Eons before the Impossible Burger, more than a million years before the first biblical burnt offerings, barbecue began, very likely after a bolt of lightning triggered a forest fire.
“Some bit of flesh, could have been human or animal, cooked in that fire and smelled delicious to our ancient ancestors,” says Jonathan Deutsch, Ph.D., a professor of culinary arts and science at Drexel University and author of Barbecue: A Global History. That’s when early humans began figuring out how to manipulate fire to cook food.
Burnt bone fragments discovered in South African caves suggest that Homo erectus did indeed cook meat. Paleoanthropologists have determined that the char on those bones was too intense to have been caused by a natural fire on the savanna, which tends to burn at a fairly low temperature. The meat was deliberately barbecued, they say.
Cooking provided significant benefits to early humans: Heat makes raw foods softer, easier to chew and digest, and it makes some nutrients more bioavailable. Roasting kills pathogens in scavenged meat, making it safer to eat. And cooked food tastes better, the heat triggering hundreds of chemical reactions that produce mouth-watering aromas and subtle flavors.
While we don’t know what homonids found tasty, experiments show (and zookeepers everywhere know) that apes prefer cooked sweet potatoes and carrots over raw ones, just as you do. Thank you, heat.
Since then, humans have continued to conjure up hundreds of ways to improve the flavor of food. To elevate your grilling game, it will help to understand how heat from the multitude of modern fireboxes changes the chemistry of protein, fats, and carbohydrates and improves flavor.
In short, becoming a great backyard chef means learning how to submit your meat to the right kind of heat. Here’s your guide.
Learn the Rules of Heat Transfer
Trevor Raab
The trick to a perfectly cooked hunk of protein is to get the temperature close to uniform throughout the flesh. That’s not easy to accomplish if you consider the physics of heat transfer. When heat hits meat, the molecules on the outside start moving quickly, and then gradually transfer their energy toward the center.
“Hot air cooks the outside of the meat, and the outside of the meat cooks the inside,” says Meathead Goldwyn, author of Meathead: The Science of Great Barbecue and Grilling. “But this takes time because meat is 70 percent water and water is a good heat absorber, especially when entrapped in muscle fibers and fat.”
So when cooking meat outdoors, it is critical to understand the makeup of your meat and match it to the right heat source. Meat is muscle tissue, made up of mostly water, protein, fats, and minerals. When you look at a steak, you see streaks of intramuscular fat woven among the thick bundles of muscle fibers called myofibrils.
You may or may not see connective tissue like collagen that surrounds the muscle fibers. Lean meats like chicken and tenderloin don’t have much collagen. Thicker, tougher cuts like ribs, shoulder, and brisket have a lot.
“A good rule of thumb is the thicker the meat, the lower the heat; the thinner the meat, the higher the heat,” says Meathead. (Goldwyn prefers to be called Meathead, a name bestowed upon him by his father during the reign of the TV show All in the Family.)
“I’m talking about skinny foods like skirt steak, shrimp, asparagus,” he says. “You want what I call Warp 10 cooking; crank that grill and give ’er all she’s got, Scottie!”
That method delivers a dark brown sear to the surface (known as the Maillard reaction) without overcooking the center. Keep the lid up or off and flip your food often, almost like a rotisserie. Thicker, tougher cuts of meat (like beef brisket, pork shoulder, and ribs that have a lot of fat and collagen) should be cooked low and really slow—“that’s when the magic happens,” says Meathead. The collagen slowly breaks down and melts into a rich, silky liquid called gelatin.
“It’s that melt-in-your-mouth moistness you get in braised meats, pork shoulder, and brisket,” says Deutsch. “It takes time, roasting slow at 200 to 275 degrees.”
One of the biggest mistakes backyard chefs make is cooking thick cuts at too-high heat to accelerate cooking. An experiment by scientist Greg Blonder, Ph.D., a professor at Boston University’s College of Engineering, demonstrated how impatience can ruin a meal.
