So, there I was at Costco looking at their special of a quarter pound hot dog and soft drink for $1.50. A good deal financially to be sure. These days I have hot dogs rarely, but I still have fond memories of the toasted hot dogs at the Forum and the steamies at the Montreal Pool Room. To try or not to try the Costco dog, that was the question. I was aware of course about the high salt and fat content, but I also knew that I didn’t have to worry about being struck down by botulism. That’s because the meat is cured with sodium nitrite. And therein lies a story.

Nitrites inhibit the growth of bacteria (Clostridium botulinum) that produce botulin, a chemical so toxic that one billionth of a gram can be lethal. No thanks. Interestingly, sodium nitrite was not developed by food scientists to prevent botulism; its journey into that hot dog is a long and circuitous one and starts long before the mechanism by which it reduces the risk of botulism was understood.

The salting of meat is one of the most ancient food preservation methods. Sodium chloride, common salt, doesn’t poison bacteria. It kills them by drawing water out of their cells. Without water bacteria cannot survive. Ancient people discovered that sometimes when the salt was gathered from desert areas, the salted meat not only lasted longer but developed a pink hue as well. As it later turned out, this “salt” was different from the salt obtained by evaporating sea water and was named “nitron” by the ancient Greeks. Today we know it as potassium or sodium nitrate. In the Middle Ages it came to be called “saltpeter” from the Latin “petra” for stone because it could also be found as a crust on rocks or crystallized on cellar walls or stable stones. It seemed as if the rocks or stones were generating this substance. They weren’t. They just served as surfaces on which organic matter deposits, such as animal feed and waste in stables. It is a collage of bacteria in the waste that produces the saltpeter.

First, ammonifying bacteria liberate ammonia from urine, manure or other waste. The ammonia is then converted into nitrite by ammonia-oxidizing bacteria, followed by the conversion of nitrite into nitrate by nitrite oxidizing bacteria. Once it was discovered, likely by the Romans, that the crystals that grew on stones were the same substance as the desert salt that preserved meat so well, they became an important commodity. Somewhere along the line it was also discovered that if the conditions that produce saltpeter in stables are replicated by piling manure, urine and other organic waste into “nitre beds,” after some time white crystals rise to the surface.

When gunpowder, a mixture of sulfur, charcoal and saltpeter was serendipitously discovered in the 9th century by Chinese alchemists in quest of an immortality potion, the need for saltpeter skyrocketed. Quite literally. Igniting gunpowder stuffed into bamboo shoots created the first rockets. As gunpowder technology matured, Europeans realized that they could kill each other more efficiently with firearms than arrows, the demand for saltpeter could not be met. This became a crucial problem for Napoleon who ordered that villagers relieve themselves on nitre beds to supply the urea that the bacteria require for conversion into nitrates. Later, in the early 1800s, Alexander von Humbodt discovered that “guano,” the white deposits of seabird poop found on rocky South America shores, was mainly saltpeter. He then went on to study the chemical composition of saltpeter and found it to be potassium nitrate. Humboldt’s discovery prompted the importing of guano into Europe, not only to be turned into gunpowder but also to be used as fertilizer.

The ready availability of saltpeter ended lives, but as it turned out, also saved lives. Especially in the case of German sausage lovers. It was common to dry these sausages for preservation, a process that resulted in an anaerobic, or oxygen-lacking, environment on the inside. Exactly the condition that allows Botulinum clostridium to thrive! In the early 1800s, German physician Justinus Kerner traced 200 cases of paralysis, blurred vision, difficulty in swallowing and even deaths to sausage consumption. He suggested that the culprit was some toxin that he was unable to identify. It was Belgian bacteriologist Emile van Ermengen who in 1895 finally identified botulin as the neurotoxin produced by bacteria as the cause of “sausage disease.” The Latin word for sausage is “botulus,” so the disease came to be known as “botulism.”

Not all sausages were linked to botulism. Those made by butchers who added saltpeter to their sausage as a preservative instead of drying rarely caused the problem. That inspired the addition of saltpeter to all sausages, but while this decreased sausage disease, it did not eliminate it. The problem was solved with the discovery in the 1920s by Swiss-American microbiologist Karl Friedrich Meyer that it was not the nitrate in saltpeter that inhibited the growth of the botulin producing bacteria. The anti-bacterial agent was actually nitrite, produced within the sausage from nitrate by naturally occurring bacteria in the meat. But there was a problem. The conversion of nitrate to nitrite was inconsistent because it was dependent on the naturally occurring microbes in the meat. The solution to the problem then became obvious. Just add nitrite to the meat! Now the botulin producing bacteria were immediately and consistently stopped in their tracks.

Nitrite was also found to account for the “bonus” of the pink colour. After all, nobody wants an unappetizing gray sausage or hot dog. The colour of fresh red meat is due to myoglobin, a protein that turns brown-gray as the meat ages. Some of the nitrite added to meat produces nitric oxide during processing. This then binds to myoglobin to form nitrosylmyoglobin that is pink-red and chemically stable. So, now we have pinkish sausages and hot dogs and we do not have to worry about these delicacies poisoning us. At least not with botulin.

In the 1950s, compounds called nitrosamines were identified in the laboratory as carcinogens. This prompted a search for their presence in the food supply, made possible by advances in analytical chemistry that allowed for the detection of substances present in very small amounts. Sure enough, nitrosamines turned up in meats that had been cured with nitrates or nitrites. Meat contains naturally occurring amines that can react with nitrites during processing to form nitrosamines. Not only can this reaction occur during processing, it can also take place in the acidic conditions of the stomach.

Researchers got to work to see how nitrosamine exposure can be reduced. Cooking temperatures were lowered, nitrite levels were reduced to the minimum necessary, and sodium ascorbate or sodium erythorbate were mandated as additives when they were found to reduce the formation of nitrosamines. These interventions have dramatically reduced the risk of nitrosamine formation but have not eliminated it.

Now it was decision time about the Costco hot dog. Botulism was off the table, and I wasn’t going to worry about traces of nitrosamines. So, I stepped up to the counter and ordered. No match for the ones in the old Forum (forget the hot dogs in the Bell Center), but not bad. Still, I think next time I’ll be able to resist, mostly because of the 1600 mg of sodium. I think it is wise to try to keep my daily intake under 1500 mg.

@‌JoeSchwarcz