MSU Extension

Sweet potatoes are a warm-weather vegetable related  to the morning glory family. Yams are a different plant species. Yams grow only in tropical climates and are related to grasses and lilies. Although Louisiana sweet potatoes are often referred to as yams, they truly are sweet potatoes. The Louisiana producers began calling the orange-fleshed sweet potatoes grown in Louisiana “yams” to distinguish them from  sweet potatoes with lighter colored flesh grown in other regions of the United States. Sweet potatoes require a long, frost-free growing season and, therefore, are best suited for southern gardens. They are a native American plant that was a main source of nourishment as long ago as the Revolutionary War.

The edible part of the sweet potato is a swollen storage root. The color of the skin and flesh of sweet potatoes ranges from white to orange to red depending on the variety. Sweet potatoes are divided into two types: dry-flesh and moist-flesh, though this is more a reference to the taste than the actual moisture in the product. Moist-flesh varieties tend to convert more of the starch present into sugars during cooking, leading to a sweeter, softer cooked product than the dry-flesh varieties provide. Both types are rich in beta carotene, which the human body converts to vitamin A. Sweet potatoes also contain vitamin C, fiber and potassium.A small bakedor boiled sweet potato has about 135 calories. 

Recommended varieties

Beauregard -- large, elongated roots with light purple to red skin and dark orange flesh.

Bush Porto Rico -- large, tapered roots with copper-colored skin and orange to light red flesh.

Centennial -- Cylindrical and medium to large, it is a moist-fleshed product and keeps well. It has orange skin with deep orange flesh. 

Georgia Jet -- purplish-red skin and deep orange flesh. This variety keeps very well. It is a moist-flesh variety and somewhat tolerant of cold.

Jewell -- narrow and cylindrical roots with red skin and orange flesh. Stores very well.

Sumor -- light skin with ivory to very light yellow flesh.

Vardaman -- golden-yellow skin with deep orange flesh.

The majority of commercially grown sweet potatoes consist of Jewell from North Carolina and Beauregard from Louisiana.

Purchasing, storing and yield

When purchasing sweet potatoes, look for firm, plump, blemish-free produce. Choose sweet potatoes with a bright, uniform color, and be sure there is no sign of decay. Raw sweet potatoes should not be refrigerated. Store in a cool, dry, dark place, unwrapped, for up to two months or at room temperature for up to a week. Cooked sweet potatoes can be stored in the refrigerator, frozen, dried or canned. Although sweet potatoes are harvested in the fall, they are available for purchase year round. They are simple to prepare by baking, boiling or cooking in the microwave.  Sweet potatoes should be cooked in their skins to retain their vitamin content. Be sure the outside is washed well in fresh running water before preparation. Allow one medium sweet potato per person.

Preservation

Canning

2-3 pounds sweet potatoes = 1 quart
Water or sugar syrup

Choose small to medium potatoes. They should be mature but not fibrous. Wash and boil  until partially soft, 15-20 minutes. Cool slightly and peel away skins. Cut into uniform pieces, either sliced or quartered, but do not mash or puree. Pack into hot jars. Leave 1 inch of headspace. Fill to within 1 inch of the top with boiling water or boiling sugar syrup. Remove air bubbles. Wipe jar rims. Adjust the lids and process pints 65 minutes or quarts 90 minutes at 10 pounds of pressure in a weighted-gauge pressure canner.

Freezing

Allow sweet potatoes to cure for at least a week. This improves the flavor and allows the conversion of starch to sugar in the sweet potato. Cure sweet potatoes by keeping them at 80 to 85 degrees F.  and a humidity of 85 to 90 percent. After curing, wash well. Cook before freezing;, wrap in freezer wrap, place in freezer bags or vacuum package. If sweet potatoes are sliced or pureed, leave ½ inch of headspace.  Seal, label with name of product and date frozen, and freeze. Use frozen sweet potatoes within a year of freezing.

Drying

Choose sweet potatoes free of blemishes and decay. Wash, peel and cut into ¼-inch slices. Steam blanch for 3 minutes. Dry at 125 degrees F. until brittle.

References

Andress, Elizabeth L., and Judy A. Harrison. 2006. So Easy To Preserve (fifth edition). The University of Georgia Cooperative Extension Service.

Ball Blue Book. 2008. Daleville, Ind.:  Hearthmark, L.L.C.

Lerner, B. Rosie. 2001. The Sweet Potato. Purdue University Cooperative Extension Service.

More information

• Michigan Fresh
• Michigan Fresh - Vegetables

Oven-baked sweet potato fry recipe

Prepared by: Christine Venema, MSU Extension Educator