In short, nowadays, people in the US get confused about the yams and sweet potatoes, mainly because the producers who sell them confuse the two. The supermarkets label sweet potatoes, especially those with orange flesh, as yams. However, the true yams are not sweet potatoes.
This issue originated hundreds years ago, when the evil human traffickers brought Africans to the US. The Africans called the local sweet potatoes nyami. Then people translated this word into yam in English.
Decades ago, when the sweet potatoes with orange flesh came into this continent, the producers called them yams, so people could distinguish them from the local ones.
However, it seems not working. So to help you tell correctly which are the yams or sweet potatoes, I prepared this guide. Now, let’s find their differences.
1. Yams and Sweet Potatoes Have Different Appearance
Observing their appearances would be the easiest way to distinguish between yams and sweet potatoes.
Yams (scientific name : Dioscorea) skin is rough and scaly, while the sweet potato (scientific name: Ipomoea batatas) skin is smooth and thin. Yam’s shape is long, cylindrical, and some of them with “toes”, while sweet potato shape is short, blocky and tapered ends.
Each of them has hundreds of different types.For yams, we can have,
- Purple yam
- Chinese yam
- India Yam
- Dioscorea cayenensis
- Dioscorea bulbifera
- Dioscorea villosa
For sweet potatoes, 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. If we classify them in shade, we can have,
- Speckled purple sweet potato
- Heirloom sweet potato
- Hannah sweet potato
- Jewel sweet potato
- Garnet sweet potato
- Korean purple sweet potato
- Beauregard sweet potato
- Creamsicle sweet potato
- Willowleaf sweet potato
2. Yams and Sweet Potatoes Taste Different
Yams taste like poverty, it’s nothing but dry starch, like eating raw flour pretty much. Sweet potatoes, on the other hand, through decades of selective breeding and genetic engineering, are sweet and now basically dessert masquerading as vegetables.
To cook yams, we can boil, fry and roast them. To cook sweet potatoes, we have more options. We can bake, roast, mash, grill, fry, saute, boil, and steam sweet potatoes.
3. Yams and Sweet Potatoes Grow in Different Environment
People in many temperate and tropical regions, especially in Africa, South America and the Caribbean, Asia, and Oceania, cultivate yams. What you need to know is that the US does not produce yams. Those sold on the US market are mainly imported from the Caribbean.
It grows in hillsides, valleys, forests, shrubs or weeds near streams and roads, at an altitude of 150-1500 meters. Yams is a short-day, temperature-loving crop. The optimum temperature for seedling growth is 15-20℃. The optimum temperature during its peak growth period is 25-28 ℃, and the growth will become slow below 20 ℃.
It is suitable for growing in loose, fertile, and deep soil. It is relatively drought-tolerant, but not flood-tolerant, and should not be planted in soils where the groundwater level is too shallow or too humid. An annual rainfall over 1500 mm distributed uniformly throughout the growing season would be great. The whole growing season would last 180 to 360 days.
However, sweet potatoes are native to the US. The suitable growth temperature for sweet potatoes is 22-30 ℃. The growth stops when the temperature is lower than 15 ℃. Different growth periods have different requirements for temperature. The temperature during the budding period should be 18-22°C. Too high or low temperature will affect the germination rate. The temperature in the seedling stage should be 22-25℃, the temperature in the stem and leaf stage should be 22-30℃. The temperature in the stem and leaf stage should not be lower than 16℃, otherwise it will hinder its growth or even stop growing; if it is lower than 8℃, it will cause plants Withered and die after frost. The temperature at the root stage should be 22-25℃.
Sweet potatoes like light and are also short-day crops. The daily sunshine time should be 8-10 hours. Adequate light can not only promote flowering and the formation of roots, but good light can also accumulate more nutrients on the roots and promote the expansion of the roots.
Sweet potatoes are highly adaptable to drought. They have good acid and alkali resistance and strong adaptability to the soil environment. Their root system is well developed and the ability to absorb fertilizer is strong. It is advisable to choose a plot with deep soil layer, loose soil, strong irrigation and drainage ability to grow sweet potatoes.
