The science of grilling with smoke

Imagine a barbecue. What do you see? Do you see a family gathered around a grill in a suburban backyard, or a community event centered around an open pit? What’s on the menu: hamburgers and hotdogs, or brisket and ribs? In the American South, true barbecue is king. In the rest of the country, grilling and barbecue are commonly conflated. The fast-and-hot grill and the slow-and-low barbecue pit are fundamentally different cooking techniques, but they do have one principal in common: they both rely on smoke to be the signature flavor.

The flavor of smoke is undeniable: earthy and sweet and with just a touch of bitterness. But how does a grill or a barbecue impart that flavor onto its target? To gain a better understanding, I called up Nate Park, a molecular gastronomy chef and the head of product development at EAT Just, Inc. As EAT Just, Inc., Chef Park is on the forefront of researching and understanding protein.

His mission to synthesize “meat” in a lab means he needs an in-depth understanding of how animal proteins respond to cooking, and what makes them delicious. Generously, he agreed to talk me through the best way to create a deliciously smoky piece of meat in a home-cooking environment.

When picking a cooking method, it’s essential to consider the nature of your piece of meat. Chef Park explains that the blitz-style cooking of the grill is best suited for naturally supple cuts, whereas the low heat and long cooking times of barbecue are designed to break down tougher sections.

The texture of a cut has a lot to do with what that muscle did while it was still part of a living animal. Hard-working muscles like the shoulder tend to have more connective tissues, which create a chewy texture. That’s not to say they’re less delicious, as Chef Park notes, the fat and collagen in a brisket or shoulder impart tons of flavor, it just takes a little longer to break down the elastin.

In addition to loosening up a stubborn cut, a long-cooking barbecue method creates ample time for smoke to penetrate the fibers of the meat.

Smoke itself is actually a cloud of tiny particles. In barbecuing culture, pitmasters pride themselves on their brisket’s “smoke ring,” a dark circle visible on the outer edge of a slice of brisket. This circle is visual evidence of the way that smoke imparts flavor: the airborne wood particles have penetrated the meat so deeply that you can actually see their effect.

Contrary to barbecue, the flavor profile of a grill is defined by ripping-hot heat. According to Chef Park, when you toss a steak on a grill there are multiple flavor-creating elements in play. The grate bars come into direct contact with the surface of the meat and create a deep caramelization. The portions of the meat between the grate bars experience convection heat, and undergo a maillard reaction. Although these chemical changes both create a brown color, the processes are different.

Caramelization is a pyrolytic reaction that occurs between sugars at extremely high temperatures. The maillard reaction is non-pyrolytic, and occurs between amino acids sugars at slightly lower temperatures. Although it’s commonly discussed in conjunction with browning meats, it’s the maillard reaction that gives bread its golden brown crust, dumplings their crispy skin, and coffee its roasted hue.

Both of these reactions create an explosion of new flavor and form new aroma compounds. The ability of the grill to quickly create both is part of what makes it a beloved and enduring style of cooking.

For a home cook craving that smoky flavor, Chef Park advises turning to the grill. Barbecuing is a complicated and time-consuming process, but grilling can easily be executed on a weeknight.

What kind of fuel should you use on the grill for the best smoke?

In addition to creating rich and satisfying flavors from the maillard reaction and caramelization, you can increase the complexity by choosing a fuel that fits. The source of the heat is where the smoke flavor will be created. Gas is quick and easy, but won’t impart much of a flavor of its own. Charcoal is a nostalgic classic, but charcoal briquettes are loaded with concerning chemical additives. Wood is a little trickier to work with, but can layer its own lovely flavor onto your dish. Each variety of tree comes with it’s own unique flavor profile. Oak for example, is laced with vanillin, the same aroma compound that is present in vanilla. When that volatile compound burns off, its flavor can become trapped in your meat.

Although I am not immune to the romance of cooking with wood, I am bound by what’s available at my local grocery store. For my steak, I'll replicate a nostalgic classic. I stock up on charcoal briquettes:

When it comes to a cut of meat, Chef Park recommends a bone-in ribeye, saying that the naturally tender and fatty meat will caramelize beautifully:

As we chat over sides, Chef Park explains that many of the same reactions that occur meat in also occur in vegetables.

Compared to meat, vegetables have a greater amount of naturally occurring sugars, and grilling will concentrate those. In the case of a grilled red pepper, the caramelization on the surface will bring out a natural sweetness:

I feel empowered after talking to Chef Park. He insisted there’s no real recipe for ribeye. Season it generously with salt and pepper, and wait about 10 minutes for the salt to begin to draw out moisture from the meat.

“Really get the grill as hot as you can,” he urges.