The scientific advisor to the barbecuing website AmazingRibs.com roasted two identical 4″ by 3″ pork loins, one at 325º F and the other at 255º F. He inserted a thermometer into the surface and center of each. When the center hit the perfect 145º F, the outer layers of the loin roasted at higher heat were overcooked and dry, while the loin cooked longer at 225º F was moist throughout, except for the delicious brown crust.
Charcoal or Gas?
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Know the Lingo
The terms grilling and barbecuing are often confused and used interchangeably. But they’re very different cooking methods.
Grilling: With the lid up, you use high-temperature direct heat on the bottom of the food, instead of all around it. This is conduction heating; food is cooked by direct contact with a heat source: the metal grates. High heat produces little smoke. It brings meat up to its internal doneness temperature quickly; typically, within five to 20 minutes. Best foods for grilling are thin steaks, chops, hamburgers, seafood fillets, and vegetables.
Barbecuing: This is “low and slow” convection cooking: low temperatures (200° to 300° F) bathe all surfaces of the food, transferring heat indirectly for 2 to 18 hours. Only slow cooking over indirect heat will break down the connective tissue on tough cuts like brisket. “Smoke is the essence of barbecue,” says Meathead.
You can barbecue with smoke on most grills by creating a low-heat zone.
Master the Reverse Sear
Trevor Raab
Your dad probably told you the first step to grilling a great steak is to sear it over high heat to “lock in the juices.” If not, countless cookbooks have taught that method. But searing first doesn’t lock in juices. Experiments have shown that very little moisture is lost when grilling meat properly. In fact, searing at the end of cooking produces a far better result.
Here’s why: Meat cooks less evenly when it’s seared first. High heat overcooks the outside surface before the inside of the steak has warmed up. When you reverse sear, you flip the sequence, cooking your steak under lower heat so it cooks evenly and, when it’s nearly done, quickly sear both sides over high heat to get that delicious, crisp dark-brown crust.
Keep An Eye On White Meat
Trevor Raab
Think of a chicken or turkey. You’ve got white meat (the breasts) and dark meat (thighs). Each is made up of a different type of muscle fiber, called “fast-twitch” or “slow-twitch.”
“Dark meats are made up of slow-twitch muscles that produce slow, steady movement,” explains Meathead. They contain more fat for energy and myoglobin, which turns the meat darker and makes it more flavorful when cooked.”
Fast-twitch muscles are used for brief bursts of energy and contain less moisture and fat, making them dry out faster when cooked. Poultry is bred for large breasts because white meat is more popular with consumers.
“I can’t understand why,” says Meathead. “I’ll take tough and flavorful meat over mild and dry any day.”
Get Down With Browning
Raw meat has little flavor. The savory taste comes as a result of heat, which produces hundreds of volatile compounds in the proteins and sugars. Some pretty technical chemistry is happening here, but the outcome is the beautiful browning on the exterior of meat.
The browning process—which can occur in many types of food, including pan-fried fish, toasted bread and marshmallows, baked goods, and roasted coffee beans—is the result of something called the Maillard reaction. Discovered by French physician and chemist Louis Camille Maillard in 1912, the process is a chemical reaction between sugars and amino acids in protein.
The Maillard reaction begins at low heat but really gets going at around 250° to 300° F when proteins and sugars transform into more complex molecules that are responsible for the characteristic smells of roasting and searing. “Because of the Maillard and caramelization reactions, steaks develop their rich, flavorful mahogany crust or bark, bread turns golden in a toaster, fried potatoes put on a crunchy coat, and dark beer gets its darkly mysterious flavor,” says Meathead.
Molecules from fat oxidation and other compounds are also involved, writes cookbook author and James Beard Award finalist David Joachim in his book The Science of Good Food. This creates such flavors as savory peptides, sulfur compounds, toasted flavors, chocolate flavors, and earthy components.
The Maillard reaction also triggers another chemical process, the Strecker reaction, in which a compound called a-dicarbonyl combines with the amino acid methionine found in meat cells to create a flavor compound called methional, one of the main aromas of cooked meat.
