How is it made?
Harvest
Sugarcane is harvested and taken to the sugar mill where it is chopped, crushed & pressed to extract the juice. Most rums are a by-product of sugar production. What remains after the sugar crystals have been removed is a black, brown liquid of a honey-like consistency called molasses.
Fermentation
The molasses is combined with yeast. The reaction of the active yeast eating the sugars creates alcohol. The length of the fermentation time ranges from 48 hrs to a week and influences the final flavour of the rum. Longer ferments can lead to a more pungent aroma and flavour profile.
Distillation
The fermented solution is then added to a column still or a pot still. Distillation concentrates this solution up to 96% abv. The distillation process uses heat to evaporate the alcohol. The vapour rises and condenses as it cools. The liquid collected is often called high wine.
Aging
Most rums, even so-called white rums, are aged in oak barrels before they are bottled. The barrel ageing of a rum has an intense impact on the flavour and colour of the final product. The longer the time spent in the barrel the richer and more characterful the liquid becomes.
Dilution
Water is added to the high alcohol by volume(ABV) spirit to lower it to the legal minimum of 37.5%. This means that rum may be over 60% water. For this reason, distilleries spend a lot of time and effort sourcing and maintaining the best water possible.
Styles of Rum
There are a vast amount of rum producing countries, each with their own cultures and traditions. These differences are celebrated in the different flavours and styles created. For example, Agricole is a French influenced rum that is produced using the sugarcane juice rather than molasses. This gives a more grassy, vegetal taste profile. Overproof rum is not usually aged in the same way as other styles but is bottled straight of the still with less dilution, usually over 63% ABV.
Modern Day
While rum sales remain dominated by major producers, consumer preferences are moving away from value options and towards an appreciation for premium aged instead.
References:
Rum: The Complete Guide - Isabel Boons, Tom Neijens (2018)
Rum - David Broom (2003)