Why do mashed potatoes made from dehydrated granules have a pasty texture?

Mashed potatoes made from dehydrated granules often have a pasty texture because the processing method causes the potato cells to rupture. When these cells break, starch is released, which creates the undesirable pasty consistency upon rehydration.1

In contrast, dehydrated potato flakes are processed using a steam-heated drum drier and include a precooking and cooling treatment, along with the addition of a monoglyceride emulsifier. These steps help the reconstituted product maintain a mealy texture that is more comparable to freshly prepared mashed potatoes.1