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"What happens to potatoes when they’re cooked?"

Dear Anne and Sue,

Can you tell me what happens to potatoes when they’re cooked?

Solihull, England


Still have more questions? You'll find more answers in our archived monthly feature articles by the Inquisitive Cooks.

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Dear Leonie,

Like other starchy winter vegetables such as squash, potatoes store well because of their low moisture content and thick skins. If the tubers don’t have any blemishes and are stored in a cool place away from light, they can last a long time.

Under a microscope, the starch granules packed inside the potato cells appear as smooth oval shells. When you bake a potato, the starch granules absorb the moisture within the potato. Within the confines of the potato skin, moisture soon turns to steam that expands with great force, separating the starch granules and making a fluffy baked potato. If there’s sufficient pressure, and the skin hasn’t been pierced before baking, the potato may even explode in the oven!
In contrast to oven baking, when potatoes are boiled the starch granules absorb not only the internal moisture but also some of the surrounding water. Extra water contributes to making potatoes gummy when mashed. To avoid this problem, once the potatoes are boiled, drain them well, return them to the pot, cover, and place them back briefly on the warm element to evaporate some of the excess moisture.

When making mashed potatoes, be careful not to mix them too long or too vigorously. This causes the starch granules to rupture and spill their moist starchy contents, resulting in mashed potatoes that are wet and pasty. Some cooks claim that heating milk or butter before adding them to mashed potatoes can make for a more pleasing texture in the finished dish.

Thanks for the question,
Anne & Sue


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