Fermentation

The fermentation that turns molasses into rum never took place on the fjord. It happened on the islands, shortly after the sugar harvest, in large vats. There, yeasts convert the sugar into alcohol and carbon dioxide, and the mash foams and heats up.

The flavor develops during these days. Depending on the yeast and duration, esters form — volatile aroma compounds that can smell of banana, pineapple or even glue. A short fermentation of just one day produces light, clean rums. On Jamaica, it used to take nine to ten days, and the result tastes much more robust.

Anyone wanting to know what once lay in Flensburg's casks need only look to Jamaica. The island's high-ester marks reach levels of 700 to 1,600 grams of esters per hectolitre of pure alcohol. These are made less for sipping neat than for blending, since a small amount can season a large volume.

This is exactly where Flensburg's craft comes in. A heavily fermented rum brings aroma enough for many bottles, while neutral spirit and water stretch it further. This is permitted as long as at least five percent of the alcohol comes from rum. The result is then called a spirit drink, not rum.

Anyone tapping a cask in Flensburg is therefore opening the result of a fermentation that took place thousands of kilometres away. No fermenting happens in the city itself. Here begins only the part where blending, waiting and tasting matter. Whether at Johannsen or at Braasch, the houses take in a rum whose fermentation is long since complete, and decide only on the blend.