“Dark” brown sugars are similar to light brown sugars in that they are refinery sugars, almost always produced by “painting”, i.e. the application of a very dark molasses. Dark brown sugar can contain as little as 85% sucrose. Up to 5% of it can be plant matter and long-chain sugars, and up to 2% various minerals and salts (the rest being water, glucose and fructose). That being the case, it has a similar flavor profile as light brown sugar, except that those flavors are stronger and are supplemented by bitter and even licorice notes. Its higher acetic acid content can make is almost tangy and/or vinegar-y tasting.