Hot search! The price of "top midnight snack" crayfish has dropped! But 4 types of people should be cautious when eating it

Recently, information related to the price reduction of crayfish has been trending on the Internet many times. Many crayfish lovers commented in the comment area, "I am happy" and "I can eat crayfish twice a day"... However, some netizens expressed concerns because they have heard that "crayfish grow in stinky ditches, like sewage, and have excessive heavy metals, so they cannot be eaten."

So, are crayfish really that dirty?

Picture taken from the Internet

Crayfish love sewage

Are heavy metals usually exceeded?

Many people have heard that crayfish live in sewage, contain excessive heavy metals, and are harmful to health.

In fact, the rumor is not true.

First of all, in terms of the growth environment, crayfish are not suitable for living in sewage. Nowadays, crayfish are all artificially cultivated in a standardized manner, and the scale of cultivation is continuously expanded through the intensive cultivation of shrimp fry. During the breeding process, it is necessary to properly fertilize and clean the water body, ensure the transparency and cleanliness of the water quality in the breeding area, and ensure that the water quality is clean.

Experiments have also shown that crayfish not only have no preference for high-concentration ammonia nitrogen sewage, but will actively avoid it when the concentration reaches a certain value. If they fail to avoid it in time, they will behave abnormally or even die. Therefore, this is enough to show that crayfish also like clean water sources, and sewage is not conducive to the survival and reproduction of crayfish.

Secondly, the issue of heavy metal content in crayfish.

Some researchers tested the heavy metal content in different parts of crayfish. The results showed that there were significant differences in the heavy metal content in different parts of crayfish. The heavy metal content in the abdominal muscle was significantly lower than that in the head. The general trend was head > shell > claws > abdominal muscle.

This is because the crayfish's liver, kidneys, pancreas and other detoxification and excretion organs are all in the head. These organs can produce a large amount of metallothionein to bind heavy metal elements. Therefore, heavy metal elements are more likely to concentrate in the crayfish's head. In addition, the shell is also an important part of the crayfish's processing of heavy metals.

Therefore, if you are really worried about the problem of heavy metals, you who love eating crayfish should not suck on the crayfish heads.

It should be pointed out that the heavy metal content of crayfish is closely related to the living environment. If the breeding is standardized and the water quality is maintained, the safety of crayfish meat can be ensured. The heavy metal content of the edible part (abdominal muscle) of regular crayfish on the market is within the safety limit and can be eaten with confidence.

How nutritious is crayfish?

Crayfish originated in North America and has now become an important freshwater shrimp farmed in the middle and lower reaches of the Yangtze River in my country. Eating crayfish has become a dietary preference for more and more people. As long as the crayfish is purchased through formal channels, there is no need to worry about heavy metal residues. Eating crayfish regularly is also good for nutrition. Let's take a look.

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The edible part of one common crayfish is about 9 grams. If you eat 100 grams, it is equivalent to eating a dozen crayfish. It is quite satisfying to think about it. So what nutrients do these dozen crayfish have? Let's talk about it in detail (taking 100 grams of crayfish meat as an example).

1

High protein and low fat

Crayfish contains 19% protein, which is high-quality protein that is easily digested and absorbed; the fat content is only 1.1%. The calories in 100 grams of crayfish are only 90 kcal, which is lower than the calories in a large apple.

This high-protein, low-fat and low-calorie food is very suitable for those who need to lose weight.

2

Rich in zinc

The zinc content is very good, at 2.79 mg/100 g. Eating 100 g of crayfish can meet 22% and 37% of the daily zinc requirements of average men and women, respectively.

Zinc deficiency can make people picky about food, and in severe cases it can lead to pica. It also affects brain function, affects wound healing, makes people more susceptible to respiratory infections, induces ADHD, affects male fertility, causes hair loss, rough skin and epithelial keratinization.

3

Rich in selenium

The selenium content is as high as 39.36 mg/100 g, which is twice that of Chinese shrimp and nearly five times that of the pork tenderloin we often eat. Eating 100 grams of crayfish can meet 66% of the daily selenium requirement of the general population.

Selenium can protect cardiovascular and myocardial health. Selenium deficiency can lead to reduced immunity, growth retardation and neurological visual damage. Severe selenium deficiency can induce Keshan disease.

4

Rich in Retinol

The retinol content is 77.6 mg/100 g. This ingredient can help us relieve visual fatigue, maintain normal visual function and protect the eyes.

So, the nutrition of crayfish is not bad! However, if the cooking method is not appropriate, eating crayfish can make people fat. We will talk about this in detail later.

4 things to note when buying crayfish

Recently, crayfish have been launched on the market in various places. What should you pay attention to when purchasing so that you can buy good crayfish?

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1

View Status

It is best to buy fresh crayfish. This is because the most important organ of crustaceans is a structure called the midgut gland or hepatopancreas, which secretes digestive enzymes to break down food and absorbs and stores fat. Once a crustacean dies, it will become the source of rapid decay. The digestive enzymes will destroy the small tubes in the gland and expand outward to the muscles, making the muscles mushy and soft, and the reproduction of microorganisms will also increase. In addition, the high temperature in summer is more conducive to the reproduction of bacteria.

