Many think “yam” is another word for “sweet potato.” They may look similar, but yams and sweet potatoes are two different vegetables.
Most of the time we are eating sweet potatoes unless they have been imported from a country such as those in Africa. Then it may truly be a yam.
Yams are perennial plants that grow in tropical zones. The part eaten is the root tuber, very much as a potato. A yam is long, with brown skin and white to orange-yellow flesh. The plants that produce several medium sized tubers are preferred - the yamshave a better, sweeter flavor - to those varieties that produce a single tuber.
On the off chance that one of the farmer's in your area has decided to grow a true yam, then you can find them at your local farmer's market. If not, you might find a true yam at a neighborhood grocery store or one that specializes in authentic ethnic foods. A true yam doesn't look much like a sweet potato at all really. The skin is brown or much darker - not the typical orange or orange-brown of a sweet potato.
Choosing a good yam
A good yam is much like a good potato of any variety. It should not have any blemishes or rotten spots. If you notice anything fuzzy, put it back. In fact, hide it or remove it from the bunch so no one else picks it up by mistake. The shapes will be funny, some oblong and some pointed or curled at the end. Soft or wrinkly yams are going bad so leave them be. The skin should be smooth and even colored.
The inside of most of the vegetables we eat that are commonly referred to as yams is yellow to orange. That color classifies the vegetable as a sweet potato. The flesh of a yam is much darker, sometimes reaching a reddish hue. In some places yams may be cut up before sold because they have the potential to grow very long. But, let's stop haggling over semantics.
When you're finished, you can store yams in the freezer to avoid spoiling. Clean and chop them up before placing in an airtight container. Yams can be frozen for up to a year without harm.
So look around carefully to see if you are getting yams or a sweeter version of the sweet potato. Both are good to eat and filled with nutrients, but yams are their own vegetable.
Preparation and Cooking
A yam is not to be eaten in its natural state. It usually needs to be thoroughly cooked - African yams may need extra preparation. Before cooking it, wash the yam thoroughly to rinse off any dirt that is still clinging to it. When you cut any vegetable that has not been washed, the dirt and bacteria on the surface is transferred to the inside flesh. Peel after washing, dice and wash the flesh again. Boiling will wash away toxic natural substances present in the yam.
Some Asian varieties of yam are less problematic and preparation of a yam is similar to that of a sweet potato. They can be boiled, baked, fried, and frozen. Cover a yam with a bit of olive oil and bake it like a white potato.
Boiled yams can be mashed like sweet potatoes for casseroles or as a side dish for dinner. Yams taste sweeter than sweet potatoes so less sugar is needed for sweetening.
A serving is 1 cup (150g) of cubed yam - 177 calories.
Yams contain mostly starches and little protein. They are a good source of vitamin C and dietary fiber, and have some vitamin A, calcium and iron. As most vegetables, yams are low in saturated far. They are also high in potassium but low in sodium, which helps to keep a healthy mineral balance in the body. Real African yams are actually toxic if consumed raw. They have natural substances harmful to humans that need to be eliminated beforehand and preparation involves pounding to pulp, washing and boiling to remove toxins before any actual cooking.
Yams - white yams, yellow yams.
white yam - dioscorea rotunda (Disocoreaceae)
yellow yam - dioscorea cayenensis (Disocoreaceae)