Megan Saynisch is a freelance writer, cook, gardener and the creator of Brooklynfarmhouse.com.
It seems like people fall into one of two factions at Thanksgiving: those who like marshmallows with their sweet potatoes, and those who find the sweet-on-sweet combination revolting. (I confess that I fall into the latter camp.) In fact, despite its reputation as a holiday for "togetherness," Thanksgiving seems to inspire much food-related conflict: should stuffing have fruit in it? (I say no. Bletch to raisins in stuffing!) Is green bean casserole yummy, or repellant? (Yummy. But really mostly because of the fried onions on top.) Is deep-frying a turkey awesome, or deeply terrifying? (Awesome! How could deep-frying an enormous bird possibly go wrong?)
One thing I think we can all agree on: the necessity of sweet potatoes on the Thanksgiving table, marshmallows or not.
First: a clarification. Sweet potatoes are not yams, and vice-versa. They are two totally unrelated botanical species, although the roots can be similar in shape. What's the difference? The true sweet potato (Ipomoea batatas) is a vine related to the morning glory (both in the Convolvulacea family) and is native to South America; the yam is from the Dioscorea family, native to Africa and Asia. All of this is especially confusing because orange-fleshed sweet potatoes have been traditionally referred to as "yams" in parts of the US. In general, true yams have a drier texture, are starchier in taste, and are much lower in beta-carotene (but higher in protein) than sweet potatoes.
A Brief History
The origin of the sweet potato is thought to be somewhere between southern Mexico and Venezuela, but current research narrows the field to Central America. It was probably domesticated in Peru between 4,000 and 5,000 years ago. Columbus took the plant home with him when he returned to Europe in the late 15th century, and from there Spanish and Portuguese explorers dispersed it to the rest of the world.
The exception to this is Polynesia: sweet potatoes were already being cultivated by the 13th century (long before European contact) on a number of far-flung Polynesian islands, and became an important staple food on some. How did sweet potatoes get there, you ask? A ho-hum "non-human mediated dispersal" (i.e., birds carried the seeds over) theory is a contender, but a way more interesting theory is that ancient Peruvian sailors, either blown off course or through deliberate navigation, brought the plant to Polynesia. This theory is supported by the fact that the names for sweet potato in several Polynesian languages are suspiciously similar to the Quechua (a native Andean language) word for the plant.
What about the Marshmallows?
But I know what you're really thinking: yeah, yeah, Peru, Polynesia, whatever. What I really want to know is the history of the (disgusting? delicious?) sweet potato-marshmallow combo. According to this Library of Congress article -- apparently they write articles about sweet potatoes, too -- marshmallows were probably an early 20th Century substitute for meringue (a.k.a., whipped egg whites), used to top a traditional baked sweet potato pudding. So there you have it.
In folk medicine, sweet potatoes have been used as a natural treatment against intestinal parasites. There may be some truth to this, as there is some evidence that the Vitamin A (beta-carotene) found in sweet potatoes provides some protection against certain gut-affecting parasites.
George Washington Carver, the remarkable resuscitator of southern agriculture and champion of the sweet potato and peanut, created a list of over 100 different sweet potato-based products from his scientific research, including glue, dye and "mock coconut."
A wild variety of sweet potato (either Ipomoea pandurata or Ipomoea leptophylla depending on whom you ask) is called "man-of-the-earth" or "man-root" (I swear, I'm not making this up). Sources get a bit muddy around the man-root, but according to Daniel Austin, a sweet potato researcher, neither species have roots as big as a man, as was posited by a couple of my food reference books. A more likely explanation for the descriptive name, Austin notes, is that the side branches of the roots resemble male genitals (blush).
Sweet potatoes do better in warmer climates. China by far leads the world in sweet potato production, followed by Uganda, Nigeria and Indonesia. North Carolina leads the US in sweet potato growing, followed by California, Mississippi and Louisiana.
