What’s the difference between sweet potatoes and yams?
While the names yam and sweet potato have largely become synonymous in the U.S., they are actually two very distinct tubers. True yams belong to a completely different botanical family and are much scarcer in North America than sweet potatoes. Generally found in Asian or Latin markets, yams are often sold in chunks because they can grow to be several feet long. Because there are dozens of varieties of yams, the flesh color can range from white to light yellow to pink and the skin color from off-white to brown. All of them, though, have very starchy flesh.
Sweet potatoes are what we usually buy: longish, knobby tubers with dark, orangey-brown skin and vivid flesh within. The flesh cooks up moist, and the flavor is very sweet. These are actually a variety of sweet potato developed in Louisiana in the 1930s. The growers called them yams simply for marketing purposes to set them apart from other sweet potato varieties. In so doing, they have confused consumers to this day.
We wondered just how deep the differences in sweet potatoes ran, so we gathered seven varieties and sampled them in Mashed Sweet Potatoes (see related recipe). We tried three traditional varieties (traditional at least to those of us raised in the United States and Europe)—Beauregard, Jewel, and Red Garnet—and four non-traditional—Japanese White, White Sweet, Batata, and Okinawa.
In the traditional category, the Beauregard (usually sold as a conventional sweet potato) was favored for its "standard sweet potato" flavor and "basic, all-around good" quality. The Jewel placed second with its "robust sweet potato flavor," though some found the flavor "weird and sour." The Red Garnet was the most savory of the bunch, with a texture deemed "very loose."
Of the non-traditional varieties, the Japanese White was the hands-down winner, praised for its "heavy chestnut flavor" and "velvety" texture. Runner-up White Sweet was dubbed by one taster as "not quite as good as Japanese White but very good." Coming in at the bottom of the ranking were the Batata and Okinawa, both ultimately losing points for color and lackluster flavor—the Batata with its "ugly gray" hue and the Okinawa with its "freaky" purple haze.
Traditional Varieties (in order of preference):
BEAUREGARD: "Buttery," "sweet, honest," "nice color."
JEWEL: "Beautiful color," "only slightly sweet."
RED GARNET: "Not very sweet," "squash-like," "watery."
Non-Traditional Varieties (in order of preference):
JAPANESE WHITE: "Unbelievable," "awesome," "rich and sweet."
WHITE SWEET: "Lightly sweet and rich," "one-dimensional."
BATATA: "Ugly," "round and rich," "not bad."
OKINAWA: "Amazing color," "nutty," "bland but beautiful."
Published September 1, 1999 in Cooks Illustrated.