As the holidays draw near, we begin planning what to serve at
family dinners. One question comes up every year: What is the difference between
a sweet potato and a yam?
For those of us middle aged folks raised in the South, some of our most precious
holiday memories center on food and good smells from the kitchen. As children,
we had just come out of the Depression and World War II. Money was short and
food had been rationed, but we still had the Victory Garden and every one shared
with those less fortunate.
Sweet potatoes were dependable crops that could be stored and used throughout
the winter.
I remember the smell of baked sweet potatoes, luscious pies, and fried and
candied sweet potatoes with marshmallows on top. My favorite was sweet potato
"surprises." Mother would mash the left over baked sweet potatoes,
form them into golf ball sized mounds, punch a hole into the center and fill it
with one or two
small marshmallows. Then she'd re-form the ball, roll it in coconut and chopped
pecans, and bake it just long enough to melt the center.
Sweet potatoes (Ipomoea batatas), a New World crop from tropical America, were
around in
prehistoric times. Yams (Dioscorea alata L.) are from West Africa and have been
cultivated for
about 50,000 years. The African word nyami, referring to the starchy, edible
root of the Dioscorea plants,
was adopted in its English form, yam. What many in the U.S. call yams are
actually sweet potatoes. Although the terms are generally used interchangeably,
the U.S. Department of Agriculture requires that the label "yam"
always be accompanied by "sweet potato."
There is a difference between the two. Yams are rough, scaly tubers with white
flesh that is dry
and tastes very starchy. They must be boiled first to remove alkaloids before
you cook them.
Sweet potatoes are smooth skinned, moist, and sweeter tasting. They have one of
the highest vitamin A contents of any food and can be prepared a variety of
ways.
Not all sweet potatoes are the same. There are several types of sweet potatoes.
One type is white-fleshed, somewhat drier tasting, and preferred by some over
the moist, yellow-fleshed ones.
The Jersey type is also yellow fleshed, but is drier tasting than the normal
moist, yellow-fleshed sweet potato. The Southern type is moist fleshed, syrupy,
and sugary.
The amount of sugar in sweet potatoes varies with cultivars. However, most of
the current varieties are quite sweet and are an excellent, concentrated source
of vitamins and minerals.
Sweet potatoes can be boiled, fried as french fries, made into chips, or
candied, but to most of us sweet potato fans baked is still best. So, put sweet
potatoes in a cold oven, turn it to 425 degrees for an hour or so depending on
the size of the roots and enjoy.
Wayne McLaurin is a horticulturist with the University of Georgia College of
Agricultural and Environmental Sciences.