If you need to store it for a while after you bring it home, it is best to store it at 0℃ ice temperature, and the shelf life should not exceed 11 days; if you refrigerate it at 4℃, the storage time of fresh crayfish is recommended to be controlled within 8 days, and if you refrigerate it immediately after the crayfish dies, the storage time should be within 4 days. However, considering the taste and safety, we should not be so extreme. We should cook the crayfish on the spot after buying it, and eat it safely to do justice to the ingredients.

Frozen lobster tails are usually processed when the crayfish are fresh and can be safely cooked and eaten. However, it is recommended that you buy less at a time. Frozen in a home refrigerator for a long time will cause the meat to become tough and the taste will deteriorate.

2

Smell

Fresh crayfish has its inherent fishy smell and aroma. If it has a fishy, ​​sour or ammonia smell, it is not fresh.

3

Touch

Fresh lobster meat is elastic when pressed, non-sticky, and has a tight texture.

4

Look at "origin"

It is best to purchase farmed crayfish through formal channels, rather than wild crayfish.

Crayfish cooking tips

Boiled crawfish give off a fruity, popcorn-like aroma and taste a bit sweet. Crawfish cooked in their shells usually taste better because the shell not only retains the flavor of the meat, but also contains proteins, sugars and pigment molecules that make the meat closer to the shell taste better.

Also, pay attention to the cooking method. As mentioned above, crayfish itself is indeed high in protein and low in calories, which is very helpful in controlling weight. However, you cannot ignore the cooking method. If you often eat spicy crayfish, fried crayfish tails, braised crayfish and other crayfish cooked with heavy flavors, you may get fatter and fatter. In comparison, steamed crayfish and garlic crayfish are healthier.

Who should eat less or not eat it?

1

Gout people

The purine content of crayfish is 174 mg/100 g, which is a high-purine food. If you have gout or hyperuricemia, it is best not to eat it. Some people like to drink a bottle of beer while eating crayfish, but this combination is more likely to induce gout.

2

People with hypercholesterolemia

The cholesterol content of crayfish is relatively high, at 121 mg/100 g, which is 2.2 times that of pork tenderloin. People with hypercholesterolemia should eat less or no crayfish.

3

People with allergies

Tropomyosin is a major allergen in shrimp. If you are allergic to other shrimp, it is best not to eat crayfish. Allergies can cause symptoms such as rash, diarrhea, asthma, shock, and even be life-threatening.

4

Other disease-related populations

For example, people with asthma, kidney disease, or those taking statins to lower blood lipids need to follow the doctor's advice to decide whether they can eat it.

Summarize:

If you only eat the tails of crayfish, then feel free to eat it; if you like to eat the heads, then it’s best to eat less!

References

[1] Wang Wenzhong. A study on the breeding habits and breeding management of crayfish[J]. Fisheries Guide to Getting Rich, 2020, No.529(01):45-47.

[2] Chen Ting, Zhang Lei, Tang Jianqing, et al. Selection of subadults and larvae of Procambarus clarkii to water environments with different ammonia concentrations [J]. Resources and Environment in the Yangtze River Basin, 2011, 20(10): 1186-1190.

[3] Sui Ke, Hang Wei. Study on the content and distribution of heavy metals in crayfish [C]//Chinese Optical Society, Chinese Chemical Society, Spectroscopy Committee of Chinese Optical Society. Proceedings of the 20th National Molecular Spectroscopy Conference and 2018 Spectroscopy Annual Conference. Peking University Press, 2018: 2. DOI: 10.26914/c.cnkihy.2018.017662.

[4] Quan Qinguo, Zhang Zewei, Chen Ming, et al. Research progress on comprehensive utilization of crayfish[J]. Food Research and Development, 2019, 40(03): 213-219.

[5] Yang Yuexin, Ge Keyou. Chinese Nutrition Science Encyclopedia 2nd Edition (Volume 2)[M]. People's Medical Publishing House, 2019

[6] Harold Mackey, Food and Cooking: Milk, Eggs, Meat, Fish. Translated by Lin Huizhen. Beijing Fine Arts Photography Publishing House. August 2013.

[7] Zhang Yanling, Xiang Junfei, Zhu Yajun, et al. Comparison of refrigeration characteristics of fresh and dead crayfish[J]. Food Science, 2022, 43(01): 206-212.

[8] Yang Yuexin. Chinese Food Composition Table 6th Edition Volume 2[M]. Peking University Medical Press, 2019

[9] Zhao Xiangjie, Ge Naiyi, Liu Yingchun, et al. Research progress on crayfish food allergy[J]. Food and Fermentation Technology, 2019, 55(02): 70-71+124.

Planning and production

Author: Xue Qingxin, registered nutritionist

Reviewer: Ruan Guangfeng, Director of Science and Technology Department, Kexin Food and Nutrition Information Exchange Center

Planning丨Zhong Yanping and Ding Zong

Editor: Ding Zong and Zhong Yanping

Proofread by Xu Lailinlin

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