What Is Molasses?

Molasses is the thick, dark syrup left over after sugar cane juice is boiled down and its crystallised sugar removed — the traditional base for most of the world's rum.

Molasses is a by-product of sugar production. When raw sugar cane juice is boiled and reduced, sugar crystals form and are extracted, leaving behind a thick, dark, viscous syrup — that syrup is molasses.

Why it became rum's default base

Molasses was historically cheap (it was a "waste" product of the sugar industry), shelf-stable compared to fresh cane juice, and easy to transport — all of which made it the natural choice for large-scale rum production, especially through the historic Caribbean sugar and rum trade.

Flavour contribution

Molasses brings a rich, slightly bitter-sweet, caramelised character to fermentation, distinct from the grassier, more vegetal profile you get from distilling fresh cane juice directly (the approach used for rhum agricole — see "How is rum made?"). This is a big part of why molasses-based rum and cane-juice rum can taste so different from each other, even though both are technically "rum."

Beyond rum

Molasses isn't exclusive to rum — it's also used in baking, as livestock feed, and in some whisky and other spirit production as a fermentable sugar source, though it's most closely associated with rum globally.