...it is impossible to develop cavities in the absence of fermentable carbohydrates.Wow! I love the word "impossible" when used somewhat scientifically.
To answer the original question, sugar-in-the-raw, or natural brown sugar, is made by not extracting as much molasses while refining. It is produced during the first crystallization of the sugarcane, while white sugar, or table sugar, is produced after the third boiling and crystallization.
Or something like that.
Natural brown sugar is different from the brown sugar we bake with, which is white sugar with molasses blended back in.
(Confession: I thought white sugar was bleached like flour is. My bad.)