Most rum in the world is made from molasses, a by-product of making sugar. Although this process varies greatly between producers and involves many steps, I will try to condense the procedure for the sake of brevity.
After making the cane syrup, the next stage is crystallization. The syrup is further evaporated in a vacuum pan to lower the boiling point and avoid caramelisation of the precious sugar. When it reaches a supersaturated stage, seed crystals are fed into the vacuum pan. As a result more sugar crystals begin to form, which in turn are separated from the liquid through centrifugation. This process is generally repeated twice. The crystallized sugar from the first two rounds are sent for further processing into table sugar. The sugar created during the third boil is sometimes sold as muscovado sugar or used as seed crystals for future batches. The thick, dark & viscous liquid left is called Grade C or Blackstrap molasses and this is the black gold that get rum-makers all over the world excited.
If sugar cane is harvested before peak maturity, some producers add sulphur dioxide to keep the cane fresh until processing, and these sulphur compounds are then concentrated in the molasses, which can cause problems for rum-production down the line and lead to undesirable aromas, flavours and textures in the final product. But we’ll cross that bridge when we get there.
Next up is one of the most exciting and interesting stages or rum-making…fermentation!