Parboiling and roughing up
Also searched as: roast potatoes, parboiling, crispy roast potatoes, baking soda trick
In short: Parboil potatoes briefly in slightly alkaline water and shake them in the pot. The rough, starchy surface turns into a thick crust in the oven.
Like sandpaper instead of glass: a rough surface has many more spots that can turn crisp.
What happens
The makes the water slightly alkaline. That loosens the glue between the outer cells faster; the edge turns soft while the core stays firm. When shaken, the edge rubs into a starchy mash that coats every piece. In the hot oven this mash dries into a crisp, craggy crust.
Why it matters
This is the opposite of soaking and still works. Both routes control starch and water on the surface, just with a different goal: a thin, smooth crust or a thick, craggy one.
How it’s done
Cut the potatoes into large pieces and start them in cold, well-salted water.
All steps as a list
- Cut the potatoes into large pieces and start them in cold, well-salted water.
- Add about ½ tsp baking soda per 2 litres of water.
- Simmer until a knife slides easily into the edge but the core still resists.
- Drain and let them steam dry for 1–2 minutes.
- Shake hard in the pot with hot fat until the edges are rough and mushy.
- Spread out on the preheated tray and roast at 220 °C, turning once.
Rules of thumb
- Let them steam dry: wet potatoes do not roast.
- Better too little baking soda than too much, or it turns soapy and mushy.
Common mistakes
1
- Parboiled too long: the pieces fall apart completely when shaken.
Sources · 2
- Food52 Genius Recipes: Kenji López-Alts Ofenkartoffeln mit Natron
- Harold McGee: On Food and Cooking (2004), Kapitel Kartoffeln, Stärke, Frittieren