Chocolate is a typically sweet, usually brown, food preparation of Theobroma cacao seeds, roasted and ground, often flavored, as with vanilla. It is made in the form of a liquid, paste or in a block or used as a flavoring ingredient in other sweet foods. Cacao has been cultivated by many cultures for at least three millennia in Mesoamerica. The earliest evidence of use traces to the Mokaya (Mexico and Guatemala), with evidence of chocolate beverages dating back to 1900 BC. In fact, the majority of Mesoamerican people made chocolate beverages, including the Maya and Aztecs, who made it into a beverage known as xocol?tl, a Nahuatl word meaning "bitter water". The seeds of the cacao tree have an intense bitter taste and must be fermented to develop the flavor.
After fermentation, the beans are dried, cleaned, and roasted. The shell is removed to produce cacao nibs, which are then ground to cocoa mass, pure chocolate in rough form. Because the cocoa mass is usually liquefied before being molded with or without other ingredients, it is called chocolate liquor. The liquor also may be processed into two components: cocoa solids and cocoa butter. Unsweetened baking chocolate (bitter chocolate) contains primarily cocoa solids and cocoa butter in varying proportions. Much of the chocolate consumed today is in the form of sweet chocolate, a combination of cocoa solids, cocoa butter or other fat, and sugar. Milk chocolate is sweet chocolate that additionally contains milk powder or condensed milk. White chocolate contains cocoa butter, sugar, and milk but no cocoa solids.
Cocoa solids are one of the richest sources of flavanol antioxidants. They also contain alkaloids such as theobromine, phenethylamine and caffeine. These have physiological effects on the body and are linked to serotonin levels in the brain. Some research has found that chocolate, eaten in moderation, can lower blood pressure. The presence of theobromine renders chocolate toxic to some animals, especially dogs and cats. [Source: Wikipedia]
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010