Many forms of shrimp are found in the marketplace - shelled or unshelled, raw or cooked and fresh or frozen. Most shrimp are sold headless but in areas close to commercial shrimp docks you will also find them available with heads on - usually frozen. Shrimp are usually sold according to size or grade based on the number of headless shrimp per pound. This is indicated by the names - jumbo, large, medium and small. Raw shrimp should smell of the sea with no hint of ammonia.
Fresh shrimp are firm in texture and have a mild odor.
When purchasing frozen shrimp, make sure the shrimp are solidly frozen, have little or no odor, no brown spots and no signs of freezer bum, indicated by a very white, dry appearance around the edges. Shrimp provide high quality protein, vitamins and minerals and are low in calorie and fat content. These shellfish are very tender and cook quickly. Overcooking is usually the greatest problem in preparing shrimp. Rock shrimp cook even more quickly than the other species.