Dunder is the yeast-rich foam leftovers from one batch of rum that is used to start the yeast culture of a second batch. It is the traditional yeast source in Jamaican Rum. Similar in process to Sour Mash in Bourbon_whiskey, it is a crucial step in achieving an authentic rum flavor. Yeasts constitute a group of single-celled (unicellular) fungi, a few species of which are commonly used to leaven bread and ferment alcoholic beverages. ... Caribbean rum, circa 1941 Rum is a distilled beverage made from sugarcane by-products such as molasses and sugarcane juice by a process of fermentation and distillation. ... Bourbon bottle, 19th century Bourbon is an American form of whiskey, made from at least 51% but not more than 80% of corn (maize in the Old World) (typically about 70%, with the remainder being wheat or rye, along with other grains), distilled to no more than 160 (U.S...