The Chemistry of Grilling
In the barbecue, the meat is placed over an open heat source, such as glowing coals, a gas flame or an electric grill. The heat is transmitted by radiation and can only be used for very tender and thin slices of meat. The high temperature ensures that the meat browns very quickly and has a crispy crust, while the interior of the meat is cooked by conduction through the meat juices. Both processes need to keep pace, otherwise the outside will be charred before the inside is cooked. Some craftsmanship is required.
Barbecuing gives the meat a very attractive and appetizing aroma. This is caused by all kinds of chemical reactions (Maillard and caramelization reactions) that take place on the meat. These reactions only occur at temperatures above 302 °F (150 °C). In cooking methods such as steaming, braising or stewing, the temperature does not exceed 212 °F (100 °C) and therefore these reactions do not take place. Due to the presence of proteins and sugars, the reactions to the meat are very complex. In this process, volatile, strongly scented, aromatic, sweet, bittersweet and brown-colored reaction products are formed.
This process can be accelerated if the meat is rubbed with a sugar-containing liquid (honey or soy sauce). These ingredients can therefore be found in marinades, barbecue- and similar sauces, usually in combination with an acid (lemon juice or vinegar). These acids convert the sucrose ("ordinary" sugar) into the two simple sugars glucose and fructose. These in turn react more quickly with the amino groups from the proteins and thus promote aroma formation and browning reactions.
One of the most efficient methods is grilling small pieces of meat (kebabs) on metal pins. The pins conduct the heat directly to the inside of the meat, allowing the meat to cook faster and lose less meat juices. Meat that is grilled outdoors on the barbecue gets a nicer, firmer crust than meat from the grill oven. In the grill oven, the resulting water vapor can hardly escape, making the crust less hard and more permeable. So more moisture will evaporate from the meat, resulting in a less juicy piece of meat.
Author Frans M. de Jong