Being diminutive by nature, size certainly is a principle consideration when choosing shrimp or the larger prawns at the market. Size is not the only culinary consideration, though. Freshness is equally important, since taste and texture are detrimentally affected the longer shrimp sits out of water — frozen or not. Other key points are the species, the weather, the food source and the time they will take to cook.
Of the 300 species of shrimp and prawns found throughout the world's salt and fresh waters, each are likely to have a slightly different size, coloring, texture, flavor and cooking time. Cold water shrimp typically take longer to grow and are reputed to have the most tender meat because of it. Some of the largest cold water varieties have especially favorable culinary reputations, from Dublin Bay and king prawns to northern and giant tiger shrimp. Other prized species are often identified commercially by their final coloring: pink, white, brown or even blue.
Frozen shellfish is the norm for households and even chefs who are not certain when they will cook the meat. If bought fresh, health officials advise they should be prepared within a full day. If fresh shrimp has an ammonia-like odor or dark spots starting to form, they should be discarded. Many chefs will buy the shellfish they believe they will need for that day's dishes and then quickly freeze what is left over for later use. In any case, those frozen should have the shells and veins intact, or they will lose valuable flavor and texture.
An important part of the way shrimp or prawns look and taste concerns whether they were raised on a farm or caught in the wild. Both have their benefits. Farm-raised varieties may be more uniform in size and flavor, though lacking in an essential seafood flavor and saltiness that is undeniable in the wild-caught varieties, which feed on a more diverse diet. Depending on the recipe, either kind may be more suitable. Diners who do not like a fishy taste may prefer a white shrimp or even the giant freshwater variety of prawn called Machrobrachium Rosenbergii, which is also known as the giant river prawn.
Large or small, shellfish take just a little time to prepare in a variety of ways. Some use traditional methods to boil, steam, sautee or grill them. Others apply a light batter and toss them in a deep-fryer. Often, chefs will unshell and devein them prior to the preparation. Other times, the shell is left on for the diner to remove.