The first stage of smoking brisket, a thick cut from the chest of a cow and the Harvard team's chosen target, must proceed at a relatively low temperature. You load the smoker's bottom with charcoal and wood and lay the meat on a platform above it. Then you let the meat heat up, over the course of several hours, to above 100F (37C). It's important that it takes a while to reach that point, because just below 105F, an enzyme called calpain reaches peak productivity, as does one called cathepsin just below 123F. These enzymes' business is to cut up a fibrous protein in the meat called collagen, which is the main component of connective tissue.

Collagen is tough and chewy, and letting the enzymes attack it serves two purposes. For one, smaller pieces of collagen will coagulate into soft, tasty gelatin later on. For another, as the temperature rises, intact fibers of collagen will contract sharply and wring moisture out of the meat. Cutting up the collagen early on means less fluid will be lost later, resulting in more tender meat. (It turns out you can use this science to get more tender steak in a sous vide cooker, without the need for a smoker.)

Smoke rings

As the temperature continues to climb, the enzymes are destroyed, and the heat triggers other reactions in the meat itself, including some involving a protein called myoglobin. When there is plenty of oxygen around, myoglobin is pink. When there's not, it turns grey or tan. According to the encyclopedic and engaging AmazingRibs.com, this is why meat that's been sitting around under plastic in the store turns grey – it will turn pink again if you let it breathe.

When you're smoking meat, two gasses in the smoke, nitrous oxide and carbon monoxide, interact with myoglobin on the meat's surface. While the rest of myoglobin degrades in the heat and turns grey, this time permanently, the myoglobin around the meat's edges hangs onto its pink colour, generating a prized, thin, rosy ring, called the smoke ring, around the brisket. And all the while, as the hours pass – 10, 11, 12 hours – the action of the smoke on the meat helps create a chewy coat of flavourful compounds on the outside.