The Deal with Dunder

A brief exploration of one of rum’s most intriguing historical aspects.


Organoleptically, there might not be a more diverse spirits category than rum. Jamaican rum, in particular, is distinct among the category primarily for its incredible funk and character.  The intense and varied aromatics associated with this style is why it is beloved by so many. Haut gout or hogo — which translates to high taste in English — is what the Jamaican rum world is all about, and it wouldn’t be the same without dunder.

The word ‘dunder’ is a loaded one among spirits enthusiasts. Although some think of it immediately preceding the word ‘Mifflin,’ and subsequently hear the jaunty sound of The Office intro playing in their heads, those who are at all familiar with Caribbean rum will probably imagine a deep pit where dead bats, severed goat heads, and other decaying matter churn endlessly in a bottomless chasm. The wash for Jamaican rum is said to consist of sugar cane skimmings, molasses, acid, flavor, and dunder, but in actual fact, dunder is not what the myth has made it out to be. In Jamaica, the term dunder is used to describe what’s left in pot stills after a run, otherwise known as stillage in the U.S. Some Jamaican distillers reserve their dunder to be added to their next distillation, same as one would add backset in the process of sour mashing.

The production of rum varies substantially the world over, but Jamaican rum is made from molasses, which is the material left over after sugar cane juice has been boiled to extract the sugar crystals. Thick, sticky, and temperamental, molasses is a huge source of flavor for Jamaican rum distillers. Fermentations for Jamaican rum can be quite long in an effort to further develop the high-ester profile they’re known for, and distillers there prefer to use pot stills, specifically double-retort pot stills.

Recognizing the excess time and money used to distill on a traditional pot system, Caribbean distillers in the 17th or 18th century had the inspired idea to hook a couple of pot stills together so that multiple distillations could be performed simultaneously. These still retorts — also referred to as ‘doublers’ or ‘thumpers’ when connected to stills in America — worked by connecting the lyne arm of the first still into an additional pot still in lieu of the condenser. Often low wines and high wines are fed into the retorts, mirroring the process of recycling the heads and tails back into the beer/wash still for a second distillation in a simple pot still system. However, stillage or dunder can also be loaded into the retorts for an even more flavorful spirit. (These stills will get their own more complete breakdown in a later post.)

This does not mean that the ominous pits of evil are a complete fabrication, however. According to the West Indian Bulletin from the Journal of the Imperial Department of Agriculture for the West Indies, published in 1906, “Generally a proportion of liquid from what is called the ‘muck hole’ is also added to this cistern. The components of the ‘muck hole’ are the thicker portion of the dunder from the still, the lees from the retorts, and cane trash and other adventitious matter which from time to time finds its way into this receptacle.” The addition of muck, made up in parts by “adventitious matter,” which is delightfully mysterious, intensifies the production of esters, which are measured in parts per million (ppm). Jamaican rums, renowned for their high-ester flavor profile, can range from an over proof rum clocking in at about 100-200 ppm to those in the 1,600 ppm range, which are not meant for consumption and are made for the purpose of flavoring in blends.

This style was developed in the 19th century after Germany dramatically increased the import duty on Jamaican rum. In response, the Jamaicans created a class of rum called “flavo(u)red rum,” which could be used in a blend. The esters present in the flavored category of rum measure between 700 and 1,600 ppm. In comparison, the other four categories of Jamaican rum — common clean, Plummer, and Wedderburn — have ester quantities up to 300 ppm. J C Nolan, special commissioner of the Jamaican Government to the UK, made his opinion of flavored rum quite clear at the 1908 Royal Commission on Potable Spirits: “It is a flavouring essence. It is not a self rum.”

The difference between flavored rum, or German rum as it was called back then, and common clean is the inclusion of muck into the wash for the latter. A 1906 document titled Report on the Experimental Work Jamaica. Sugar Experiment Station describes in great detail the distillation process for Jamaican rum that was developed over a century ago. It says that flavored or German rums were made with acid, which was prepared from the skimmings of cane juice in a succession of cisterns. A muck hole would be prepared outside the distillery and was the receptacle for the thick matter from the stillage to which was added lees and cane trash. It would then undergo a slow fermentation and putrefaction, and a calcium-carbonate or lime-rich mud, called marl, would be added to keep the acidity low. Eventually, the muck pit would contain large amounts of butyric and higher fatty acids, both free and combined with lime, and it would be added to the different acid cisterns, which would release the butyric and other acids. The resultant material was the flavor and would be added to the wash after fermentation had begun.

The above document also gives information on the specific kind of matter that made up a muck pit. Usually, the muck pit contained semi-solid materials settled at the bottom of the wash pre-distillation, semi-solid materials found in the dunder, the residue remaining in the field after harvesting cane stalk, and residue leftover in the retorts. Muck pits were fed waste and debris from various stages of the distilling process, and their pH levels controlled through the addition of marl, to create a feeding ground for acids that would eventually become enjoyable esters.

Jamaican rum is a complicated spirit to get a complete understanding of and has evolved significantly throughout its lifetime. Knowing its history, however, is always important.

Although far too brief to be considered required reading, this piece hopefully gives insight as to what dunder is and is not so that everyone can speak about it from a more informed position moving forward. 

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