"Processed meat refers to any meat, including pork, poultry, lamb, goat or others, that has been salted, smoked, cured, fermented or otherwise processed for preservation or to enhance the flavor. The category includes hot dogs, ham, bacon and turkey bacon, corned beef, pepperoni, salami, smoked turkey, bologna and other luncheon and deli meats, sausages, corned beef, biltong or beef jerky, canned meat and meat-based preparations and sauces, among others."
Consuming processed meats increases the risk of colon cancer.
Sodium nitrite is the usual additive. Sodium nitrite is a preservative which also improves color and flavor. Certain natural products such as celery juice contain nitrites and are sometimes substituted in "natural" processed meats.