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TYPES OF CHOCOLATE
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There are various diferent types of chocolate.
Unsweetened chocolate-that's the chocolate liqour's cooled form of a bar. It's uses are for cooking and baking.

Cocoa butter-it's the extracted fat from the chocolate liqour.
Cocoa powder or Cocoa solid-it's basically whatever is left after cocoa butter is removed.Then it goes under a "dutch process" that neutralizes it's natural accidity. 
Bittersweet chocolate- contains at least 50% chocolate liqour.
Semi-Sweet chocolate- contains at least 35% of cocoa solids.
Milk chocolate- it contains cocoa butter, 10% chocolate liquor, 3.39% butterfat and 12% milk solids.
White chocolate- doesn't contain any chocolate liquor, but does contain 20% cocoa butter, 14% milk solids and 55% sugar. 
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