On October 5, 2020, in Jidong County, Heilongjiang, 9 people suffered from food poisoning while having a dinner at home. So far, 8 people have died, and the remaining one is still being rescued. They ate a homemade fermented food called "sour soup" during the dinner. At first, the incident was judged to be "aflatoxin poisoning," but in-depth investigation revealed that the food was actually contaminated by a microorganism called "pseudomonas cocovenenans." The deadly toxins produced by the bacteria killed these residents.
QC bacteria: If you pay attention to previous news, you will find that this type of poisoning incident is not new at all, and has happened many times in the past few years.
For example, on July 28 this year, 11 customers developed symptoms of food poisoning after eating rice noodles at the "Stone Rice Roll Rice Noodle Shop" in Shenquan Town, Huilai County, Jieyang City, Guangdong Province. In the end, five people were sent to the hospital, and one person died after resuscitation failed. After investigation, it was confirmed that the rice noodles were contaminated with "Pseudomonas cocotoxin".
In 2019, Ms. Zhang, a Shenzhen citizen, developed vomiting symptoms after eating black fungus that she had soaked for several days at home, and her liver, kidney, and heart functions were severely damaged. In the end, she underwent an emergency liver transplant to save her life. After investigation, the black fungus was contaminated with "Pseudomonas cocotoxin". There have been many poisoning incidents caused by "soaking black fungus for a long time" in the past, and they were all related to "Pseudomonas cocotoxin".
Xinxin: This kind of bacteria is really dangerous! How can we prevent this type of food poisoning?
QC bacteria: To understand these in depth, we have to start with a traditional Indonesian food.
The discovery of different paths leading to the same destination
"Tempei" is the collective name for many fermented foods in Indonesia. The more common "tempeh" is a cake-shaped food made from soybeans and other cereals and fermented after inoculation with rhizopus.
A special kind of "tempeh" was once popular on the island of Java, which was made from fermented coconut meat. It is this "tempe bongkrèk" that has become a deadly "killer".
As early as the 1930s, poisoning caused by eating "coconut tempeh" has been recorded. Poisoners often start with gastrointestinal symptoms such as vomiting and diarrhea, followed by headaches, dizziness, and fatigue. , severe cases may result in convulsions and coma, and ultimately death due to respiratory and circulatory failure, cerebral hematoma and uremia. The poisoning mortality rate is as high as 30-50.
Microbiologists Mertens and Van Veen extracted a never-before-seen bacterium from poisonous tempeh and ultimately identified it as the culprit of food poisoning. Because it belongs to the genus Pseudomonas and was first discovered in fermented coconut meat products, it was named "Pseudomonas cocotoxin". Unfortunately, this discovery did not receive enough attention at the time, and the poisoning has never stopped. From 1951 to 1975, an average of 288 people were poisoned and 34 died each year in Indonesia due to eating this "coconut tempeh". Eventually, the Indonesian government had to completely ban the production and sale of this food in 1975.
At almost the same time, thousands of kilometers away in the northeast of the motherland, another kind of food poisoning was also killing people.
Fermented rice noodles are traditional Chinese food materials. They are generally made from corn, sorghum rice and other grains soaked in water. After natural fermentation for 10 days to a month, they are wet-ground into a paste, and then filtered and air-dried. become. Due to natural fermentation, fermented rice noodles usually have a certain sour smell. In the north, it is used to make foods such as stinky rice dumplings, sour soup, and checkered beans. Some areas in the south also use it to make glutinous rice balls and other foods.
Poisoning caused by fermented rice noodles has always been common in Northeast China, but for a long time, this poisoning was thought to be caused by mold. It was not until the 1970s and 1980s that, after careful research by a series of Chinese scientists, it was discovered that this was caused by a brand-new bacteria. This bacterium was first called "toxigenic Flavobacterium" and later "Pseudomonas rice yeast". Finally, people discovered that this bacterium seemed to be very similar to Pseudomonas cocotoxin found in Indonesia. For example, the types of toxins they produced were exactly the same!
Finally in 1987, after comparing more than 200 traits, Chinese scientist Zhao Naixin and others confirmed that the bacteria causing yeast rice noodle poisoning and the bacteria causing tempeh poisoning in Indonesia were actually the same bacteria - —Pseudomonas cocotoxin! Moreover, this kind of bacteria can also cause many other types of food poisoning. For example, black fungus and white fungus are particularly susceptible to this kind of bacterial contamination. Raw wet rice and flour products such as rice noodles and rice rolls are also susceptible to this kind of food poisoning if they are not stored properly. Bacterial contamination! If people eat these contaminated foods, their lives may be in danger.
QC bacteria: Until this time, humans have just begun to understand "Pseudomonas cocotoxin".
One bacterium, two toxins
Many domestic reports directly refer to food poisoning caused by Pseudomonas cocotoxin as "rice acidosis". In fact, this is There are some one-sided claims, because this bacterium can produce two toxins, namely Bongkrek acid and toxoflavin, both of which cause poisoning symptoms.
Rice fermentation acid can bind to the "energy factory" in cells - the ADP/ATP transporter of mitochondria, preventing the transfer of ADP. The "energy factory" directly shuts down, and toxins act on the electron transport chain in cells, affecting respiration and producing a large amount of toxic hydrogen peroxide molecules. Both work together to cause cell death.
Although their toxicity is not particularly high in the toxin world, generally the food that causes poisoning is seriously contaminated, and the content of these two toxins itself is high. In addition, fermented rice and noodles are considered a staple food, and I will eat more. Taken together, it is reasonable to reach a lethal dose. It should be noted that both toxins are relatively stable to heat and cannot be destroyed by normal cooking processes.
