Agriculture Reference
In-Depth Information
duction of very potent poisons called glycoalkaloids. These are always present at low
levels in the tuber and at very high levels in the leaves, flowers and stems - the most vul-
nerable parts of the plant. If the temperature gets too cool, if the ground gets too wet, if
there aren't enough nutrients available, if pests or diseases attack the plant or if the tuber
is bruised or damaged in any way, the plant begins to step up its production of glycoalkal-
oids.
Even after harvest, exposure to light or heat can spur glycoalka- loid production. That's
why some people warn against eating potatoes that have begun to turn green on the skin.
The color is caused by the development of chlorophyll rather than by the poisons them-
selves, but the two usually occur simultaneously. Sprouting potatoes are much higher in
glycoalkaloids. Extremely rare cases of"po- tato poisoning" do occur, almost always the
result of people eating potatoes that are spoiled or drinking tea made from potato leaves.
In most potatoes, the concentrations of glycoalkaloids are extremely low, less than
1,000 parts per million. Since the glycoalkaloids are concentrated just under the skin, you
can eliminate most of them by peeling deeply. In fact, in small doses these poisons are one
of the things that make potatoes so delicious, contributing a slight bitterness that nicely
complements their natural sweetness and earthiness.
Potatoes grow in several stages. First, seed potatoes (pieces of potatoes) are planted.
They produce a green plant above the ground. When the plant reaches a certain stage of
maturity, rather than produce more foliage, it begins to pump nutrients below the ground
to the tubers. Since the potato is actually a perennial (although it's farmed as an annual),
the tuber stores the nutrients in the form of starches and sugars so that the plant can last
the winter. Gradually, the tubers swell and grow, increasing in size. One potato plant can
produce as many as a dozen potatoes, with a wide range of sizes. When the tubers have
absorbed as many nutrients as they can hold, the green plant begins to wilt and die. This
"lay down" signals the farmer that it is time to begin the harvest.
What happens after the harvest is almost as important as what occurs before. Although
a very few potatoes are sold immediately after digging, most go into storage. Those that
go straight to market are true "new" potatoes, no matter the variety or size. (The sign of a
real new potato is a peel that rubs off with a thumbnail.) These potatoes are usually very
moist, with a complex flavor due in no small part to their being naturally higher in gly-
coalkaloids. The potatoes that go to curing rooms are stored at between 60 and 70 degrees
with high humidity for ten days to two weeks.
