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Foodborne Botulism From Homemade Fermented Tofu

Foodborne botulism is a common health problem that needs attention. Foodborne botulism is caused by eating contaminated food with botulinum toxin produced by bacterium Clostridium botulinum. It can be fatal. The center for diseases control and Prevention (CDC) estimates that each year, approximately 1 to 6 people in the US get sick from foodborne illness.1 This article discusses foodborne botulism from homemade fermented tofu and reported cases.

Foodborne Botulism From Home-Made Fermented Tofu – Case Study

Foodborne Botulism From Home-Made Fermented Tofu

Tofu is a home-made preparation by fermentation at home. It includes exposing unrefrigerated tofu to bacteria for weeks to get fermented. It is refrigerated after mixing it with salt and spices. It is boiled, dried out and then cut into pieces that are stored in a bowl covered with plastic wrap and at room temperature for 10-15 days. Then, it is transferred to glass jars with white cooking wine, chili powder, vegetable oil, salt, and chicken bouillon to marinate at room temperature for 2-3 more days and finally making it available to eat.

The fermentation of tofu under low acid and the low salt condition is suitable for the bacteria spores to germinate and grow. People with symptoms of botulism include vomiting and difficulty breathing among many more symptoms to be considered. They should be immediately hospitalized and intubated. It is necessary to understand foodborne botulism from home-made fermented tofu to be able to prevent such occurrences in the future.

In March 2012, The Department of Health and Mental Hygiene of New York obtained two records of people who recently migrated to New York from China and were admitted to a local hospital for 23 days.2 They were suffering from botulism. One of the two patients had foodborne botulism confirmed by the laboratory test while the other one had a probable cause. The reports clearly said that the first patient was affected by food botulism due to the consumption of home-fermented tofu. The second patient’s case was not that clear but relating to the common symptoms of both the patients it was concluded that the second patient might also have been associated with the same case of consumption of home-fermented tofu.

Recent purchase records pointed out that both of the patients had bought their tofu from the same Chinese grocery store located in Queens, New York. Both of them used the same recipe for the preparation of home-fermented tofu. This fact was concluded after it was found out that both of them were affected due to the presence of the toxin, which gets produced due to the fermentation of tofu using a specific practice. Further testing on both the patients confirmed the presence of toxin type B, which was the cause of botulism and was consumed by the first patient. Further investigations showed that the grocery stores in New York stored tofu uncovered and kept in water-filled buckets instead of refrigerating them. The supply chain tracking revealed that the supplier supplying fresh tofu to the grocery stores was nowhere to be found. After this incident, DOHMH issued instructions to every Chinese grocery for storing tofu in bulk.

Exposure and Transmission in Foodborne Botulism

Botulinum is an anaerobic bacterium, which means it can grow only in the absence of oxygen. The growth of the bacteria and the formation of toxins happens when there is no sufficient oxygen with a certain combination of storage temperature and preservation parameters. Thus, the bacteria are commonly present in lightly packed food, home-fermented, and home-canned food.

The bacteria do not grow in acidic conditions. Thus salt content is used to avoid the production of the toxin as the salt makes the food acidic. However, the botulinum toxin is found in many varieties of food with low-acidic content such as spinach, beans, mushroom, beet, fermented, salted and smoked fish, tin canned tuna, etc. the food concerned differs between countries and reflect their eating habits and packaging procedure.

Also, the spores growing out of the bacteria under anaerobic conditions can be destroyed by boiling as botulinum is heat-resistant. While heating helps destroy many pathogens, they can still form toxins in foods exposed to unsafe temperatures. cooking does not help destroy them.

How To Prevent Food-Borne Botulism From Homemade Fermented Tofu?

Though fermented foods are extremely healthy, they can be contaminated, if not properly stored. Usually, soy milk is thoroughly heated before making tofu, destroying most bacteria and viruses in the soy. Thus, well-handled tofu is not likely to be contaminated. The risks can be low but fatal.

There are certain ways to keep the fermentation process toxin-free. Here are some of the effective ways to prevent food-borne botulism from homemade foods.:

  • Use clean hands and utensils for fermentation and keep the entire process clean
  • Cabbages and other vegetables should be kept under the brine, not exposing it to the air.
  • There should be sufficient water/brine to keep bacteria away
  • Leave space for fermentation. Do not pack the utensil too much.
  • Salt it appropriately to make it less friendly to bugs.

Make sure the environment is oxygen-free, which would ensure the proper sealing of the container.

When preparing tofu, use clean utensils and containers to avoid cross-contamination. Follow the package directions to store it. Some forms of tofu are required to store in room temperature until opened and then refrigerated. Many forms of tofu are initially water-packed and refrigerated. If one purchases tofu in bulk, refer reputable sources and gain information about how often a new batch is made and how often the water is changed. Foodborne botulism, while rare, remains an important public health emergency.

However, fermented foods, including seal, fish, and whale, have also been associated with botulism. Homemade fermented bean products and tofu, are the most common foods causing botulism. The most direct and effective way to diagnose botulism is by stool and serum examination as well as mouse neutralization test .antitoxin can treat foodborne botulism well if treated early. This can prevent the patient from worsening though it cannot reverse the damage made to the body. Fermented tofu is also known as stinky tofu which is a popular Chinese dish. The health department suggests throwing away tofu that is not refrigerated. Strict regulations and proper food processing measures can help prevent food-borne botulism from home-made fermented tofu or any other food.


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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:May 9, 2020

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