Canned food poisoning

Foodborne Botulism

Foodborne botulism is a rare but highly dangerous illness. According to a 2023 report by the World Health Organization (WHO), it can be fatal in 5 to 10 percent of cases. The disease is caused by consuming a toxin called botulinum toxin. This toxin is a neurotoxin, which attacks neurons, or nerve cells, disrupting their function.

Botulinum Toxin

The average lethal dose of botulinum toxin for humans is estimated to be about 2 nanograms per kilogram of body weight, according to a 2023 WHO report. For example, 140 nanograms of this toxin, roughly equivalent to a speck of dust, is lethal for a 70 kilogram person. The lethality of this tiny amount of botulinum toxin indicates how extremely dangerous this toxin is, which is produced by the bacterium Clostridium botulinum.

Clostridium Botulinum Bacteria

Clostridium botulinum is an anaerobic bacterium that can grow in oxygen-free environments. It multiplies rapidly in warm, moist conditions, especially between 25 and 37 degrees Celsius. In unfavorable conditions, such as lack of water, low temperature, or lack of nutrients, the bacteria turn into spores. Spores are resistant structures that allow bacteria to survive in harsh conditions, even against pasteurization processes. When conditions become favorable again, the spores revert to the active bacterial form, and the bacteria begin producing botulinum toxin.

Clostridium Botulinum in Canned Foods

Clostridium botulinum and its resistant spores may enter food as initial contaminants or be transmitted during the canning process. Under typical heat processes, active bacteria of this microorganism are destroyed at 85 degrees Celsius within 5 minutes. However, resistant spores are only destroyed at temperatures above 121 degrees Celsius and under high pressure for at least 3 minutes.

To maintain the safety of canned goods, thermal processes must be adjusted based on the type and quantity of food. In canned foods with a pH close to neutral or slightly acidic (approximately between 5 and 7, such as meat and some vegetables), the use of high temperature and pressure is essential. In this pH range, not only can resistant spores survive, but they can also revert to active bacteria and produce botulinum toxin if suitable conditions (lack of oxygen and optimal temperature) exist. However, in acidic foods (pH less than 4.6), although spores may survive, they cannot revert to active bacteria due to unfavorable conditions (acidic environment) and are therefore unable to produce toxins. Also, larger packages or dense materials require more time for complete heat penetration to ensure complete sterilization.

Therefore, precise control of time, temperature, and pressure at each stage of the sterilization process is crucial to ensure food safety. Failure to properly manage these factors may allow Clostridium botulinum spores to become active bacteria and produce botulinum toxin, leading to dangerous food poisoning.

Symptoms of Botulism Food Poisoning

Initial symptoms of botulism usually appear between 12 and 36 hours after consuming contaminated food. However, this time can vary from 4 hours to 8 days, depending on the amount of toxin consumed. In the early stages, individuals may experience symptoms such as nausea, vomiting, abdominal cramps, diarrhea, or constipation. As the disease progresses, botulism gradually causes a descending flaccid paralysis. This paralysis is called "flaccid" because in this type of paralysis, muscles become weak and limp, and "descending" because the paralysis caused by botulinum toxin typically progresses from the top down, starting with drooping eyelids, blurred or double vision, facial muscle weakness, difficulty swallowing, and slurred speech, gradually spreading to the neck, arms, and eventually the respiratory muscles. If treatment is not administered promptly, paralysis of the respiratory muscles can lead to respiratory failure and ultimately death.

Safety Tips to Prevent Botulism

To prevent botulism and ensure food safety, it is essential to follow these tips:

• Check the appearance of the can:

Before consuming any canned food, the can's appearance must be carefully examined. Any physical damage or deformation, such as dents, swelling, rust, cracks, holes, or leakage, can indicate contamination or spoilage of the contents. If any of these signs are observed, consumption should be avoided, and the can should be discarded.

• Proper method for heating canned food:

To ensure the safety of canned goods, it is recommended to boil them for 20 minutes at 100 degrees Celsius (the boiling point of water), ensuring the can is fully submerged in water so that heat reaches all parts of the can evenly. This process destroys active bacteria and botulinum toxin if present. Alternatively, transferring the contents of the can to another container for heating is safe, provided the original can has no physical damage (as described in the "Check the appearance of the can" section) and the contents are boiled for 20 minutes.

After heating the can, consumption may be delayed, or some of the contents may be consumed, leaving a portion remaining. In either case, it is essential to follow safety tips to prevent botulism and maintain food quality:

1. Heated, unopened can, consumption delayed:

The can may have sustained changes or damage during heating that are not visible from the outside, such as micro-cracks or changes in the can seams. These changes can create conditions that facilitate the entry of air or new contaminants and increase the likelihood of bacterial growth. Therefore, it is recommended to refrigerate the can after heating. Refrigeration prevents bacterial regrowth due to the lower temperature, enhancing food safety. It is also recommended to consume the canned food within 3 to 4 days and boil it again before consumption to ensure the destruction of any potential bacteria or toxins.

2. Heated, partially consumed can:

If some of the can's contents remain, it is recommended to transfer the remaining contents to a clean, sealed container to avoid contamination that may occur if stored in the opened can. Be sure to refrigerate this container and consume the contents as soon as possible (within a maximum of one day). Also, to ensure the destruction of any potential bacteria or toxins, it is recommended to reheat the remaining contents thoroughly before consumption.