What Is Rum?

Pirates. Caribbean vacations. Jimmy Buffett fans. What do all of these things have in common? They are all filled to the brim with rum. But what exactly is rum? It might seem like the “Wild West” of spirits (especially compared to the much more restrictive scotch and bourbon), but there’s a fascinating history and some interesting differences in definition between the US and EU. So lets dive right in.


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With a spirit like rum, the interesting things are in the details and the sub-varieties. But before we get there, let’s first take a look at the basic template of a rum. It’s a spirit that is primarily known for its Caribbean heritage, a region split between United States and the European Union influence, and so it makes sense that those two regions are the ones that have legal definitions of the term (with minor differences between the two).

Raw Materials

Pretty much every liquor in the world was created as a way for farmers to turn their otherwise useless excess crops or waste products into something that they could sell for extra cash. (Or, at least, something that wouldn’t spoil or go bad until they could sell or use it.)

The Caribbean islands were, at one time, the biggest producers of sugar in the world. The sugar cane was harvested by hand — mainly by slave labor — and then refined before being shipped around the world. This refining process starts with pressing the sugar cane into liquid sugar juice, with the excess raw material (called “bagasse”) discarded. Next the liquid would be boiled off in a large pan before sugar seed crystals are introduced to encourage the sugar to crystalize.

Sugar is typically refined into three levels of decreasing quality: “A” sugar and molasses, “B” sugar and molasses, and the lowest grade of “backstrap” molasses which contains the most impurities. While the A and B quality sugar is perfectly saleable, the backstrap molasses doesn’t really have much of a market.

It was this backstrap molasses that, according to history books, the slave population realized could be fermented into an alcoholic liquid and then distilled into something described in 1651 as “a hot, hellish, and terrible liquor”. The fact that the sugar was already available meant that, unlike grain based spirits, there was no complex cooking or malting processes needed to start fermentation — rather, just adding it to some water and waiting for the yeast to do its business.

Modern rum still often uses backstrap molasses, but given the fact that rum has improved greatly over the few centuries it has been around and now commands a much higher price, it is often economical enough for distillers to use higher grade sugar, molasses, or even straight sugar cane syrup for their raw materials.

Fermentation

Once the sugary liquid has been created, modern distillers will commonly use specific strains of cultured yeast to create a mildly alcoholic liquid that they can then distill.

Some distillers will enhance their mash by adding “dunder” — the leftover remnants of previous distillation runs that increases the acidity of the sugary liquid. Yeast can thrive in an acidic environment, but bacteria (which can compete for the sugar and create unwanted flavors) are less likely to survive. This is a process similar to the use of “backset” in an American sour mash bourbon.

Rum often has a funky component to the flavor profile, which commonly comes from esters that are created during the fermentation process. There are two ways that this happens.

The most straightforward way is to simply let the fermented liquid sit for a while. After the yeast has had its fill, local bacteria start to work their way into the liquid in search of whatever nutrients they can find. These bacteria create interesting and funky flavors that carry on through the distillation run and end up in the final product.

Another way to encourage this is through the addition of “muck” to the mash. This stuff ain’t for the faint of heart — typically muck is created by throwing waste products (bagasse from the sugar cane, rotting food, anything really) into a large pit and letting it rot. Adding that to the fermenting mash adds some flavors that you wouldn’t hesitate to call “interesting” and are often highly prized in a finished rum.

Distillation

Once the fermented liquid is ready, it’s time to distill.

Really, any type of still works here. Some locations prefer column or continuous stills, others use pot stills. It’s all up to the distiller’s choice in most cases, except the handful of situations we’ll discuss in a minute here.

If there’s one type of still that is most synonymous with rum, it’s probably the Double Retort Pot Still. This design starts with a traditional single pot still where the contents are added and heated to a large copper pot. From there, the hot vapor coming off the still is funneled through a piece of tubing into a secondary chamber filled with liquid. The hot vapors interact with the liquid in this secondary chamber, some of it condensing, others re-vaporizing into a more highly refined (~35% ABV) spirit that passes to a third chamber where it happens all over again. The end result (~75% ABV) is finally piped through a condenser and captured as newly made rum.

In any case, for the US and the EU, the only hard limit is that the spirit coming from the still cannot exceed 95% ABV or 96% ABV, respectively. Anything beyond that point would be considered a “neutral spirit” like vodka or the base for a gin.


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Maturation and Post Production

Typically, there isn’t much maturation that takes place with rum. The hot temperatures in the Caribbean encourage faster maturation than you’d expect with a scotch, meaning that less time is required for the same level of impact. There’s also an increased loss from evaporation, which makes it difficult for distillers to turn a profit from heavily aged rums. As a result, many rums are put out as a white rum but some are an aged expression.

Common to most rums, there’s often some filtration of the spirit to remove particles and some addition of caramel coloring to get just the right shade in the bottle.

For European rums, the spirit needs to go into the bottle at a minimum of 37.5% ABV. After maturation, some blending can take place as well as a bit of dilution, and even up to 20 grams per litre of sugar can be added for smoothness. But that’s it — no flavoring. This is why you’ll never see a spiced rum in the EU.

That’s where ‘murica comes in. Requiring at least 40% ABV in the bottle, American rum can include flavoring and spices, but no sugar.

There are dozens of interesting varieties of rum, but we’re well over 1,000 words at this point and I think it’s time I grab a glass of rum myself. If you’re interested in diving into that in a separate article, let me know in the comments!

In the meantime, I’d urge you to take a break, check your local shelves, and start trying a few glasses yourself as well! You can check out all our rum reviews we’ve done so far at this link right here.


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