Several
decades ago, when orange-fleshed sweet potatoes
were introduced in the southern United States,
producers and shippers desired to distinguish
them from the more traditional, white-fleshed
types of sweet potato. The African word "nyami",
was adopted in its English form, "yam". The so
called yams sold for food in Africa are also
sweet potatoes. "Yams" in the U.S. are sweet
potatoes with relatively moist texture and
orange flesh. Although the terms are generally
used interchangeably, the U.S. Department of
Agriculture requires that the label "yam" always
be accompanied by "sweet potato." The following
information outlines several differences between
sweet potatoes and true yams (which are
never grown as food).
|
|
Sweet
Potato
|
Yam
|
|
Scientific
Name:
|
Ipomoea
batatas
|
Dioscorea
|
|
Plant
family:
|
Morning
glory (Convolvulaceae)
|
Dioscoreaceae
|
|
Plant
group:
|
Dicotyledon
|
Monocotyledon
|
|
Flower
character:
|
Monoecious
|
Dioecious
|
|
Origin:
|
Tropical
America (Peru, Ecuador)
|
West
Africa, Asia
|
|
Edible
storage organ:
|
Storage
root
|
Tuber
|
|
Appearance:
|
Smooth,
with thin skin
|
Rough,
scaly
|
|
Shape:
|
tapered
ends
|
Cylindrical,
with "toes"
|
Wild yam,
or Dioscorea, is the tuber of a tropical plant.
Don't expect to find it in your grocery store,
it's completely unrelated to the sweet potatoes
that many people call yams in this country. All
sorts of claims have been made about wild yam
because it contains a precursor of steroid
hormones called diosgenin, which was used as the
starting material for the first birth control
pill. But diosgenin itself has no hormonal
activity. Nor can the human body convert it into
something that does.
So to
answer the question at the top of this page
"When is a yam not a yam?":
When
it's a Sweet Potato!
(which
is most of the time)
-
End
