In corn as in life, be careful what you wish for. Just try finding an ear that tastes the way it used to, and you’ll see what good intentions can do. For generations, Americans have worshipped a sweet corn as one of our national culinary treasures. But it was a gem with a flaw. Cooked immediately after picking, corn was superb; cooked a day later, it was much less so. Much of its flavor comes from sweetness, and that sugar converts to starch very quickly—an ear of regular corn loses half of its sweetness within twenty-four hours. So plant breeders worked to overcome that difficulty, developing new varieties, some that are much sweeter than the traditional ones, some that go starchy more slowly and some that do both.
Today these new and improved varieties are almost the only kinds you can find. Although plant breeders have inarguably succeeded in making corn sweeter, it’s not altogether clear that we’re better off for it. There’s a lot more to corn flavor than sweetness, and in those respects, these new varieties come up short.
Corn is a grain, but one that we eat in an immature state. If left on the stalk to full maturity, the kernels would become as hard as wheat and almost as full of starch. In fact, this is the state in which most of the corn grown in America is harvested—but those are different varieties that are processed for use in a whole range of industrial applications, including sweeteners, textiles and automobile fuels.
The kinds of corn we eat are picked within a month of pollination. In agriculture these varieties are referred to as “sweet corn.” Because of their immaturity when picked, in the past they have also been called “green corn.” (In the Southwest you still find green corn tamales, which are made with sweet corn rather than purely from masa, or ground dried corn.)
Almost every ear of sweet corn grown today was developed for a certain set of characteristics. This is not an example of modern-day Frankenfood genetic tinkering; it has been going on for centuries. (The ur-corn, teosinte, had cobs about two to three inches long that contained at most a half-dozen kernels.) But lately the march of progress has been especially swift. Besides traditional corn—which is practically nonexistent today (and would be so starchy you probably wouldn’t like it even if you could find it)—corn breeders recognize three main families, or genotypes, of the new varieties, each with its own set of attributes. Agronomists refer to them by a two-letter shorthand.
The oldest improved variety is “su,” for “sugary.” This kind of sweet corn started being mentioned in seed journals in the 1820s but had probably existed before—the result of farmers selecting seed from the sweetest plants to propagate the next year. Most varieties of this type of corn have a sugar content ranging from 10 to 15 percent. That sugar starts converting to starch the moment the corn is picked. If left at room temperature, an ear of “su” corn will lose half of its sugar in less than a day. Even if chilled to normal refrigerator temperatures, it will lose two thirds of its sweetness within three days.
The next advance was a variety called “se,” for “sugar-enhanced.” This kind of corn is a lot sweeter than normal corn, containing as much as twice the sugar. The sugar-to-starch conversion occurs at about the same rate as for traditional corn, but because “se” corn starts out so much sweeter, it takes up to a week of storage before it falls to the sweetness level of normal corn.
The King Kongs of the corn world are varieties that are not only supersweet but that also go starchy much more slowly. These are called “sh2” corns because of the way their kernels shrivel and appear shrunken after drying. These varieties contain sugar levels between 30 and 45 percent—two to three times that of traditional corn. And their sugar-to-starch conversion rate is so slow as to be almost nonexistent. Even after being stored for a couple of days at warm room temperature (80 degrees), these varieties still have more than twice as much sugar as a freshly picked normal ear. They have been slow to win acceptance because the seed is significantly more expensive than that for the other improved corn types, and shoppers have been reluctant to pay the extra money.
Supersweet corn is the result of traditional plant breeding spurred by naturally occurring genetic mutations. Think of this breeding in terms of basketball players. In the general population, the occurrence of extremely tall humans is rare. But if two extremely tall people should find each other, fall in love and have children, the odds that their offspring will be extremely tall are, well, pretty short. And so it is with corn. Once breeders started working with a few “freak” corn plants that produced ears with very sweet kernels, it was just a matter of breeding and crossbreeding a few dozen generations to get where we are today.
The first real work on these supersweet corns was done by a University of Illinois professor named John Laughnan in the 1950s. But these varieties didn’t catch on until the mid-1980s, and then they caught on quickly. In Florida, a prime winter corn-growing state, the percentage of supersweet corn went from 2 percent to 90 percent within five years. Today it is hard to find fresh corn grown anywhere that is not one of the improved supersweet varieties.
Understandably, these have become overwhelmingly popular among farmers and produce managers, who no longer have to listen to their customers complain about corn not being sweet enough. Unfortunately, that plaint seems to be giving way to another—that corn no longer tastes like corn. To an extent, that is true. Genetics is complicated, and it’s hard to alter one factor without changing another. In the case of corn, increasing the sugar content has meant a decline in that amorphous quality called “corn flavor,” as well as kernels that are no longer creamy (but crunchy) in texture.
