E250: Sodium Nitrite (Curing Salt / Anti-Botulism Preservative)

Direct Answer

Sodium nitrite (E250, NaNO2) is an inorganic salt used in cured charcuterie, bacon, and processed meats to inhibit Clostridium botulinum neurotoxin germination, fix cured pink nitrosyl-myoglobin color, and retard lipid autoxidation.

Source: Codex Standard 192-1995 / EFSA ANS Panel (2017) / USDA FSIS 9 CFR 424.21 · Last reviewed Aug 28, 2026

Specs

INS / E-Number	INS 250 / E250
Chemical Formula	NaNO₂ (Molecular Weight: 68.995 g/mol)
Functional Class	Preservative / Color Retention Agent (Curing Salt)
Acceptable Daily Intake (ADI)	0–0.07 mg/kg body weight per day (EFSA / JECFA)
USDA Maximum Residual Level	156 ppm in cured meat / 200 ppm in dry cured ham / 120 ppm in bacon with ascorbate
Botulism Inhibition Threshold	Inhibits Clostridium botulinum spore outgrowth at ≥50–100 mg/kg in presence of NaCl

Antimicrobial Botulism Inhibition & Curing Chemistry

Sodium nitrite performs three irreplaceable biochemical functions in cured meats:

Anti-Botulinal Action: Nitrite generates nitric oxide radicals that disrupt iron-sulfur ferredoxin clusters within Clostridium botulinum spores, preventing deadly botulinum toxin synthesis in anaerobic sausages and vacuum packs.
Nitrosyl-Myoglobin Color Fixation: Nitric oxide binds to meat muscle myoglobin, forming deep red nitrosomyoglobin which denatures upon cooking into stable pink nitrosohemochrome.
Antioxidant Rancidity Retardation: Scavenges free radicals and chelates pro-oxidant non-heme iron ions.

Nitrosamine Formation Mitigation (E300 / E316 Co-Administration)

Under high-temperature frying (>130°C / 266°F in bacon), residual nitrite can react with secondary amines to produce trace volatile nitrosamines (NDMA). Global food regulations (USDA FSIS and EFSA) strictly mandate adding sodium ascorbate (E301) or sodium erythorbate (E316) at 550 ppm (0.055%) alongside nitrite to rapidly reduce nitrite to nitric oxide gas before amine coupling can occur.