Sodium Nitrite and Nitrate Curing Salts

Sodium nitrate and sodium nitrite, also known as curing salts, are preservative food additives widely used in the food industry, they can be used together or alone. They have a very similar chemical composition. Precisely for this reason, many people get confused when deciding which of the two is best used when preparing preserves or meats that will require periods of curing, smoking, fermentation or extending their shelf life for later consumption. The difference in the chemical composition of these two additives is just one oxygen atom, sodium nitrite (NaNO2) has two oxygen atoms, while sodium nitrate (NaNO3) has one more oxygen atom.

Nitrates can transform into nitrites when losing oxygen and the opposite can also occur. They are widely used in the food industry because they prevent the growth of bacteria, help combat rancidity and change the color of the meat to a reddish tone, typical of cured products (ham, bacon, sausages, etc.), which occurs due to reaction of nitrite with myoglobin present in meat. The pink color is obtained due to the pigment nitrosylhemochrome, which is the heat-denatured form of nitrosomyoglobin, which, in turn, is formed through the reaction between nitric oxide (NO) from nitrite (NO₂) and natural myoglobin from meat. Understanding the set of reactions that involve nitrite is essential for understanding the formation and color stability of cured products.

Preservatives are added to extend shelf life and prevent the growth of harmful microorganisms. In the specific case of processed meat foods, they have been used for more than five decades and nitrates and nitrites have been playing an important role in preserving, providing color, flavor and texture to such products. They are among the most effective preservatives as they have antimicrobial action, inhibiting anaerobic bacteria, such as, for example, Clostridium botulinum (botulism).

Should I use sodium nitrite or nitrate?

Previously, sodium nitrate (NaNO3), from mining in Chile, was the component used in the curing process, but after the discovery that, during curing, sodium nitrate is converted into sodium nitrite, and this is responsible for the benefits sought during the process, isolated sodium nitrite began to be used predominantly.

Therefore, essentially, the difference is the immediate action of sodium nitrite, as it does not require time for this conversion of one component to another during the curing process compared to the need for chemical conversion of sodium nitrate. As nitrate is converted into nitrite, the dosage is also easier to control using nitrite directly. Another point is that nitrite acts at low temperatures, between 2 and 4°C. Sodium nitrate is widely used in products that have a long cure, such as salami and Parma ham, for example, as it works slower and longer.

Read too curing salt what it is and how much to use

Is nitrite bad for your health?

Nitrates are naturally present in vegetables and can be found in these foods in very high concentrations. Spinach or celery, for example, can naturally contain more than 2g/kg of nitrate (ten times more than the maximum concentration authorized as an additive). Nitrates may also be present in other vegetables, such as beets and chard, or in drinking water.

In the human body, nitrite can form nitrosamines. This formation only occurs under certain conditions, including strongly acidic conditions, such as that inside our stomach.

Studies, carried out mainly in the USA, suggest that excessive consumption of processed meats may be related to an increased chance of developing cancer, diabetes and heart disease. But there is no unanimity in this understanding as other studies present divergent conclusions.

Ascorbic acid (vitamin C) or similar antioxidant compounds such as sodium erythorbate and vitamin E can be added to cured foods to reduce the formation of nitrosamines.

Read the post Nitrite conversion time in cured meats where studies are presented on the reduction/conversion of nitrite in products.

Nitrates and nitrites and the risk of cancer

There is a controversy that began in the 1970s that the ingestion of nitrates/nitrites is problematic for human health, mainly as potential causes of gastric cancer due to their reaction with secondary amines and the eventual formation of nitrosamines. In 1975 it was discovered by MIRVISH (1975) that ascorbic acid (and the various forms of vitamin C) effectively inhibits the formation of this undesirable compound. Later, in 1996, it was also confirmed that α-tocopherol (vitamin E) has the same positive effect. Therefore, these antioxidants are commonly used in modern cured meat processes and in various sausages, and are also covered by Brazilian legislation.

Studies

Despite the controversies, several epidemiological studies have failed to clearly prove the paradigm of the association between nitrate/nitrite intake and the risk of human cancer. Its conclusions are considered by many authors to be discrepant, inconsistent and limited, when carefully analyzed on scientific merit.

In 1980, a study was carried out on lymphatic cancer in rats in a multidisciplinary project involving the FDA and the USDA, this study was conducted by the Massachusetts Institute of Technology(MIT) and published by the FDA in 1980. The conclusion is that it is not possible to demonstrate the relationship between the incidence of this tumor and sodium nitrite intake.

In 1982, the US National Academy of Sciences required an assessment on this topic. The evaluation was carried out by the FDA and the results were published in 2000 without evidence of carciogenicity of nitrite. This study definitively sealed the approval of sodium nitrite as a safe food additive.

Why do we continue to use nitrite in food?

The answer is simple, after tests and experiments, modern science has not yet found a better solution to aid the process of food healing and elimination of harmful microorganisms.

Alternatives for preserving meat are citrus substances, such as vinegar (in the form of a pH controller), citric acids (such as ascorbic acid) and common salt (sodium), however, taking into account that, if the pH is not controlled, the loads of the proteins that make up the meat muscles are affected, degrading important properties of the meat, such as liquid retention.

Should we eat foods with sodium nitrite?

It is better to ingest sodium nitrite moderately than to run the risk of potentially fatal food poisoning, such as that caused by a toxin produced by the bacteria clostridium botulinum (botulism), present in the soil and in contaminated and poorly preserved food. There are regulations that control the amount that can be included in food, therefore, moderate consumption is considered safe by public health agencies.

Eliminating the intake of processed foods with nitrites and nitrates does not eliminate them from the body. While less than 3 mg/day is generally ingested through food, about 12 mg/day is transferred through saliva, and intestinal bacteria produce about 70 mg/day. Therefore, they are compounds that will always be present in our body. Diets rich in vegetables can contain much more of these compounds than a moderate consumption of processed foods.