Curing meat means treating it to keep it from spoiling, thereby preserving it for future use. Interesting that the “cure” prevents, rather than treats, the problem.
Ancient methods of curing meat include smoking, drying, and salting. When refrigeration and mechanical packaging came along, these flavor-intensive methods became unnecessary and experimentation with chemical curing began.
Meats cured with pure salt (sodium chloride, NaCl ) tend to turn an unappetizing brownish-gray color. But about a hundred years ago it was found that if saltpeter (potassium nitrate, KNO3 ) was added to the salt, the meat turned a nice, rosy pink. Today, we know that the potassium nitrate was being reduced to potassium nitrite (KNO2 ) by microorganisms on the meat and that it’s the nitrite that does the job.
So potassium or sodium nitrite is now added to the curing salt directly, and saltpeter is rarely used. Nitrites give the meat a tangy flavor and an appetizing color, owing to the reaction of nitrite with myoglobin to form nitric oxide myoglobin. They also fight rancidity and the development of off odors and off flavors during storage.
But the most important function of nitrites is to inhibit the growth of pathogenic bacteria such as Staphylococcus aureus and Clostridium botulinum, the bacteria that cause botulism.
There’s only one hitch in this rosy (literally) picture: Not only does nitrite kill botulin bacteria, but in doses of about 20 milligrams per kilogram of body weight it can kill humans as well. Fortunately, much of the nitrite added during curing is decomposed by cooking.
The USDA limits the amount of residual nitrite in any finished meat product, cooked or raw, to a maximum of 70 parts per million. At that level, a 150-pound person would have to eat 43 pounds of the product at one sitting to get a lethal dose of nitrite. That’s a lot of bologna.
The bad news is that nitrites in cured meats can react with amines from the amino acids in heated meat protein to form chemical compounds called nitrosamines, many of which have been shown to cause cancers in experimental animals and are likely to be carcinogenic in humans as well. Bacon is a special case, because the high temperatures at which it is cooked are particularly conducive to nitrosamine formation. For that reason the USDA permits less nitrite to be used in curing bacon than in curing other meats.
Small amounts of nitrosamines occur naturally in some of our foods, such as fish. Moreover, bacteria in our mouths can change nitrate, which is present in many vegetables, to nitrite, which can then act upon the amines in the vegetables’ proteins to form nitrosamines. Nitrosamines can also be formed by the action of the highly acidic juices in our stomachs upon a wide variety of amine containing foods. Small amounts of nitrosamines can also be found in beer and tobacco.
All this may sound frightening, but don’t give up on cured meats as a way of avoiding nitrites and nitrosamines. In our society we can’t always eat fresh meat; some meat products must be cured before being distributed widely. Their small and carefully regulated nitrite content is a winning tradeoff against the risk of botulin poisoning.
On the other hand, it might be prudent not to tempt the nitrosamine gods by smoking a couple of packs of cigarettes while consuming 43 pounds of cured sausages and washing it down with a few gallons of beer.
In other words, stay away from Oktoberfest.