Rum distinguishes itself from other spirits by the plant from which it is made.

Sugar cane, a member of the grass family has its origins in Papau New Guinea but this hearty plant is grown in tropical climes around the world. The sweet juice of the mature plant is extracted by pressing the hard stalk in mechanical mills.

Some distilleries use this fresh juice while others use the by product of the sugar refining process known as molasses as the raw material for the fermentation process.

Fermentation

The addition of yeast to the sugar cane juice or molasses converts the available sucrose to alcohol in a process called fermentation. Typically this takes about a day but some distilleries use yeast that takes as much as ten days. To make other spirits, the starches found in grains must be cooked and then enzymes are used to convert the glucose to sucrose which can be fermented. The resulting fermented wine contains only about 10% alcohol by volume.

Distillation

To concentrate the alcohol in the sugar cane wine, the wine is boiled while the vapor is collected and condensed. The earliest pot stills resembled a tea kettle with a long spout and were capable of distilling only a few liters of alcohol at a time. Modern continuous stills are vertical columns about 10 meters high and are capable of distilling as much as 20,000 liters per day.

In the French islands, spirits made from sugar cane juice are typically distilled to a relatively low distillation purity resulting in a heavier tasting spirit.

Since molasses contains higher amounts of sulphur than does sugar cane juice, spirits distilled from fermented molasses are generally distilled to a high distillation purity to reduce the congeners that have been concentrated in the molasses.

Aging

Immediately after distillation, the fresh or raw spirits contain small amounts of hydrogen sulfide gas formed during fermentation which gives the spirit a hot harsh taste. Although some connoisseurs prefer fresh rum, most consumers prefer the more elegant taste of an aged spirit. Today, almost all rum is aged in used oak barrels that once held whiskey or bourbon. Aging can last from one to thirty years or more, making rum one of the most varied of the distilled spirits. During the aging process the rum acquires a golden color that changes to a dark brown with time.

Blending and Bottling

Although some rum is bottled directly from the still, most rum is aged and then blended before it is bottled for consumption. Once the spirit is bottled the benefits of age are arrested and little change occurs.

Alcohol Content

The bottled strength of rum depends greatly on consumer preferences. While some rum is bottled at about 40% alcohol by volume, other rums are bottled at the strength at which it was distilled or aged.