Final answer:
In Jamaican rum production, 'dunder' is a sour mash that is added to a new fermenting wash to enhance the rum's flavor and complexity by producing additional esters and other compounds.
Step-by-step explanation:
In Jamaican rum production, "dunder" refers to a sour mash added to the fermenting wash to increase flavor components. During rum production, after the initial fermentation, the liquid is distilled. The distilled liquid eventually becomes rum, while the leftover is known as "dunder". This dunder is rich in organic material and acids, which, when added to a new batch of fermenting wash, can enhance the flavor and complexity of the rum through the creation of additional esters and other flavor compounds during fermentation. Dunder is an integral component in traditional Jamaican rum production, where high-ester rums are often prized.