Molasses
A byproduct of the process that refines sugar found in Sugarcane into crystaline sugar. Molasses is often sold as sulfured or unsulfured. The sulfured kind of molasses may have a preservative in it which is harmful to yeast. Molasses is the sugar and nutrient source used when producing rum.
Molasses, or black treacle (British, for human consumption; known as molasses otherwise), is a viscous product resulting from refining sugarcane or sugar beets into sugar. Molasses varies by amount of sugar, method of extraction, and age of plant. Sugarcane molasses is agreeable in taste and aroma, and is primarily used for sweetening and flavoring foods in the United States, Canada, and elsewhere, while sugar beet molasses is foul-smelling and unpalatable, so it is mainly (mostly) used as an animal feed additive in Europe and Russia, where it is chiefly produced. Molasses is a defining component of fine commercial brown sugar.