Science Supersized Thanksgiving Dinner

The maize would have looked like the ear pictured on the left. Eventually, this type of corn was crossed with the Virginia Southern dent on the right to create the field corn that we feed to animals. You wouldn't want to eat any of these.

"It wouldn't have been particularly sweet," Tracy said.

Sweet corn is the result of a mutation that replaces some of the corn's starchiness with sugar. It spread from the Iroquois to European settlers in the late 1770s. While it's considerably sweeter than the nasty stuff the Pilgrims ate — due to a mutation in a gene called Sugary1 — it wouldn't taste much like the corn we know.

"From that time, it has gone through quite a few changes. Today, through conventional breeding, we have genes in it that make it sweeter, maintain its quality longer, and make it much more tender," Tracy said. "If people had the opportunity to taste Jeffersonian sweet corn and modern sweet corn, there'd be no question what they'd prefer." That original sweet corn was only about 10 percent sugar, but it also was about 25 percent phytoglycogen, lending it a nice, creamy texture. In the next major corn transition — to supersweet corn in the 1970s through a variation in the Shrunken2 gene — that creamy texture was lost, even as the sweetness of the corn skyrocketed.

Among the thirteen genes known to affect corn sweetness, however, industrious agronomists have found an even better gene to work with, called SE, and they made "sugar enhanced corn."

"That's the most popular for fresh market today," Tracy said. "It gives a sugar level of 20 to 25 percent and it turns out to be very tender."

But even as modern consumers prefer the SE corn — and often find the supersweet corn too sweet — the Shrunken2 corn is making a comeback as retailers prefer its longer shelf life.

Retailer and food processor demands, rather than your fresh-vegetable interests, play a major role in the evolutionary history of potatoes as well. Though they were not present at that original feast, they have been a major part of the holiday since Lincoln created it in 1863.

Potatoes are now driven by a decidedly nonfestive activity: the making of french fries and potato chips. Almost a mirror of corn genetics, agronomists have ratcheted up the starch in potatoes and turned down the sugar, said Gregory Porter, a potato specialist at the University of Maine.

"High-starch french fries, when they fry, don't get soggy," Porter said. "Low sugars are important because high sugars in potatoes would result in a dark brown discoloration. High-starch potatoes result in a nice golden-colored fry."

So the modern potatoes of today, even the round ones that look more like their colonial predecessors, have undergone major biological changes.

"When you look at potatoes that would have initially come in the 1700s, those potatoes weren't being selected for processing ability," Porter explained. "Those potatoes probably would have been round and had lower starch content and high sugars. They would not have made good french fries or potato chips."

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