Since the main subject in the text is "Sugar" - a theme that would commonly be associated with taste -, the authors deemed it a clever idea to use dials of flavor (sweet, sour, bitter, salty...) as adjectives to describe the individuals (characters) involved.
For example:
- We, the human race, are stated to "crave sweetness" since birth.
- "... the bitter lives of the enslaved Africans..." are responsible for the spreading of "pure sweetness... around the world".