Sodium nitrite in meat

Sodium nitrite plays an important role in curing and preserving, along together with sodium erythrobate which is also curing agent and preservative.
Preservation is added to inactivate, delay or prevent the growth of microbes. Usually, nitrites and salt are used to preserve dry cured ham. Nitrite plays a significant role in stability of cured meats. But some nitrites will disappear during processing and storage. The main preservative was believed to be salt.

Nitrite in meat greatly delays development of botulinal toxin (botulism), develops cured meat flavor and color, retards development of rancidity and off-odors and off-flavors during storage, inhibits development of warmed-over flavor, and preserves flavors of spices, smoke, etc

Adding nitrite to meat is only part of the curing process. Ordinary table salt (sodium chloride) is added because of its effect on flavor. Sugar is added to reduce the harshness of salt. Spices and other flavorings often are added to achieve a characteristic "brand" flavor. Most, but not all, cured meat products are smoked after the curing process to impart a smoked meat flavor.

Sodium nitrite, rather than sodium nitrate, is most commonly used for curing (although in some products, such as country ham, sodium nitrate is used because of the long aging period). In a series of normal reactions, nitrite is converted to nitric oxide. Nitric oxide combines with myoglobin, the pigment responsible for the natural red color of uncured meat. They form nitric oxide myoglobin, which is a deep red color (as in uncooked dry sausage) that changes to the characteristic bright pink normally associated with cured and smoked meat (such as wieners and ham) when heated during the smoking process.

Nitrite in meat. (2011). Retrieved from: http://www.extension.umn.edu/distribution/nutrition/DJ0974.html
Chua Hui Qing