Molasses is a byproduct of the sugar cane or sugar beet refining process. Recipes that call for molasses are mostly referring to light molasses, which comes from the first boiling of sugar cane or sugar beet juice.
Dark or full molasses comes from the second juice boiling. It is thicker and less sweet than light molasses. Cooks use this molasses instead of light molasses for its deeper flavor and color. Derived from the final boiling of juice, backstrap molasses has almost no sucrose and is slightly bitter; however, it has more minerals than light or dark molasses. Five tablespoons has 400 milligrams of calcium, 13 milligrams of iron and 300 milligrams of magnesium. Because of its intense, non-sweet flavor, cooks tend to use backstrap molasses in savory recipes such as barbecue sauces and baked beans.