Nitrogen dioxide (NO2) is among the compounds formed in the high heat combustion of wood, charcoal, and even propane. As these compounds land on the surface of meat, especially cool moist meat from the fridge, some, including nitrogen dioxide, are moved deeper into the meat as cells lower in the smoke compounds pull them in with a diffusion and absorption process. The cells are simply seeking equilibrium. The process is the same as when someone lights a cigar in a room. All the smoke starts out near the cigar, but eventually it spreads throughout the room as it achieves equilibrium. After a while it penetrates clothes, furniture, and even food. Because it is water soluble, cigar smoke will get into wet things first, like your wife's eyes. Before long you and your cigar will be seeking equilibrium in the garage.
The smoke ring in meat is caused by four things:
1) low temperature cooking,
2) combustion of the wood at high temperatures to form nitrogen dioxide,
3) nitrogen dioxide, and
4) moisture on the surface of the meat to help move the water soluble nitrogen dioxide into the meat.
When these conditions are met, nitrogen dioxide in wood smoke reacts with the pigment myoglobin in meat to form nitrites and nitrates. These are the same compounds added to hot dogs and other cured meats to preserve them and they also give them their pink color.
There's no avoiding nitrates/nitrites in cooked meat, especially smoke cured meat
Practically every hot dog has had sodium nitrite added. It is also common in other cured meats such as bacon, ham, some luncheon meats, some sausages, and occasionally in poultry and fish. Nitrite is added because it inhibits the growth of Clostridium botulinum, a pathogen that creates the most lethal toxin known to man, botulinum, the cause of botulism.
Sodium nitrite also gives cured meats their characteristic reddish-pink color and adds to their taste and texture. Nitrites also expand when cooked, helping the pups plump when hot. A few companies make hot dogs without nitrites, but most do not taste very good. Only one, Hans' All Natural Uncured Beef Hot Dogs, ranked "Highly Recommended" in my tastings.
About 5% of our nitrite intake comes from cured meats. Most of the nitrites we consume come from the natural compounds in vegetables such as lettuce, spinach, and carrots, and even some drinking water. They contain nitrates (with an "a") that are converted by our digestive system to nitrites (with an "i"). Interestingly, most nitrates are eliminated in our urine within a few hours.
Preliminary research in the 1970s indicated that sodium nitrite could cause cancer in laboratory animals. It got a lot of publicity and as a result some people began calling hot dogs "death dogs." Since then more thorough research by scientists around the world on the safety of nitrites has contradicted these early experiments. The international scientific community seems to be satisfied that the quantities of nitrites and nitrates people typically take in from the environment and from food additives is safe, that the body actually needs small amounts of nitrites and nitrates, and they may possibly have some beneficial effects. In the stomach, nitrite can create nitric oxide, a compound that is thought to be important in healing wounds and burns, controlling blood pressure, and boosting immunity. In 2003, the World Health Organization published a comprehensive survey of dozens of research papers on the subject by scientists in the Netherlands. It stated "In the studies on dietary nitrate, no association was found with oral, oesophageal, gastric, or testicular cancer. No other cancer sites have been studied." The greatest health risk from nitrites and nitrates seems to be in badly polluted drinking water.
Based on this research, two US Government agencies, the Food and Drug Administration (FDA) and the US Department of Agriculture (USDA), have set a maximum amount allowed in food. Over the past 30 years the meat industry has significantly reduced the amount of nitrates and nitrites added to meats and the amounts actually used are typically way below the allowable amount. In other words, Americans would have to eat a lot of hot dogs every day to exceed the amount deemed safe.
There's plenty of exposure to nitrates/nitrites in out everyday food. We have also been cooking meat on the flame for up to 2M years.
I think we should have evolved with some way of handling them effectively by now...
The "Seven Deadly Sins"
Grains (wheat/rice/oats etc) . . . . . Dairy (milk/yogurt/butter/cheese etc) . . . . . Nightshades (peppers/tomato/eggplant etc)
Tubers (potato/arrowroot etc) . . . Modernly palatable (cashews/olives etc) . . . Refined foods (salt/sugars etc )
Legumes (soy/beans/peas etc)