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Cooking Tips

When You Can—and Can’t—Prep Potatoes Ahead

Learn the dos and don’ts for mashes, gratins, and latkes.
By

Published Dec. 21, 2023.

Lots of cooks, including myself, love to peel and slice potatoes ahead of time to make holiday meal prep go more smoothly—but we wondered if there is any downside to doing so.

Associate Editor Erica Turner took it upon herself to find out: She stashed thickly sliced, thinly sliced, and shredded potatoes in water (a common method to prevent them from discoloring) in the refrigerator overnight. The next day, she tested them side by side with fresh potatoes in three different recipes. Heres what she found.

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Do Prep Potatoes Ahead For Mashing

When we used freshly prepared and pre-prepared peeled and thickly sliced potatoes to make mashed potatoes, the two samples looked and tasted identically creamy, buttery, and lush. So, good news: There is no downside to getting a leg up on your mashed potato prep.

Don’t Prep Potatoes Ahead for Gratins and Latkes

Other applications, however, weren’t as successful. When we used the thinly sliced pre-prepared potatoes to make potato gratin, the gratin overflowed in the oven and the consistency was liquidy and loose. And when we used the pre-prepared shredded potatoes to make latkes, the pancakes were more watery and thus spread considerably in the oil and took longer to cook.

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THE BOTTOM LINE: Potatoes soaked in water lose some of their surface starch and simultaneously absorb some of the water. In recipes where the starch is a crucial component, the loss of starch coupled with additional water results in a watered down and incohesive final texture. If you’re making mashed potatoes, an overnight soak in water will still yield ideal results. But for starch-dependent recipes, save the potato prep and cooking for the same day.  

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