Food-Borne Pathogens: Clostridium Botulinum


To open my series on food-borne pathogens, it made sense to begin with one of the worst. Clostridium botulinum (C. botulinum) is the pathogen responsible for causing botulism.

Sources of C. Botulinum

C. Botulinum can be found in many places, soil, floors, carpets, countertops, and even honey. Despite being so prolific, consuming the bacteria is not a health issue for healthy individuals above the age of 1. If you’ve ever wondered why you shouldn’t feed honey to a child under the age of 1, C. Botulinum is your answer. Knowing that, some may begin to worry about contracting botulism, fear not, for the bacteria alone is harmless (outside of certain cases, such as wound infection).

The Danger

As mentioned before, the Botulinum itself is harmless, rather it is the toxin it produces that causes botulism. When conditions are favorable (not too hot, cold, acidic, etc.) Botulinum cells produce the toxin. The most notable symptom of botulism is muscular paralysis, though this is more common in later stages of the disease. Earlier onset symptoms include double vision, slurred speech, muscle weakness, and a thick-feeling tongue. (Botulism)

Prevention in Food Preparation

Understanding the manner in which C. Botulinum works is a key factor in combating it during food preparation. C. Botulinum can take one of two forms: An active, growing, toxin-producing “vegetative cell”, or a dormant “spore”. The vegetative cell is the more dangerous, but is more susceptible to elimination efforts. While the spore form is more resilient, it is unable to produce the botulinum toxin. Below, I have outlined the various ways of controlling C. Botulinum, according to a Risk Profile prepared on behalf of the New Zealand Food Safety Authority. (Gilbert, Lake, Hudson, & Cressey)

Vegetative Cell

Temperature for Growth: 3.0° ~ 50°C (Optimum 25° ~ 40°C)
Lowest pH for Growth: 4.6
Atmosphere: Low-/No oxygen
Water Activity: 0.9707 ~ 0.9353 (NaCl = 5% ~ 10%)
Preservatives: Nitrites (most commonly, sodium nitrite), sorbic acid, and antioxidants can be used to control C. Botulinum.
Competitive Organisms: Organisms, such as Lactobacillus, produce lactic acid, which can inhibit the growth of C. Botulinum.

Botulinum Spore

Temperature to inactivate: 121°C for 3 minutes to achieve “12 log” reduction (99.9999999999% of spores inactivated); At 100°C for 25 minutes, 90% of spore can be inactivated.
Lowest pH: As 4.6 is considered the minimum for growth, anything more acidic would cause any vegetative cells to become spores.

The Toxin

The easiest way to render the neurotoxin inactive is to apply heat. A commonly accepted range of temperature and time is 65°C for 1.5 hours to 85°C for 1 minute. An alternative range of 80°C for 30 minutes to 100°C for 10 minutes has also been suggested.

Addressing Botulism in Period

One common way of dealing with the potential for Botulinum contamination is the generous use of salt in the preparation and storage of preserved meats and other goods. The addition of saltpeter (potassium nitrate) was also a well-known preservative to the medieval cook, functioning in a similar way to the sodium nitrate/nitrite used modernly. Because of the hardness of many Period preserved meats, a long boiling process was not uncommon, and would help to render any possible spores inactive as well.

Works Cited

Botulism. (2017, May 08). Retrieved June 20, 2018, from

Gilbert, S., Lake, R., Hudson, A., & Cressey, P. (2006, April). Risk Profile: Clostridium Botulinum in Honey. Retrieved June 20, 2018, from

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