Potassium nitrite

Potassium nitrite (E249) is an inorganic salt used as a curing agent in processed meats and fish products. Its antimicrobial action against Clostridium botulinum — the bacterium responsible for botulism — is the primary safety rationale for its use; nitrite reacts with haem iron to prevent spore germination and neurotoxin production under anaerobic conditions. Secondarily, nitrite reacts with myoglobin to form the characteristic pink-red colour of cured meats (nitrosomyoglobin) and contributes to the distinctive cured flavour through complex reaction chemistry during processing.

JECFA has established a group ADI of 0.07 mg/kg body weight per day for potassium nitrite and sodium nitrite (E250), expressed as sodium nitrite equivalents (evaluated 2002). This is one of the strictest ADIs assigned to any approved food additive, reflecting the dual toxicological concern of methaemoglobinaemia (conversion of haemoglobin to a form that cannot carry oxygen, particularly dangerous in infants under three months) and the formation of carcinogenic N-nitrosamines when nitrite reacts with secondary amines under acidic conditions, such as in the stomach or during high-temperature cooking. The European Food Safety Authority's 2017 re-evaluation concluded that dietary exposure from cured meats alone can approach or exceed the ADI for high consumers, particularly children, and classified the nitrite/nitrosamine interaction as a potential carcinogenic concern.

Potassium nitrite is authorised under EU Regulation (EC) No 1333/2008 at strictly controlled maximum permitted levels (typically 100–150 mg/kg in finished product) and is included in FDA 21 CFR regulations for cured meats. Use is prohibited in foods intended for infants and young children. The World Health Organization's International Agency for Research on Cancer (IARC) has classified processed meat consumption as Group 1 (carcinogenic to humans), with nitrite-induced N-nitrosamines identified as a contributing mechanism. Manufacturers increasingly co-apply nitrites with ascorbic acid (a nitrosamine inhibitor) to reduce this risk.