What we think of as corn flavor is primarily based on aroma and is mainly a function of a chemical compound called dimethyl sulfide, which is also found in foodstuffs ranging from cabbage to lobster meat. (This chemical also poses a significant problem for brewers and vintners when it shows up in beer and wine.) Dimethyl sulfide is one of about half a dozen sulfurous compounds that appear in cooked corn (but not in raw corn, which is why raw corn always tastes so simple and sweet). It has a distinctive smell that is familiar from canned corn. Other sulfurous smells in corn are not so pleasant. For instance, the second-leading compound is hydrogen sulfide, which is familiar to anyone who has cracked a rotten egg. But put together in relatively low concentrations, these compounds add up to a lovely complex aroma.
Within the past couple of years, breeders have introduced varieties with complicated genetics that offer variations on the three basic genotypes. The goal is an ear of corn with the sweetness and slow sugar-to-starch conversion of “sh2,” but with the creaminess and strong corn flavor of “su” and “se.” Some of the new varieties try to accomplish this with a straight genetic blend—combining the best characteristics of each genotype in every kernel. Others take a different route—combining on the same cob kernels of each type of corn, so a single ear might contain 25 percent “su,” 50 percent “se” and 25 percent “sh2.” This last type is still scarce. It is expensive to grow, and so far, farmers say, their customers haven’t been willing to put up with the additional expense.
Of course, when you’re at the farm stand or produce market shopping for corn, odds are you won’t have a clue as to whether the corn is “su,” “se,” “sh2” or any combination thereof. At best you’ll be offered a choice of yellow or white—or bicolor, a cross-pollinated combination of the two. But despite what you may have been led to believe, one color of corn is not necessarily sweeter or “cornier” than another. The carotene that gives yellow corn its color is flavorless, and there are “su,” “se” and “sh2” varieties of both white and yellow corn.
Really, then, it’s all just packaging, and which color you prefer will depend to a great extent on where you live. Different areas of the country prefer different colors of corn. Generally speaking, white corn is preferred from the mid-Atlantic region through the South, bicolor is popular in the Northeast and yellow rules almost everywhere else. Most corn varieties have yellow kernels, so it could be that in some cases white varieties are preferred because they are less common and therefore in some way “special.” Usually, though, preferences are determined by which color has traditionally been grown in the area. Sometimes, however, one special variety can influence buyers for generations. A study in Maine, for example, found that most of the state preferred bicolor corn because of the high quality of an old variety called Butter & Sugar—but this variety hasn’t been grown commercially in the area for more than twenty years. In the southern part of the state, people preferred white corn because of a variety called Silver Queen, which is similarly antique.
Silver Queen, a very fine “su” variety introduced in 1955, has cast an inordinately long shadow in the sweet corn world. It has come to represent high quality, the “Cadillac of corn” as it were. This attraction exists despite the fact that blind taste tests have consistently shown that eaters prefer new “se” and “sh2” varieties. Perhaps more to the point, hardly anyone grows true Silver Queen commercially anymore, contrary to farm stand claims.
WHERE THEY’RE GROWN: Corn is one of the most widely grown vegetables, harvested in significant amounts in twenty-five states. More than half of the total U.S. production comes from just three states: Florida, California and New York.
HOW TO CHOOSE: The husks should be fresh and green with no drying. The silk should be golden and fresh-looking. Check out the tips of each ear: the kernels should be well filled out and evenly spaced. Pop a kernel with your thumbnail: it should spurt milky juice.
HOW TO STORE: Refrigerate corn, still in its husks, away from strong-flavored foods (corn absorbs odors). Keep it in its husks to help preserve the moisture in the kernels.
HOW TO PREPARE: Shuck corn right before cooking. Use a vegetable brush to remove the fine silk. If you want to cut the corn from the cob, place the cob tip down in a large bowl and slice downward along its length with a very sharp knife. You can then “milk” the corn to get any extra bits and juice by firmly stroking the length of the cob with the back of your knife (dull edge down).
ONE SIMPLE DISH: Everyone knows how to boil an ear of corn, but some people still don’t know about grilling. It couldn’t be easier. Soak whole, unhusked cobs in water for at least 20 minutes, then pop them on the grill. Grill the ears over a hot fire until they are a dark yellow and are well marked by the grill. This will take longer than you might expect—probably 25 to 30 minutes. Don’t worry if the husks start to char; that just adds to the smoky flavor. Cool slightly and remove the husks and the silk before serving. (The fine filaments will come away more easily after grilling.)