June 5, 2020 10, Jidong County, Heilongjiang Province, 9 people suffered from food poisoning. Up to now, 8 people have died, and the remaining 1 people are still being rescued. They ate a homemade fermented food called "sour soup" at dinner. At first, the incident was judged as "aflatoxin poisoning", but after further investigation, it was found that the food was actually contaminated by a microorganism called "Pseudomonas cocoanum", and it was the deadly toxin produced by this bacterium that caused the deaths of these residents.

QC bacteria: If you pay attention to the previous news, you will find that this poisoning incident is nothing new. There have been many cases in recent years.

For example, on July 28th this year, 1 1 customers suffered from food poisoning after eating rice noodles at Shitou rice rolls Store in Shenquan Town, Huilai County, Jieyang City, Guangdong Province. Finally, 5 people were taken to the hospital, and 1 person died after being rescued. After investigation, it was confirmed that the river powder was polluted by Pseudomonas cocoanum.

20 19 Ms. Zhang, a citizen of Shenzhen, vomited a few days after eating black fungus soaked at home, and her liver, kidney and heart functions were seriously damaged. Finally, she had an emergency liver transplant to save her life. After investigation, Auricularia auricula was polluted by Pseudomonas cocoanum. There have been many poisoning incidents caused by "long-term soaking of black fungus" before, all of which are related to "Pseudomonas cocoanum".

Xinxin: This kind of bacteria is really dangerous! How can we prevent this kind of food poisoning?

QC bacteria: To learn more about this, we should start with a traditional Indonesian food.

Found that all roads lead to the same goal.

"Danbei" is a general term for many fermented foods in Indonesia. The common "Danbei" is a cake-like food fermented by inoculating soybean and other miscellaneous grains with Rhizopus.

A special "Danbei" was once popular in Java, which was fermented from coconut meat. It is this "Tempe bongkrèk" that has become a deadly "killer".

As early as the 1930 s, there were records of poisoning caused by eating "coconut meat Danbei". Poisoned people often have gastrointestinal symptoms such as vomiting and diarrhea first, then headache, dizziness, fatigue, severe convulsions and coma, and finally die of respiratory and circulatory failure, cerebral hematoma and uremia. The mortality rate of poisoning is as high as 30%~50%.

Microbiologists mertens and Van Veen extracted a bacterium that had never been seen before from poisonous Danbei, and finally determined that it was the chief culprit of food poisoning. Because it belongs to Pseudomonas, it was first discovered in coconut fermentation products, so it was named "Pseudomonas cocoanum". But unfortunately, this discovery was not paid enough attention at that time, and the poisoning incident never stopped. From 195 1 year to 1975, an average of 288 people in Indonesia were poisoned and 34 people died every year because of eating this kind of "coconut danbei". Finally, the Indonesian government had to completely ban the production and sale of this food in 1975.

Almost at the same time, thousands of kilometers away in northeast China, another kind of food poisoning is taking people's lives.

Fermented rice flour is a traditional food raw material in China. Generally, it is made by soaking corn, sorghum and other miscellaneous grains in water, naturally fermenting/kloc-0.8 days to a month, wet grinding into a paste dough, filtering and air drying. Due to natural fermentation, fermented rice noodles usually have a certain sour taste. The north uses it to make stinky dregs, sour soup, gege beans and other foods. Some areas in the south will also use it to make glutinous rice balls and other foods.

Poisoning caused by fermented rice flour has always been common in Northeast China, but for a long time, this kind of poisoning has been thought to be caused by mold. It was not until 1970s and 1980s, after a series of careful studies by scientists in China, that people realized that it was caused by a brand-new bacterium. At first, this kind of bacteria was called "Flavobacterium producing toxin", and later it was called "Pseudomonas fermented rice". Finally, it was found that the bacteria seemed to be very similar to Pseudomonas cocoanum found in Indonesia. For example, they all produce the same toxins!

Finally, on 1987, China scientist Zhao Naixin and others compared more than 200 characters and confirmed that the bacteria that caused fermented rice flour poisoning and Indonesian Danbei poisoning were actually the same kind of bacteria-Pseudomonas cocoanum! Moreover, this kind of bacteria can also cause many other kinds of food poisoning, such as auricularia auricula and tremella, etc., which are particularly vulnerable to pollution by this kind of bacteria; Wet rice flour products, such as rice noodles and rice rolls, can be easily contaminated by this kind of bacteria if they are not stored properly! People who eat these contaminated foods may be in danger.

QC bacteria: Until now, people's understanding of "Pseudomonas cocoanum" has just begun.

One bacterium, two toxins.

Many domestic reports directly refer to food poisoning caused by Pseudomonas cocoanum as "Aspergillus oryzae acidosis". In fact, the name is a little one-sided, because this bacterium can produce two toxins, namely Bongkrek acid and toxoflavin, which together lead to poisoning symptoms.

Oryzanol can combine with ADP/ATP transporter in mitochondria, which is the "energy factory" in cells, to prevent the transfer of ADP and make the "energy factory" strike directly, while toxoflavin acts on the electron transport chain in cells, affecting respiration and producing a large number of toxic hydrogen peroxide molecules. Together, they lead to cell death.

Although their toxicity is not particularly high in the toxin world, the food that generally causes poisoning is seriously polluted, and the contents of these two toxins are high. Coupled with fermented rice noodles as a staple food, you will also eat more. On the whole, it is reasonable to reach the lethal dose. It should be noted that these two toxins are relatively stable to heat, and there is no way to destroy the toxins in the usual cooking process.

