Grâce à une chimie intéressante, la cuisson des aliments à la flamme nue produit des saveurs uniques.
La simple pensée des odeurs de fumée et des saveurs enivrantes du barbecue suffit à mettre l’eau à la bouche de la plupart des gens. L’été est là, et pour de nombreuses personnes aux États-Unis, cela signifie que c’est la saison des barbecues.
Je suis un chimiste qui étudie les composés trouvés dans la natureet je suis également un amoureux de la nourriture, y compris du barbecue. La cuisson sur un gril peut sembler simple, mais il y a beaucoup de chimie complexe qui distingue le barbecue des autres méthodes de cuisson et qui en fait une expérience si délicieuse.
La cuisson sur une flamme nue – qu’elle soit au gaz, au bois ou au charbon de bois – permet d’utiliser à la fois la chaleur radiante et la chaleur conductive pour cuire les aliments. Crédit : Romary/Wikimedia Commons
Cuisiner avec du feu
Tout d’abord, il est important de définir le barbecue car le terme peut avoir des significations différentes selon les lieux géographiques et les cultures. Le barbecue, dans sa forme la plus simple, consiste à faire cuire des aliments sur une flamme nue. Ce qui distingue le barbecue des autres méthodes de cuisson est la façon dont la chaleur atteint les aliments.
Sur un barbecue, les grilles chaudes chauffent les aliments par contact direct grâce à un processus connu sous le nom de ” cuisson à la flamme “. conduction. Les aliments se réchauffent et cuisent également en absorbant la chaleur. rayonnement directement des flammes en dessous. La combinaison des méthodes de chauffage vous permet de saisir les parties de l’aliment qui touchent la grille tout en cuisant simultanément les parties qui ne touchent pas la grille – comme les côtés et le dessus – par rayonnement de la chaleur. La gamme de températures qui en résulte produit un mélange complexe de saveurs et d’arômes. En revanche, lorsque vous cuisinez sur une cuisinière, il y a beaucoup moins de rayonnement et la plupart de la cuisson se fait là où les aliments sont en contact direct avec la poêle.
Les deux grandes options du barbecue sont la cuisson directement au-dessus des flammes avec une chaleur directe, ou plus loin avec une chaleur indirecte.
Lorsque vous faites un barbecue, vous pouvez soit placer la nourriture directement au-dessus des flammes – ce que l’on appelle chaleur directe – ou plus loin, en chaleur indirecte. La méthode de cuisson directe soumet les aliments à des températures très élevées, car la surface de grillage peut être entre 500 et 700 degrés Fahrenheit. (260 à 371 °Celsius). The indirect cooking method places the heat source to the side of the food or far below, exposing the food to temperatures around 200 to 300 °F (93 to 149 °C).
Cooking is the process of using high temperatures to drive chemical reactions that change food at a molecular level. When you cook meat at higher temperatures – like over direct heat on a barbecue – the first thing to happen is that water near the meat’s surface boils off. Once the surface is dry, the heat causes the proteins and sugars on the outside of the meat to undergo a reaction called the Maillard Reaction. This reaction produces a complex mixture of molecules that make food taste more savory or “meaty” and adds depth to scents and flavors. The reaction and the flavors it produces are influenced by many variables, including temperature and acidity as well as the ingredients within any sauces, rubs, or marinades.
A similar process occurs with vegetables. Barbecuing allows the water to evaporate or drip down without getting trapped by a pan. This keeps the vegetables from becoming soggy and promotes caramelization reactions. These reactions turn carbohydrates and sugars into smaller compounds like maltol – which has a toasty flavor – and furan – which tastes nutty, meaty, and caramel-like.
It’s much easier to control the level of charring on food when cooking on a barbecue. Credit: Lablascovegmenu/Wikimedia Commons
Char and crisp
Another hallmark of barbecued food is the unique char it develops. When foods are exposed to heat for prolonged periods of time, non-carbon atoms in the food break down, leaving behind the crispy, black carbon. This is the process of burning or charring.
Almost no one likes a completely burnt piece of meat, but little splashes of crispy char flavor can add such depth to foods. Cooking over the direct heat of a barbecue allows you to add just the amount of char to match your taste.
Unfortunately for those who like a little extra crisp, some of the chemicals in charred meat – molecules called heterocyclic amines and polycyclic aromatic hydrocarbons – are known carcinogens. Though the dangers are far lower than smoking cigarettes, for example, limiting the amount of charring on meats can help reduce the risk of developing cancer.
Smoke gives barbecued foods much of their unique flavor.
Smoky flavors
The final quintessential barbecue flavor is smokiness. Cooking over wood or charcoal involves a lot of smoke. Even on a gas grill, melting fats will drip onto the heat source and produce smoke. As smoke swirls around the barbecue, the food will absorb its flavors.
Smoke is made up of gases, water vapor and small solid particles from the fuel. Burning wood breaks down molecules called lignans, and these turn into smaller organic molecules – including syringol and guaiacol – that are mainly responsible for the quintessential smoky flavor.
When smoke comes in contact with food, the components of the smoke can get absorbed. Food is particularly good at taking on smoky flavors because it contains both fats and water. Each binds to different types of molecules. In chemistry terms, fats are non-polar – meaning they have a weak electric charge – and easily grab other non-polar molecules. Water is polar – meaning it has areas of positive charge and an area of negative charge similar to a magnet – and is good at binding to other polar molecules. Some foods are better at absorbing smoky flavors than others, depending on their composition. One way to use chemistry to make food more smoky is to periodically spray it with water during the barbecuing process.
Smoke can contain hundreds of possible carcinogens depending on what you are burning. Only a small amount of research has been done on whether grilled foods absorb enough smoke to pose a significant risk to health. But researchers know that inhaling smoke is strongly correlated with cancer.
While the idea of barbecuing your favorite dish may evoke the feeling of simple pleasures, the science behind it is quite complex. The next time you enjoy the smoky goodness of food from a grill, you will hopefully appreciate the diverse nature of the compounds and reactions that helped produce it.
Written by Kristine Nolin, Associate Professor of Chemistry, University of Richmond.