Sweet potatoes are number 38 on the Environmental Working Group's Shopper's Guide to Pesticides in Produce (*see our vegetable rule of thumb). The roots are susceptible to a number of different pests and diseases that are controlled with insecticides and fungicides, so check with your local sweet potato farmer if you're concerned about this.
In the US, sweet potatoes are generally harvested in September and early October. However, it can take up to eight weeks of curing and storage after harvest before sweet potatoes sweeten and develop the texture we are accustomed to, as this article discusses, putting the root's peak seasonality at... right around Thanksgiving. Sweet potatoes will be in season in most parts of the US through very early spring.
Sweet potatoes come in a rainbow of colors, shapes and sizes. Most sweet potatoes are large and football shaped, with a fat middle and tapering ends, although some heirloom and indigenous varieties are quite small and slender (like the taputini, a traditional Maori cultivar). Their skin can be russet, tan, cream, light purple or red. Sweet potato flesh is just as colorful: it may be orange (like the common Jewel sweet potato), yellow, creamy white (like the Japanese sweet potato) or even purple-magenta (as seen in the stunning Okinawan sweet potato). Sweet potato varieties are also divided into "dry" varieties (better for frying or boiling, because they hold their shape better) and "moist" or "baking" types.
Sweet potatoes are really good for you, especially varieties with orange or purple flesh. They contain truly awesome amounts of Vitamin A -- I'm talking between 500% and 700% of your recommended daily intake in just one cup. (Vitamin A is a vitamin necessary for eye, immune system and skin health, and is also a powerful antioxidant.) Sweet potatoes also contain fiber, excellent amounts of Vitamins C and B6, manganese, potassium and a number of other vitamins and minerals. They are even good sources of iron and calcium. Sweet potatoes are also thought to be helpful in blood sugar regulation.
Interestingly, traditional sweet potato breeding techniques (as opposed to genetic engineering) may help some countries combat Vitamin A deficiency. In parts of Africa, where Vitamin A deficiency causes hundreds of thousands of kids to go blind or to die, the white-fleshed sweet potato, much lower in vitamin A, is better adapted. But plant breeders have now developed an orange-fleshed sweet potato variety high in Vitamin A that tolerates African growing conditions.
What To Do with It
Look for sweet potatoes that are firm, with no bruises, shrivel-y spots (especially common on their tapered ends) or brown bits. Avoid sweet potatoes that have begun to sprout.
Sweet potatoes can be stored for several weeks under the right conditions: cool, dry and away from light. Don't store them in the refrigerator, as this accelerates their decline -- they don't like to be too cold or too moist. Sweet potatoes that get too warm tend to sprout and become shriveled and mushy.
Sweet potatoes can be the star of just about any part of the meal, from side dish to main course to dessert. The root can be baked, roasted, boiled, fried, grilled, mashed or pureed. (Also, check out this technique for a quick microwaved sweet potato, so you can get your sweet potato fix even at the office.)
Sweet potatoes are commonly paired with cinnamon, nutmeg, ginger and other warming spices, along with brown sugar or maple syrup. They also are delicious paired with oranges (juice or zest) and apples. They can be mashed and added to any number of baked goods, like muffins, biscuits and cakes. (Sweet potato bourbon Bundt cake? Yes please. And for those of you firmly entrenched in the sweet potatoes-with-marshmallows camp, check out these sweet potato biscuits with marshmallows.) Personally, I prefer sweet potato pie to pumpkin. Is that Thanksgiving blasphemy?
I also love the savory (rather than sweet) side of sweet potatoes, especially in these combinations: sweet potatoes and rosemary; sweet potatoes and chipotle chiles; and sweet potatoes and cumin. (When I roast sweet potatoes, I often throw in a few sprigs of rosemary or sprinkle them with a pinch of cumin before roasting. Or serve sweet potato fries with chipotle ketchup.)
