Barbecuing at the atomic level

Editor’s note: the following is an updated version of a column that first appeared in the Aug. 22, 2013, edition of The Citizen.

With the first days of summer upon us, barbecue season has arrived. There is something strangely appealing about a steak, a hamburger, a fillet of salmon or even vegetables cooked on a barbecue.

Cooking a meal over an open flame just seems to make for a more satisfying meal. Even a campfire adds a certain flare, although over the years, I have found campfires tend to add more ash and soot.

Outdoor cooking, over a flame, just seems to make food taste better. Knowing a little science can step it up a notch further.

Almost all of the flavour we associate with meat results from cooking. Raw meat is chewy, somewhat bland, with a heavy, fleshy, metallic taste. It is not very appealing and certainly doesn’t match the taste of a well-cooked steak.

Applying heat – cooking - results in chemical reactions between sugars, proteins, fats, and other molecules.

It even results in chemical transformations producing new molecules such as the polyaromatic hydrocarbons generated by burning. Burnt food is not good for you.

The combination of molecules is distinctive for different types of meats and even for different cuts. The subtle flavour differences between a filet mignon and ground beef are a consequence of the molecular re-combinations occurring while cooking.

In the parlance of food-tasting professionals, the flavour of cooked meat is a composite of at least two distinct components. The first is the meaty, brothy “base notes”. They are similar in all forms of meat and are the flavours telling us the stuff we are eating is meat, not broccoli or turnip. These base note flavours arise from the amino acids which are the building blocks for protein. Reaction of amino acids in meats with the sugar present result in the Maillard browning reaction. All animal proteins are made up of the same 20 amino acids and sugar is present in every cell so it is not surprising the underlying flavour of all meats is roughly the same.

The second component of the flavour for cooked meat is the lighter “species notes”. These compounds are specific to the type of flesh being cooked. They identify a flavour as beef and not chicken or lamb. Indeed, it is an absence of species notes which leads to the “everything tasting like chicken” syndrome.

These lighter flavours are primarily due to compounds formed in the fats of the animal as the meat is heated and they are vapourized during cooking, resulting in the aroma we smell while tasting barbecue.

Our sense of smell is as involved in the overall experience of a meal as our taste buds. And species notes can be quite specific, reflecting not only the type of meat but such things as an animal’s diet since many metabolites are stored in fat.

As to the actual chemical compounds producing flavour in meat, it is very complex list and not completely understood. There are more than 30 different starting compounds involved and several hundred molecules which result from cooking. Flavour is also dependent upon cooking time, cooking temperature, the acidity of the meat, the structure and acidity of any marinade used, the degree of moisture when cooking, and a host of other factors.

Still, even with all of this complicated chemistry, the basic principles of cooking over a barbecue haven’t changed much since pre-historic campfires. Generally speaking, the more heat applied the more flavour developed but the drier meat gets. A good steak is a delicate balance between flavour and texture.

All of the chemical transformations taking place require energy and the amount of energy is controlled by both the temperature and the duration of the cooking process. As a consequence, slow cooking over a low heat can sometimes be more effective than fast cooking over a high heat if flavour is important.

But for some types of meat slow cooking can result in toughness. In broad terms, animal tissues contain two general types of proteins – muscle and connective tissue. The long fibres in muscle tissue contract with heat and dehydrate so they toughen up with time. Connective proteins, on the other hand, turn to gelatin.

Cooking any meat over a barbecue is a competition between these two types of material. Muscle protein starts off soft and gets hard with heat and time whereas connective tissue starts chewy and tough but softens up as it cooks.

Good barbecuing must take into account a proper balance of tenderness and toughness. Time and temperature must be adjusted for the cut of meat. For example, with a well-marbled cut, a longer cooking time at a lower temperature produces better results. On the other hand, with a nice lean piece of meat, a quick flash on the barbecue might be just the thing to get a rare steak.

And for some people, that makes for a perfect summer meal.