- Crisp, juicy kernels
- Simple, foolproof method
I almost didn’t pursue a boiled corn recipe. I’d never consulted one, and as one of my colleagues asked dubiously, what was wrong with the usual method? Bring a pot of water to a boil, drop in the ears, and wait. When the kernels turn bright yellow, they’re done.
I was inclined to agree with her, until I thought about how rarely I’ve produced perfectly crisp, juicy corn. Usually, I pull the ears out too early and the kernels are underdone and starchy, or I let them sit in the cooling water while I get the rest of dinner on the table—and find that they’ve shriveled and turned to mush. Given how fleeting corn season is, I decided it was worth figuring out a method that delivers perfect results every time.
First, I took a close look at exactly what happens to corn as it goes from raw to cooked. There are two key variables at play: the starches and the pectin. Anyone who’s bitten into an ear of raw corn knows that the liquid inside the kernels (referred to as the “milk”) is chalky, thanks to the presence of raw starches. As corn heats, those starches absorb water, swell, and gelatinize, and the starchy liquid becomes seemingly smoother, silkier, and more translucent. Simultaneously, the pectin (which is essentially glue holding together the cell walls inside each kernel) dissolves, and the cell walls no longer stick together, so the corn softens. The more pectin that dissolves, the mushier the corn becomes.
It’s easy to overcook boiled corn, since the corn’s temperature soon approaches that of the boiling water (212 degrees) and its pectin rapidly dissolves. But if the heat is shut off right before the corn is added to the water, the temperatures of both will equalize somewhere between 150 and 170 degrees, the sweet spot where the corn’s starches have gelatinized but little of its pectin has broken down and the kernels still remain snappy.
All of this meant that the key to perfectly cooked corn would be pinpointing when the starches had gelatinized but the pectin hadn’t dissolved so much that the kernels lost their crisp bite. Fortunately, I was able to attach temperatures to these phases: Corn starch begins to gelatinize at 144 degrees, while pectin starts dissolving at 176 degrees and does so rapidly at 194 degrees. Using those temperatures as parameters, I would aim for a doneness zone of 150 to 170 degrees—hot enough to cook the starches quickly but cool enough to keep the majority of the pectin intact.
On to the cooking method: Figuring that the only way to guarantee consistent results would be to cook a certain number of ears in a measured amount of water for a certain amount of time, I settled on six ears and began experimenting with various amounts of boiling water and cooking times. But it wasn’t that simple; sometimes the corn would cook perfectly, and other times it would emerge under- or overdone. Eventually I realized that the problem was the varying sizes of the ears. They weighed anywhere between 6 and 9 ounces, so depending on the total weight of corn in the pot, the water temperature dropped accordingly, and the cooking time varied.
I wasn’t about to settle for a recipe that worked only with a specific size ear, but it occurred to me that I could ensure that the water never got hot enough to overcook the corn in the first place. The idea is based on the popular restaurant method of sous vide, where food cooks in a water bath set at a specific temperature and can get only as hot as that temperature. We’ve hacked that technique in the past by bringing water to a boil, adding the item(s), and shutting off the heat. The food increases in temperature as the water temperature decreases, until an equilibrium is reached; the final temperature depends on the relative amounts of water and food.
We couldn’t tell the difference between corn cooked in water seasoned with sugar or salt and corn cooked in plain water. To find out why that might be, we ran a test. We cooked three ears of corn for various amounts of time. To represent the seasoning, we dissolved a blue compound known as copper sulfate in the water. We chose copper sulfate because its penetration rate would be comparable to that of the sodium ions in salt.
Interestingly, the blue dye made its way into the kernels by traveling through the cob and then into the kernels. Given this long route, it wasn’t too surprising that it took a very long time to “season” a whole ear. Even after 3 minutes, the first ear showed hints of blue only in the kernels at the tip and base of the cob. After 30 minutes, the blue had progressed a mere ó inch from each end toward the middle. It took a full 2 hours for all of the kernels in the last ear to take on any color, and even then the color was very faint toward the center of the cob.
The takeaway? Salt will eventually season an ear of corn if added to the cooking water, but it will take so long that it’s just not worth it. Sugar molecules are larger than salt, so they would take even longer to penetrate—if they could at all. Season corn on the cob at the table instead.
So I experimented: I dropped six ears of various sizes into 3, 4, and 5 quarts of boiling water; shut off the heat; and let them sit for between 10 and 30 minutes. About a dozen batches later, I’d nailed the formula: six ears of any size in 4 quarts of cooling water ensured that the water didn’t stay hot long enough for much pectin to dissolve, yielding snappy, not starchy, kernels every time.
My method had another perk: I could achieve these results whether I left the corn in the water for as little as 10 minutes or as long as 30 minutes, since the water temperature continued to drop and the corn would never overcook—an advantage for those who eat a couple of ears but don’t want to pull both from the water at the same time. When all was said and done, my method was not only more reliable but also more forgiving than not using a recipe at all.
Crisp, juicy kernels
Adding the corn to boiling water and immediately shutting off the heat ensures that the corn’s starch cooks through but its pectin, which keeps the kernels firm, remains mostly intact.
Simple, foolproof method
By relying on diminishing heat, this recipe accommodates six to eight ears of corn of any size. Furthermore, while there is a minimum cooking time, there’s no fear of overcooking.