On "Bitter"

"We can probably all agree that Fernet-Branca, rapini, citrus zests, and beer are bitter, but I became more aware of the diversity of what we think of as bitter when numerous friends, all working in the food world, sent me suggestions for foods to include in the book. 

"While I agreed with most of their ideas, some surprised and even shocked me. Among them were Camembert, celery, cucumber, Campari, Belgian Chimay cheese, eggplant, lemons, pickled onions, rhubarb, Seville orange marmalade, sorrel, coffee, and white Chateauneuf-du-Pape wine. 

"Aren't rhubarb and sorrel simply sour? Lemon is both sour - its juice - and bitter - its peel. Celery, cucumber, Seville orange marmalade, Campari, and white Chateauneuf-du-Pape wine all have bitter notes, but eggplant is rarely bitter today."

Jennifer McLagan in "Bitter: A Taste of the World's Most Dangerous Flavor, with Recipes"