4. Yams and Sweet Potatoes Contain Different Nutrient Contents
Nutrient contents of yams and sweet potatoes per 100g,
|Vitamin C (mg)||17.10||2.40|
|Thiamin (B1) (mg)||0.11||0.08|
|Riboflavin (B2) (mg)||0.03||0.06|
|Niacin (B3) (mg)||0.55||0.56|
|Pantothenic acid (B5) (mg)||0.31||0.80|
|Vitamin B6 (mg)||0.29||0.21|
|Folate Total (B9) (μg)||23||11|
|Vitamin A (IU)||138||961|
|Vitamin E, alpha-tocopherol (mg)||0.39||0.26|
|Vitamin K1 (μg)||2.60||1.80|
|Saturated fatty acids (g)||0.04||0.02|
|Monounsaturated fatty acids (g)||0.01||0.00|
|Polyunsaturated fatty acids (g)||0.08||0.01|
***Data source: Wikipedia.org
As you can see from the table above, yams are very rich in Potassium and Vitamin K1, not just compared to sweet potatoes, but also many other food staples (maize: 287mg Potassium and 0.3ug Vitamin K1; rice: 115mg Potassium and 0.1ug Vitamin K1; wheat: 363mg Potassium and 1.9ug Vitamin K1; potatoes: 421mg Potassium and 1.9ug Vitamin K1).
Because of its abundance in Potassium, yams would be great to help your body reduce blood pressure, protect against strokes, prevent osteoporosis and kidney stones, reduce water retention, and increase bone mineral density. And owing to its Vitamin K1, yams are really helpful to activate proteins required for bone growth and development, prevent heart disease, and make the proteins involved in blood clotting do their jobs well.
By comparison with other food staples, sweet potatoes get plenty of Sodium, Vitamin A, and Beta-carotene. We know that Vitamin A is essential for preserving our eyesight. So eating sweet potatoes can assist us to protect our eyes from night blindness. Vitamin A in sweet potatoes can also reduce the risk of acne, a chronic, inflammatory skin disorder, and maintain our body’s natural defenses. Besides, the Vitamin A in sweet potatoes is also necessary for proper bone growth and development, even though the vital nutrients needed for maintaining healthy bones are protein, calcium and vitamin D.
As for the beta-carotene, it mainly functions as an antioxidant. So the beta-carotene in sweet potatoes can improve memory and cognitive function, maintain skin health and appearance, and may protect the skin against UV radiation from the sun.
5. Yams and Sweet Potatoes are Stored Differently
When you have bought lots of yams and sweet potatoes at home, you can store both raw yams and raw sweet potatoes in a dry, cool and well ventilated place, which is away from direct heat, light, and moisture. A practical tip of mine is placing them on a wooden stand.
The difference is that each of them has different requirements for the temperature. Ideally, we should save raw yams at 54 to 61°F (12 to 16°C), and raw sweet potatoes at 55 to 60°F (13 to 15°C). Never put your raw sweet potatoes at over 80°F. Because at 80 to 86°F (27°C to 30°C)), the raw sweet potatoes would be cured.
Another difference between yams and sweet potato storage is whether we can freeze them. We should never put the raw sweet potatoes in the fridge, because low temperature will make them hard center and unpleasant taste.
But for the raw yams, we can freeze them in the fridge, with some preparations. And here is the how-to.
- Peel off the skin of the yam neatly.
- Cut the yam into about 2 inch long pieces.
- Rinse the peeled yam with clean water.
- Put the yam pieces into a zip lock bag and seal it.
- Put the sealed yam into a freezer to freeze.
With this method, we can save the yam for many months and even years without going bad.
- If you want to cook the yam after a period, all you need to do is to take them out of the freezer and let it defrost naturally. And then, you can cook them into something delicious.
|Scientific Name||Dioscorea Species||Ipomoea batatas|
|Origin||West Africa, Asia||Tropical America (Peru, Ecuador)|
|Edible storage||Tuber||Storage root|
|Number/plant||1 to 5||4 to 10|
|Appearance||Rough, scaly||Smooth, with thin skin|
|Shape||Long, cylindrical, some with “toes”||Short, blocky, tapered ends|
|Nutrient||High in Potassium and Vitamin K1||High in Sodium, Vitamin A, and Beta-carotene|
|Growing season||180 to 360 days||90 to 150 days (120 = Jewel)|
|Storage Temperature||54 to 61°F (12°C to 16°C)||55 to 60°F (13°C to 15°C) (Cured at 80 to 86°F (27°C to 30°C))|
|Climatic requirements||Tropical||Tropical and temperate|
|Availability||Imported from Caribbean||Grown in USA|