Sweet potato leaves and young shoots are also eaten as part of the cuisines of a number of cultures, including Chinese, Polynesian and Filipino. (Here's a great recipe roundup for sweet potato leaves.)
Cook sweet potatoes in their skin to retain the most nutrients (you can peel after cooking). To enhance the sweetness of your sweet potatoes, this tip from the Kitchn is fascinating: an enzyme in sweet potatoes that converts starch to sugar is most active between 135 - 170 degrees (Fahrenheit), so cook sweet potatoes for a longer period of time at a lower temperature to get the sweetest sweet potatoes. Baking sweet potatoes in the oven at 350 degrees or lower will achieve this. (Or cook in a crock-pot!)
Stretching Your Fresh Food Dollar Though Preservation
Sweet Potato Soup with Apples and Sage
You will need about 2 ½ cups of cooked sweet potatoes for this recipe -- perfect for using up leftover sweet potatoes. Before a big meal, I like to serve creamy, filling soups like this in teacups so my guests don't fill up before the main event. Or serve the soup as a main course with a green salad and crusty bread or biscuits. If you want to be really fancy, it's pretty easy (and much cheaper) to make your own crème fraîche (seriously!). You could also substitute plain yogurt for the crème fraîche.
1 tablespoon extra virgin olive oil
1 tablespoon unsalted butter
1 medium yellow onion, diced
1 small, tart apple (like granny smith), peeled, cored and diced
1 carrot, peeled and diced
1 celery stalk, diced
8-10 small sage leaves
3 cups chicken or vegetable stock
2 ½ cups peeled, cooked sweet potatoes, from about 1 large, mashed or diced (see note)
¼ teaspoon cayenne pepper
¼ teaspoon freshly ground nutmeg
Juice of half a lemon
¼ cup crème fraîche or plain yogurt
1. In a medium Dutch oven, heat the extra virgin olive oil and butter on medium-high heat until the butter is just melted. Add the onion, and cook and stir until translucent (but not browned), about 5 minutes.
2. Add the diced apple, carrot, celery and sage and cook and stir for another 2-3 minutes.
3. Add the chicken or vegetable stock. Bring the mixture to a gentle boil, then turn the heat to low. Simmer until the carrots and celery are tender, about 15 minutes.
4. Add the cooked sweet potatoes, cayenne and a grating of nutmeg. Stir to combine. At this point, taste for salt - depending on the saltiness of your chicken or veggie stock, you will have to adjust the seasoning. Simmer for 2-3 minutes to allow the flavors to meld.
5. Puree the soup in batches in a blender (take care with hot liquids!) or food processor. (Or use a stick blender, my kitchen BFF.)
6. Stir in the lemon juice to taste. Taste and adjust for salt again.
7. To serve: swirl a dollop of crème fraîche or yogurt on top of the soup. Serve hot.
Serves 3-4 as a main course.
Note: Starchier sweet potatoes, like Japanese sweet potatoes, will produce a soup more like a traditional potato soup. Sweeter, moister sweet potatoes, like the orange-fleshed Jewels, will make a sweeter, more sweet potato-y soup. You can also cook the sweet potatoes directly in the soup, rather than use cooked sweet potatoes: just add the uncooked sweet potatoes before you add the stock, and adjust the timing accordingly (sweet potatoes will take a little longer than carrots to become tender).
(*Vegetable rule of thumb: We think that first and foremost, in terms of nutrition, people should eat lots of fruits and vegetables whether they are organic or not. The EWG's guide is a handy list, but we will point out here that the impacts of pesticides are not limited to your ingestion of them - agricultural chemicals also affect farmworkers and local waterways, both good reasons to buy organic, even those vegetables that carry a light pesticide load. Also, it has been demonstrated that produce grown by small-scale farmers, even those who are not certified organic, tends to have a lighter pesticide load than its industrially-produced counterpart, owing to industry's tendency toward large monocrops.)
This post was originally published in November 2012.