I received a box of hairy crabs, but I can’t finish them. What should I do?

"When the autumn wind blows, the crabs' feet itch. When the chrysanthemums bloom, the crabs come to you." When you receive a box of plump hairy crabs with surprise, do you also feel "happy troubles"? How should you preserve so many crabs? You can't eat them all at once, but you're afraid they'll go bad if you keep them for a long time?

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01 Tips for preserving hairy crabs

Live crab

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• Refrigeration method: Place the hairy crabs in the refrigerator and set the temperature to about 5°C. In a low temperature environment, the hairy crabs' metabolism slows down and they enter a dormant state, which helps reduce their physical exertion. To maintain the required humidity for the hairy crabs and prevent dehydration, you can cover them with a wet towel or cotton towel. Using this method, hairy crabs can usually be kept alive for 3 to 5 days. Interestingly, some people have found that hairy crabs can still survive even if they are stored for up to two weeks. However, due to the long period of inability to eat, the meat quality and taste of hairy crabs may be affected to a certain extent, so long-term storage is not recommended.

• Water culture method: Use a plastic bucket and add clean water to half the height of the crab's body. Change the water every day to keep the water clean. It can be kept for about 7 days.

• Foam box method: Similar to the refrigeration method, it reduces the metabolism of hairy crabs by simulating a low temperature environment, thereby extending their survival time. Prepare a foam insulation box and put the hairy crabs in the foam box. Be careful not to stack them to avoid squeezing and injuring the crabs. Place some ice cubes or ice bags at the bottom of the foam box to keep the box low. Add water to cover the crabs and cover the foam box, but do not seal it completely to maintain proper air circulation. Put the foam box in the refrigerator and control the temperature at about 5°C. Although this method is complicated, the preservation time will be longer than the refrigeration method.

Cooked crab

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The ambient temperature in autumn is still relatively high, and even after the hairy crab is cooked, it is very easy for bacteria to multiply, so it is best to eat it while it is hot. If you can't finish it in one go, you need to put it in the refrigerator in time, but it is best to eat it within 1-2 days to ensure food safety and taste. It needs to be thoroughly heated before eating.

02How to tell if the hairy crab is alive?

• Observe the eyes: Touch the eyes of the hairy crab with your hand, and the living hairy crab will blink in response.

• Observe the bubbling: Put the hairy crab into water, the living hairy crab will spit bubbles.

• Observe the claws: Straighten the smallest claw of a living crab and it will naturally bend very quickly.

• Observe crawling: After untying the crabs, they will crawl alive.

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03Can we still eat dead hairy crabs?

It is not recommended to eat hairy crabs that have been dead for more than 2 hours. After the hairy crab dies, the bacteria in its body multiply rapidly, especially pathogenic bacteria such as Vibrio parahaemolyticus . These bacteria will be released in large quantities, causing the crab meat to rot and deteriorate, and may produce harmful substances such as histamine . Histamine is a toxic substance that cannot be completely destroyed even after high-temperature cooking. Ingestion may cause food poisoning, dizziness, vomiting, allergies and other symptoms, and in severe cases may even be life-threatening.

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The Chinese Academy of Fishery Sciences took samples of hairy crabs when they were fresh and at different time periods within 24 hours after death, and measured the total colony count and harmful biological amines contained in them. The results showed that the total colony count of hairy crabs increased sharply from just after death to 2 hours after death, with the total colony count increasing by 22%; histamine was detected 5 hours after death; the total colony count increased by 55% in 24 hours after death, and the hairy crabs had a distinct foul smell.

Therefore, if you can confirm that the hairy crab has been dead for less than 2 hours, has no peculiar smell, and is fully cooked, the risk of eating it is low. If you cannot confirm that the hairy crab is dead, or has a peculiar smell, it is recommended to discard it directly.

04Can live hairy crabs be frozen?

It is not recommended to put live hairy crabs directly into the freezer. Low temperatures will quickly kill hairy crabs, and the crab meat will easily dehydrate during the freezing process, affecting the taste and flavor. If live hairy crabs are placed in the freezer for too long, their muscle tissue will be severely dehydrated, the juice will be lost, resulting in a poor taste, and the characteristic flavor of the crab will be weakened, and unpleasant flavors such as "overheated smell", ammonia smell and fishy smell may be aggravated.

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In short, only by properly preserving hairy crabs and ensuring their safety can you enjoy this delicious autumn delicacy happily and with peace of mind.

References

[1] Fan Zhihong. Not suitable for pregnant women, cannot be left overnight, can only be eaten with rice wine… Is the taboo on eating crabs true or false? [J]. Decision Exploration (Part 1), 2020(11): 88.

Author: Wang Zhengyuan, PhD in Nutrition, Associate Chief Physician, Shanghai Center for Disease Control and Prevention Planning & Editing: Tiara