Crayfish (source: cq.qq.com)
As the saying goes, "there are not many red people". Since crayfish became an online celebrity, rumors about crayfish are also common.
1.？ Crayfish is too dirty for foreigners to eat at all?
I not only ate, but also ate early.
When we usually say crayfish, we mean freshwater crayfish, that is, crayfish. Procambarus clarkii originated in the southern United States and northern Mexico. In 1930s, the Japanese introduced it as bait for bullfrogs, and in the late 1930s, it was introduced from Japan to China. It first entered the area near Nanjing, and then spread along the Yangtze River basin.
Crayfish (source: wikipedia.org)
Although crayfish was introduced late, it does not belong to "China traditional cuisine", but it can't hold up people's critical eyes and think it is delicious and nutritious. After 60 years, crayfish began to walk on the table; Subsequently, the output surged, 1988, and crayfish began to be exported to Europe and America. [ 1]
As of 20 17, China has become the world's largest producer and consumer of crayfish. [2]
2.？ Wouldn't it be bad to ship it all the way abroad?
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The so-called bad is caused by bacterial reproduction. The main bacteria that crayfish "provoke" are pathogenic Vibrio and Staphylococcus aureus.
Staphylococcus aureus (source: wikipedia.org)
Pathogenic Vibrio belongs to moderate thermophilic bacteria, likes moderate high temperature and reproduces rapidly in summer. Once the intake exceeds the safe value (inconsistent, about 1 10,000), it may cause gastroenteritis and other diseases, leading to fever, headache, diarrhea, vomiting and other symptoms.
Staphylococcus aureus has two optimal temperatures. 37℃ is the best breeding temperature for bacteria, and 2 1℃ is the most exuberant time for enterotoxin secretion. Below 6.7℃, it can neither reproduce nor secrete enterotoxin. Enterotoxin is the main cause of food poisoning caused by Staphylococcus aureus. [3]
Therefore, the treatment of crayfish includes two links. Take the crayfish exported this time as an example. First, after cleaning and high temperature (200℃) treatment, most of the living pathogenic bacteria were killed. Then, it was frozen at low temperature (-190℃). Cryopreservation can not only protect the taste of crayfish, but also avoid the release of toxins such as enterotoxin.
3.？ Crawfish can spread parasites?
It depends.
The most common parasite on crayfish is Paragonimus westermani. Because this parasite can swim in the human body, adults are mainly parasitic in the lungs, so it is commonly known as paragonimiasis.
Paragonimus adults [4]
Paragonimus is a master who can "hold his thighs" especially. Its first host is some snails, such as snails; Then, it will find crabs, squid, crayfish and so on. As its second host; People or other animals, such as pigs, wild boars, rats, rats, chickens, ducks and geese, may be infected if they eat the second host. [5]
Therefore, crayfish is neither the only food that can spread paragonimiasis nor the main source of infection of paragonimiasis. [6] thoroughly cooking food and not drinking raw water is always the first principle to avoid parasitic infection.
In addition, the onset cycle of paragonimiasis is very short. If you eat contaminated food raw, you will usually have acute symptoms such as abdominal pain, diarrhea and loss of appetite within a few days to a month. "Will the crayfish I ate last year be polluted?" There's no need to worry.
4.？ I heard that crayfish is seriously polluted by heavy metals?
That's not true.
There are not enough wild crayfish for people to eat, and now we buy mostly farmed products.
Although crayfish have strong viability and obvious enrichment, they are not cockroaches after all. The growth, molting, development, reproduction and limb regeneration of crayfish are inseparable from enzymes, and heavy metals will inhibit the activities of related enzymes of crayfish. [7]
In other words, heavy metal pollution will affect farmers' income. They will try to avoid this situation.
Since 2000, freshwater crayfish have been included in the national animal-derived food residue monitoring plan, and they are sampled regularly and in batches for testing. The test results show that, except for a few samples with lead exceeding the standard (the total exceeding standard rate was 4% in 2006 54 38+0-2002, and it showed a downward trend), the contents of other heavy metals did not exceed the standard. [3]
Of course, this matter of heavy metals, in the final analysis, depends on the dose.
