crayfish
Like its fiery red body, since April, crayfish have begun to burn all over the country's wet markets, fresh supermarkets, catering establishments, and personal tables.
The momentum is clearly outpacing its older brother lobster (in fact, crayfish is river fresh, while lobster is seafood, not a species at all).
Large lobsters
Seeing the boiling situation of everyone eating shrimp, the passion for the popularization of Rui Rui mushroom food has also risen. Heard that crayfish are invasive species? Are there "horrifying natural food toxins"? (Poke here to see the natural toxins in food) What are the hidden dangers of eating?
This concern is not out of thin air: Recently, a notice from the Market Supervision and Administration Bureau of a district in Hangzhou showed that of the 17 batches of river shrimp sampled, 15 batches were unqualified, with a failure rate of 88.23%, and the unqualified item was detected as a non-edible furacillin metabolite (see figure below).
(Image source: Official announcement, dated May 2020)
Furacillin drugs and their metabolites: banned veterinary drugs. Long-term intake has carcinogenic, teratogenic and other side effects on the human body.
With enthusiasm and concern, this article focuses on 2 points:
(Friends who only care about how to eat safely jump directly to section 2):
How did crayfish "invade" China and "occupy" the world?
What do crayfish eat to grow up? Food safety hazards and avoidance
<h1 class="pgc-h-arrow-right" > how crayfish "invaded" China and "occupied" the world</h1>
Crayfish, also known as American shrimp, Latin name Procambarus clarkia, English name Red swamp crawfish.
After eating so many crayfish, can you take a serious look at it?
(Image source: http://www.seagrant.umn.edu/)
(Image source: https://www.researchgate.net/)
Invasive species.
In 2019, crayfish were included in the "List of the First Invasive Alien Species in Yunnan Province" by Yunnan Province, and belonged to the class II severe invasion class (the highest level is the class I malignant invasive class).
It is reported that the invasion of alien species, followed by the survival of the fittest, is the biggest threat to local biodiversity, ecological environment, economy and human living environment.
(Image source: www.frontiers.org)
So, how did the crayfish occupy the world? And, of course, China.
Crayfish: Have the ability to beat me (Credit: The book Red Swamp Crayfish, published by Froebel-Kan in 2009)
In 2019, Spain's National Research Council (CSIC) published a scientific paper confirming that crayfish invasions beyond its home country ( the Gulf of Mexico in the southeastern United States ) first occurred around 1920.
Crayfish came to Japan in 1927 and to China in 1929. Around 1965, it arrived in Uganda and Kenya, as well as other African countries. Later, around 1970, it settled in Mexico, Venezuela and other countries, and was legally introduced to Spain in 1973.
At present, crayfish have successfully invaded at least 40 countries! Crayfish are able to travel the globe, and human activities play a leading role.
Through genetic sequence testing, CSIC once again confirmed that Chinese crayfish originated from Japan, which was first "invaded". Is it true that the Japanese introduced crayfish in China for water cleaning work or other purposes, as previously rumored?
Professor Sidney Cheung of the University of Hong Kong claimed in 2018 that his research showed that the Japanese adopted crayfish as pets and did not introduce them to China on purpose.
The first crayfish to enter China landed in a lake at Nanjing Airport, and after the End of the Sino-Japanese War (1937-1945), the Japanese left China and left their pet crayfish behind.
Research from the Doñana Biological Station ( Spain ) in Spain showed that crayfish were introduced by the Japanese and marketed in Changchun in August 1939. At that time, the price of a crayfish used to breed was 0.5 yen, which is equivalent to $3 today (based on data from the website of the national diet library in 2019). Biostatics speculates that because the price of crayfish fry is not expensive, crayfish began to multiply in large quantities in East Asia.
So what do crayfish feed on? Is there a hidden danger to human consumption?
< h1 class="pgc-h-arrow-right" > what do crayfish eat to grow up? Food safety hazards and avoidance</h1>
Standard scavengers.
Crayfish are omnivorous, and their food includes small fish, dead animals, feeding, etc. They are also not picky about the living environment, lakes, rivers, streams, ponds, swamps can be found.
(Image source: Nauplius Journal, Vol. 23, 2015, by Tainã Gonçalves Loureiro)
Ecology of crayfish
Food: tadpoles, snails, etc
Predators: birds, fish, capybara, otters
Parasites: flagellar, lung flukes, horseshoe trematodes, echinococcus
Pathogenic bacteria: baculovirus WSSV, fibrous algae filaria (shrimp plague), parasitic water mold
In the study by Tainã et al., published in the Nauplius Journal, the parasites and pathogenic bacteria carried by crayfish are clearly listed.
Food safety hazards: Huff disease
According to reports, in 2010, after diners in Nanjing ate crayfish, soy sauce colored urine appeared, and some severe cases developed acute kidney failure, and were diagnosed with Haff Disease, professionally known as rhabdomyolysis. Unfortunately, the specific causative factors of Huff's disease are still unknown, but only related to the intake of aquatic products.
Other food safety hazards
In addition, in the recent random inspection of the market supervision and management department, the banned veterinary drug furacillin metabolite was also detected.
So how to avoid food safety hazards?
First of all, after the banned substances are detected in freshwater shrimp, the market supervision and management department will carry out special rectification actions for freshwater shrimp to ensure that the crayfish sold in the market do not contain prohibited drugs such as malachite green and furacillin. Remind your friends to be sure to go to the regular market to buy crayfish.
The crayfish that are regularly sold are basically raised through formal scientific farming, eating feed rather than animal corpses, so the possibility of crayfish having infectious diseases is also very small.
In addition, when it comes to safe consumption, keep in mind 8 points:
Avoid eating raw. The parasites carried by crayfish must be cooked at a high temperature of more than 95 ° C before they can be killed.
Avoid eating dead crayfish. After death, the histidine in the body is converted into a toxic substance.
(Image source: South China Morning Post, scmp.com)
Do not eat shrimp noodles. Inside the shrimp line is the droppings of crayfish.
Do not eat shrimp heads and remove them before cooking. Because shrimp heads are most likely to accumulate toxins, germs, and parasites.
Do not eat shrimp yellow (in the head position). There are the digestive glands of the shrimp.
People with allergies to seafood should avoid it.
Wash well, especially the gills. The gills are the accumulation of bacteria. Do not buy crayfish with gray or dirty gills.
Avoid cross-contamination. In home cooking, do not use a plate filled with raw shrimp to hold cooked shrimp, otherwise the bacteria carried by raw shrimp will be ingested.
Finally, please pay attention to the FoodPanel science knowledge in time, when a certain type of food has a food safety risk, Reed bacteria will make a timely reminder.
See you in the next issue.
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