called polyphenol oxidase. Normally, it’s kept separate from polyphenols by cell walls, with each in its own space. When you cut into the apple, the cells break, and the two finally meet. Add oxygen from the air, and they quickly react to form a bunch of brown pigments that stain the wound a scab-like color. Bananas, potatoes, and eggplants all work the same way: leave them cut open for a while, and they’ll turn dark too.
That brown layer is useful, too: it makes it harder for microbes to get in, acting like a line of defense for the wound. It’s easy to slow the process down. Squeeze on a few drops of lemon juice—the acidity puts the enzyme out of action. Soak the apple in lightly salted water to keep out the air, or put it in the fridge, where the low temperature will significantly slow the reaction.
Next time you see an apple turn brown, don’t be so quick to judge it—it’s just scabbing over its wound. Do you soak your sliced apples in water first?
Actually, the apple is bandaging itself. The flesh contains a protein called polyphenol oxidase. Normally, it’s kept separate from polyphenols by cell walls, with each in its own space. When you cut into the apple, the cells break, and the two finally meet. Add oxygen from the air, and they quickly react to form a bunch of brown pigments that stain the wound a scab-like color. Bananas, potatoes, and eggplants all work the same way: leave them cut open for a while, and they’ll turn dark too.
That brown layer is useful, too: it makes it harder for microbes to get in, acting like a line of defense for the wound. It’s easy to slow the process down. Squeeze on a few drops of lemon juice—the acidity puts the enzyme out of action. Soak the apple in lightly salted water to keep out the air, or put it in the fridge, where the low temperature will significantly slow the reaction.
Next time you see an apple turn brown, don’t be so quick to judge it—it’s just scabbing over its wound. Do you soak your sliced apples in water first?
