Blackstrap molasses, or simply blackstrap, is the dark, viscous molasses remaining after maximum extraction of sugar from raw sugar cane. This residual product of sugar refining is used in the manufacture of ethanol for industry and as an ingredient in cattle feed. The term is an Americanism dating from the 1870s. First known use is in a book by detective Allan Pinkerton in 1877.
The third boiling of sugar syrup yields blackstrap molasses. The majority of sucrose from the original crystallizes through this process, though the calorific content of blackstrap molasses is still mostly due to the small remaining sugar content. However, unlike refined sugars, it contains significant amounts of vitamin B6 and minerals, including calcium, magnesium, iron, and manganese; one tablespoon provides up to 20% of the recommended daily value of each of those nutrients. Blackstrap is also a good source of potassium. It is sometimes used in baking or as fertilizer.