What causes black spots on frozen French fries?

<p>Black spots are usually bruises which are caused by rough handling. One type of bruising happens when the skin is broken. The potato forms a thicker layer of skin to protect and/or heal the wound.&nbsp;</p> <p>The second type of bruising shows up just under the skin or deeper inside the potato as a blackspot. This happens when potatoes are dropped more than six inches or something heavy is placed on top of them.&nbsp;&nbsp;</p>