What's July Fourth without the sizzle of the grill and plates piled high with hot dogs and burgers (and veggie burgers for the non-carnivores among us)? But if you want to avoid shriveled dogs and tough patties, you've got to understand not just the art of grilling, but the science. Don't worry: LiveScience is here to help.

We got on the phone with Dave Joachim, a food writer and author of "Mastering the Grill: The Owner's Manuel for Outdoor Cooking" (Chronicle Books, 2007) and "Fire It Up. 400 Recipes for Grilling Everything" (Chronicle Books, 2011). When Joachim says "everything," he means it: His cookbook contains recipes for everything from bison cheeseburgers to grilled watermelon.

We asked Joachim what's really going on when you cook on charcoal, gas or wood and why a seared steak is so delicious. Read on for what we learned — and for Joachim's recipe for those bison burgers.

What's the difference between grilling and barbecue?

People sometimes use the terms "grilling" and "barbecuing" interchangeably, Joachim said, but they're actually polar opposites.

"Grilling is typically cooking directly over a heat source at relatively high heat, 350 degrees Fahrenheit (176 degrees Celsius) or above for a relatively short amount of time, about 30 minutes," Joachim said. "Barbecue is somewhat the opposite. It's cooking at 250 degrees F or less for a long period of time, usually at least two hours."

What happens to meat as it cooks?

Meat goes through a few stages when you put it over heat. At about 110 degrees F (43 degrees C) internal temperature, muscles fibers begin to coagulate and toughen, Joachim said. At around 115 degrees F (46 C), fats start to melt.

When the internal temperature of the meat hits 130 F (54 C), the proteins in the muscle fibers denature, meaning that long, convoluted strands of protein lose their shape and unravel. Then they coagulate back together. That's when meat starts to take on an opaque look. At 160 F (71 C), the connective tissues that hold together the muscle fibers start to melt and turn into gelatin. That's the jelly-like yellowish-white stuff you see at the bottom of a roasting pan that you've cooked meat in, Joachim said. [7 Foods Your Heart Will Hate]

When you barbecue, Joachim said, the goal is to use those long, not-so-hot cooking times to melt the connective tissues and create barbecue's trademark tender mouthful. Grilled cuts of meat usually contain less connective tissue, so they don't need hours of heat to taste delicious.

Does it matter if I cook on gas, charcoal or a wood grill?

Absolutely, Joachim said.

"The big difference is the temperature and the moisture," he said. "Charcoal and wood burn hotter and drier than gas."

That's because propane contains moisture, Joachim said. For every hour of grilling on gas, you release a half-cup to a cup of water vapor into your grill. That keeps the temperature down and prevents the formation of a seared, browned crust on your meat.

Some gas grills now come with a sear burner, Joachim said, which is a ceramic block that holds heat better than the grill grates. Because the burner can build up more heat, home grillers can use it to brown the outside of a steak or pork chop to get that dark crust.

Okay, but why does a seared crust taste so good?

Time for a chemistry lesson: When you apply heat to meat, you get something called a Maillard reaction. The amino acids that make up the meat's proteins react with sugars in the meat, creating hundreds of flavor compounds.

Maillard reactions make pretty much everything taste awesome, including roasted coffee, grilled vegetables and even your morning toast.

"Any browned food tastes so good because it's something new added to the food," Joachim said. Browning doesn't just lock in flavors; it creates new ones.

What's the key to the perfect Fourth of July burger?

"The trick with ground meat is once you grind up meat, you're grinding up the muscle fibers, and these are what hold the moisture in," Joachim said. "What I recommend doing is adding moisture back in."

That added moisture can take many different forms, Joachim said. He uses apple butter in turkey burgers and steak sauce in hamburgers. Simplest of all, he said, you can just mix ice water into the ground meat, along with whatever seasonings you want to use to spice up your burger. The ice water adds in moisture while keeping the inside of the burger cool so it doesn't overcook. [Grilled to Perfection: Joachim's Recipe for Bison Cheeseburgers with Horseradish Mustard]

Fat is another important component of a good burger, Joachim said. He recommends a ground beef that's 80 percent protein and 20 percent fat. Contrary to popular belief, though, extra fat doesn't make a burger juicier. Instead, fat stimulates saliva production, moistening your mouth.

When you add fat to a burger, Joachim said, it's not getting juicier: "You're getting juicier."

I'm a vegetarian, get me out of here.

Wait, come back! Just because you don't eat meat doesn't mean you're doomed to an Independence Day full of limp veggie burgers. The grill is the perfect place to cook plants, Joachim said.

"Grilling plant foods completely changes their character and makes them taste better," Joachim said. "Grilled tofu, for instance, tastes so much better than braised or steamed or sautéed."

The trick to grilling vegetables is remembering that they're edible raw, Joachim said, so you don't need to leave them on the grill until they scream for mercy. Just oil them, sear them over medium-high heat and enjoy. For firmer veggies like corn, you'll need a little more time. For corn, Joachim says simple is best: Throw the ears, husks and all, on the grill over medium-high heat and let them cook for 15 or so minutes, turning occasionally, until the husks are blackened. Inside, the corn will be perfectly done. [Read: How to Have a Healthier Cook Out]

What is the craziest thing I could possibly put on the grill?

You can grill doughnuts, Joachim said. Make them or buy them, coat them with cooking spray and put them on the grill over medium heat. The heat will caramelize the sugar and puff up the dough.

"It's unlike a regular doughnut, and it's just so completely delicious," Joachim said.

If that's not impressive enough for your July Fourth guests, confuse them by grilling watermelon. These fruits are more than 90 percent water, Joachim said, so putting them on the grill concentrates their flavor and gives you an entirely new texture.

This article was reprinted with permission from LiveScience.

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