May be derived from waste animal or vegetable matter. Used in the preservation of meat products, such as, cured meats, bacon, ham, tongue, sausages, smoked frankfurters, pressed and tinned meats such as corned beef and some Dutch cheeses.

Potassium nitrate is probably better known for its use in gun powder and fireworks or as a fertiliser for intensive crops such as tomatoes and potatoes. As a food preservative it is one of the most effective (and oldest) ways of preserving meat, in particular inhibiting the growth of the bacterium responsible for botulism.

Whilst in general it is rapidly excreted, under some specific conditions it may be converted in the stomach and saliva to potassium nitrite, which can prevent haemoglobin in the red blood corpuscles performing as an oxygen carrier. This can lead to cyanosis, sometimes called 'blue baby syndrome' in infants. May provoke hyperactivity and other adverse reactions. Potentially carcinogenic. Restricted in many countries. Also see E249.

In addition, prolonged exposure to even small quantities may cause anaemia or kidney inflammation, with ingestion of large amounts possibly causing severe abdominal pain and vomiting, muscular weakness, vertigo and irregular pulse.

Not recommended for consumption by children.