How to tell if potato is edible?
I'm peeling potatoes and there's a few that have these quarter-sized "tumor" looking like things (see photo). You can't peel them off. I cut them out, each one of the "tumors" are pretty deep. Its slightly black, moldy and the potato is discolored wherever the "tumor" is. Does anyone know what happen to this potato? Is the rest of the potato still edible after you cut out the "tumors"
Yep, the rest of the potato is fine. It's just a rotten spot that came from exposure to too much moisture. As long as you cut out the whole discolored area, you're good to go.
It's rot. If you really want to (have to) use the potatoes cut a generous margin around the bad spots and use the good part... but personally, once a potato has a rotten spot more than a quarter inch across, I bin it. (the tiny spots aren't a problem, they're easy to remove with the point of a knife, but that big one is going to take out nearly half the spud unless it's very very shallow.)