Science

Nitrate vs. Nitrite: What’s the Difference?

When you buy bacon at the supermarket, you often see packages labeled “nitrate-” or “nitrite-free” or “no nitrates added.” What are nitrates, and how do they differ from nitrites? Should you be worried about them?
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Published Apr. 10, 2019.

Historically, potassium nitrate (KNO₃)—known as saltpeter—was used to cure meat, as it was thought to improve the meat’s flavor, texture, and shelf life.

But at the turn of the last century, German scientists discovered that it wasn’t nitrate that was responsible for these changes. Over time, nitrate (NO₃) converts to nitrite (NO₂), which then converts to nitric oxide (NO).

Both sodium nitrite and nitric oxide are responsible for curing and preservation. Most important, they inhibit the growth of dangerous microbes such as Clostridium botulinum, the bacteria that causes botulism.

Eventually, most commercial ham and bacon producers switched from nitrate to the intermediate form, sodium nitrite, cutting out the waiting period and saving themselves valuable time during processing.

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In an ideal world, all nitrite would be converted to nitric oxide during the curing process. Any nitrite that remains can form carcinogenic compounds called nitrosamines when heated in the presence of proteins, such as those in bacon.

To combat this problem, manufacturers often add another ingredient to the curing solution: either sodium ascorbate or its isomer (chemical mirror image), sodium erythorbate.

These ingredients accelerate the process by which nitrite breaks down into nitric oxide, leaving less nitrite that can form nitrosamines in the finished product.

The acceptable levels of all three additives (sodium nitrite, sodium erythorbate, and sodium ascorbate) are closely regulated by the U.S. Department of Agriculture (USDA) to keep bacon safe for consumption.

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What is uncured bacon?

Still, because many Americans are concerned about nitrite’s health effects, some companies have developed “nitrate-” or “nitrite-free” or “no nitrates added” bacon. These products must be labeled “uncured” because they don’t use any of the four additives (including sodium nitrite) that the USDA recognizes as curing agents. Instead, they use “natural” ingredients, including celery juice and celery powder.

But make no mistake: These “uncured” bacons are still being cured.

Both celery juice and celery powder contain either nitrite or organic nitrate that eventually transforms into nitrite. Once this happens, the chemical process of curing remains the same, and so do the potential benefits and risks. Despite this, it’s still correct to label the bacon “no nitrates or nitrites added” because the compounds are formed before or during production, not added as ingredients. Manufacturers are also required by law to include the qualifying statement that no nitrates or nitrites have been added “except for those naturally occurring in celery powder,” celery juice, or other natural sources of nitrite.

In a previous test, we found that a “no nitrates or nitrites added” bacon actually had slightly higher nitrite levels than a bacon made by the same company using sodium nitrite. Happily, both bacon samples were well within the USDA’s limit of 200 parts per million.

The bottom line: All bacon is likely to contain some sodium nitrite, whether added at the outset or formed naturally during processing. If you want to avoid this compound, you’ll have to avoid bacon—and any other processed meats containing celery products—altogether.

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