Dunder is the liquid left in a boiler after distilling a batch of

rum Rum is a liquor made by fermenting and then distilling sugarcane molasses or sugarcane juice. The distillate, a clear liquid, is usually aged in oak barrels. Rum is produced in nearly every sugar-producing region of the world, such as the Ph ...

. It is a traditional

flavor Flavor or flavour is either the sensory perception of taste or smell, or a flavoring in food that produces such perception. Flavor or flavour may also refer to: Science *Flavors (programming language), an early object-oriented extension to Lis ...

source used in the fermentation of the

wash WASH (or Watsan, WaSH) is an acronym that stands for "water, sanitation and hygiene". It is used widely by non-governmental organizations and aid agencies in developing countries. The purposes of providing access to WASH services include achievin ...

of Jamaican rum. Similar in process to

sour mash Sour mash (or sourmash) is a process used in the distilling industry that uses material from an older batch of mash to start the fermentation of a new batch, analogous to the making of sourdough bread with a starter. The term can also be used a ...

Bourbon whiskey Bourbon () is a type of barrel-aged American whiskey made primarily from corn. The name derives from the French Bourbon dynasty, although the precise source of inspiration is uncertain; contenders include Bourbon County in Kentucky and Bourbo ...

, it is a crucial step in achieving an authentic rum flavor. In Europe, waste liquors from alcohol distillation are referred to as

vinasse Vinasse is a By-product, byproduct of the sucrose, sugar or ethanol industry. Sugarcane or sugar beet is processed to produce crystalline sugar, pulp and molasses. The latter are further processed by Ethanol fermentation, fermentation to ethanol, as ...

. Dunder contains many by-products that help in future fermentations, including dead yeast cells, which are an excellent yeast nutrient. Subsequent fermentations using dunder must be carefully controlled to prevent stress on the yeast which will cause a greater amount of mutations. Also if planning to store dunder before use it is advised to refrigerate the dunder to suppress cell division as to prevent mutations. These mutations change flavor, alcohol content, and overall affect consistency of the finished product. Dunder, if not used to re-pitch the yeast colony, can also be applied as fertilizer. Traditionally, 20% to 35% of a new wash is dunder from one or more previous washes. This lowers pH, conserves liquid, provides yeast nutrient, and concentrates two critical flavoring

esters In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides are ...

("rum oils") such as

ethyl formate Ethyl formate is an ester formed when ethanol (an alcohol) reacts with formic acid (a carboxylic acid). Ethyl formate has the characteristic smell of rum and is also partially responsible for the flavor of raspberries. It occurs naturally in th ...

propyl isobutyrate In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula for the linear form. This substituent form is obtained by removing one hydrogen atom attached to the terminal carbon of propane. A propyl substituent is of ...

to ensure good rum flavor. Also traditionally, after a run, the spent liquid from the still (dunder) was tossed in "the dunder pit", where it would settle, and where bacterial action would develop the rum oils. It was then removed to make wash as needed.

References

Yeasts {{distilled-drink-stub