Purposeful curing appears to date back to as far back as 3000 B.C., when the Sumerians were believed to have salted their meats for preservation. The Chinese and Greeks are also believed to have performed such practices around the same time. By 63 B.C., fish-salting centers existed in Spain.

An important ingredient in curing is salt, which draws out water, blood, and other impurities in food, making them less susceptible to spoilage and rot. It aids in Osmosis, Dehydration, Fermentation, and the Denaturing of proteins.

Sugar and other sweeteners aid the curing process by lessening the harsh flavor salt-cured food may take on. The sweetener also helps balance the flavor, counteract bitterness in liver products, stabilize color in cured meats, increase moisture in finished products, and provide a good nutrient source for fermentation. Spices and herbs are also often used to enhance flavor, especially sweet spices such as cinnamon, allspice, nutmeg, mace, and cardamom.

Dry Cures are sometimes made up of salt alone, but usually contain a mixture of salt, a sweetener, flavorings, and a prepared curing blend such as TCM or Prague Powder. These agents should have direct contact with the food to ensure an evenly preserved product. A dry cure that has been dissolved in water is known as brine.

Smoking, which can be done in the open or in a smoking device, helps preserve and add flavor to foods including salmon, ham, bacon, sausage, or even cheese and fruit. Woods from trees including hickory, oak, cherry, walnut, chestnut, apple, alder, and mesquite are often used since they provide a rich, aromatic smoke with few particles that can make food sooty or bitter, and other flammable materials such as teas, herb stems, whole spices, grapevine clippings, corn husks, fruit peels, and peanut shells are also sometimes added to add flavor. Cured foods that are to be smoked should first be air dried long enough to form a tacky skin known as a pellicle, which acts as a protective barrier from bacteria for the food and helps capture the smoke's flavor and color. Smoking is not generally done on its own though, as its preserving properties only have a limited effect. The process can take anywhere from 20 minutes to several days.

References: Garde Manger: The Art & Craft of the Cold Kitchen; CIA 2000l; Pages4 - 7, 133 - 142
Oxford Companion to Food; 1999; Page 728 - 729
Larousse Gastronomique; 2001; Page 1098