An article in 2003 conducted an epidemiological analysis of 9 cases of fermented rice noodle poisoning in Guangxi. The average amount of fermented rice noodles eaten by the 13 poisoning victims was 175 grams, while the 11 poisoning survivors The average food intake is 65 grams. All those who ate more than 200 grams died without exception. But those who ate less than 100 grams all survived.
Weaknesses of Pseudomonas cocotoxin
Xinxin: Oh my God! This is terrible! I won’t dare eat any fermented food in the future! I also don’t dare to eat rice noodles, fungus, white fungus and other foods!
QC bacteria: Don’t panic!
Don't panic! Pseudomonas cocotoxin has many "weaknesses". It does not reproduce in large numbers at all times. Rather, it requires very harsh conditions. Only when the conditions are met, will they multiply in large numbers and cause food safety hazards.
QC bacteria: The most important condition is "temperature".
The optimal reproduction temperature of Pseudomonas cocotoxin is 22~30 degrees Celsius. It is almost impossible to reproduce under refrigerated conditions (4). Therefore, once products fermented for a long time under relatively hot temperatures are contaminated by this bacteria, the bacteria may multiply rapidly and produce toxins, causing food safety hazards.
Whether it is Indonesian coconut meat tempeh or Chinese fermented rice and noodles, they all meet this characteristic. Moreover, the toxins produced by Pseudomonas cocotoxin can also inhibit the reproduction of fermentation bacteria in fermented food (such as mold), thus creating more favorable conditions for their own growth.
QC bacteria: In addition to temperature, "moisture" is also very important.
It is also difficult for Pseudomonas cocotoxin to reproduce in drier environments. There must be a surface with high humidity, and the humidity of the air is also high, so that it can quickly multiply on the surface of food (such as fermented rice noodles in the air-drying process, fresh fungus/tremella, wet rice dough, etc.). This is why my country’s State Administration for Market Regulation has repeatedly reminded everyone to be careful when buying fresh fungus and tremella, and not to buy self-picked fresh fungus and fresh tremella. For the same reason, wet noodle products such as fresh rice noodles and rice rolls are prone to problems, while dried ones are less susceptible to food poisoning.
QC bacteria: The third condition is "neutral, alkaline, low-salinity environment".
Pseudomonas cocotoxin is not acid-resistant. If acid is produced during the fermentation process and the pH of the entire system drops below 5, Pseudomonas cocotoxin will basically not survive. Therefore, we don’t have to worry about fermented foods such as sauerkraut and kimchi being contaminated by this bacteria. Likewise, Pseudomonas cocotoxin is not salt-tolerant. Therefore, generally pickled foods such as pickles, bacon, etc. will not cause food poisoning by Pseudomonas cocotoxin (of course, these foods may cause other types of food poisoning, such as Clostridium botulinum as mentioned before)
Xinxin: It seems that as long as we learn certain skills, we can stay away from Pseudomonas cocotoxin!
QC bacteria: That’s right! So don’t worry
How to prevent Pseudomonas cocotoxin food poisoning?
First, let’s talk about fermented foods. Not just any "fermented product" is worth worrying about.
For example, if you make steamed buns, bread, yogurt, sauerkraut, etc. at home, you generally don’t need to worry about this. Just here to remind everyone: Homemade fermented food usually means greater food safety risks. Even if there is no Pseudomonas cocotoxin, there is still the possibility of contamination by other bacteria. Therefore, it is recommended that everyone buy pre-packaged fermented products from well-known brands on the market, which will give you peace of mind.
What needs to be noted is that try not to make fermented cereal products such as fermented rice noodles. If you must do it, you need to closely control environmental sanitation, inoculate commercial strains if possible, change the water frequently, cook and eat immediately after fermentation, and do not store it. (Remind me again: even if you do these, you may not be able to guarantee safety. Therefore, try not to do it is the best way)
Let’s talk about black fungus, white fungus and other bacteria that are often "infected" kind.
If black fungus and tremella are contaminated by Pseudomonas cocotoxin, their appearance will look different. For example, it is shapeless, sticky, inelastic, smelly, etc. Regardless of whether it is fresh or soaked, once this kind of deterioration occurs, it must be thrown away and cannot be eaten again. If you see someone selling fresh white fungus, don't buy it.
In addition, the soaking process must not take too long. A few hours is enough, and there is no need to soak the hair for a whole day or even more. You can choose to soak it in the refrigerator if possible. Cook and eat immediately after soaking. Do not store it in a wet state for too long.
Finally, let’s talk about “wet rice flour products”
If you make wet rice flour products such as rice noodles, river noodles, and rice rolls at home, it is best to eat them on the same day. Don't store it for too long. If you buy pre-packaged products, try to buy them with a brand name, and confirm the production date to make sure not to eat expired wet rice flour products.
If there is any deterioration or peculiar smell, throw it away immediately and do not eat it again.
Summary
QC bacteria: To summarize, if you want to prevent poisoning, the main thing to pay attention to is the "cliché" things about food safety:
1) Make any fermentation You need to be careful with all kinds of food. If you can't make fermented rice and noodles, don't make them.
2) Don’t soak food for too long, and eat wet noodle products as soon as possible after they are made.
3) If you find signs of food spoilage, throw it away and do not eat it.
If the above can be done, then Pseudomonas cocotoxin is not terrible, and the food poisoning caused by it is completely preventable and controllable.
Reference:
1. Nugteren D H, Berends W. Investigations on bongkrekic acid, the toxine from Pseudomonas cocovenenans[J]. Recueil des Travaux Chimiques des Pays‐Bas, 1957, 76 (1): 13-27.
2.Wikipedia - Burkholderia gladioli /2015/07/09/toxic-tempeh-death-by-bongkrekic-acid/
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