Capers are actually pickles made from the unopened flower buds of the Capparis spinosa shrub, which grows in the Mediterranean. In France, Italy and Spain, the shrubs are cultivated for capers, and Roquevaire, in Provence, is known as the "caper capital."
Capers are never used fresh, and are preserved one of two ways: in a salt and water brine, sometimes with added vinegar, or in salt. More often, the flower buds are soaked in saltwater, then packed in brine or a mixture of brine and vinegar. This is how capers are sold in most supermarkets. The other option is to cure them with salt. This kind of caper costs more and is available only in specialty markets.The brine method is most common, and available in most supermarkets—the salt preserved capers are more costly, and available only in specialty stores.
Capers also vary in size, from the tiny non-pareilles to surfines, capucines, fines, and capotes—increasing in size and decreasing in value. Caperberries, quite large and usually complete with a stem, are formed when the buds are allowed to open and set fruit. While capers of any size may be used in myriad dishes, caperberries are usually only used as a drink garnish.
To make sense of these variables, we purchased six brands of capers and held a small tasting. We tasted small and large capers packed in brine and vinegar as well as one brand of salted capers. For cooking, tasters agreed that small capers are best because they can be used as is; larger capers are too potent to eat whole and should be chopped. Besides adding an extra step, chopped capers disintegrate when added to sauces.
The taste differences from brand to brand were subtle, although most tasters felt that the brand packed in wine vinegar was the least harsh and therefore the most flavorful. (Labels on the other bottles just said "vinegar.") Capers packed in salt were unbearably salty straight from the bottle. Rinsing didn't do much to lessen their sting. Soaking in cool water for at least 20 minutes (preferably an hour) washed out enough of the salt to reveal the flavor of the capers. Without the salt (and because there's no vinegar), we picked up hints of herbs (especially oregano) and mustard that we never tasted in the brined capers. These salted capers were delicious, but once we used them in piccata, their subtle traits faded behind the flavors of the other ingredients.
Many sources suggest rinsing brined capers, too. We think you can skip this step. Drain the capers well and taste one. If they seem very salty or vinegary, you can rinse them. In most cases, this step won't be necessary.
Many recipes that use capers recommend adding capers directly to hot oil for "fried" capers. But, as we recently discovered in the test kitchen, this method can be dangerous; the moisture-packed capers explode when they open and splatter hot oil everywhere (think of popping popcorn with the pan lid off and you’ll get the picture).
After several tests, we found a couple of ways to minimize the potential for disaster. First was to remove moisture from the capers by pressing them between several layers of paper towels. Second was to start the capers in cold oil, then heat them gradually.
Here’s how to fry enough capers to garnish 1 pound of pasta: Drain, rinse, and press 2 tablespoons of capers between several layers of paper towels to remove as much liquid as possible. Add the pressed capers and 2 tablespoons of olive oil to an 8-inch skillet and turn the heat to medium-low. Cook until most of the capers have split open (a few will still pop) and are crisp, 3 to 5 minutes. Transfer the capers to dry paper towels to drain, and enjoy!