White Rum Primer
Distillation ABV (Alcohol By Volume)
This is the concentration (% ABV) at which the alcohol was distilled, which is usually much higher than the concentration at which it is bottled. Many different alcohols are formed during fermentation (see “Congener Composition” below), distillation concentrates and separates these alcohols. The higher the distillation ABV, the more neutral/rectified the alcohol will be (it will have less water and fewer congeners).
Congener Composition
The primary alcohol in all distilled beverages is ethanol, but many others are formed during fermentation. These alcohols, along with their aldehydes, acids and esters, are collectively called “congeners.” Different yeast varieties and environmental/nutritional conditions lead to their formation. Some congeners have pleasant aromas and tastes while others do not.
Source of Fermentable Sugars
In the case of rum, all fermentable sugars must come from a sugarcane co-product. These include: juice, concentrated juice (“miel virgen” or High Test Molasses), granulated sugar (from brown to white), non-granulated sugars (jaggery, panela, piloncillo, etc.) and all grades of molasses (from Grade A to Blackstrap). Each of these sugar sources has a unique combination of aromatic and flavor compounds (primarily Maillard) that survive fermentation. Distillation to lower ABVs preserves more of them, while distillation to higher ABVs tends to remove them.
Congener Quantity
The congener composition can tell us, for example, if a rum is “heady” or “taily” or if it can be considered “high esters.” The congener quantity (usually expressed in milligrams per liter, grams per hectoliter or in ppm) is the best (most scientific) way to understand the fermentation and distillation processes behind a rum.
What about the distillation apparatus (pot versus column)?Although most Pot stills are normally used to distill at low ABV (high-congener alcohols), they can also be used to produce neutral alcohol (most “craft” vodkas are made using pot stills). By the same token, while most multi-column stills are normally used to distill at high ABV (low-congener alcohols), they can also be used to produce heavy alcohols. Classifying rums based on the distillation equipment alone, while ignoring the Congener Composition and Congener Quantity can be very misleading.