Buying

Prawns perish easily, so they are often frozen on board the ships from which they are fished. They can be bought shell on or shelled, head on or off, cooked or uncooked. Avoid frozen prawns covered in frost or with freezer burn. If buying them raw (when they are sometimes called ‘green’), they should have a pleasant smell and firm shells. Avoid any that smell of ammonia or with dark discolouration around the head or legs — this means they are starting to deteriorate. As a guide, 500 g (1 lb 2 oz) of prawns with their shells on will give you about 250 g (9 oz) shelled weight.