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"Never ever press down on your burger!"
How many times have you read that in a book or heard a TV chef say it? "It squeezes the juices out!" they cry. "It turns your lunch into a hockey puck!"they scream. Sometimes they'll try and appeal to your compassionate side. "Certainly there are some things that deserve crushing. Evil grapes. T-800 model Terminators. Rebel scum trapped in trash disposals. But what has that poor, defenseless little burger ever done to you to deserve such a fate?"
You've heard it so many times you can't help but believe it's true, right?
Well ok, Mr. Smarty-Chef, I'll believe you, but first! You must answer me these questions three:
- Question the first: One of my favorite burgers in New York—the one that folks'll stand in line for an hour to get—is smashed. How does the Shake Shack burger still retain such abundant juiciness?
- Question the second: The SmashBurger chain of fast-casual burger joints has built its reputation on its smashing technique. Are all of its fans (which are legion) deluded into enjoying the flavor of dry hockey pucks?
- Question the third: I just had what was the finest burger I've tasted in recent memory at Off-Site Kitche in Dallas where—guess what?—the burgers are smashed. What gives?
Now, these questions are largely rhetorical, and anybody who's been making burgers for a while or has been reading The Burger Lab for long enough knows the answer: not smashing your burgers is always sometimes only sort of occasionally good advice.
When is it ok to smash your burgers and when is it not? Well first, let's consider the advantages of smashing a burger.
In Crust We Trust
There's really only one reason to do it, and it's the reason that all three of the burgers I mentioned above (as well as countless others) taste so good: The Maillard Reaction. The Maillard Reaction—also known as the browning reaction*—is a series of chemical reactions that take place when protein-rich foods are heated. Large proteins break into smaller compounds which react with others, recombining into new configurations. They break apart again, recombine, and on and on in a cascade of chemical reactions that creates hundreds of brand new compounds.
* This is not to be confused with caramelization, which is a reaction that takes place when sugar is heated—you can't caramelize a steak or a burger, no matter what any TV chef tells you!
It's what creates the crust on your steak or burger, the golden brown color on your toast, and the complex, pleasing aromas and flavors that accompany that browning. It's the smell of a steakhouse and fresh bread from the oven. And it's the smell of a good burger joint. It doesn't just make meat taste good, it actually makes it taste more meaty.
Most of the browning reactions don't take place until foods are heated to at least 300°F or so, and are greatly accelerated at temperatures higher than that, so if maximizing browning is your goal when cooking a burger (and it should be!), then it's plain to see why smashing a burger can improve its flavor: It maximizes contact with the pan, increasing the surface area directly in contact with the hot metal, and maximizing browning.
While it's true that given enough time you can brown even a non-smashed burger, there are a couple problems. If the heat is too high, the browning will be uneven—at worst, the bits of meat directly in contact with the skillet or griddle will burn before the bits elevated above it can even begin to brown properly. With lower heat, you can get more even browning, but it takes longer—long enough that your burger will end up overcooking in the middle (and overcooking is the real path to dry burgers).
Smashing allows you to get a deep brown crust before the interior overcooks, even with a relatively small patty.
The Juice is Loose
So when is it not a good idea to smash? Well there's the obvious: you can't smash a burger on a grill.
But what about in the skillet or griddle? I cooked through a couple dozen burgers smashing at various stages during cooking in order to make sure. The results? If you don't want to lose juices, you must smash within the first 30 seconds of cooking.
When ground beef is cold, its fat is still solid and its juices are still held firmly in place inside small, chopped up segments of muscle fibers. That's the reason why you can push and press on ground meat without squeezing out too much liquid, and the reason why you can smash a burger during the initial phases of cooking without fear of losing moisture.
But what happens after that initial cooking phase as the meat warms up?
When you look at a burger under a microscope, you basically see what amounts to an interconnected network of proteins interspersed with fat and water-based liquids. Like all meats, as a burger cooks, this protein network tightens, squeezing out liquids. Simultaneously, the fat begins to render and liquefy, allowing it to be squeezed out right along with the other juices.
In a properly formed burger—one that is made with meat that's been ground properly and kept chilled and minimally handled while shaping—the protein matrix is relatively loose. Even once fat has been liquefied and juices have been squeezed out, they can remain trapped in the patty, only getting released when you bite into the burger, in much the same way that liquids can be trapped in a sponge and only released by squeezing.
Press down on a burger during this phase, and the juices come gushing out into the skillet or onto your coals. You're left with what amounts to a meat patty with the texture of a sponge that's been run through a ringer.
All burgers will lose weight as you cook them—it's not possible to hold on to all liquefied fat and exuded juices. In my testing, four-ounce burgers that started as round pucks and were smashed down to a half-inch thickness any time before 30 seconds still lost a little over 20 percent of their weight while cooking. This was comparable to four-ounce burgers that were formed into 1/2-inch disks and cooked with no smashing at all. Both burgers tasted quite juicy, while the smashed burger had better flavor (obviously!).
Once you start smashing after the 1 minute mark, that's when juices really start to flow and you end up with a dramatically drier burger—a good 50 percent more moisture is lost in a burger smashed after 1 minute versus one smashed within 30 seconds.
Move into the territory of double or even triple smashing—that is, smashing once at the beginning, then getting impatient and smashing again and again during the middle and latter phases of cooking—and a burger can easily lose half of its weight to the evil griddle gods. I've seen more than one short order cook at a greasy spoon with a backup of orders resort to this dastardly method, and not once have I ever taken more than one bite of a burger that's been exposed to it.
If you've read my breakdown of the Fake Shackburger, you already know the best way to cook a smashed burger at home, but I realized that I've never produced a more generic recipe for one.
Three Rules For Smashing Success
Other than the basic rules of burgers (use meat with at least 20 percent fat, a good blend of cuts or straight ground chuck, preferably freshly ground, don't add salt or other seasonings until after the patties are formed), making a smashed burger is simple. Just follow these basic rules:
Rule 1: Use a good stainless steel or cast iron skillet.
The goal is steady, even heat, so you want to use a relatively thick pan and allow it to preheat for long enough that there are no hot or cool spots. I let my pans preheat over medium heat for a few minutes, pumping them up to high just before I add the meat. Don't use a non-stick pan, as the high heat required for a good crust is damaging to non-stick coatings and can cause them to vaporize. You don't want to breathe that junk in.
Rule 2: Smash early and smash firmly.
I have a thick, flat, sturdy metal spatula specially devoted to the task of smashing burgers. You'll need one to do this properly. Form four to five ounces of meat into a puck about 2-inches high, season liberally with salt and pepper, and place it on the preheated skillet, then smash down on it with the spatula, using a second spatula to add pressure if necessary. Then just cook without moving until a deep brown crust develops. This'll take about a minute and a half.
Rule 3: Leave no crust behind.
The whole goal of smashing is to develop a nice browned crust, so it's important that you scrape it all up intact. Once again, a sturdy metal spatula is your friend. I find that flipping the spatula upside down to help scrape the crust off is pretty effective. If you crust is properly developed and your burger properly smashed, it should spend very little time on its second side—just enough to finish cooking through and to allow cheese to melt (if added). 30 seconds or so.
And, well, that's it. So simple, so fast, so freaking delicious. Do it.
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About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.