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First things first: If you've been buying pre-cooked shrimp or even peeled and deveined shrimp, stop right this instant! I mean it!
Pre-cooked shrimp are unfailingly pre-overcooked-shrimp, and are impossible to add flavor to the way you can with raw shrimp. Shrimp that are raw but peeled and deveined are a small step up, but often get mangled and beat up in the cleaning. You are much better off buying whole, headless shrimp (or at the very least E-Z peel) and cleaning them yourself. It's a little more work, but worth the effort. This video will show you everything you need to know.
Shopping and Storage
There are a number of choices to make when it comes to buying shrimp:
- Frozen vs. Fresh: The vast majority of shrimp are processed and frozen right at the farm or on the boat before they ever get anywhere near your fishmonger or supermarket. This means that the "fresh" shrimp you're seeing at the fish counter are simply their frozen shrimp that have been defrosted and put on display. There's no way to know how long they've been there, so you're better off buying frozen shrimp and defrosting them at home. In a bowl under cold running water, shrimp should take about 10 minutes to defrost. Small price to pay for freshness.*
- IQF vs. Block Frozen: IQF stands for Individually Quick Frozen, and means that each shrimp was frozen on its own before being bagged. Block shrimp come frozen together in a large block of ice. As a general rule, the faster you freeze something, the smaller the loss in textural quality, so go with the IQF. They also have the advantage that they are much quicker to defrost.
- Size: Forget labels like "medium," "large," or "jumbo." These are unregulated terms that are decided on by the packager or the supermarket. Instead, look for a set of two numbers, such as 26-30 or 16-20. This number indicates the number of individual shrimp that it takes up to make a pound. So a package labeled 16-20 will contain shrimp that weigh in at a little less than an ounce a piece. The smaller the number, the larger the shrimp. For super large shrimp, you may see a number like U-15, which means that it takes under 15 pieces to make up a pound. As far as flavor goes, there's not much difference between the sizes—look to individual recipes to specify the right size of shrimp.
- Additional Ingredients: Shrimp, like scallops, are often treated with STP (sodium tripolyphosphate), a chemical designed to help them retain moisture. More than anything, this is a ploy to bulk up their weight and sell them at a higher profit. Check the ingredients list on your packages of frozen shrimp. They should list shrimp, possibly salt, and nothing else.
*N.B. Some really good fish markets will have never-been-frozen wild shrimp. If they carry these, they will advertise them as such. As long as you can trust them that they are fresh, snatch'em up and eat them immediately! They're a real treat.
About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.