Cooks turn to low-starch, or waxy, potato varieties when they need the potatoes to keep their shape. If you've ever churned out a mushy bowl of potato salad or served dry, gritty roasted potatoes, you've likely learned the novice cook lesson that not all potatoes are created equal. Different varieties contain different levels of starch and moisture, which give them different densities, textures and flavors.
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Low-Starch Potato Qualities
Low-starch potatoes, also called waxy potatoes, are high in moisture and have a low starch content, which helps them keep their shape. Think of low starch vs. high starch as the difference between firm and fluffy. When you bake a high-starch potato, you get a light, fluffy baked potato that you can easily break apart with your fork. When you bake a low-starch, or waxy potato, you get that firm, roasted potato texture.
When Low-Starch Potatoes Work
Low-starch potatoes really shine in dishes where a firm texture matters. For example, when you use low-starch potatoes in soups or stews the potato chunks will keep their shape without getting mushy. High-starch potatoes tend to fall apart or get too soft when boiled. Low-starch potatoes also work best in gratins and scalloped potatoes, which require the potatoes to remain firm. Perhaps the most popular dish that calls for a tuber low in starch, or a waxy potato, is potato salad.
Some Low-Starch Potato Varieties
If you're not sure what kinds of potatoes are low or high in starch and they're not labeled, red-skinned potatoes are a safe bet. Most varieties of red potatoes have a low to medium starch content. Popular varieties include red thumb, French fingerling, Ida Rose and red la soda.
The brown-skinned Russet potatoes you see in abundant supply at most grocery stores have a high starch content. Sweet potatoes are also starchy. Yellow potatoes such as Yukon gold and and some red varieties such as Norland red have medium starch contents and work well in many dishes.
How to Tell It's Low in Starch
If you purchase loose or unlabeled potatoes and you're not sure if they're waxy potatoes, there's an easy trick for determining starch content. Cut one of your potatoes in half using a knife with a broad blade. Starchy potatoes leave a gritty white starch residue on your knife. Your potato will also stick to your knife. If you slice through the potato and your knife looks clean, you likely have a low-starch potato. Low-starch potatoes also slide off the knife more easily and stick less.