Q. Why do shredded potatoes turn gray?

By Kathleen Purvis

Q. Why do shredded potatoes turn gray?

A. It depends on whether your potatoes are turning gray before you cook them or after.

When you grate raw potatoes, you release starch that can cause them to oxidize, or turn dark. The best way to keep that from happening is to cover the potatoes with cold water, then drain them very well and pat them dry before cooking.

A trick I have heard from Jewish cooks who make latkes every year is to shred the potatoes together with onions, which is supposed to minimize the darkening of the potatoes. But you’d have to decide how you feel about onion in your shredded potato dish.

What’s really frustrating are potatoes that turn dark after cooking. That’s a reaction that can have several causes, including how the potatoes were grown or a reaction with aluminum cookware. It doesn’t happen with all potatoes, and it can be hard to predict.