the storage parts of the plant. About 80 % of a potato is starch, and therefore potato cells are very
densely concentrated in starch granules. On cooking in water, these starch granules take up water
and swell, causing the potato to increase in volume. As the starch granules gelatinise, the potato
becomes digestible. Raw potatoes are unique in being one of the few vegetables that cannot be eaten
raw – their high quantity of ungelatinised starch in their raw state can not be digested easily be the
bodies digestive enzyme amylase. Also, because of its high starch content, potatoes tend to become
dry, tough and less digestible. This is because the network of starch molecules becomes stronger and
tougher over time, and this tends to squeeze water out of the network.
Different potato varieties differ in particular in their overall starch contents, and this is why different
potato varieties are used for different food preparations. Potatoes with a low starch content are known
as “waxy”, and include red and white potatoes. The potatoes do not absorb as much liquid during
cooking, and therefore the potato structure is less affected and the potato hold its shape much better.
They are therefore the preferred choice in gratins, boiled potatoes and potato salad, where the potato
needs to keep its shape.
“Floury” potatoes, however, have a much higher starch content. The starch granules in their cells
therefore absorb much more water, and cell structure is much more likely to be disrupted, producing a
fluffy texture. These potatoes are therefore the best choice for mashing, baking or frying, where a
softer texture is desired.
On top of the damage caused to the cells on cooking, when the potato is mashed or riced, the cells
are broken open even more, releasing more starch, which acts to thicken the added liquid (usually
milk) which makes the potatoes creamy and smooth. If waxy potatoes were used, much less starch
would be released during mashing to thicken the liquid, to the same smooth texture can not be