Do not wash potatoes before you store them nor store them in the refrigerator; damp-
ness encourages the growth of molds.
Preparing This Food
Discard potatoes with green spots, sprouting eyes, or patches of mold on the skin, and scrub
the rest with a stiff vegetable brush under cool running water. When you peel and slice pota-
toes, throw out any that have rot or mold inside.
Don’t peel or slice potatoes until you are ready to use them. When you cut into a potato
and tear its cell walls you release polyphenoloxidase, an enzyme that hastens the oxidation
of phenols in the potato, creating the brownish compounds that darken a fresh-cut potato.
You can slow this reaction (but not stop it completely) by soaking the peeled sliced fresh
potatoes in ice water, but many of the vitamins in the potatoes will leach out into the soak-
ing water. Another alternative is to dip the sliced potatoes in an acid solution (lemon juice
and water, vinegar and water), but this will alter the taste.
What Happens When You Cook This Food
Starch consists of granules packed with the molecules of amylose and amylopectin. When
you cook a potato, its starch granules absorb water molecules that cling to the amylose and
amylopectin molecules, making the granules swell. If the granules absorb enough water,
they will rupture, releasing the nutrients inside. If you are cooking potatoes in a stew or
soup, the amylose and amylopectin molecules that escape from the ruptured starch granule
will attract and hold water molecules in the liquid, thickening the dish.
However you prepare them, cooked potatoes have more nutrients available than raw
potatoes do. They may also be a different color. Like onions and cauliflower, potatoes con-
tain pale anthoxanthin pigments that react with metal ions to form blue, green, or brown
compounds. That’s why potatoes may turn yellowish if you cook them in an aluminum or
iron pot or slice them with a carbon-steel knife. To keep potatoes pale, cook them in a glass
or enameled pot.
See Adverse Effects Associated with This Food.
How Other Kinds of Processing Affect This Food
Freezing. A potato’s cells are like a box whose stiff walls are held rigidly in place by the
water inside the cell. When you freeze a cooked potato, the water in its cells forms ice crys-
tals that can tear the cell walls, allowing liquid to leak out when the potatoes are defrosted,
which is why defrosted potatoes taste mushy. Commercial processors get around this by
partially dehydrating potatoes before they are frozen or by freezing potatoes in a sauce that
gives an interesting flavor to take your mind off the texture.
Potatoes