Q. What are the differences among unsweetened, bittersweet, and semisweet baking chocolate? Can they be used interchangeably?
A. Chocolate is made from roasted cacao beans. The beans are crushed and ground, a process that generates heat and liquefies the fat or cocoa butter. The resulting liquid is called "chocolate liquor." (There is no alcohol involved; in this case, "liquor" merely means "liquid.") The liquor is poured into molds and allowed to solidify; the resulting bars are what is called unsweetened chocolate.
To make eating or baking chocolate, sugar, vanilla, and lecithin are added to the liquor, along with more cocoa butter. By U.S. government standards, bittersweet chocolate must contain at least 35 percent chocolate liquor; semisweet can contain between 15 and 35 percent, according to the Chocolate Manufacturers Association.
Bittersweet chocolate contains sugar, but generally not as much as semisweet chocolate, although, by government standards, they could contain practically identical amounts of chocolate liquor and sugar and still retain their bittersweet and semisweet labels. What this means is that one brand's bittersweet chocolate could be close in sweetness to another brand's semisweet chocolate, and vice versa.
Because of this, bittersweet and semisweet chocolate could be used interchangeably in most recipes; unsweetened, obviously, could not because it contains no sugar. But if your recipe calls for bittersweet chocolate and you have semisweet on hand, taste it first to determine if you could substitute.
For more information about chocolate, see: