I helped a caterer friend all day Friday by scrubbing, piercing and wrapping 450 potatoes for a banquet Saturday night. At the banquet I helped serve and my job was to unwrap the potatoes and slice them down the middle for our guests. You can't imagine our horror when we started slicing into the potatoes to discover they were partially black inside. I didn't know why this happened until one of our guests explained that if you pierce a potato with a fork but don't cook it right away, the air goes into those holes and oxidizes the potato. The taters that had been sliced with a thin, sharp knife were perfect. Lesson learned! So, there I stood explaining to 225 guests (we had two potato lines for our potato bar) why the potatoes looked rotten. Most guests were so grateful for the food, others just couldn't get past the look of the Frankenstein spud.
TAKE AWAY: Use a thin, sharp knife to pierce your taters
before you cook 'em! If you don't pierce your potatoes before
you cook them, you run the high risk they will explode in the oven.