How does your rum go from a straw of grass to an expensive top shelf rum? It all begins with the tropical grass called saccharum officinarum or sugar cane. It had been used for thousands of years in Asia before the Europeans “discovered” it. It was brought to the Caribbean by Cristopher Columbus in 1493. The sugar cane grown today is a hybrid of several different species of cane to get a good mix of characteristics to make it suitable for the region where it grows.
In the tropics it's possible to get two harvests per year. The fields are first cleansed by fire and the cut either by machete or machine. After cutting it's brought to a sugar mill or distillery to get chopped up and crushed so all the juice can be extracted. Normally the juice gets boiled so the sugar crystallizes and can be separated from the remains. For cane juice rums the cane juice gets fermented and distilled without the sugar production.
Unlike some other spirits, rum has no defined production methods. Instead, rum production is based on traditional styles that vary between locations and distillers.
Sugarcane is harvested to make sugarcane juice and molasses. The fields are normally torched before harvesting to cleanse the fields from leaves, snakes and other animals. Due to the tropical climates in which sugar cane is grown it can be harvested two times a year. Sugar cane can either be manually harvested by cutting with a knife or mechanically cut which is most widely practiced today. After cutting the cane should be crushed as soon as possible.
Most rum produced is made from molasses. A notable exception is the French-speaking islands, where sugarcane juice is the preferred base ingredient.
Crushing and extraction
At the entrance of the grinding mills, cane is first minced by a series of knives. It is then crushed by a battery of mills. Each mill is set differently so that the clamping action is becoming stronger.
For a better extraction cane is sprayed with water after each grinding. Cane juice collected in channels is filtered and then pumped to the fermentation tanks or boiled for sugar production. Molasses is produced by the boiling of the juice, which separates crystallized sugar from this dark treacly by-product. The molasses is delivered from the sugar factory to the distillery where it is pumped into storage tanks.
Recycling powering the operations
At the outlet of the mill, bagasse (sugar cane fiber remaining after extraction of the juice) is fed to the furnace to be burnt. It serves as a fuel for the furnaces that heat the boiler water and turn it into steam. Steam might be used for driving the mills, distillation columns and sugar production. The power generated by the bagasse allows the distillery to be completely independent on one hand and to have a low carbon foot print from an ecological point of view..
Yeast and water are added to the base ingredient to start the fermentation process. This is done under controlled conditions where ph, temperature and degrees Brix (sugar content, sucrose as percentage by weight) is carefully monitored. The sugar content can't be too high or too low so molasses needs to be diluted. While some rum producers allow wild yeasts to perform the fermentation, most use specific strains of yeast to help provide a consistent taste and predictable fermentation time.
Dunder, the yeast-rich foam from previous fermentations, is the traditional yeast source in Jamaica. "The yeast employed will determine the final taste and aroma profile," says Jamaican master blender Joy Spence. Distillers who make lighter rums, such as Bacardi, prefer to use faster-working yeasts. Use of slower-working yeasts causes more esters to accumulate during fermentation, allowing for a fuller-tasting rum. Fermentation takes two to three days. The yeast converts uncrystallised sugar to ethyl alcohol, called a ‘wash’, and carbon dioxide (CO²) gas which can be sold as a separate product. In the end, it says that the tank is "dropping", which means that its surface is smooth. This gives a cane wine containing between 3.5% and 7% alcohol vol. A lot of the rums flavour originates from this stage of the process.
As with all other aspects of rum production, no standard method is used for distillation. While some producers work in batches using pot stills, most rum production is done using column still distillation.
Continuous Column Stills use a method in which fermented molasses (wash) is added to the top of the column, while steam is injected at the bottom. This process of adding the steam and the wash simultaneously allows the alcohol vapours to rise to the top of the column into the condensers where they are condensed to form liquid rum. Each Continuous Still has the versatility to produce both heavy or light bodied rums depending on the addition of varying degrees of congeners.
Pot still output contains more congeners than the output from column stills, so produces fuller-tasting rums. The production of these rums, unlike that of the continuous still rums, is done in batches. A quantity of fermented wash is put into the pot and boiled. The vapours released are trapped in the condensers to produce high gravity rum. After all of the wash has been distilled, the pot is emptied and the process is repeated.
Cooperage and Aging:
Many countries require rum to be aged for at least one year. This aging is commonly performed in used bourbon casks, but may also be performed in other types of wooden casks or stainless steel tanks. The aging process determines the color of the rum. When aged in oak casks, it becomes dark, whereas rum aged in stainless steel tanks remains virtually colorless. Due to the tropical climate common to most rum-producing areas, rum matures at a much higher rate than is typical for Scotch or Cognac. An indication of this higher rate is the angels' share, or amount of product lost to evaporation. While products aged in France or Scotland see about 2% loss each year, tropical rum producers may see as much as 10%. The size of the barrels makes a huge difference since small barrels means more wood contact for the rum. Oak barrels are usually torched on the inside, and the fire opens up the wood and the carbon helps to filter the rum. It also adds flavour and sweetness due to the charring of wood sugars. Ageing at ambient temperature under tropical climatic conditions contributes crucially to the mellow smoothness of the final spirit, with its complex flavours and rich aromas.Ageing at ambient temperature under tropical climatic conditions contributes crucially to the mellow smoothness of the final spirit, with its complex flavours and rich aromas.
After aging, rum is normally blended to ensure a consistent flavor. Blending is the final step in the rum-making process. The final step is carried out by the Master Blender. It is his careful selection and hand crafting which adds individuality and style to the final blend. All the complex elements of the blend are then allowed to marry together until the desired aroma and flavour are achieved. As part of this blending process, light rums may be filtered to remove any color gained during aging. For darker rums, caramel may be added to adjust the color of the final product.
When the rum is ready in the blending tanks, it is filtered once more and then bottled. The rum is then ready for distribution.
Source: Cane is able by Cap'n Jimbo