All chefs agree: “The best trick to get roasted potatoes crispy on the outside is to add baking soda and semolina.”
Chefs and food chemistry experts agree on the ultimate trick for making roasted potatoes crispy on the outside and tender on the inside: add baking soda to the cooking water and semolina before putting them in the oven.
The method does not depend on vinegar or ice, two popular tricks that do not achieve the same result, but on two very specific chemical reactions on the surface of the tuber.
The technique has become popular among both professional and amateur cooks because it requires no expensive ingredients or special equipment. Simply boil the potatoes in alkaline water before roasting them and cover them with a thin layer of semolina just before baking to achieve a golden crust that stays crispy even as the dish cools.
The chemical effect of bicarbonate and semolina on crispy roasted potatoes
Baking soda alters the pH of cooking water, making it alkaline, unlike tap water, which is usually neutral or slightly acidic. This pH change breaks down pectin, the substance that holds potato cells together, whereas in an acidic environment, pectin hardens and has the opposite effect.
When the pectin breaks down, the surface cells release their starch, which mixes with the hot water and forms a thick mashed layer around each piece. Draining the potatoes and shaking them in the pot breaks down this layer and multiplies the micro-roughness and irregular edges, greatly increasing the surface area in contact with the heat and fat during baking.
Once in the oven, this textured layer quickly loses moisture, and the alkaline environment created by the baking soda further accelerates the Maillard reaction, the chemical process responsible for the browning and toasted flavor. The semolina, added just before baking, creates an additional rough physical barrier that absorbs moisture and oil from the surface, providing a fine crunch that lasts much longer than that of a conventional baked potato.
The step-by-step recipe for crispy roasted potatoes with baking soda and semolina
It's simple to make, but the order of the steps matters as much as the ingredients: skipping the stirring or rushing the baking ruins the final result.
Ingredients
- Potatoes: 1 kilo, preferably of a floury variety or suitable for frying.
- Baking soda: half a teaspoon.
- Fine wheat semolina: one or two tablespoons.
- Extra virgin olive oil: between four and five tablespoons.
- Salt and spices to taste, such as pepper or rosemary.
Preparation of oven-roasted potatoes
Peel the potatoes and cut them into large chunks, about four or five centimeters, so they remain creamy inside. Boil them in plenty of water with a tablespoon of salt and half a teaspoon of baking soda, and cook over medium heat for 8 to 10 minutes, until they are soft on the outside but firm in the center.
Drain them completely and return them to the empty, still-hot pot with the lid on. Shake vigorously up and down several times to break up the outer layer and form a coarse mash around each piece. After letting it rest for two minutes to allow the steam to dissipate, add the olive oil and sprinkle the semolina evenly over it along with the spices, stirring gently to coat the surface.
The potatoes are spread out on a baking tray in a preheated oven at 210 degrees Celsius (410 degrees Fahrenheit), leaving space between them so they don't overlap, and baked for 20 minutes without being touched. Then all the pieces are turned over and baked for another 20 to 25 minutes, until they have a deep golden color and a visibly bubbly texture.
