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Grilling fast-cooking foods is always a balancing act. Hot and hard is the only way to develop those characteristic deep brown grill marks and charred spots that give grilled foods their unique flavor—a process called the Maillard reaction that takes place rapidly at around 300°F (150°C) and higher. On the other hand, for the most tender, juicy meat, gentle and slow is the way to go. This is never more true than when you're cooking shrimp.
You see, shrimp happen to be quite moist, and since the Maillard browning reaction can't begin to take place until surface moisture has evaporated, you need plenty of high heat to get those shrimp browned and flavorful. On the other hand, shrimp meat is also quite delicate. It goes from tender and juicy with a nice snap to overcooked and rubbery within the span of a few degrees.
With a big fat steak, it's relatively easy to get the best of both worlds. You can brown the exterior before the interior overcooks. Shrimp, on the other hand, are so darn small* that even with the most powerful grill and ultra-high heat, it's very difficult to brown them significantly before they begin to overcook. Under normal conditions, you've got two choices: flavorful and rubbery, or tender and bland. I'm not particularly happy settling for either of those.
* I mean, they're shrimps, after all. (Get it?)
What does it take to get grilled shrimp that are as tender and juicy as the most delicately poached shrimp? Shrimp that burst with a decisive snap in your mouth, all with a deep, sweet, crisply charred crust?
Solution #1: The Sugar Solution
I had quite a few questions I wanted to answer. What's the best way to season the shrimp before cooking? Shell on or shell off? And what's the best way to arrange them? But first things first: picking the right shrimp. Even though it happens to be live spot prawn season 'round these parts, I decided to stick with the standard wild pink shrimp or farm-raised white shrimp I can find year-round. I knew that if I was gonna have any chance of developing char on them without completely overcooking them, I'd have to use larger shrimp. I went with the widely available 15- to 20-count shrimp (that is, 15 to 20 shrimp per pound).
I peeled the shrimp, seasoned them with salt, threaded them onto a skewer, patted them dry (remember—surface moisture is the enemy of browning), brushed them with a bit of olive oil to help conduct heat more evenly, then tossed them on a ripping-hot grill, letting them cook until nicely browned on the exterior. This took about four to five minutes per side. As expected, they were nearly inedibly rubbery by this point. How to speed up browning?
Well, working with a hotter grill was obviously part of the solution. The hotter the grill, the faster I can char the exterior before the interior gets a chance to overcook. With my charcoal grill, that meant using a full chimney of coal and piling it all up under one side of the grill to produce maximum heat. With my gas grill, it meant turning the burners on full blast and letting the grill grates heat up, with the lid closed, for a full 15 minutes before attempting to sear the shrimp.
But what about the shrimp themselves?
My first thought was to season my shrimp with a bit of sugar. Even though the Maillard reaction (a reaction involving proteins and sugars) and caramelization (a reaction involving sugars alone) are technically different, their end products share a lot of the same characteristics, namely browning, along with sweet and bitter flavors. Tossing my shrimp with a bit of salt and sugar before grilling them helped them brown just a touch faster. More sugar meant more browning, but it also ended up making the shrimp taste cloyingly sweet. Almost there, but still not the final answer.
Solution #2: Don't Peel Off!
What if messing about with sugar and marinades isn't the solution? One surefire way to guarantee juicier, more tender shrimp is to cook them with their shells still intact. Those shells act as a temperature buffer, helping to keep the meat from overcooking while developing plenty of flavor in the shells themselves.
Personally, I like being served shell-on shrimp. Those shells give a ton of flavor to the meat, and if you're feeling bold, you can go ahead and eat the grilled shells as they are. But shelling shrimp as you eat them can be a messy-fingered affair. Nothing wrong with that per se, but there had to be a solution that could work for those who only want to use a fork.
You caught me. The title of this story is "Five Steps to the Best Grilled Shrimp," yet here I am saying I'm not gonna use one of those steps. Ever hear of poetic license? Thanks.
Solution #3: The Baking Soda Trick
So far, I'd been looking at methods of improving browning. What if I were to instead look at methods to keep the shrimp juicier and plumper as they cooked? I recalled some testing I'd done on shrimp while developing a recipe for wonton soup. In that recipe, I recommend tossing the shrimp with a mixture of salt and baking soda and letting them rest for at least 15 minutes. The salt helps the shrimp retain moisture as they cook, while the baking soda gives them a firm, crisp texture. I wondered if the same method would work for other cooking techniques, so I gave it a shot.
I grilled a batch of shrimp treated with baking soda next to a batch of shrimp with no baking soda and compared them side by side. Turns out, it works quite well. No question, the baking soda–treated shrimp came out plumper and juicier than their untreated brothers. What's more, the baking soda actually helped the shrimp brown faster as well. The Maillard reaction, responsible for producing those delicious browned flavors, takes place faster at higher pH levels. Alkaline baking soda raises the pH, giving you superior browning in less time.
Solution #4: Too Close for Comfort
With my shrimp pre-treatment taken care of, it was time to consider my grilling method. Thus far, I'd been threading the shrimp on a pair of skewers (which makes them much easier to flip and maneuver on the grill—individual shrimp have a tendency to slip through the grill grates) and spacing them apart, thinking that this would maximize their exposure to the heat of the grill. It also makes the shrimp look all nice and pretty when you toss that skewer on a serving platter. But is it really the best way?
My old employer Cook's Illustrated says otherwise. They recommend squeezing the shrimp tightly together on a skewer. The reasoning is that with less surface area, heat takes longer to penetrate into the center of the shrimp, thus buying you extra time on the grill to give the exteriors a nice char. Makes sense to me, so I tried it.
They were absolutely right here, as they often are. By skewering the shrimp so that they were snugly spooning each other, I could easily leave them on the grill an extra minute or two before they started turning rubbery, buying me precious browning time. There was only one thing left to address: moisture.
Solution #5: Get Dry to Stay Moist
We like moist food. We want our shrimp to be juicy. But there's a difference between surface moisture and internal moisture. Internal moisture is what we're really after. For the exterior, we actually want the exact opposite. Browning reactions can't take place until surface moisture has evaporated, and it takes an awful lot of energy to evaporate that moisture. When you place a damp skewer full of shrimp on the grill, for at least the first several minutes, you're waiting for surface moisture to evaporate. All the while, the interiors of those shrimp are getting hotter and hotter, thus expelling more moisture, which then has to be evaporated again, thus exacerbating the problem.
Fact is, if you want shrimp that stay moist inside, they have to start dry outside. Carefully blotting them with paper towels helps, but there's an even better solution. After skewering my shrimp, I lay the skewers over the edges of a baking dish so that the shrimp are completely elevated. I then place the whole thing, uncovered, in the refrigerator for an hour. Good air circulation means the shrimp dry out rapidly.
When I'm ready to grill, I brush the shrimp with some olive oil (unlike water-based liquids, oils and other fats can improve browning) and place them over the highest possible heat, pressing down on them slightly to ensure good contact with the grill grates.
The result is juicy shrimp with a texture that practically pops in your mouth as you bite into them, all with a sweet, richly browned crust that packs plenty of flavor. In all honesty, you don't really need much more than salt and pepper and perhaps a squeeze of lemon with shrimp this tasty...
...but who am I kidding? Garlic, parsley, and olive oil are always welcome at shrimp parties. I brushed this batch of shrimp with garlic and olive oil before grilling them, then tossed them with a bit of chopped parsley, more garlic, olive oil, and lemon after they came off the grill.
They may be shrimps, but as far as flavor is concerned, they're giants.