Frozen fish and shellfish should be thoroughly defrosted before cooking. If it's still frozen or partially frozen, it will take longer to cook and the outside could be cooked but the centre might not be - which means it could contain harmful bacteria.
There are two main options for defrosting:
1) In the fridge: ideally, plan ahead to leave enough time and space to defrost small amounts of food in your fridge overnight or for as long as it takes to defrost fully. Putting food in the fridge will keep it at a safe temperature while it is defrosting.
2) Cold water thawing: if you're more pushed for time or fancy a spontaneous meal, the cold water thawing method speeds things up.
For smaller items like frozen prawns, place them in a bowl in the sink and fill with cold water. Cold water helps speed up defrosting without allowing the outside of the food to get too warm. Replace the water every 10 minutes until the prawns have thawed. Alternatively, you can place the prawns in a colander in the sink and run cold water over them until they're thawed.
For larger items like fish fillet portions, the method is quite similar but will take a bit longer. Remove any paper packaging from the fish and place it in a resealable zip-top plastic bag. Push all of the air out of the bag before sealing. Place the fish in a large bowl in your sink and fill it with cold water. If the bag floats weigh it down to fully submerge it. Replace the water every 10 minutes until the fish has thawed. Alternatively, keep cold water running into the bowl at a very slow rate - this has the effect of replacing the water continuously. Depending on the size of your fish, this method should take anywhere between 20 minutes to 1 hour.
It's important to cook defrosted fish or shellfish immediately, and never re-freeze. Our pack labels indicate whether items have been previously frozen.