Sunday, November 14, 2010

Sweet potatoes vs. yams: what's the difference at my Thanksgiving table?

Sweet potatoes (often confused with yams) are a big part of most family Thanksgiving dinners. Most people aren't quite sure how to prepare them and boil them to within an inch of their lives. I have found that  sweet potatoes are much more flavorful if baked in the oven, whether in their skins or peeled and cut into chunks. You can still use them in your traditional sweet potato casserole topped with marshmallows, but you may find that you don't need as much sugar or honey to sweeten them.

What's the difference between a sweet potato and a yam?

There are several kinds of sweet potato. You're most likely to see the light yellow, drier variety, and a darker, moister, sweeter variety, often mislabeled as a yam. You can use either variety of sweet potato, moist or dry, in recipes, but not both together, as they have different cooking times. The dry variety cooks more quickly than the moist variety.

Although yams and sweet potatoes are both angiosperms (flowering plants), they are not related botanically. Yams are a monocot (a plant having one embryonic seed leaf) and from the Dioscoreaceae or Yam family. Sweet Potatoes, often called ‘yams’, are a dicot (a plant having two embryonic seed leaves) and are from the Convolvulacea or morning glory family.

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.

Some 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!

How do you bake a sweet potato?
Bake sweet potatoes in their jackets. Wash, cut off the ends and bake in a preheated 400*F oven for 40 to 60 minutes (depending on the size of the potatoes and how firm you want them to be). Bake the potatoes on a baking sheet; the sugars in the potatoes can drip out and burn on the floor of your oven.

Bake peeled chunks of sweet potatoes with sweet white or yellow onions in a 400*F oven for 40 to 60 minutes. Drizzle a little olive oil and honey over the potatoes first.

You're now ready to mash your cooked sweet potato. A well-cooked sweet potato will mash almost instantly with just a fork.and blend with butter and a little milk for a smooth puree. Add honey or brown sugar plus cinnamon, cloves or ginger if you wish. You may find you like them this way and forgo the overly sweet marshmallow-topped sweet potato casserole this Thanksgiving.

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