curedmeat.com / Safety / Hazards

Botulism

Clostridium botulinum

A spore-forming organism that grows without oxygen, in low-acid food, at ambient temperature, and produces a neurotoxin as it does.

Controls, with the source for each

Sodium nitrite. FSIS states that use of sodium nitrite at 50 ppm, or a water activity of 0.92 or below, is sufficient to ensure C. botulinum will not grow in fermented, salt-cured and dried products, citing Reynolds et al. 2001, Johnston et al. 1969 and Tompkin 1976.

Water activity. The alternative to nitrite in the same sentence of the same guideline.

Water activity, stabilisation. Appendix B gives 0.93 as the water activity below which C. botulinum will not grow, citing ICMSF 1996. Note that S. aureus can still grow below 0.93, which is why the shelf-stability figures are lower.

pH. The acidity route to the same control, as an alternative to water activity.

Nitrite or nitrate with salt. Given by FSIS as a combination that can control C. botulinum in fermented products during fermentation and drying.

Performance standard. The federal stabilisation standard is stated as an outcome, not a procedure: no multiplication of C. botulinum, and no more than 1 log multiplication of C. perfringens.

Why it matters here

A drying salami in a casing, or a ham resting under salt, is an anaerobic low-acid mass held at room temperature. That is the environment this organism is defined by. It is the reason curing is a regulated activity rather than a matter of taste, and the reason nitrite is in the cure.

Notes

• FSIS records several European outbreaks associated with non-proteolytic C. botulinum and home-prepared salted ham, citing Mazuet et al. 2015 and Peck et al. 2015. Home preparation is where these cases come from.
• The resting or equalisation phase is identified by FSIS as a critical step for inhibiting C. botulinum growth in dry-cured hams, citing Merialdi et al. 2016.

Steps that bear on this hazard

• Dry curingSalt and curing salts applied to the surface of a whole musc
• Equilibrium curingThe cure is weighed as a percentage of the meat, and all of
• Immersion briningThe meat sits in a salt solution until the two equalise, or
• Injection and pumpingBrine is pumped into the muscle rather than allowed to diffu
• Equalisation and restingThe product is held, wrapped or unwrapped, while the cure di
• Cold smokingSmoke is applied at a temperature too low to cook the produc
• Hot smokingSmoke applied while the product is cooked to a lethality end
• Curing without added nitriteProducts cured with a vegetable source of nitrate, or with n
• Cooking and stabilisationA heat step to a validated endpoint, followed by a controlle

FSIS guideline identifiers and their URLs are listed on the methodology page. CFR citations are to the Electronic Code of Federal Regulations, Title 9, as in force on 1 January 2026.