Bittersweet chocolate is a sweetened form of dark chocolate that does not contain milk in either liquid or dry form. It is essentially a mixture of chocolate liquor, sugar, cocoa butter, and sometimes vanilla. Often, lecithin is added as an emulsifying agent. Chocolate liquor, despite what its name seems to suggest, contains no alcohol. Rather, it is a form of cocoa produced by grinding cocoa beans down into liquid form. Solidified chocolate liquor formed into blocks is known as unsweetened baking chocolate.
In North America, bittersweet chocolate is required, according to Standards of Identity established by the Food and Drug Administration, to contain a minimum of 35 percent chocolate liquor. In Great Britain, the figure is somewhat higher, rising to 43 percent. The more chocolate liquor the chocolate contains, the more intense its flavor will be. Especially high-quality chocolate may contain 65 to 70 percent, or more, of chocolate liquor.
Although the terms bittersweet and semisweet are sometimes used interchangeably, there is a difference in the standards that define the two. Although not formally regulated across the industry, bittersweet chocolate generally contains more chocolate liquor and less sugar than semisweet chocolate does. However, since semisweet chocolate can contain up to 35 percent liquor, the two chocolates can be very much alike. Bittersweet and semisweet chocolate can be used interchangeably in baking, with good results.
Both the semisweet and bittersweet chocolates are occasionally labeled “couverture,” which designation indicates that the chocolate contains not less than 32 percent cocoa butter. Couverture must be tempered, a process that involves manipulating the temperature of the chocolate during the process of fat crystalization in its cocoa butter, before using. It is a favorite for dipping, coating, and molding. When melted, it is smooth and fluid, and when it hardens, it has a lovely sheen and a creamy texture.
Recent studies have revealed certain health benefits from the regular consumption of small quantities of bittersweet chocolate. Due to its high cocoa content, dark chocolate is a good source of certain flavonoids — namely epicatechin and gallic acid — that may be protective for the heart.
Bittersweet chocolate also possesses antioxidant compounds and may also play a role in lowering blood pressure. It should be noted, however, that the flavonoids present in this chocolate are destroyed by processing with alkali, as with Dutch-processed cocoa powder.
Chocolate, including the bittersweet variety, is extremely sensitive to factors of temperature and humidity. The ideal—but relatively narrow—temperature window for storing chocolate is between 59 and 63 degrees F (15 and 17 degrees C), with a relative humidity at a finicky 50 percent or less. Conditions of varying temperature may cause changes in the appearance or texture of the chocolate, including a whitish “bloom” on the surface due to the presence of fat and/or sugar crystals there. Although the appearance of the chocolate may suffer, it is perfectly safe to eat.
Bittersweet chocolate, like other varieties, contains theobromine, an alkaloid found in the cacao plant. Theobromine is alternately credited with aphrodisiac and antitussive properties and blamed for sleeplessness, anxiety, and polyuria. Theobromine, even in small amounts, is poisonous to dogs and cats and care should be taken to keep all chocolate away from animals’ reach.