Usually, little black stuff on the inside of a mandarin is either mold or a harmless spot from natural breakdown of the fruit tissue. If it looks fuzzy, smells off, or the fruit is soft or leaking, toss it; if it’s just a few tiny spots and the rest looks and tastes normal, the fruit is often still okay to eat.

What it might be

  • Mold growth. Black, gray, or dark fuzzy patches can be mold, especially if the fruit was damaged or stored too long.
  • Natural discoloration. Tiny dark specks can come from stress, bruising, or minor internal browning rather than spoilage.
  • Pest-related residue. On the peel, black marks are sometimes linked to scale insects or sooty mold from insect activity, though that is usually on the outside rather than deep inside.

When to throw it out

  • There is a bad smell.
  • The fruit feels slimy, mushy, or wet.
  • The dark area is spreading or looks fuzzy.
  • The inside tastes sour, fermented, or “off.”

Safe rule of thumb

If the black stuff is only a tiny spot and everything else looks normal, you can often cut that part away. If you’re unsure, the safest choice is to discard the mandarin. TL;DR: small black spots are often mold, bruising, or minor spoilage; fuzzy, smelly, soft fruit should be thrown away.