Caramelizing is yet another chemical process driven by heat that imparts enticing depths of flavor to foods. Think of the sweetness of grilled vegetables, especially onions, corn, and peppers, or fruits like pineapple and peaches. This happens when fructose molecules burn at around 230º F, creating undertones of caramel or butterscotch.
Some sugars caramelize quickly and can burn—like the sugars in barbecue sauce (16 grams in just two tablespoons)—so you want to caramelize ribs slathered in sauce slowly at low temperatures.
Invest In Temperature Control
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Understand the Two-Zone Setup
Popular Mechanics
The best way to get the versatility of both very hot direct radiant heat and ovenlike indirect convection heat is to create the two-zone system. In the cooler, indirect zone, you can roast chickens or ribs slowly until they are completely cooked before transferring the meat to the direct zone to crisp the chicken skin, or caramelize the dry rub or sugary barbecue sauce without burning. You can use the same technique on charcoal and gas grills.
On a gas grill, turn off all the burners except for one. This creates a cooler zone and an adjustable hot zone. Manipulate that burner until you achieve that 225° F sweet spot for convection cooking. For searing later on the hot zone, you can crank the burner all the way up.
On a charcoal grill, push all the coals into a pile on one side of the grill, creating a hot zone for searing, and start your meat on the lower-temperature no-coal zone. Add wood chips to the pile of charcoal and a water pan above the radiant heat and you’ve just turned your charcoal grill into a smoker.
Follow Your Nose to Flavor
Trevor Raab
The tongue detects at least five distinct tastes—sweet, salty, sour, bitter, and umami (a savory, meaty taste). But our tongues don’t act alone in tasting. “We actually ‘taste’ food with all of our senses, and it is scientifically inaccurate to think of flavor as just the taste of food in the mouth,” says Charles Michel, flavor expert and former food scientist at Oxford University’s Crossmodal Research Laboratory.
Scientists suggest that about 75 percent of what we think is taste is actually smell. We think we taste in our mouths, but most of the experience happens through our nose and in our brain.
“Our noses are more sensitive than our tongues,” says Joachim. “We have about 40 million olfactory neurons picking up odors from the air and from food vapors traveling up to the nose from the back of the mouth.”
Aroma chemicals are volatile, meaning they can float through the air. When we put food in our mouths, those vapors strike olfactory receptors in the back of the throat, contributing to the taste experience. But as 1st-century gourmand Apicius said, “We eat first with our eyes.”
Indeed, the mere sight of delicious morsels can trigger our salivary glands as our brains remember enjoyable meals past, especially savory, high-fat foods. Electrical neuroimaging analysis has found that human brains become alert to images of high- energy foods within 100 milliseconds, faster than our brains react to the sight of foods lower in nutritional value.
Researchers say that we find high-energy foods more appealing because they have a high incentive value. Visual hunger may be an evolutionary adaptation that helped us find foods that would sustain us longest.
In another experiment, a study called “The Butcher’s Tongue Illusion,” researchers at the University of Oxford’s Crossmodal Research Laboratory set out to prove that one sensory organ—namely the eyes—can influence another organ’s assessment of flavor. Researchers instructed subjects to place their heads inside a box fitted with an angled mirror that would allow them to view their tongue when they stuck it out and held it motionless between their teeth.
Unbeknownst to them, the mirror showed a fake tongue, not their own. When the scientists touched the rubber tongue with a Q-tip, the subjects reported feeling their own tongue being touched. In a second test, the fake tongue was illuminated with a red laser pointer. Some participants reported feeling heat on their tongues; others, a cool stimulation.
When we see and smell the smoke rising from the grill, when we salivate to the fat dripping off roasted meat and ultimately taste its savory flavor on our tongues, we are participating in an ancient multisensory experience that continues to draw us to the seductive tango of fire and flesh. So, when you spark up that barbecue, show respect to those meat-eaters who singed their forearm hairs before you.
Don’t overcook that steak.
This article appeared in the September 2019 issue of Popular Mechanics. You can subscribe here.