Most varieties of rum are produced in the Caribbean due to their perfect climate for the growth of sugar cane, although there are some great rums produced elsewhere, such as in India, the Philippines and in Central America. Cuban rums are unique due to the wide variety of sugar canes produced on the island.
Rum can be made from sugar-cane molasses or from the juice of crushed sugar cane. Molasses is the dark sticky syrup that’s left over after the sugar crystals have been boiled off and separated. Molasses contains large quantities of vitamins and minerals as well as sugar, which all will have an effect on the final product. Rums made with sugar-cane juice have a naturally smoother taste. The juice, or mixture of molasses and water, is fermented with yeast for anything from a few hours up to two weeks. The lighter the style of the rum, the shorter the fermentation process will have been. Most rums are distilled from fermented molasses.
The fermented liquid is then heated to the required temperature in sealed vessels where the alcohol evaporates from the liquid. The alcohols are then collected and recondensed. Distillation separates the alcohol from the water as they both boil and evaporate at different temperatures. The rum can be distilled in either column or pot stills, and the spirit needs to exit the still below 96% ABV, otherwise it is considered as ethanol instead of rum.
Normally, the spirit is distilled twice if a pot still is used to define the characteristics of the rum. Rums from pot stills are aromatic, heavy and oily and often require maturation before bottling. A column still is often used for the production of lighter rums, although it could be used to produce the full range of rums; it is up to the distiller to collect the spirits at the right temperatures. All spirit from the still is colourless.
White, silver and light rums can be bottled without maturation, although some countries require all their rums to be aged in barrels for a minimum period. It is not uncommon to let the spirit breathe through the wood as this softens the hard characteristics of the raw spirit. For example, some white rums may be rested in wooden barrels for a few months for oxidation, and the rum is filtered afterwards to remove any colour absorbed from the wood.
Golden and dark rums, on the other hand, get their colour and character from the wood as well as from burnt sugar. Some use burnt sugar to cover up the lack of maturation and some to improve the taste. In hot tropical countries, maturation is up to three times faster than in Europe, for example, although they lose around 6% through evaporation, while in colder climates it’s closer to 2%. White and light rums are more suitable for cocktails such as mojitos and daiquiris, while golden and dark rums are better enjoyed neat, although it has become common to serve these with mixers, such as Coke or Castro’s favourite, lime and ginger ale.
There are many ways to make blended rum and most rums are actually blended. The blend may be from both pot and column stills, different levels of ageing or different wood types, or the rums can be produced with different alcohol levels. It is the master distiller who knows all the secrets of the final blend. The blending is done in large quantities in big tanks before the rum is returned in barrels for further maturation.
After blending and maturation, the spirit is reduced with water to meet the required strength. Most common are 37.5%, 40% or 43% ABV, although overproof ‘navy’ strength rum can be as high as 57% ABV. Navy rum doesn’t technically exist; the term is used to indicate heavy, strong rums and it’s linked to the British Royal Navy. It is said the rum served on the boats had to be strong enough to burn in case it leaked over the gunpowder.