Carol Sanders | School of Agriculture, Fisheries and Human Sciences
Even though you may think you were having yams for the holidays, chances are you were enjoying sweet potatoes, which are not the same as yams, says Dr. Obadiah Njue, University of Arkansas at Pine Bluff (UAPB) Department of Agriculture chairman and horticulturist. In most supermarkets, vegetables sold as yams are really sweet potatoes, says Dr. Njue.
True yams are members of the Dioscoreae family, and their flesh may be of varying colors including white, ivory, yellow or purple while their rough and scaly textured skin is thick and may be either white, pink or brownish-black. Sweet potatoes belong to the family Convolvulaceae.
True yams are rarely grown commercially in the United States, but some international markets may sell yams in chunks. Some of the true yams might resemble sweet potatoes in color or shape, but yams grow on a tropical vine.
Yams have a starchy and slippery texture and when cooked will either be creamy or firm, depending upon the variety. Their taste is earthy and hardy with most varieties having minimal, if any, sweetness.
Sweet potatoes are lower in calories, have a lower glycemic index and are much higher in beta carotene especially the orange-flesh varieties. The production, harvesting, handling and storing processes are different for these two vegetables, says Dr. Njue.
In all probability, yams originated in West Africa as a food staple of that region while sweet potatoes were cultivated in Peru, as far back as 750 B.C.
Several sweet potato varieties are now grown in the United States. These include the common and commercially grown orange-fleshed Beauregard. It has an orange, soft-flesh and is moist and sugary when cooked. This is the variety most often advertised and sold under the name of “yam.” Others include Covington, Evangeline, Centennial and Jewel. O’Henry and Bonita have a pale, creamy or yellowish flesh and a dry texture when cooked.
How did sweet potatoes come to be called yams? When the orange-fleshed sweet potatoes were introduced into the southern United States, producers and shippers wanted to distinguish them for the traditional (at that time) white-fleshed type. Yams in the United States are sweet potatoes with relatively moist texture and orange flesh, according to North Carolina State University horticulturists. The United States Department of Agriculture requires that the label “yam” always be accompanied by “sweet potato.”