If you were to hire a location scout, armed with everything modern science has discovered about distilling and ageing spirits, it would still be hard to find a more ideal setting for a rum distillery than an island like Jamaica in the heart of the Carribean.
But while the island’s fertile soil and pristine, soft water make it the perfect place to ferment its local sugarcane, the region’s unique tropical microclimate is perfectly suited for ageing premium rum, thanks to the intense tropical heat and humidity that help the oak barrels work their magic on the spirit.
Tropical vs. continental ageing
When the sugarcane distillate comes off the still, it’s clear and colorless, with a hint of grass and delicate sweetness. That’s a great start, but as colonial-era pioneers in the rum industry discovered, ageing the liquid in an oak barrel transforms the spirit by coaxing out the rum’s natural rich flavours. During the seventeenth century, a Dutch ship captain noticed the effect of the barrels during transit, writing in his log that “the spirits are now smoother to the tongue and have acquired a golden colour during the voyage.”
Interestingly, this rum-changing discovery was likely accidental. Rum was often stored and shipped in wooden casks, and if it spent enough time in transit, merchants discovered that the spirit had picked up a deep, dark color and subtle hints of vanilla and caramel—flavours imparted by the wood.
They also discovered that the duration of ageing was a key ingredient in premium rum. That said, because climate plays an important role in the ageing process, a spirit aged in the tropics will have a much fuller and richer mouthfeel and flavour than one aged elsewhere—even if it’s been aged for the same number of years.
That’s why spirits that are barreled and aged in the Caribbean’s unique tropical climate are said to age three times faster than those in temperate “continental” climates. Continental ageing also tends to produce spirits that are lighter in colour and flavour profile than tropical-aged rums, which tend to be richer and darker.
The influence of the barrel
Why does climate make such a difference? Heat causes both the rum and the wood to expand, which means that the liquid swells and seeps into the wood, giving the spirit and the oak more of an opportunity to interact with each other. Since oak is full of natural sugars, tannins and vanillin compounds, some of these flavours become part of the spirit.
At Appleton Estate, after years of experimenting with ageing, the master blenders chose Number One Select American Oak for ageing, in part because this wood is particularly rich in vanillin.