Sodium nitrite is added to various meats and fish as a preservative and color fixative. It retards the growth of bacteria and also develops a pink color in the meat, according to "Nitrite in Meat" by Richard Epley et al. The U.S. Department of Agriculture regulates the amount of sodium nitrite that can be safely added to meat, recognizing that higher amounts can be toxic.
How It Works
After the addition of sodium nitrite to meat, the nitrite is converted to nitric oxide. This reacts with a natural red pigment in meat called myoglobin to form nitric oxide myoglobin, which has a deep red color. If the product is smoked, heat during the smoking process changes to the color to pink. The heat can result in the formation of compounds called nitrosamines, which are known to be carcinogenic, but the federal government believes that the benefits of sodium nitrite outweigh the risks.
Limits
The amount of sodium nitrite that a manufacturer can legally add depends on what the food is. The amount cannot exceed 10 parts per million in smoked, cured tuna when used as a color fixative. The level cannot exceed 200 ppm when it is used as both a preservative and a color fixative in smoked, cured fish like salmon. When used as both a preservative and a color fixative in combination with sodium nitrate, another preservative, sodium nitrite must not exceed 200 ppm after processing in cured poultry, meat or wild game.
Regulation
The manufacturer must also include the use of sodium nitrite on the consumer product label, along with instructions for the proper preparation for consumption. The USDA regulates the use of sodium nitrite by meat processors, while the Food and Drug Administration validates studies concerning its safety for human beings. The conditions under which amines from proteins combine with sodium nitrite to produce nitrosamines is not clear. Factors like the amount of sodium nitrite, other ingredients, and processing and storage conditions may be involved.
Toxicity
The fatal dose of sodium nitrite is thought to be from 22 mg to 23 mg per kilogram of body weight. Such levels can cause a condition called methemoglobinemia, when hemoglobin in red blood cells loses its ability to carry oxygen. However, to ingest a dose of 22 mg per kg of body weight, a person weighing 154 lbs must eat more than 18.6 pounds of meat containing 220 ppm sodium nitrite in one sitting.
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