Take lead for example. The WHO tentatively recommended dose is 25 μ g/(kg/week). In other words, a person weighing 65kg should consume less than 232 μ g of lead every day; The average lead content of crayfish in China was 0.68mg/kg. In addition, crayfish produce less meat, and the edible part is less than a quarter. Theoretically, eating crayfish above 1.4kg every day may cause health problems.
However, the threshold of heavy metal exposure is still controversial. Of course, the less the better. The results show that heavy metals mainly exist in the gills of crayfish, and the content in abdominal muscles is the lowest. So, I really don't trust, so I eat shrimp. [8]
5.？ Can you get rhabdomyolysis if you eat crayfish?
There is no clear evidence.
Rhabdomyolysis after eating crayfish is called Huff's disease. The disease was first reported in Europe on 1924. Subsequently, similar cases appeared in Sweden 1932, and there were sporadic reports in the United States, Brazil, Japan and other regions. Its * * * features are:
All patients eat products such as freshwater pomfret and salmon.
All patients have obvious symptoms such as general weakness and muscle soreness.
Laboratory examination showed that the patient's creatine kinase was significantly increased. [9]
There is a case in China and Nanjing. From July to September of 20 10, 23 patients were diagnosed with Haff disease. Despite this, these patients have eaten crayfish, but not all customers who have eaten crayfish are sick, and the prevalence rate is only about 4‰; [10] Studies in other places show that there is no linear relationship between the value of creatine kinase and the consumption of crayfish. [1 1] All these make it difficult to find the reason.
At present, Haff disease may be related to an undetected toxin. This toxin is not unique to crayfish, and its toxicity is weak. Generally, the prognosis is good, and no sequelae will be left.
In short, crayfish can be steamed, fried, boiled and roasted. As long as the source is reliable and thoroughly cooked, there is no problem. It's just that you can't take it as the protagonist of a rumor.
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refer to
[1] Lu Jianfeng, Lai Nianyue, Cheng Yongxu. Comprehensive utilization and development value of freshwater crayfish resources [J]. Processing of agricultural products. Journal, 2006, 10.
[2] Shrimp printing machine! Official report: Last year, the total output value of crayfish in China was 654.38+046.6 billion, ranking first in the world [EB/OL]. [2065.438+08-06- 15]./ Economy/2065.438+07 _ 06 _13 _ 465438+.
[3] Chen Xiukai. Risk analysis of exporting freshwater crayfish products [D]. China Ocean University, 2004.
Lu, Kuang Haocheng, Shen Haoxian, et al. First report on the ultra-high focus of Paragonimus westermani in the northern suburb of Guangzhou [J]. China * * * is sick, 2009,25 (6): 602605.
[5] Li Yonglong. Human parasitology [M]. 2008.
Li Yousong, Lin Jinxiang. Analysis on the change of infection rate in paragonimiasis endemic areas in Fujian Province and its causes [J]. China Journal of Parasitic Disease Prevention and Control, 1999, 12(4): 275277.
Zhang, Chen Xinying, et al. Effects of four heavy metal ions on nagase activity of Procambarus clarkii [J]. Journal of Applied and Environmental Biology, 20 12, 18(6): 943947.
Wu Jiming, Wu Jiefei. Study on the authenticity of heavy metals in crayfish and vomit [J]. Journal of Nanchang Institute of Aeronautical Technology, 2006,20 (2): 4144.
Huang X, Li Y, Huang Q, et al. An outbreak of Huff's disease caused by eating freshwater pomfret in South China [J].BMC Public Health, 20 13, 13 (1): 447.
[10] Han Lilan, Xu. Investigation and handling of "Crayfish Incident" in Nanjing [D].1996017
[1 1] Liu Caixin, Liu Peng, Wang, et al. Epidemiological and laboratory characteristics of rhabdomyolysis caused by crayfish [J]. Journal of yichun university, 2017,39 (9): 6264.
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Author: Zhao Yanchang