Yams
Yams are closely related to lilies and grasses. Native to Africa
and Asia, yams vary in size from that of a small potato to a
record 130 pounds (as of 1999). There are over 600 varieties
of yams and 95% of these crops are grown in Africa. Compared
to sweet potatoes, yams are starchier and drier.
Sweet Potatoes
The many varieties of sweet potatoes (Ipomoea batatas) are members
of the morning glory family, Convolvulacea. The skin color can
range from white to yellow, red, purple or brown. The flesh also
ranges in color from white to yellow, orange, or orange-red.
Sweet potato varieties are classified as either ‘firm’ or ‘soft’.
When cooked, those in the ‘firm’ category remain
firm, while ‘soft’ varieties become soft and moist.
It is the ‘soft’ varieties that are often labeled
as yams in the United States.
Why the confusion?
In the United States, firm varieties of sweet potatoes were produced
before soft varieties. When soft varieties were first grown commercially,
there was a need to differentiate between the two. African slaves
had already been calling the ‘soft’ sweet potatoes ‘yams’ because
they resembled the yams in Africa. Thus, ‘soft’ sweet
potatoes were referred to as ‘yams’ to distinguish
them from the ‘firm’ varieties.
Today the U.S. Department of Agriculture requires labels with
the term ‘yam’ to be accompanied by the term ‘sweet
potato.’ Unless you specifically search for yams, which are
usually found in an international market, you are probably eating
sweet potatoes!
Related
Web Sites |
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Further
Reading |
- Coursey,
D. G. Yams: an account of the nature, origins, cultivation
and utilization of the useful members of the Dioscoreaceae. London, Longmans, c1967. 230 p.
- Davidson,
Alan. Sweet potato. In The Oxford companion to food.
New York, Oxford University Press, c1999. p. 774-775.
- Davidson,
Alan. Yam. In The Oxford companion to food. New
York, Oxford University Press, c1999. p. 856-857.
- Edmond,
J. B. Sweet potatoes: production, processing, marketing. Westport,
CT, AVI Publishing Company, c1971. 334 p.
- Kiple,
Kenneth F., and Kriemhild C. Ornelas, eds. Sweet potatoes
and yams. In The Cambridge world history of food. New
York, Cambridge University Press, c2000. p. 207-218.
- Sweet
potatoes getting to the root of the demand. Agricultural
outlook, no. 269, Nov. 2002: p. 13-16.
http://www.ers.usda.gov/publications/agoutlook/Nov2002
/ao296e.pd
- Voorhees,
Don. What’s the difference between a sweet potato
and a yam? In Why does popcorn pop? Seacaucus, NJ., Carol
Pub. Group, c1995. p. 42-43.
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For
more print resources...
Search on "cookery," "sweet potatoes," "Sweet
potatoes," or "Yams"
in the Library of Congress Online
Catalog. |
New
sweet potato cultivar Ruddy
Agricultural Research Service,
U.S.
Department of Agriculture.
Yams
at market. From the Web site of The
American International
School at Lagos, Nigeria.
Man coming out
of jungle with wild yam "cabezo de negro". Prints
& Photographs Division, Library of Congress.
Picking
up and loading sweet potatoes. Prints & Photographs Division,
Library of Congress.
Preparing sweet potatoes for dinner.
Prints & Photographs Division,
Library of Congress.
National Center for Genetic Resources
Preservation, U.S. Department
of
Agriculture,
Agricultural Research Service
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