How to identify fresh fish from stale ones in lockdown days

When one small glass of formalin is dissolved in a bucket of water, the solution is sufficient to preserve 250 kg of fish for four days.

Food safety authorities in Kerala have been busy seizing and destroying stale fish ever since the lockdown was announced. Most of these fish are laced with poisonous preservatives such as formalin and ammonia. However, you can follow these tips to identify fresh fish and protect the health of everyone at home.

Ammonia is added to the ice in which fish is stored in order to delay the melting process. Formalin, the liquid form of formaldehyde, is normally used in mortuaries to preserve bodies. It has a high poisonous content and can cause cancer and ulcers. Formalin is also harmful to the digestive process and leads to diseases of the liver, kidneys, lungs, heart and central nervous system. Another disease attributed to formalin is peritonitis.

Signs of fish laced with formalin

Fish in which formalin is present can be identified by discolouration of the eyes; absence of natural odour of fish and change in colour of scales. Moreover, when formalin is applied to stale fish, it becomes stiff.

When one small glass of formalin is dissolved in a bucket of water, the solution is sufficient to preserve 250 kg of fish for four days. Many unscrupulous merchants choose this method as storing fish in ice is not only expensive but also consumes more space.

However, once formalin is applied to the fish, it cannot be removed entirely. In fact, it remains in the fish even after thorough washing and cooking.


For your safety, always buy fish from places from where you can be certain that it is fresh. Before cooking, remove all the scales. For fish varieties for which skinning is required, do it properly. In addition, wash fish at least thrice. Applying Bengal gram flour to the fish before washing is another way to remove toxic substances. Before making a purchase, check for the smell of ammonia or formalin and avoid such fish.

Tips to identify fresh fish

» Good fish can be located by sight, smell and touch. Fresh fish would come with bright, clear and round eyes. Stale fish have dull, shallow eyes with light blue colour.

» Check the gills. Those of fresh fish would have the blood red colour.

» If blood of normal colour flows out from the area of the spine while removing the internal organs, the fish would be fresh.

» In case a bad odour is felt, you can assume that the fish is stale.

» Fish that begins to turn stale would have a heavy smell similar to that of ammonia.

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