With this in mind, I head to a local butcher. There, I’m presented with a big rack of ribeyes. As I point to the one I want, the butcher looks me in the eye: “Salt, pepper, 3 minutes, 3 minutes, 3 minutes, 3 minutes.”

As he speaks, he flips his hand to mimic the 4 turns (or quadrillage, au Français) method of rotating a steak. For this preparation, place a steak on a grill for 3 minutes, and then 90 degrees without flipping it. After an additional 3 minutes, you flip it over and repeat the process on the other side: cooking, rotating, and cooking again. Executed correctly, this process ensures even doneness on all sides and also yields fancy criss-crossed grill marks. I understand my mission. I take the wrapped steak and nod solemnly.

As a home cook, you can research and you can prepare. You can read recipes, interview chefs, and try to understand the science of cooking, but that can’t protect you from a basic fact of life: Sometimes, bad things happen to good steaks. If you are a fan of happy endings, turn back now. Buy a piece of meat, grill it for someone you love, and don’t worry about what happened to the writer of this story and her fancy ribeye. If, on the other hand, you’re curious about the science of pyrolysis, the form of chemical decomposition sometimes known as burning, read on.

A charcoal briquette is a compact log made of previously charred wood, coal, and chemical additives that make it easier to burn. When working with briquettes, you should light the grill well before you introduce the meat. Not on does this heat up the grill, it also gives the briquettes time to burn off their chemical additives, so that no lighter fluid finds its way into your dinner.

After charcoal briquettes are initially lit, they will flare up wildly. After about 10 minutes, the flames will die down and the charcoal will be covered in white ash. Following the instructions on the side of my bag of charcoal, I patiently waited for the fireball in my grill to die down and got to work on the plan I had laid out with both a renowned chef and my butcher.

After my second turn, I flip the steak.

It was a shaggy blackened mess.

I was horrified.

All carbon-based compounds have a decomposition temperature. There is a heat threshold, and if a compound is heated above that threshold, it will break. All the water is cooked out, the proteins completely unfold, the carbons combust and turn black. My beautiful ribeye had a threshold, and I had exceeded it. To name this process, you could say that pyrolysis had occurred. Or, you could say that I had burned a perfectly good piece of meat.

I mourned for the cow who gave its life to create this meal. I texted my neighbor, who I had told to “come over for steak!,” and told her that we could no longer be friends; such was the depth of my shame and humiliation.

Shaken, I attempted to gather myself and form a new plan. Clearly, this grill was too hot. I knocked the time down, and grilled just two minutes per turn for the remaining side. The time flew by as I stared at the burnt edges of my steak and panicked. I managed to hold on to enough rational thought to remember Chef Park’s final piece of advice: Never puncture a cooking protein.

Taking the steak off the grill by stabbing it with a fork is like popping a water balloon. The point of entry creates an opportunity for all of the moisture to run out. I grab the sides of my charred steak with tongs and move it onto the plate I had optimistically placed next to the grill earlier. Mercifully, the second side has more of the maillard reaction’s golden brown color:

At this point, I don’t know what I will find when I cut into this piece of meat, but carving into it now would exacerbate any damage. When a piece of steak comes off the grill, the extreme heat that was applied to the surface of the meat is still radiating through the meat. That means that its internal temperature is still rising, proteins are still contracting, and water is still moving around inside of the meat.

Resting a piece of meat allows the tissues to relax, and juices to find their resting places. Basically, you just need to leave it alone for a few minutes. I take this opportunity to grill a few peppers, but in my distressed state I burn a few of those as well.

Before cutting into the meat I press its surface with my index finger. This old-school method of checking a meat’s doneness actually has some scientific merit: Cooking changes the texture of meat. A well-done steak will feel firm to the touch. A rare steak will squish like a wet sponge. While prodding my steak, I think about what went wrong.

The charcoal instructions that I followed suggested using 4 pounds of charcoal in a grill. Unfortunately, I neglected to account for the fact that the grill on my roof is tiny. The charcoal was concentrated inside a small area, stacked high on top of itself, in a pile that reached close to the meat. My steak was hovering only inches above the searing hot briquettes.

As I slice into my steak, I’m shocked to see the familiar brown to pink gradient. A nibble confirms: my fears were not totally justified. The shockingly dark color on the outside of my steak seems to mostly have been caused by close proximity to the smoke.

The surface is dark because it’s coated in so many tiny smoke particles. The steak has a crispy caramelized exterior and a soft, rich interior. It’s accentuated perfectly by the salt and pepper crust, and the nostalgic flavor of charcoal. I text my neighbor and tell her we can be friends again, the meat feast is back on.

---

SEARED is an occasional series from INVERSE: What makes food taste great isn't just the ingredients — it's what you do with them. This series explores the chemical transformations that happen when you cook on the grill, or with beer, or in the kitchen, or over the campfire, all from a scientific point of view.