Mention the word Dunder to most rum drinkers and you will generally get a blank stare in return. Then there are the rare few who will recognize the term and turn a little green around the gills at the thought. While this reaction might seem a little extreme, the muddy history of Dunder means that a little nausea is a given. With rum’s return to popularity around the world, I believe that it is past time that old myths are debunked. In this post I hope to explain a little more about what dunder is and how it can be incorporated into a modern craft distillery to produce flavourful rums.
So what is Dunder?
At its most basic level Dunder is made up of the leftovers from previous distillations. This is more commonly known as stillage in most distilleries and is generally disposed of. The difference in the case of Dunder is that it is kept and allowed to age for a time. A close parallel can be found in the bourbon industry, where it is referred to as a sour mash.
Unfortunately Dunder is not seen in the same good light as sour mash and this bad reputation can be traced back to one source, the Dunder pit. When delving into the history of rum in the Caribbean, you will more than likely come across descriptions of Dunder pits. Back in the day, the Ye Olde Dunder pits could be described as nothing short of cesspools. Quite literally an open pit in the ground, rum distillers would throw all their distilling related waste into this pit, including dunder, molasses, fruit and other cane solids. As happens with open pits of waste, the chances of animals falling in and dying or being dumped there by neighbours was also quite high. This is where the belief that a good Dunder pit needs goats heads and dead bats comes from. It goes without saying that this is no longer the case at modern Caribbean distilleries.
During the product development stage for our rum, I came across two very interesting documents from the 1900s which list in depth the working of old rum distilleries. The documents (linked at the bottom of the page) reveal that the substance in these pits is actually something referred to as “muck” and as such, it would be more accurate to call them muck pits. The term “flavour” is also used interchangeably with muck and I have no doubt that these pits would produce massive amounts of the acids and bacteria required to make a high flavour rum; something I will explain in the next section. While there are a few distilleries in the Caribbean still using muck, it goes without saying that the sheer smell of these pits can stop most people in their tracks. In the end, the bad reputation given to Dunder is simply down to an error of naming perpetuated over time.
Before moving on, I would like to mention that the distillation process by its very nature completely separates the alcohol from any organic matter. As such there is never any danger of ingesting any of the bacteria or other substances in muck or any other fermented substance that is distilled.
With many craft distilleries (including our own) operating within cities and close to other businesses, it is virtually impossible to set up a muck pit. The health and safety issues alone would be enough without the guaranteed odour complaints from neighbours. So how do you go about creating flavourful Caribbean inspired rums in a craft setting? By turning to Dunder and understanding a little bit about the chemistry behind why it works.
When left to age, the pH of Dunder begins to drop; meaning that certain acids are being produced. These acids bind with the alcohol in a fresh fermentation to produce compounds called esters. These esters give alcohols a large portion of their flavour, obviously not including things like ageing and the natural flavour of the substance fermented to make the alcohol. So in very broad terms, the longer your Dunder ages, the more acid it has and the more flavour your rum will have after it has been distilled. However if the Dunder is left to age for too long or is kept in an open container, then natural bacteria can kick this process into overdrive and this is where the bad smells start to come in. At this stage, the Dunder is becoming a lot like muck and as mentioned above, that can become a problem.
At Cape of Storms Distilling Company, we have implemented several measures to strike a balance between getting the maximum amount of flavour out of our Dunder without letting the process go too far. First off, our process ensures that there is no bacteria carry over between batches. We also store our Dunder in closed containers, this stops wild yeast and bacteria from putting the ageing process into overdrive. Finally we age our Dunder for a very specific amount of time, allowing us to stop the process well before the time that any strong smells can start. This method effectively allows us to bring Caribbean style flavourful rums into a craft setting.