Symbolism, Imagery, Allegory
For a long time, scientists believed that different regions of the human tongue tasted the different elements of flavors, including sweet, salty, bitter, sour, and umami. Even though that's since been proven bunk, we would swear that Ms. McCullers's tongue has two settings: sweet and bitter.
As opposite as Miss Amelia and Cousin Lymon, or the jockey and the rich man, "sweet versus bitter" is an ongoing motif to point to the difference between once thing and, well, the other.
For example: when Miss Amelia gives Cousin Lymon her father's snuffbox, he fills it with cocoa and sugar, explaining, "The very teeth in my head have always tasted sour to me." (Ballad.64) His sweet tooth sure does infantilize him! It's a reminder that no one actually knows if he's a boy or a man.
Lymon is Lymon, always looking for the sweetest-tasting food and the most exciting thrills. His sour mouth? Probably some clever foreshadowing of his later-revealed capacity for being a total villain.
A Spoonful of Sugar
For Miss Amelia, it isn't alien that someone she's taking care of should love sweetness so much. When treating children with her special brand of country doctoring, she makes sure to give them enough homemade cough syrup to set them snoozing before doing anything that might hurt a little patient.
She soothes both a child suffering a boil and Cousin Lymon with her "Kroup Kure," "a medicine made from whiskey, rock candy, and a secret ingredient" (Ballad.113). Also, it's worth noting that sweetness isn't always for the mouth, as when the narrator notes: "for burns she had a cool, sweet syrup" (Ballad.53).
Bitterness Isn't Always Bad…
It saves Miss Amelia from poisoning herself, after she's mixed up her plate with Marvin's: "This she quickly realized by the slight bitterness of the food, and that day she ate no dinner" (Ballad.183).
And Sweetness Isn't Always Soothing…
Marvin and Lymon pouring "a gallon of sorghum syrup all over the kitchen floor and smashed the jars of preserves" (Ballad.223) is pretty freakin' evil. It's the ultimate subversion of her care taking, the sugary syrup making a mess of the café, a place that once represented community and love.