|Former Bourbon Barrels Filled With Rum|
|Barrels Repaired in Cooperage|
Rum can, and often does, contain added sugar or other sweeteners. Most sweetened rums are sugared at the bottling phase, but sometimes sugar or molasses, cane juice, fruit etc has been added already into the cask and some of that sugar is bound to get into a cask that was used previously for rum. Up to 40 grams/liter sugar contents have been reported in rum and up to 100 g/l in spiced and flavored rums, but when the sugar added directly to cask the finished product is usually in the range of 5-20 grams/liter.
What does this all mean in the finished product? It basically that sweetness in you rum may not be coming from added sugars. By aging in final finishing in casks that were used for finishing sweet spirits and wines can impart their sweetness to the rum as it is being aged. This is a process that takes time in the barrel, but it does give you not only a sweetness, but picks up some of the previous fill in the barrel. I love rums that have been finished in wine casks, they add a really nice finish to the final product.
There is a lot more information you can read on the subject at http://whiskyscience.blogspot.dk/2016/12/sugars-in-whisky.html?m=1