Nitroso compounds react with
primary amines in acidic environments to form
nitrosamines, which human metabolism converts to mutagenic
diazo compounds. Small amounts of nitro and nitroso compounds form during meat
curing; the toxicity of these compounds
preserves the meat against
bacterial infection. After curing completes, the concentration of these compounds appears to degrade over time. Their presence in finished products has been tightly regulated since several food-poisoning cases in the early 20th century, but consumption of large quantities of processed meats can still cause a slight elevation in
gastric and
oesophageal cancer risk today. For example, during the 1970s, certain
Norwegian farm animals began exhibiting elevated levels of
liver cancer. These animals had been fed
herring meal preserved with
sodium nitrite. The sodium nitrite had reacted with
dimethylamine in the fish and produced
dimethylnitrosamine. The effects of nitroso compounds vary dramatically across the gastrointestinal tract, and with diet. Nitroso compounds present in stool do not induce nitrosamine formation, because stool has neutral
pH.
Stomach acid catalyzes nitrosamine compound formation and is the main location of the reaction during digestion. concentration (e.g. high-fruit diet). However, when 10% of the meal is fat, the effect reverses, and ascorbic acid markedly increases nitrosamine formation. Vitamin C and erythorbic acid are already commonly used in the meat industry because they enhance the binding of nitrite to myoglobin, encouraging the formation of the desired pink color. ==References==