On Curing Salts (and Fearmongering)

Have you seen this commercial for McCain's frozen pizza?

"What do other companies put in their pizzas? Something called sodium nitrite..." Those last two words are pronounced with a blend of confusion and self-righteous disgust. The molecular diagram of the compound is flashed across the screen for further effect.

The food industry is quick to pick up on trends.

My generation was taught to read labels, and to mistrust "chemical" ingredients. However:

The resistance to... 'scientific' ingredients has always seemed to me misguided. In the objector's mind a line is drawn between science and cookery, which usually turns out to be entirely arbitrary. No one objects to table salt (sodium chloride) or table sugar (sucrose) in a recipe, but an ingredients list that includes fructose or sodium citrate is viewed by some with suspicion.^[1]


The Complete Skinny on Curing Salts

How salt preserves food

Imagine microbes within a piece of meat. When salt is first added to the meat, there is a relatively high concentration of salt outside the microbes, and a relatively low concentration inside. The cells of the microbes try to equalize the salt concentration on both sides of the cell membrane by expelling water and taking in salt. This ultimately either kills the cells or severely reduces their functionality. The meat itself also loses water and takes in salt, thus making it inhospitable to any microbes that show up later. That is how salt preserves food.

The difference between table salt and curing salt

Cured meats were once made with table salt, sodium chloride. This is the salt on your kitchen counter, and the salt you taste when you swim in the ocean. However, for hundreds of years we have known of other salts, naturally occurring in small quantities, that are even better at improving the flavour and storage-life of cured meats.

One such salt is potassium nitrate, or saltpeter, which is still used in Europe. In North America, potassium nitrate has been replaced by sodium nitrate, which was found to be more reliable.

The reasons why these nitrates are better than table salt at preserving meat are several and complex. Here's an example. Iron oxidizes fat, turning it rancid. When added to meat, nitrates form nitric oxide, which binds to iron atoms, preventing them from oxidizing the fat, and prolonging the storage-life of the meat.^[2]

The difference between sodium nitrate and sodium nitrite

While nitrates have been added to cured meats since at least the 17th century, in the 19th century it was discovered that salt-resistant bacteria in the meat convert the nitrates to nitrites, and that nitrites are actually the active curing agents.

Now sodium nitrite can be added directly to curing mixes. Meats that will be cured for only a short while (say, a few hours in a smokehouse), are treated with sodium nitrite. Meats that will be hung in a cellar for several weeks are treated with a blend of sodium nitrite and sodium nitrate, which is slowly converted to nitrite, thus protecting the meat for the entire curing process.

Retail forms and terminology

Here's where it gets really confusing.

You can't buy 100% sodium nitrite (unless you work at a pharmacy, maybe). It will always be cut with regular salt. In the US the most common form is a mixture of 93.75% sodium chloride, and 6.25% sodium nitrite. Brand names include Insta Cure #1 and Prague Powder. When buying from butcher suppliers in Edmonton, the most common mixtures are actually 95% sodium chloride, and 5% sodium nitrite, possibly with trace amounts of sodium bicarbonate (baking soda), which is an anti-caking agent. The mixture will likely be called F.S. Cure, which is made by a company called First Spice, then packaged for the supplier that you are buying from.

In the US, curing salts are tinted pink so that they aren't confused with table salt. This gave rise to the terms "pink salt" and "tinted cure mix" (TCM) for sodium nitrite. For some reason, this precaution is not taken in Canada. The curing salts I buy are white as snow, though they are still sometimes called pink salt. It's commonly believed that the pink colour of cured meats is from the pink die in some curing salts. This isn't true: it has to do with the chemical reactions taking place in the meat.

In the US sodium nitrate is sold in a mixture of 92.75% sodium chloride, 6.25% sodium nitrite, and 1% sodium nitrate. It, too, is usually died pink in the US, but left white in Canada. The most common brand name is Insta Cure #2. From butcher suppliers around Edmonton you are more likely to be sold the F.S. Salami Cure, which can be used for all kinds of dry-curing, not just salami.

Health concerns

Curing salts have been demonized as a carcinogens. Here is a quote on the subject from the preeminent food scientist, Harold McGee.

...at present there's no clear evidence that the nitrites in cured meats increase the risk of developing cancer. Still, it's probably prudent to eat cured meats in moderation and cook them gently.^[3]


Conclusion

Curing salts are in fact what make traditionally cured meats safe to eat. The simple truth is that dried sausages like salami that will be hung in a cellar for several days or weeks must be treated with nitrite and nitrate.

To completely avoid curing salts is to avoid the unique flavours and textures of traditionally cured meats like salami and bresaola. As for the "nitrite-free pepperoni" on McCain pizzas: traditional pepperoni is dried, and therefore requires the addition of curing salts. If McCain pizzas have nitrite-free pepperoni, this means one of two things: either they are improperly curing their meat, or they are not drying their pepperoni. Obviously the latter is what is happening. I would argue that the sausage on their pizza cannot properly be called pepperoni, as it isn't dried. Too bad pepperoni isn't a protected designation.


References

1. This is Heston Blumenthal in the history section of The Fat Duck Cookbook. I wrote the quote on a scrap piece of paper, without the page number, and have since returned the book to the library. Bad journalism.
2. McGee, Harold. On Food and Cooking. ©2004 Scribner, New York. Page 174.
3. Ibid. Page 125.