Curing salt is central to the art of charcuterie, a broad category of cooking that includes preparing cured meat products, such as bacon, sausages, pancetta and prosciutto. Ready-made curing salt is table salt mixed with either sodium nitrate or sodium nitrite in a ratio that is specified by the U.S. Department of Agriculture. Some of curing salt's aliases are Prague powder #1, Prague powder #2 and pink salt.
Curing Salt's Curious Longevity
Curing salt has no hard expiration date. If your curing salt is only salt and sodium nitrate or sodium nitrite, it's good forever. Salt itself never goes bad, though yellowing and other discoloration is common. Moisture is a potential problem as it attracts microbes. To prevent such threats, store curing salts in dry, moisture-lock, airtight containers and in a cool dry place, such as your pantry or a dry goods storage closet. Do not refrigerate or freeze curing salt.
Other Ingredients, Other Lifespans
Manufacturers often add to curing salts other flavors, fat stabilizers and chemical humectants, such as propylene glycol, an agent that attracts and retains water. Dye is another common ingredient, especially red and pink, the reason for calling it pink salt. The color allows you to distinguish curing salt from table salt, which is important because nitrites in large doses are lethal. Artificial flavors and propylene glycol are perishable, yet they too don't have standard expiration dates. One curing salt manufacturer suggests its product is good for three years beyond the best by date printed on the bottle. If your curing salt smells rancid, throw it out and buy a fresh bottle.
Curing Salt's Confusing Names
Prague powder #1, Prague powder #2, tinted cure and pink salt are all curing salt. Prague powder #1 contains table salt and sodium nitrate; Prague powder #2, table salt and sodium nitrite as do tinted cure and pink salt. Pink curing salt is not Himalayan pink salt, or halite, a naturally colorful edible salt that does not contain sodium nitrate or nitrite. Keeping these curing salts dry will keep them fresh and usable indefinitely.
Sodium This, Sodium That
When curing salt comes into contact with meat, any bacteria present in the meat react with the sodium nitrate. The sodium nitrate releases nitrite. Sodium nitrite is the true preserving ingredient. Nitrite kills bacteria and stabilizes hemoglobin, retaining the rosy pink flavor associated with fresh meat. Nitrite also draws water out of the meat, concentrating the flavor; and it unravels the proteins in a process called denaturation, similar to "cooking" the meat over heat. Eventually, the nitrite kills all the bacteria, leaving flavorful, cooked, salted meat behind. The nitrates in curing salt are partly responsible for keeping the product fresh, free from bacteria and usable for years.