At this month’s Beard on Books, authors David Joachim and Andrew Schloss gave us a lesson in the science of the grill. We also asked them some of our burning questions (pun intended) about the technique. Curious about the pros and cons of gas vs. charcoal grilling? Looking for a great dry rub recipe? Want tips on grilling different cuts of meat—as well as fruits and vegetables? Have a look at their generous responses below, and impress your friends with your newfound grilling wisdom at your next cookout.
There are countless gas grills out there. Is there something specific we should look for when purchasing a new one?
Look for a grill that's big enough to handle your average grilling session. If you ever want to grill-roast a whole turkey or other large roast, the grill should have a total area of at least 600 square inches (or 22 inches in diameter).
As for charcoal or gas, ask yourself the following question: do I prefer a stick-shift car or an automatic? Charcoal grills are more like a stick shift, requiring some manual maintenance to light the coals and adjust the heat. Gas grills are automatic.
The biggest difference is in the fuel: charcoal burns hotter and drier than gas, giving you better browning, more complex flavor, and a thicker crust on steaks, burgers, and other quick-cooking foods. Gas—propane or natural—consists of about 30 percent moisture from hydrogen, so it doesn't produce the same sort of crusty surface on a steak that charcoal can. Most residential gas grills also max out at about 600º F, so it's harder to get the great browning and flavor of charcoal. But gas is undeniably convenient.
Many grillers get caught up on BTU ratings, but they may not understand what it means. A BTU (British Thermal Unit) is a measure of how much heat it takes to raise the temperature of 1 pound of water by 1º F. On a gas grill, the BTU rating measures how much gas it takes per hour to fire up all the burners; it doesn't measure how hot the grill gets. So larger grills don't necessarily get any hotter than smaller ones—they just use more gas.
Can you explain what happens to the molecules and chemical makeup of protein when it hits the hot surface of a grill?
Chefs call the process "browning," while scientists call the process a Maillard reaction, named for the French chemist who discovered it in the early 1900s. Browning happens when the proteins and sugars in meat are heated to temperatures above 300º F and water evaporates. The higher the temperature gets and the longer the meat is heated, the more browning takes place.
The process starts at about 250º F with a reaction between a sugar molecule (like the glucose in meat) and an amino acid (the protein). This reaction forms an unstable structure, causing several other reactions that create hundreds of tasty by-products, which are flavor compounds that give grilled meat some of its characteristic savory, roasted flavors.
As the temperature on the surface of meat climbs, the initial Maillard by-products break down even further, creating hundreds more flavor compounds, such as hints of earth and caramel. The more darkly browned the meat gets, the more complex the surface flavor becomes, hence the importance of a hot grill when searing a steak to crusty deliciousness.
However, browning eventually turns to burning, and the flavor compounds turn from savory and roasted to bitter and unpleasant. That's why many grill cooks sear and brown a steak over high heat, then move it to lower heat to finish cooking to the desired internal temperature without burning the surface. Red meat browns more than white meat, which is why beef is so often grilled.
How should different cuts of meat be handled on the grill?
A basic rule of thumb is to grill tender meat with direct heat and tough meat with indirect heat. Direct heat basically means high temperatures and fast cooking, while indirect heat is more like barbecue: low and slow.
Tender meat generally comes from muscle groups on the animal that get less exercise, like the loin and rib areas. Retail cuts here would be beef and pork tenderloin, beef T-bone, porterhouse and strip steaks, rib roasts and rib steaks, pork loin roast, loin chops, and baby back ribs. Any ground meat can also be considered tender. These meats can be grilled directly over the heat, or seared over high heat then moved to medium or low heat to finish cooking.
Tough meats, on the other hand, need more gentle heat and added moisture (basting, mopping, or spritzing) to help break down and gelatinize the tough connective tissue. Tough meats, like those in the shoulder, leg, belly, and chest of the animal, get more of a workout. Retail cuts here would be chuck roast and brisket, pork spareribs, and pork shoulder. These are best grilled with indirect heat, meaning you heat the grill to medium-low, leave one side unheated, and put the meat over the unheated side. Then you cover the grill to trap the heat and create more oven-like conditions. Adding wood smoke is a big plus here.
Keep in mind that there are exceptions to the rule. Butchers can help you navigate the murky territory between tender and tough cuts.
Are there certain cuts of meat that work best with a dry rub? With a marinade?
The best cuts for a dry rub are those that you want a good crust on, like steaks and chops. A good crust depends on the dryness of the surface; dry spices and herbs help absorb surface moisture. A rub also helps create a visibly thick crust on a steak.
You can also pair a marinade with a rub. One of my favorite tailgating recipes is for steaks with a marinade of beer, Worcestershire, and hot sauce, and a dry rub of ground coffee, chipotle powder, cumin, salt, and sugar. Using both a marinade and a dry rub allows you to layer flavors on the surface and just below the surface of the meat.
What makes a delicious dry rub? Are there any particular ingredients that are essential to a great rub?
Salt and sugar: keep the salt and sugar proportions the same and swap out any spices and herbs you like. Here's a basic rub that I enjoy: 2 tablespoons coarse salt, 1 tablespoon sugar, 2 tablespoons paprika, 1 tablespoon ground ancho chile, 1/2 teaspoon ground cumin, and 1/2 teaspoon ground black pepper.
Another important ingredient is time. Let the rub rest on the meat for at least 15 minutes so the salt can start breaking open the protein and the sugar can combine with the amino acids, kickstarting the process of creating a delicious browned crust on your meat.
Sometimes vegetables and fruits are left behind when people break out their grills. Why do they make great grilling ingredients?
Chalk it up to sugar. We're so used to tasting fruits and vegetables raw or lightly steamed or sautéed that tasting them grilled can be a revelation. What we're tasting is their sugar—transformed.
Raw or lightly cooked fruits and vegetables taste mostly bitter, sour, salty, umami, or plainly sweet. A lack of heat leaves their natural flavor compounds intact. But grilling a wedge of pineapple or a slice of zucchini caramelizes its sugars and adds new dimensions of flavor like toffee and molasses.
Caramelization is similar to Maillard browning, minus the amino acids. If you like asparagus steamed or sautéed, try it grilled. Caramelizing its sugars intensifies the flavor and balances some of the bitterness. Same with bell peppers. The rich, roasty, lusciously browned flavor of grilled red bell peppers is much more complex and intriguing than the simply sweet and bitter flavor of raw bell peppers.
There’s no need to grill fruits or vegetables to death. Put them over medium-high heat until lightly grilled marked, yet crisp-tender.
One of our favorite vegetables to grill is corn on the cob. We've tried all sorts of methods for soaking, wrapping with the husks, without the husks, and on and on. In the end, our favorite method is to just throw the whole raw ears, husks and all, right onto a blazing hot grill. Turn occasionally and burn the hell out of them. When the green husks are black all over, they're done. Let the corn rest for 10 minutes, then peel back the husks. The silks will come right along with the husks and you can use the peeled back husk as a handle. Slather on butter, sprinkle with salt or other seasonings, and enjoy.