Deciphering dunder: an examination of rum fermentation

Flavour in distilled spirits is the culmination of a great variety of factors, ranging from the raw ingredients right through processing until the final preparation for packaging and consumption. In traditional rum fermentations, distillers maintain an undefined culture of wild bacteria and yeast derived from the leftovers of previous distillations known as “dunder”, a portion of which is added to fresh molasses fermentations. In this research, the addition of dunder was assessed in terms of ester and other volatile compound production. It was found that the addition of 5% v/v dunder led to a significant increase in the level of higher alcohols and esters that were tested. Microbiological examination of the dunder revealed the presence of a range of wild yeasts and bacteria. Further investigation through sequencing identified a range of Lactobacillus species. The implications of these results in terms of flavor contribution will be presented.