Feasting on fresh seafood is a delectable experience. Food poisoning on the other hand is a dreadful experience that everyone wants to skip.

Food poisoning derived from bad seafood can happen easily if you’re not careful in Thailand. Who can resist seafood especially in Thailand where there is an abundant supply?  Over the years my immune system has learned to adapt better to the local food here. And as much as I like eating seafood, I know I still have to be very careful whether I buy them fresh or order them cooked in a dish. Street vendors especially have very limited cleaning facilities and cold storage thus the stake is higher.

My grandfather was a fisherman. When we were young, we were ‘trained’ to crush the crab’s legs with the corner of our molars, twist the shells off the shrimps in less than 4 seconds, or determine whether the fish is fresh by one look. But if the seafood is served on the plate cooked, there’ll be lesser ways to determine its freshness. But there are always some telltale signs that tell you that something is not right.

The very first rule of thumb for raw seafood. If it stinks, it’s not good. Like any other kind of meat, same theory works on seafood. Apart from that,

here’s some tips from a fisherman’s granddaughter:



Squid tend to look more translucent than white. When “freshly” caught, squid have an attractive translucent flesh and if the pigment on the skin is still sparkling and moving, it indicates that the squid is still alive.  Squid’s flesh that is whitish with torn skin and loose heads indicates a significant time that it has been dead.




Squid is naturally firm but can be toughened by incorrect cooking or overcooking. Best squids shouldn’t be overcooked or they’ll taste like rubber tires. When it’s fresh and well cooked, they should be firm, slightly chewy and not slimy. If the squid tastes soft, slimy or gritty, they’re a danger.




Fresh shrimps uncooked have their heads firmly attached to the body. When the shells are soft it might not mean that they’re not fresh but that they’re moulted (old shells making way for the new ones). They will also look shiny, glossy and more translucent gray.



Black spots or brown head need not mean that the flesh quality has been affected. It is OK to have black spots on shrimps.


Yellowing around legs on the other hand can be sign of excessive use of sodium metabisulphite. It is a chemical commonly used by vendors or fishermen to control black spot and to extend the shelf life of the shrimps. Metabisulphate will be lowered by more than 50% when the shrimps are cooked.

Sodium metabisulphite can cause wheezing, nausea, pain and a skin rash or itch to people who are intolerant to it.

Here’s a photo with a comparison to the percentage of dipped and undipped shrimps: 

Percentage of sodium metabisulphite used.





Fresh shrimps when cooked should taste sweet, crunchy and firm. If they taste soft, powdery or even extremely chewy, it could be a sign of the shrimps going way past its lifespan perimeters.




Uncooked fresh fish should have bright, shiny eyes with red gills and firm flesh intact to the bones. the flesh varies from each type of fish but usually should look more shiny, translucent. If the fish have cloudy cornea, opaque flesh or even worse beginning to turn brown, then avoid.




Cooked fish should have certain sweetness in the taste. The firmness of the flesh depends on the types of fish but they should look intact. When poking the tines of a fork to the thickest part of the flesh, the flesh should be able to pull out and stay in chunky form . If the flesh resist flaking and looks translucent, that would mean that the fish is not fully cooked. This could happen in a seafood restaurant when you order for a Thai steam fish dish with lime. The flesh of a cooked stale fish will not stay in chunks. They could also be powdery and look like cotton.




Shellfish needs to be alive before cooking. The legs should move when touched. More vigorous movement signifies better quality.  Chilled seafood will move less and be slightly limp. There are basically two main types of crabs in Thailand. The mud crab and the Blue Swimmer crab. Shell should normally be harder on the mud crab than blue swimmer unless the crab has recently moulted. Weight may not necessary be the guide to the quality as some vendors inject liquid into the crabs to give a fake impression of the quality.

There shouldn’t be any missing parts nor cracks. Losing limps signifies stress on crabs that loses tension in muscles. Dead crabs should not be purchased as it is very difficult to know assess how long ago they died. Flesh should be translucent when raw. Opaque flesh or spots in green, yellow, brown and/or with dark spots when raw is a calling for food poisoning. Smell is also a really powerful guide to the quality. For crabs, lift up the abdominal flap to check the smell. Scrap off any mud or foreign matter before checking the smell.


We support sustainable living thus we will advise you to choose male crabs to female crabs. In Asia, most people prefer to eat female crabs for their crab roes. Some markets sell female crabs at a higher price than the male.


This video from Spice N Pans provide a pretty clear information on how to choose the right fresh crab.


If the tail of a rock lobster or freshwater crayfish does not curl under the head when cooked, it could be undercooked or not “fresh” when cooked. The shell should not have any discolouration when cooked. It should be bright red or orange. Any discolouration from the joint signifies stale shellfish. Cooked crustacean should be firm, sweet and juicy. If flesh is dry, it signifies that the shellfish has already ‘bled’ or being overcooked. If flesh is soft and fluffy, it signifies that the shellfish is probably dead before cooking or undercooked.




Be extremely cautious with consuming raw oysters or other mollusc as this is one of the easiest route to hit your toilet. Other than oysters, gaping shells indicates that the shellfish is dead or dying and it should be thrown away. In the case of the oysters, the flesh should be plump and clear. Milky liquid tells you that its not so alive. Do note that milky in the flesh is common during reproduction season though. If the oysters are opened and still intact with the other half of the shell, take a knife or fork and slightly pulled the corner of flesh towards the exterior. When the flesh retracts, it is still alive and kicking. If there’s no reaction, then you should pick another one.



Cooked mussels tend to be either bright orange or cream orange with a black rim. If the colour is fading and dull, that’s a red light warning. One very commonly eaten shellfish here in Thailand is the blood clams. They’re are usually boiled and eaten with the Thai spicy sauce (nam chim). Blood clams should be bright red bloody when they’re fresh. Discard those that has dull red or brown colour. There is always some tiny mud residue at a corner of each blood clam when opened. Be sure to remove the mud before consuming.


Enjoy your meal!


Georgi has lived in Thailand on & off for almost 7 years now. French, born and grownup in Singapore, she has always believed that sustainability is the solution for the future. Having lived in several developed countries, she devotes herself to create more awareness on simple sustainable lifestyle for Thai locals and foreigners living or visiting Thailand.  

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September 5, 2018