Overview
Nitrates are chemicals containing the nitrate ion, and at least one other atom or molecule. Nitrate compounds have been recognized for centuries as effective food preservatives and curing agents. Today, nitrates and their sister compounds remain widely used in food safety and meat preservation, retarding bacterial growth and enabling long-term storage. Concomitant safety concerns limit the levels of nitrate permitted in food products.
Nitrates History
For thousands of years, various societies have noticed that salt acts as a preservative agent on meat, and have used salt to extend the storage life of meat and other foods. Salt retards bacterial growth directly, and also exerts a drying effect, reducing the amount of water available for microbial activity.
While most salts resulted in a gray-colored meat product, certain salts tended to impart a lasting red color. The reason for this effect was not known. However, in the 1800s, it was found that only nitrate salts resulted in this outcome.
Sodium Nitrate and Saltpeter
Saltpeter is the classical term for potassium nitrate salt, which, along with sodium nitrate, became common preservative agents in the 19th and 20th centuries. These two salts became common curing agents for meats intended for long-term storage, and also became sought-after additives in many types of retail meat because of their ability to impart a characteristic salty flavor and attractive red color, which lasted even when meats were cooked.
Further research discovered that nitrate compounds were actually broken down into related nitrites in meat, and that these nitrites exerted the majority of the preservative and coloration effects. After this finding, sodium nitrite surpassed nitrates as the dominant preservation agent for cured meats.
Nitrate and Nitrite Safety Benefits
Nitrates, and their nitrite successor products, fulfill critical roles in preventing the growth of clostridium botulinum bacteria, which can lead to fatal botulism poisoning. The non-ventilated, anaerobic conditions inside sealed or vacuum packed meat containers provide a hospitable environment in which C. botulinum can grow to dangerous levels.
Nitrites, combined with salt, also retard the growth of other bacteria that can cause meat to become rancid, off-flavor or unhealthy in storage.
Nitrosamine Safety Concerns
While generally recognized as safe by the U.S. Food and Drug Administration, some concerns remain over the long-term safety of nitrate and nitrite compounds in high concentrations. When nitrites are cooked at high temperatures, or digested in the acidic environment of the stomach, byproducts called nitrosamines can be formed. There are several hundred variants of nitrosamine compounds, many of which may be carcinogenic in sufficiently high concentrations. Animal safety interests drove the removal of high nitrosamine content from animal feeds, while human health concern led to the modification of beer production processes that had generated nitrosamines.
Preventing Nitrosamine Formation in Meats
Since the late 1970s, the U.S. Department of Agriculture has mandated the addition of vitamin C or its erythorbate precursor to cured meats. These compounds have been found to suppress nitrosamine formation without interfering with nitrites' food safety benefits.
USDA regulations also restrict maximum nitrate preservative content to 200 parts per million, a level that has been found to hinder bacterial growth while posing a low risk to humans. By contrast, some leafy vegetables such as spinach and lettuce have been found to naturally exceed this nitrate level by several times, according to "The Encyclopedia of Food Sciences and Nutrition."
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