BBC Science Focus

WHY DOES PORRIDGE GO SO HARD WHEN IT DRIES?

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Simple: oats are up to 60 per cent starch, which is a thickening agent. Starch is a carbohydra­te that forms granules made from polymers called amylose and amylopecti­n. When you cook oats in water or milk, the starch granules swell to absorb liquid and the porridge starts to thicken.

When porridge cools, the amylose and amylopecti­n polymers become less energetic. This means they interact with each other to expel water and form a stronger scaffold. And, as the freed water evaporates, the porridge hardens.

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