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Why cook corn sous vide at all, when there are plenty of other already-incredible ways of cooking it like microwaving in-the-husk ears whole, boiling it in salted water, or any number of ways to grill it? Because sous vide allows you to get results that cannot be achieved through any other method. Juicier, more evenly tender-crisp, and packed with corn flavor.
I really dislike when techniques get crowbarred into places where they don't really make sense, but I understand the urge. You've just gotten yourself a new sous vide precision cooker and you want make the most out of it, which means cooking as many things as possible using it. Is it really easier or better to cook that asparagus in a plastic bag? Maybe, maybe not, but I'm sure as heck gonna do it anyway because I got this new device!
Sous vide cooking is fantastic for cooking most meats, seafood, shellfish, and eggs, but it's not the most useful tool for vegetarians, by and large because vegetables generally require high temperatures. Pectin, the cellular glue that keeps vegetables together, doesn't start breaking down until 183°F (84°C), and that's close enough to the simmering point of water that most of the advantages of sous-vide cooking in terms of precision go out the window.
Where sous-vide can improve vegetables is with flavor retention. Trapped inside a plastic bag, vegetables cooked sous-vide come out as more intense versions of themselves. For some vegetables, like carrots or sweet potatoes, this is a good thing. For others, like onions or brassica, this can lead to overly concentrated smells that are not desirable.
Add corn to the list of vegetables that benefit from more intense flavor. Sealed in a bag with some salt and a pat of butter and cooked at 183°F (84°C) for just half an hour, corn cooked sous vide will be the corniest, juiciest corn you've ever tasted, with butter distributed deep down the cracks between every kernel.
The very first time I tried it a few years ago, all I did was drop the corn in a bag with butter, seal it, and cook it. Since then, I've made a few tweaks to my technique and have tested out a half dozen or so more variables to arrive at a technique that I think produces the best results so far. Let's go over the basics.
Should I Brine my Corn?
Many folks recommend brining corn in a salt water solution before grilling, steaming, or boiling it. I am willing to bet that the people who recommend it have never done a simple side-by-side A/B test, for if they had, they would come to the conclusion that brined corn is dryer and tougher than un-brined corn. It's a pretty dramatic difference too.
For the best tasting corn, do not soak it in salt water before cooking. (You can read up more on the science of brining corn and why you shouldn't do it here.) And as for deep seasoning, don't worry, cooking your corn sous vide will guarantee that. Don't you just love it when the easiest, laziest method actually turns out to be the best?
What's in the Bag?
My next question was whether or not I could take advantage of the tight quarters inside that sous vide bag by flavoring the corn with a few aromatics. I tried corn bagged up with a dried ancho chile, with cilantro stems, with lemon zest, and with garlic, all to good effect. By adding some butter into the bag with the aromatics, you can spread their flavor around nicely.
One of the best proved to be, once again, the simplest: the corn husks. Cooking the corn directly in its husk in the bag gives the kernels a much more complex corn flavor with some nice grassy notes. Trimming off the bottom and top of the husks before bagging the corn also makes them much easier to shuck in the end. The only downside? The butter doesn't penetrate through that husk, which means you'll have to apply butter the old fashioned way at the table. Big deal.
There are two issues that are bound to come up when you cook corn or any relatively light vegetable that floats in water. The first is getting it to stay submerged. I insert my corn into the arms of a $12 stainless steel pot lid rack that I bought at IKEA. Another solution is to use a binder clip to attach a weight to the corn (a knife or spoon works nicely), which will hold it down under the water.
The other issue you're bound to hit eventually is a leaking bag. I use my FoodSaver to seal vacuum bags, which seals the bags with a heat strip. It's a pretty strong hold, but it can fail at higher temperatures.
When bagging up corn or other vegetables that are going to be cooked to 183°F (86°C), I strongly suggest triple-sealing the bag, using your vacuum sealer's manual seal function to close the bag with three distinct seals. If one or two of the break in the heat, you'll still have the backup.
Corn can also overcook if left in the circulator too long, turning a little mushy after about an hour or so at 183°F (86°C), though still perfectly edible. If you must cook the corn then hold it far a later time, cook it and hold it in a cooler water bath, at 170°F or below, in order to keep it hot but prevent further cooking.
I serve the corn directly out of the bag—the corn juices and butter will have mingled into a nice sauce that coats each ear. Of course adding a little extra butter tableside couldn't hurt either.