Wednesday, July 17, 2019

Yam or Sweet Potato?

Most consumers are confused when it comes to determining the difference between sweet potatoes and yams.  Signs in stores say "Sweet Potatoes", "Yams" and even "Sweet Potatoes - Yams".  So, what are the differences between these two products?
Yams at an African MarketWhat is marketed in the United States as “yams” are really a variety of sweet potato, grown in the South. A true yam is a starchy edible root of the Dioscorea genus, and is generally imported to America from the Caribbean. It is rough and scaly and very low in beta carotene.
"Yams", as the industry and general public perceives them, are actually sweet potatoes with a vivid orange color and a soft moist consistency when cooked, and tend to have a sweeter flavor. Other varieties of sweet potatoes are lighter skinned and have a firmer, drier texture when cooked. Sweet potatoes are smooth with skins that can vary in color, depending on the variety, from pale yellow to deep purple to vivid orange. Flesh colors can range from light yellow to pink, red or orange.
So where did all of the confusion come from? Several decades ago when orange flesh sweet potatoes were introduced into the southern United States, producers and shippers desired to distinguish them from the more traditional white flesh types. The African word "nyami" referring to the starchy, edible root of the Dioscorea genus of plants was adopted in it's English form, "yam".
Yams in the United States are actually sweet potatoes with relatively moist texture and orange flesh. Although the terms are generally used interchangeably, the US Department of Agriculture requires that the label "yam" always be accompanied by "sweet potato."
The following information outlines several differences between sweet potatoes and yams.
Factor Sweet Potato Yam
Scientific Name Ipomoea batatas Dioscorea Species
Plant family Morning Glory (Convolvulaceae) Yam (Dioscoreaceae)
Plant group Dicotyledon Monocotyledon
Chromosome number 2n=90 (hexaploid) 2n=20
Flower character Monoecious Dioecious
Origin Tropical America (Peru, Ecuador) West Africa, Asia
Historical beginning Prehistoric 50,000 BC
Edible storage organ Storage root Tuber
Number/plant 4 to 10 1 to 5
Appearance Smooth, with thin skin Rough, scaly
Shape Short, blocky, tapered ends Long, cylindrical, some with "toes"
Dry matter 22 to 28% 20 to 35%
Mouth feel Moist* Dry
Taste Sweet* Starchy
Beta carotene (Vit. A) High (orange vars.)* Very low
Propagation Transplants/vine cuttings Tuber pieces
Growing season 90 to 150 days (120 - Jewel) 180 to 360 days
Maturity None At senescence
Storage (Cured at 80 to 86oF) 55 to 60oF 54 to 61oF
Climatic requirements Tropical and temperate Tropical
Availability Grown in USA Imported from Caribbean
*Characteristic of most Sweet Potato varieties grown in United States.
Information Courtesy of: Department of Horticultural Science North Carolina State University
Copyright 2012 by Wayne Bailey Produce Company