Potassium nitrate

Potassium nitrate (E252), historically known as saltpetre, has been used in food preservation for centuries — its presence in naturally occurring salt deposits led to the discovery of meat curing long before its chemistry was understood. Like sodium nitrate (E251), it serves as a slow-release nitrite precursor in long-matured cured and fermented meats, where bacterial nitroreductases gradually convert nitrate to active nitrite over the extended maturation period. Potassium nitrate is preferred over sodium nitrate in some applications where sodium reduction is a formulation goal, as potassium carries no sodium load.

JECFA evaluated potassium nitrate under the same group ADI as sodium nitrate: 3.7 mg/kg body weight per day (as nitrate ion equivalents, evaluated 2002). The toxicological basis is identical — potassium nitrate's risks derive from its enzymatic reduction to nitrite and the subsequent potential for N-nitrosamine formation rather than from nitrate ion toxicity per se. The European Food Safety Authority's 2017 systematic re-evaluation of nitrites and nitrates in food confirmed the group ADI and noted that cured meat use of nitrates adds only modestly to the total nitrate exposure dominated by naturally nitrate-rich vegetables.

Potassium nitrate is authorised under EU Regulation (EC) No 1333/2008 at maximum permitted levels of 150 mg/kg for non-heat-treated meat and up to 300 mg/kg for certain heat-treated and fermented meat products. In the United States, FDA 21 CFR §172.170 permits its use in cured meats. It is also approved for certain cheese curing applications (preventing late blowing by Clostridium tyrobutyricum) in the EU and several other jurisdictions. As with all nitrate/nitrite curing agents, co-application of ascorbic acid or erythorbic acid is common industry practice to scavenge nitrosamines and is encouraged by regulatory guidance.