Why do shredded potatoes turn black?

Why do shredded potatoes turn black? Can I do something to prevent this? How can I pre-make my potato pancake mix then bring to a party to cook? I tried this last christmass, but ended up with something that looks like tar.

Short story: they’re oxidizing. I don’t understand exactly what is oxidizing, or what have you, but I’m sure someone will. You can put lemon juice on your shredded taters to keep them fresh.

It’s not really oxidation. Potatoes and fruit will go black if they are damaged and never exposed to oxygen as anyone who has ever eaten a ‘bruised’ apple will know.

The actual biochemistry is quite complex, but the shortened version is that once the cells are ruptured they release chemicals that produce melanin. Melanin is a natural antibiotic and the process has evolved to prevent microbes from attacking the wound before it heals. Of course melanin is a dark pigment, the same one that makes humans and other animals black. Not surpsingly it also makes your potatoes turn black.

How to stop it? You can’t really I don’t think. Every cell that you destroy will release the chemicals and produce the black pigment, and by grating and mashing the potato you destroy pretty much every single cell. There are some varieties of potato that have been bred to not manufacture as much of the required chemicals, but with the amount of damage you are doing I think even they would go black.
You could try adding some proteolytic meat tenderisier. That might work to destroy the potato enzymes before they have a chance to work. But that’s just a suggestion. Or you could try blanching the mashed potates to denature the enzymes. That should work but getting the timing right could be tricky. trial and error time.

Generally, the advice to prevent this is to keep the potatoes in ice water. Oxygen is definitely part of the process, and by keeping things away from it (and slowing chemical reactions by keeping it cold), the process will be stopped.

Ask Jeeves replied with:COOKING NOTES:

POTATO CHIPS.–The potatoes must be pared raw and cut in long pieces; put them into water, or they will turn black; then in a cloth to dry. Shake a little flour over them, and be sure to have the lard quite hot, otherwise they will boil instead of crisping. Before dishing up, sprinkle a little salt over the chips.

I never saw a potatoe turn black in all my life. My grandmother, mother, and wife always peeled and cut up potatoes into a pan of cold water.

In your case shred the potatoes into cold water, rinse well. Take them to party in water. Drain and blot dry prior to use. Take a trial run on the procedure today!

McGee’s “On Food and Cooking” has the following notes: