Just the thought of the smoky and intoxicating flavors of barbecue is enough to make most people salivate. Summer is here, and for many, that means grilling season. Cooking on a grill may seem simple, but there are a lot of complex chemical ingredients that make grilling different from other cooking methods and result in such a delicious experience.
Cooking over an open fire with hot coals - whether gas, wood, or charcoal - uses both radiant and conductive heat to cook food.
Cooking with Fire
First, it's important to define barbecue because the word can mean different things in different geographical locations and cultures. Barbecue, at its most basic, is cooking food over an open fire. What makes grilling different from other cooking methods is how the heat reaches the food.
On the grill , the hot grill heats the food through direct contact, a process called conduction. Food also warms and cooks by absorbing direct radiation from the flame below. This combination of heating methods allows you to grill the parts that are in contact with the food while simultaneously cooking the parts that aren't in contact with the grill - like the sides and top - with radiant heat. The resulting temperature range creates a complex mixture of flavors and aromas. In contrast, when cooking on the stovetop, there is much less radiation and most of the cooking occurs where the food is in direct contact with the pot.
The two main options for grilling are cooking directly over the flames with direct heat, or cooking farther away with indirect heat.
When grilling, you can place the food directly over the flame, which is called direct heat, or use indirect heat further away. The direct cooking method subjects food to very high temperatures, as the temperature of the grill surface can range from 500 to 700 degrees Fahrenheit (260 to 371 degrees Celsius). Indirect cooking places the heat source to the side or far away from the food, exposing it to temperatures of approximately 200 to 300°F (93 to 149°C).
Cooking is a process that uses high temperatures to drive chemical reactions that change food on a molecular level. When you cook meat at a higher temperature - such as direct heat on an grill - the first thing that happens is that the water near the surface of the meat is boiled off. Once the surface dries, the heat causes the proteins and sugars on the outside of the meat to undergo a process called the Maillard reaction. This reaction produces a complex mixture of molecules that makes food taste saltier or "meatier" and adds depth of aroma and flavor. This reaction and the flavors it produces are affected by many variables, including temperature and acidity, as well as the ingredients in any barbecue-added sauces, powders, or food-prep marinades.
A similar process occurs with vegetables. Grilling allows moisture to evaporate or drip off without being trapped in the pan. This keeps the vegetables from becoming soggy and promotes the caramelization reaction. These reactions turn the carbohydrates and sugar into smaller compounds such as maltol - which produces a toasty flavor - and furans - which taste nutty, meaty and caramelized.
It is easier to control the degree of charring of food when cooking on the grill.
Burnt and crispy
Another characteristic of grilled food is the unique char aroma it creates. When food is exposed to high temperatures for an extended period of time, the non- carbon atoms in the food break down, leaving behind crunchy black carbon. This is the process of burning or charring.
Almost no one likes a completely charred piece of meat, but a little bit of crispiness can add that depth to food. Cooking under the direct heat of a grill allows you to add just the right amount of carbon to suit your taste.
Unfortunately for those who like that extra crispy crust, some of the chemicals in the charred meat—molecules called heterocyclic amines and polycyclic aromatic hydrocarbons —are known carcinogens, Although it's far less dangerous than smoking, limiting the amount of charring in meat can help reduce the risk of cancer .
Smoke gives barbecue food many unique flavors.
Smoky flavor
The last typical barbecue flavor is smoky flavor. Cooking over wood or charcoal involves a lot of smoke.Even on a gas grill, melted fat can drip onto the heat source and create smoke. As the smoke swirls around the grill, the food absorbs its flavor.
Smoke is composed of small solid particles of gas, water vapor and fuel. Burning wood breaks down molecules called lignin , which turn into smaller organic molecules -- including eugenol and guaiacol -- that are largely responsible for the typical smoky flavor.
When smoke comes into contact with food, the components of the smoke are absorbed. Food is particularly good at absorbing the flavor of smoke because it contains fat and water. Each of them binds to a different type of molecule. In chemical terms, fats are nonpolar -- meaning they have a weak electrical charge -- and tend to latch on to other nonpolar molecules. Water is polar - meaning it has areas of positive charge and areas of negative charge similar to a magnet - and is good at binding to other polar molecules. Some foods absorb smoky flavor better than others, depending on their ingredients. One way to chemically give your food a smokier flavor is to regularly spray it with water during the grilling process.
Smoke can contain hundreds of possible carcinogens, depending on what you're burning. There has been only a small amount of scientific research into whether grilled food absorbs enough smoke to pose a significant health risk. But researchers know that smoke inhalation is closely linked to cancer.
While the idea of grilling your favorite dish may evoke feelings of simple pleasure, the science behind it is quite complex. The next time you enjoy smoked food from the grill, hopefully you can appreciate the diversity of compounds and reactions that help create it.
