Some confusion exists regarding capers and caperberries. The two are not interchangeable though they both derive from the same plant, Capparis Spinosa, which grows throughout the Mediterranean, and is now being grown in places like California. To clarify, the round, lemony, small capers are not the berries. These tiny pealike bursts of flavor are actually immature buds of the caper bush.
In addition to the tiny buds, caperberries are also harvested, and some may prefer their taste to the stronger caper buds. The berries on the caper plant are oblong, semi-green fruits, about the size of or slightly larger than a table grape. Though they still have some lemon taste, they are much milder than caper buds. You can include sliced caperberries in recipes calling for capers if you want a dish that is a bit less acidic. The substitution doesn’t work well in reverse—generally when a recipe calls for caperberries, using capers instead will provide too much acid in a dish.
There is some argument regarding the taste of caperberries. Some sources refer to them as stronger than capers themselves, while others describe them as milder. Taste may depend upon when the berries are harvested and additionally how they are prepared. The unripe caperberry may be off-putting to some because of its smell. It often exudes a pungent smell due to the high concentration of mustard oil, called methyl isothiocynate. It may be that references calling the caperberry more pungent than the caper are referring to berries harvested before they are fully ripe.
Caperberries are frequently prepared brined and may be eaten very much in the same manner you might eat olives or pickles. They could also be an interesting substitution for olives in dishes like pasta or Greek salad. According to Aryuvedic medical texts, the berries may also be good for you. They can supposedly stimulate the liver, relieve flatulence, and reduce rheumatism.
One use of caperberries and the caper plants that has not been successful is their use in cosmetic preparations. Some people develop contact dermatitis when exposed to crushed caperberries or lotions using the caper bush leaves. If you do buy a skin product with the berries as an ingredient, you might want to test it out on a small amount of skin prior to applying it everywhere. A couple of uses on a small patch of skin should tell you whether or not you’re likely to be allergic to it.