How do roast potatoes stay so hot for so long? © Getty Images

How do roast potatoes stay so hot for so long?

The science behind your burnt mouth during Sunday roasts.

It’s mostly to do with the fatty, starchy crust that acts like an insulating layer. First, pre-boiling a potato causes its starch granules to absorb water and swell until carbohydrate molecules seep out to create a kind of thick gel.

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The high temperature in the oven then drives off moisture, causing the gelatinised starch on the outside of the potato chunks to form a crispy crust, trapping the heat inside. The fat from the baking tray also collects in cracks and crevices and strengthens the heat-keeping structure.

Asked by: Sarah Fullerton, London

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