I started cutting a white sweet potato. But within minutes an area on the outside of the potato started turning black/brown. Other sides of the cubed chunks didn't seem as affected. Here's a photo with the black and better bits separated. Even the good ones were rapidly browning and oxidizing in a speckled fashion.

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  • 2
    Does this answer your question? Sweet Potatoes going black when peeled
    – Luciano
    Dec 14, 2020 at 10:00
  • Not entirely. I suspect the more subtle browning was just oxidization, but the darker black spots were more pronounced than anything I can find an example of.
    – pnewhook
    Dec 14, 2020 at 13:51
  • it happens to me all the time when cutting sweet potatoes. I've been steaming / roasting them whole whenever I can, it seems to avoid the issue.
    – Luciano
    Dec 15, 2020 at 10:26

1 Answer 1


It is, as you said, oxidation. As soon as you cut them, put them in a bowl under water. Kills the oxygen supply/reaction.

  • I am not sure if this case falls under the standard explanation - why is it happening only on one corner of the cubes, and "within minutes"?
    – rumtscho
    Dec 14, 2020 at 12:43
  • 1
    The corner of the cubes where the most black appears looks like the part of the potato closest to the peel, which means those parts have been exposed to air longer than the sides of the cube that were just cut. Plus there may be slight chemical/physiological differences in the vegetable matter closest to the peel compared to deeper inside the potato.
    – csk
    Dec 14, 2020 at 16:54

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