Why Cold French Fries Taste So Gross

Science Explains Why Cold French Fries Taste So Bad

Cold french fries get soggy and taste nasty because water from the potatoes migrates to the surface. This makes the coating soft and the inside grainy.
Cold french fries get soggy and taste nasty because water from the potatoes migrates to the surface. This makes the coating soft and the inside grainy. Andy Crawford / Getty Images

Fresh, hot french fries are golden, crispy deliciousness, yet cold fries are limp, grainy, and disgusting. How can changing the temperature turn fries from crave-worthy to cringe-worthy? Science has the answer and it's all about starch and water.

Perfect Fries— A Marriage of Starch and Water

Potatoes are mostly starch, which is a carbohydrate polymer. When you cook fries, the starch swells with water.

The inside of the fry puffs up into tender, tasty goodness. Meanwhile, the processes of carmelization and the Maillard reaction turn the exterior of the fry into golden, flavorful crispness.

When french fries cool down, they keep the golden color and the browned flavor, but the water that was on the inside migrates to the outside. This makes fries soggy on the outside, while the inside turns coarse and gritty.

There's no going back. If you've ever tried reheating fries, you know you can bring them back to a semblance of their former glory, but they'll never be quite as good. A lot of the water is gone, never to return to the inside of the fries. This is why frozen partially-cooked fries come coated with a thin layer of ice (and also why soaking cut potatoes in water yields amazing fries).

Temperature and French Fry Flavor

Temperature also plays a part, particularly with respect to flavor. Warm food has more flavor than cold food because the chemical reactions that enable you to taste food occur more rapidly (up to a point) at a higher temperature.

Temperature also affects how readily molecules enter air so that you can smell them. Since the senses of taste and smell are closely aligned, you taste hot foods more because you can smell them better.