The cut surfaces of potatoes brown when the enzyme tyrosinase comes into contact with air, which water submersion prevents. But you can take this enzymatic browning out of the equation altogether with the addition of an acid or salt in the water or by blanching the potatoes.
Don't store potatoes in water longer than overnight, or eight to 12 hours. After that, the potatoes start to develop a slight sweet flavor and their structure weakens – good for mashing, bad for frying and roasting.
Stopping Enzymatic Browning
Water minimizes the air contact that causes browning, so if you need to store the spuds from the time it takes you to slice until you cook them only, you're good to go. Also, if you plan on boiling the potatoes, by all means, store them overnight in water in the refrigerator and rinse them before cooking; the potatoes will get waterlogged when you boil them anyway. But if you need to keep the potatoes for more than an hour or two before cooking them, either blanch them for 1 to 2 minutes in boiling water and store them dry in a covered container, or treat them with saltwater and store them dry and in a covered container.
Saltwater Treatment vs. Acidulated Water
You'll find no shortage of internet chefs who suggest storing potatoes in water with a little lemon juice, citric acid, ascorbic acid or vinegar in it, to prevent browning. True, acidulated water does inhibit enzymatic browning – but not without sacrificing the potatoes' taste and texture.
Concentrated acids like citric and ascorbic often prove too overpowering for the amount of water used to store potatoes. If they soak too long, they take on too much of an acidic flavor; if they don't soak long enough, or if you use a small amount of acid to prevent flavor alteration, their browning prevention decreases. So what's a spud lover to do when she wants to prep the night before but doesn't want to sacrifice quality? She uses salted water.
A simple 10-minute soak in a mixture of 1/2 teaspoon of kosher salt and 1 cup of water prevents browning for much longer than acidulated water, and it won't saturate the potatoes or leave a salty aftertaste. The amount of salt and water you need varies with the amount of potatoes you have, but if you follow the 1/2 teaspoon salt-to-1 cup water ratio (or 4 teaspoons of kosher salt per 1/2 gallon of water), you can't miss.
After soaking the potatoes in saltwater, rinse them to remove any salt residue and let them air dry. Store the potatoes up to 12 hours in an airtight container in the refrigerator.
- Place a paper towel on top of the water surface after you add the potatoes. The water won't cover the potato pieces that float to the surface, but a wet paper towel will.
- Store potatoes up to 12 hours in plain water if you plan on boiling them.
- Blanch the potatoes for 2 or 3 minutes or treat them with saltwater for 10 minutes and store them dry in an airtight container in the refrigerator for 12 hours if you're going to fry or roast them.