Nitrites and Nitrates in Food: Uses, Risks, and Safety
Nitrites and Nitrates: E-249 Potassium nitrite (KNO2), E-250 Sodium nitrite (NaNO2), E-251 Sodium nitrate (NaNO3), E-252 Potassium nitrate (KNO3)
1. Nitrates and Nitrites: Growth Inhibitors
Nitrates and nitrites are potent inhibitors of the growth of Clostridium botulinum, a bacterium that produces botulinum toxin, which is extremely toxic. A dose of 0.1 to 1 millionth of a gram can be fatal, although the toxin is destroyed by heat. This toxin causes botulism, a potentially fatal disease.
2. Historical Use in Curing Meats
Nitrates, particularly potassium nitrate (saltpeter), have been used in curing meat products since Roman times. The effect of curing, which also involved salt and spices, is to ensure the conservation of meat and enhance the color change. The cured color is formed by a chemical reaction between the meat pigment, myoglobin, and the nitrite ion. When nitrates are added, they are converted into nitrites, in part by the action of microorganisms.
3. Natural Occurrence in Plant Foods
Nitrates are natural constituents of plant foods and can be found in very high concentrations. Nitrites are found in much lower concentrations.
4. Production of Nitrites
Nitrites are obtained from the oxidation of ammonia.
5. Food Applications and Restrictions
In Europe, nitrites and nitrates are not allowed in heat-treated, cured, dried meat products, foie gras, cheese, processed cheese, and escabechado.
6. Herring and Risks
a) Acute Toxicity
Nitrite is toxic (2 g can be fatal) and can bind to hemoglobin in the blood, forming methemoglobin, which cannot carry oxygen. Food poisoning can be fatal. Several fatal cases of sausage ingestion with high nitrite amounts have been reported due to improper mixing during manufacturing. To avoid this, nitrite can be pre-mixed with salt. In many countries, this is mandatory.
Children are more susceptible to this poisoning due to lower hemoglobin levels, and in very young children, the fetal form of hemoglobin, which is more sensitive to nitrites, can persist in their blood for some time after birth.
b) Formation of Nitrosamines
Nitrosamines, which are carcinogens, can form in food or the body. Techniques to minimize nitrosamine formation include:
- Reducing the concentration of nitrite and nitrate. The amount of nitrates reaching the consumer is always much less than that added to the product, as they are highly unstable and reactive.
- Using other additives that block the chemical mechanism of nitrosamine formation. These additives include ascorbic acid (E330) and its derivatives, and tocopherols (E-306 et seq.). Ascorbic acid is frequently used, and in some countries (USA, for example) its use with nitrite is mandatory.
However, eliminating nitrites as additives does not exclude them from the body. While usually less than 3mg/day are ingested in food, about 12 mg/day are secreted in saliva, and about 70 mg/day are produced by intestinal bacteria.
7. Risk/Benefit Ratio
The risk of nitrosamine formation (carcinogenic potential) must be weighed against the benefit of avoiding botulism. With measures such as restricting levels and using inhibitors of nitrosamine formation, regulators in all countries accept the use of nitrates and nitrites as food additives, as necessary to ensure the safety of certain foods.