An article in 2003 made an epidemiological analysis of 9 cases of fermented rice flour poisoning in Guangxi. 13 people died of poisoning, 1 1 people survived from poisoning, and the average consumption of fermented rice flour 175g. Those who ate more than 200 grams died without exception. Those who ate less than100g survived.

The weakness of Pseudomonas cocoanum

Xinxin: Oh, my God! This is terrible! Never dare to eat any fermented food again! I dare not eat rice noodles, fungus and tremella!

QC bacteria: Don't panic!

Don’t panic！ Pseudomonas cocoanum has many "weaknesses". It doesn't always reproduce in large numbers. It needs very harsh conditions, and only when the conditions are met will it multiply in large numbers, causing food safety hazards.

QC bacteria: The most important condition is "temperature".

The optimum breeding temperature of Pseudomonas cocoanum is 22~30℃. It is almost impossible to copy under the refrigeration condition (4) of the refrigerator. Therefore, once the products fermented for a long time at a relatively hot temperature are contaminated by this bacteria, the bacteria may multiply rapidly and produce toxins, causing food safety hazards. Indonesian coconut Danbei and China's fermented rice-flour food all conform to this feature. Moreover, those toxins produced by Pseudomonas cocoanum can also inhibit the reproduction of fermentation bacteria (such as mold) in fermented food itself, thus creating more favorable conditions for its own growth.

QC bacteria: Besides temperature, "moisture" is also very important.

In a relatively dry environment, Pseudomonas cocoanum is also difficult to reproduce. Only when there is a high humidity surface and the air humidity is high can it propagate rapidly on food surfaces (such as fermented rice flour, fresh fungus/tremella, wet rice flour, etc.). ). This is why the General Administration of Market Supervision of China has repeatedly reminded everyone to be cautious when buying fresh fungus and tremella, and not to buy fresh fungus and tremella collected by yourself. Similarly, fresh rice noodles, rice rolls and other wet noodle products are prone to problems, while dry ones are less prone to food poisoning.

QC bacteria: The third condition is "neutral alkaline low salinity environment".

Pseudomonas cocoanum is not acid-resistant. If acid is produced in the fermentation process, the pH value of the whole system will drop below 5, and Pseudomonas cocoanum will basically die. Therefore, we don't have to worry about fermented foods such as sauerkraut and kimchi being contaminated by this bacteria. Similarly, Pseudomonas cocoanum is not salt tolerant. Therefore, generally preserved foods, such as pickles and bacon, will not suffer from food poisoning caused by Pseudomonas coconuts (of course, other types of food poisoning may occur in these foods, such as Clostridium botulinum mentioned above).

Xinxin: It seems that as long as you learn certain skills, you can stay away from Pseudomonas coconuts!

QC bacteria: That's right! So you don't have to worry.

How to prevent food poisoning caused by Pseudomonas cocoanum?

First of all, talk about fermented food. Not all "fermented products" are worth worrying about.

For example, cooking steamed bread, bread, yogurt, sauerkraut and the like at home generally does not need to worry about this. Just to remind everyone here: homemade fermented food usually means greater food safety risks, even if there is no Pseudomonas cocoanum, there is the possibility of other miscellaneous bacteria pollution. Therefore, it is recommended that you buy pre-packaged fermented products with brands on the market if you have the conditions, so you can rest assured.

Then it should be noted that you should try not to make fermented cereal products such as fermented rice noodles. If you must do it, you need to strictly control environmental hygiene, inoculate commercial strains conditionally, change water frequently, cook and eat immediately after fermentation, and don't store it. (Again: Even if you do this, you may not be able to guarantee safety. So, trying not to do it is the best way)

Let's talk about fungus, tremella and other fungi that are often "caught".

Auricularia auricula and tremella fuciformis will look different if they are contaminated by Pseudomonas cocoanum. For example, it is amorphous, sticky, inelastic and smelly. Whether it is fresh or soaked, once this deterioration occurs, it must be thrown away and can't be eaten any more. If someone sells fresh tremella, don't buy it.

In addition, the process of soaking hair must not be too long, a few hours is enough, there is no need to soak it all day or even longer. You can choose to soak your hair in the refrigerator if you can. Cook it immediately after soaking, and don't store it in a wet state for too long.

Finally, talk about "raw wet rice flour products"

Wet rice flour products, such as rice flour, rice noodles and rice rolls, should be eaten on the same day if they are made at home, and should not be stored for too long. If you buy prepackaged products, try to buy branded products and confirm the production date to ensure that you don't eat expired wet rice noodles.

If there is any deterioration or odor, throw it away immediately and don't eat it again.

abstract

QC bacteria: To sum up, if you want to prevent poisoning, you should mainly pay attention to those "platitudes" about food safety:

1) You need to be careful when cooking any fermented food. Don't do it if you can't.

2) Food should not be soaked for too long, and raw and wet flour products should be eaten as soon as possible.

3) If food is found to be spoiled, throw it away and don't eat it.

If we can do the above, Pseudomonas cocoanum is not terrible, and the food poisoning caused by it can be completely prevented and controlled.

Reference:

1.[ 10] Lu Deren, Belendez. Study on the toxin of Pseudomonas coconuts [J]. Wage and labor records,1957,76 (1):13-27.

2. Wikipedia-Burkholderia gladiolus/2015/07/09/toxic-tempeh-death-by-bongkrekic-acid/

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